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Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001

SCIENTIFIC PAPERS ON

GROUNDWATER AND

LANDSCAPE

SUSTAINABLE

MANAGEMENT

WORKSHOP OF THE COMPLUTENSE-

CHARLES UNIVERSITIES.

“CÁTEDRA COMPLUTENSE” PROJECT

Principal editor: Redondo, C.

Madrid, 2001

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GROUNDWATER AND

LANDSCAPE SUSTAINABLE

MANAGEMENT

WORKSHOP OF THE COMPLUTENSE-

CHARLES UNIVERSITIES.

“CÁTEDRA COMPLUTENSE” PROJECT

2 ND EDITION

Editors:

Clara Redondo

Juan D Centeno

Almudena de la Losa

M Ángel de Pablo

M Teresa López Bahut

Esperanza Montero

M Eugenia Moya-Palomares

Olga San Juan

Fermín Villarroya

Printed by Department of Geodynamics. Faculty of Geological Sciences. Complutense

University (Spain). Madrid, 2001

2


Presentation

CONTENTS

“The University Complutense of Madrid (UCM)”.

Centeno, J. D. ……………………………………………………………………………4

“The Faculty of Geological Science”.

Centeno, J. D. …………………………………………………………………………5

“Spain: general features of the country (Geology and Hydrogeology)”.

Villarroya, F. ……………………………………………………………………………6

Scientific Fieldtrips

“Hidrogeologic and environmental issues of the Llanura Manchega

and Campo de Montiel aquifers”.

Montero González, E. .............................................................................................…….14

“Hidrogeologic and environmental issues of Aragón Region”.

Sánchez, J.A., Pérez, A., Roc, A.C. and Rubio, J.C. ……………………………………39

“Fieldtrip to the upper Lozoya valley and Peñalara hanging glacier cirque”.

Centeno, J.D. and Moya-Palomares, M.E. ..…………………………………………67

Scientific Sessions

“Evaluation of the runoff erosion in the drainage basin of the Puente

Alta Reservoir (Segovia)”.

Bodoque, J.M ..............................................................................................................…73

“Terrain analysis in coastal erosion and fluvial morphometry”.

Garrote, J. ................................................................................................................….78

“Naturally occurring arsenic in groundwaters of the Madrid Tertiary

Detrital Aquifer (Spain)”.

Hernández, M.E. ...........................................................................................................82

“The origin and significance of phosphorous in a periurban, alluvial aquifer”.

Himi, Y. and Alvarez-Cobelas, M. ................................................................................90

“Hydrogeological and hydrochemical study of Lozoya River High

Catchment (Madrid, Spain)”.

López, M.T., De la Losa, A. and Redondo, C. ............................................................….95

“Preliminary sedimentological and geomorphological evolution in

a part of the Guadiana Basin between Mérida and Badajoz (Spain)”.

Moya-Palomares, M.E., Centeno, J.D. and Azevedo, T.M. ........................................102

“Present and past floods in the Guadiana River Basin: hydro- and

paleohydrological approach”.

Ortega, J.A. and Garzón, G. ….…………………………………………………….107

“Historical floods analysis between the Atlantic and the Mediterranean

watersheds in Central-South Spain”.

Potenciano, A. and Garzón, G. ……………………………………………………112

“Microbiological study of the incrustations and corrosions in

groundwater wells”.

Senderos, A., Villarroya, F. and De Castro, F. ............................................................116

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Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001

PRESENTATION

Since the beginning of the nineties our universities (University Complutense of Madrid

and Charles University in Prague) collaborate by mean of the project "Cátedra Complutense".

Since then, two fields of the project had been accomplished: an humanist part in order to

improve the Spanish culture and language in the Czech Republic and a scientific side related

mainly with Hydrogeology. In such manner some people (faculty and studies) had the

opportunity to work in Prague and Madrid respectively extending their professional knowledge

and meeting scientists and people.

Last year, the 1 st Workshop of the project devoted to "Sustainable development of water

resources in fractured rocks: environment issues", was held in the Czech Republic, and made

possible to organize this second Workshop of the "Cátedra Complutense".

Our meeting on "Groundwater and Landscape Sustainable Management" will be

performed between 21 st of September to 1 st October 2001. We devote our field trips to see and

discuss specials problems related with water and landscape management in La Mancha, the

Ebro basin, the Pyrenees and the Guadarrama range.

We plan to start with a lectures and discussions day, devoted both to give the

participants basic information for the following days field trip and to discuss the related

research of the Department of Geodinamic.

In La Mancha, where Cervantes imagined Don Quijote heroic deeds we will visit the

overexploited aquifer of La Mancha and work on its big problems like overexploitation, and

critical environmental problems like contamination, rivers and cracks completely dry and

spontaneous combustion of peat who were the bed of the Guadiana river, and the interland

wetland of Natural Park of Ruidera lakes, where wetland conservancy and agricultural

development are the main conflict to solve.

In Aragón will have the opportunity to visit the most important aquifer in Ebro basin:

the Alfamén-Cariñeña Area. In Pyrenees mountains we have the opportunity to visit some

thermal springs and spaas.

In Guadarrama range we will visit the mountain wetland of Peñalara glacier cirque, a

good example of integral conservation of geomorphological, hidrogeological and ecological

conditions.

The organizers want to show their acknowledge to the University Complutense, that

founds this project specially to the Vice-Rector of International Affaires for this invaluable

help and energy and to the Faculty of Geology and the Department of Geodinamic for their

support.

We want to welcome the Czech and Spanish participants to this Workshop. Moreover,

we hope it will be successful in the scientific and human aspects. For sure, the discussion of

ideas in such a large body of faculty and students will allow a productive exchange of

experiences on the field of both environment and hydrogeology.

On behalf of all my colleagues and ph-students and postgraduates students who helped

us in order to prepare this Workshop we would like to welcome all participants to Madrid and

Spain!.

Dr. Fermín Villarroya

Head of Department of Geodynamics

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Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 4

THE UNIVERSITY COMPLUTENSE OF MADRID (UCM)

The University Complutense of Madrid recently celebrated its seven hundred

anniversary. The 20 th May 1293, the Castilian king Sancho IV ordered its foundation in Alcalá

de Henares the former Roman town of COMPLUTUM - in a time of Muslin-Christians war the

roman name was chosen by the new University.

Such foundation date makes the Complutense the third Spanish University, after

Salamanca and Valladolid Universities. But a second foundation should be cited. In 1495

Cisneros (later Cardinal Cisneros) is designated Archbishop of Toledo and becomes the real

founder of our University in a difficult process that last until 1513 when himself declare to be

the “School and University of Alcalá founder”. This double foundation seems to be in the

destiny of our University for in October 1836 the University of Alcalá de Henares is closed to

create in Madrid the Central University, forgetting the term Complutense until the 1970’s when

it is recovered and the new University of Alcalá de Henares is created.

The first production of the University Complutense is the opera magnum of the

Cardinal, the Bible Poliglota (multilingual) that made the University a leading publishing centre

in western Europe. Since then, many Spanish humanist and scientist have studied or worked in

the Complutense making it a basic centre for Spanish development and culture. Antonio de

Nebrija, San Juan de la Cruz, Pedro Calderón de la Barca or Francisco de Quevedo can be cited

among de classics. But also Manuel Bartolomé de Cossío, Santiago Ramón y Cajal, Gregorio

Marañón, José Ortega y Gasset or Severo Ochoa are between the Complutense outstanding

members.

Nowadays the University Complutense is the biggest University of Spain and one of the

biggest of Europe. Around 90.000 students and 5.000 faculty in 25 centres, 70 degrees and

many postgraduates study plans make it an pivot teaching institution. But also it is a main

research establishment, leading the Spanish science and humanity in many fields and devoting

to fringe science more space and effort than any other Spanish University.

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Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 5

THE FACULTY OF GEOLOGICAL SCIENCE

The Faculty of Geological Science history goes back to 1944 when the Faculty of

Science establish four sections (Mathematics, Physics, Chemistry and Natural Science) and a

Doctorate on Geological Science. In 1964 the section of Natural Science is divided in two

sections of Biology and Geology and, finally, in 1975 the Faculty of Geological Science is

created.

In the meantime, the degree “Licence in Geological Science” was former regulated in

1953, following official changes in 1962, 1969, 1975 and 1994 (changing the last one the

official name to “Licence in Geology”). This degree on Geology can be obtained also in the

universities Autónoma of Barcelona, Barcelona, Bilbao, Granada, Huelva, Oviedo, Salamanca y

Zaragoza. In addition, since 2000 a title of Geology Engineer can be followed in our Faculty

and the universities of Alicante, Barcelona and Polytechnic of Madrid.

The Faculty of Geological Science is organised into five departments:

• Crystallography and Mineralogy

• Estratigraphy

• Geodynamics

• Palaeontology

• Petrology and Geochemistry

There are around 1200 students, 112 faculty staff and 70 technical and auxiliary staff.

Moreover, some 60 postgraduate students follow some of the two PhD Programs (Geology and

Geodinamics) or the interunivesities PhD Program on Palaeontology.

Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 6-12

6


SPAIN: GENERAL FEATURES OF THE COUNTRY

(GEOLOGY AND HYDROGEOLOGY)

VILLARROYA, F.

Department of Geodynamics. Faculty of Geological Sciences. Complutense University. 28040 Madrid (Spain)

INTRODUCTION

By virtue of its relief (average altitude of 600 m and one-sixth of its area above 1.000

m), the variety of its climate, the length of its coastline (more than 7.000 km with many

beaches) and his historical and cultural heritage, Spain is a microcontinent where virtually all

types of crops can be found. All these factors, together with an intermediate level of economic

development and an acceptable network of infrastructures and amenities, have turned the

country into a prime destination for tourists. Tourism represents close the 11% of the Gross

Domestic product, accounts for annual revenues exceeding more than 26.000 millions of euros

and generates more than one million jobs. Earnings from tourism cover 21,5% of all imports. In

1997, Spain received 64,5 million visitors. Of these, 43,4 million were real tourists, who

consumed tourist service on Spanish soil. The remaining 21,1 million were on day trips, cross

border visitors, or in transit. (MEH and MIMAN, 1999). The other hand, management of

twelve National Parks and other statutorily protected areas has made it possible for conservation

of places of special environmental importance to be combined with an annual influx of visitors

numbering over nine millions, (we expect visit some of them during field trips). Apart from

National Parks, the Autonomous regions have brought in different legal formulae for

environmental protection purposes; in total, there are 580 protected areas in Spain , extended

over 2.700.000 hectares.

The main figures of Spain are:

• 40 million inhabitants

• 504.745 km 2

• 174.745 km 2 permeable outcrops

• recharge 100 mm/y (20.000Mm 3 /y)

• 442 aquifer systems

• surface runoff 95.000 Mm 3 /y

• groundwater extraction 6100 Mm 3 /y

18% water supply

6% industrial use

76% agricultural use (irrigation)

Spain is a partially industrialized country with a modest economy in comparison with

some other members of the European Union. It is the most arid country in Europe. The

economy have relied heavily on irrigated agriculture, which is a major consumer of fresh-water

resources but now is not a major contributor to the Gross National Product of Spain. This

situation is quite different from that in most other countries of the European Union.

Water has long been recognized as a valuable resource and a critical factor in public

health and welfare. For several decades, water has also become recognized as being essential for

the functioning of most ecosystems. The role of groundwater in the hydrological cycle has been

known for more than three centuries. Nevertheless, the potential role of groundwater is often

downplayed in the water policy of many countries. Water planners often prefer surface-water

solutions even at the expense of conjunctive use of surface water and groundwater, which is

either not considered or misapplied. In the early 1970s, the attitude of some hydraulic engineers

to draw a sharp distinction between groundwater and surface water, and disregarding the

former, was characterized as "hydroschizophrenia" by Nace (in Llamas, 1985). Llamas, studied

7


this syndrome and concluded that one major cause of hydroschizophrenia in Spain was the

failure during the previous century to cope with the increasing water demand of the city of

Madrid by means of groundwater using infiltration galleries and water wells. At that time it was

decided to import surface water from the nearby mountain ranges with the aid of dams and

aqueducts. The centralized nature of the Spanish Administration until the drafting of a new

Constitution in 1978, the unhealthy competition between two rival ministries in charge of

surface and groundwater, and the promulgation of hydroschizophrenia through most civil

engineering schools and research institutions in Spain have helped to spread the malaise across

the entire country, thus adversely affecting Spain's national water policy. The private sector did

develop groundwater when surface water from public projects was not available, but often

without sufficient knowledge or safeguards to sustain this precious resource. There have been

some exceptions, such as the successful management schemes of water in Barcelona, but even

in those cases the public water administration has often been more of a hindrance than help in

the initiation and maintenance of sound groundwater management practices.

OUTLINE OF SPAIN'S GEOLOGY, HYDROGEOLOGY AND GROUNDWATER USE

Spain is located in the southwestern corner of Europe, separated from Africa by the

western Mediterranean Sea. Spain comprises the larger part of the Iberian Peninsula (the rest is

Portugal) and includes (a) two main archipelagoes, the Balearic Islands in the Mediterranean

Sea and the Canary Islands in the Atlantic Ocean, which face the African continent (b) two

small peninsulas in northern Africa, Ceuta and Melilla; and (c) several small islands. (Locations

are shown in Figure l).

Since the democratic system was restored by the 1978 Constitution, Spain has

comprised 17 autonomous communities, plus the enclaves of Ceuta y Melilla in North Africa.

Geology

The basement of the Iberian Peninsula is formed by folded and partly metamorphosed

Hercynian-age rocks. These rocks crop out in the northern and northeaster parts of Spain and

form the basement of the central highlands (Mesetas). Thick Mesozoic-age sediments,

predominantly carbonates and marls with evaporites, were deposited around and on the

basement rocks. These formations were covered by early Cenozoic-age sediments that contain a

large proportion of carbonates along the Mediterranean coast (Fig. l). Mountain ranges,

reactivated during the Alpine orogeny, occur at the margins and across the Central highlands,

with intensive folding and thrusting of sediments of pre-Miocene age. Large and deep grabens

were formed, which are filled with a variety of materials, from arkosic sand to playa-lake

evaporitic sediments, mostly unfolded. They constitute a major part of the main river

watersheds and contain some extensive aquifers such as those of the Duero and the Madrid

basins. General descriptions can been found in Custodio et al 1997, and López Geta et al, 2001).

In broad terms, the Iberian Peninsula consists of a western and northwestern hard-rock

domain; a central domain, dominated by clastic, often fine-grained and clay-rich sediments; and

a northern and Mediterranean domain, with extensive thick carbonato formations. Restricted,

but thick and well-developed, Quaternary-age deposits along the major river valleys and the

coastal plains play important roles as aquifers. Gypsum and anhydrite are widespread in the

southeastern part of the Peninsula, where the associated saline waters occur.

The Balearic Islands are part of the carbonato region of the Mediterranean basin, with a

deep sea-occupied trough in between. The Atlantic volcanic archipelago of the Canaries consists

of high and large volcanic formations arising from the deep ocean floor, except the easternmost

islands, which rest near the African continental shelf. Some islands are very high, up to 3700 m

above sea level in Tenerife, from a submarine base more than 3000 m deep. Volcanism started

in the Miocene epoch and comprises several episodes of basic to intermediate eruptions, with

intensive landslides, and with intervening dormancy, during which deep gullies (barrancos)

were incised. Volcanism is still active episodically. The oldest parts of the islands have low

permeability, but young volcanics are often very pervious. A core of low-permeability material

exists that is sometimes exposed but more often buried below recent lava flows that extend

down to the coast. The groundwater body may occur at high altitudes, but most of the

8


groundwater flows within the cover of young volcanics.

Fig 1.- Spain and main aquifers.

Climate

Spain has a diversity of climates due to its position between a temperate European zone

and a subtropical area. It includes some of the most rainy areas of Europe, such as Galicia in the

northeastern part and Grazalema in the southeastern part, with more than 2 m/a; and the most

arid areas, such as Cabo de Gata (Almería) in the southeastern part, with less than 0.2 m/a and

some regions of the Canary Islands, with 0.1 m/a). The coastal plains along the Mediterranean,

the Ebro central basin and the two main archipelagos (except their high mountains) are

semiarid, with a distinct, long dry summer season, during which there is a pronounced soilmoisture

deficit and little aquifer recharge.

Groundwater Resources and Aquifers

9


Of a total surface area of 504,750 km 2 , according to official data of "Dirección General

de Obras Hidráulicas" (DGOH 1994), 174,745 km 2 are permeable outcrops. Aquifer recharge

along these outcrops is approximately 20 x 10 9 m 3 /a, at a rate of 100 mm/a. This amount has

been estimated by the Water Administration by assigning recharge rates that range from 16-479

mm/a, to the area of each aquifer system. The Water Administration (SGOP 1990) has

identified 442 aquifer systems.

Surface runoff across Spain is officially estimated to be approximately 95 x 10 9 m 3 /a, or

approximately five times larger than groundwater recharge. This questionable and poorly

supported ratio has been in the past and still is today frequently quoted in order to make a case

for the construction of large dams at the expense of utilizing, managing, and protecting

groundwater.

Groundwater Use and some problems

Groundwater is tapped directly at the springs (which often are considered as surface

water) or abstracted by means of wells, some of them deeper than 500 m. The number of wells

is officially estimated at approximately half a million, but in fact more than one million

groundwater uptake points may exist. Following the Water Act of 1985, groundwater became a

public community. Prior to this act, it was the private property of well owners (Water Act of

1876).

According to DGOH (1994), groundwater uptake increased from 0.5 x 10 9 m 3 /a in 1900

to the current rate of approximately 6.1 x 10 9 m 3 /a. Approximately 1.1 x 10 9 m 3 /a (18%) is used

as public drinking water for 31% of the nearly 40 million inhabitants of Spain. Approximately

0.4 x 10 9 m 3 /a (6%) supplies the industrial sector. The rest, approximately 4.6 x 10 9 m 3 /a , is

allocated to irrigation; 700,000 ha of land is irrigated solely by groundwater, and approximately

300,000 ha by groundwater and/or surface water. The total irrigated area of Spain is

approximately 3.5 x 10 6 ha. Surface water is used for the irrigation of 2,500,000 ha at a rate of

approximately 20 x 10 9 m 3 /a. In other words, the applied water per hectare in surface-waterirrigated

areas is approximately double that of areas irrigated with groundwater.

Most surface-water irrigation projects were constructed in the second half of this

century and were financed with public funds. In contrast, groundwater development has been

pursued and financed by private farmers and small -or middle-sized towns. This virtually

uncontrolled and unplanned development has led to real or apparent problems of (a) overdraft or

overexploitation, (b) seawater intrusion, and (e) wetland degradation.

Official data (DGOH 1994) suggest that 51 aquifer units from the total 442 are

overexploited, with pumpage exceeding recharge by 0.7 x 10 9 m 3 /a, and 48 units are close to

being overexploited. Some complex and partially effective legal action has been taken in 18

aquifer units with a surface area of 13,000 km 2 . Abstraction rate is 1.1 x 10 9 m 3 /a, which is

assumed to exceed recharge by 0.5 x 10 9 m 3 /a. In some areas in southeastern Spain and the

Canary Islands, groundwater drawdown rates as much as several m/y are not rare, but this is not

necessarily due to an excess of abstraction over recharge. In some cases a dry period in which

recharge is low and/or a long-term transient situation can explain a significant part of such

drawdown rates. The term overexploitation has often been used to imply different meanings

within different contexts (Simmers et al 1993; Villarroya and Adwell, 1998).

Intensive development of coastal aquifers has often produced problems related to

seawater intrusion, although many such problems can be attributed to poor management and

inadequate well location or construction. These -coastal aquifers play, or should play, a key role

in peak, emergency, and drought water supplies for towns as well as a complementary source of

water for irrigation in coastal areas. According to DGOH (1994), of 82 coastal aquifer units, 15

have been seriously invaded by seawater, 27 other units have large areas with intrusion and 6

units have local problems.

According to the Water Act of 1985, wetlands have to be protected and preserved. The

DGOH (1994) study mentions 1533 groundwater-related wetlands of various sizes, with a total

current surface area of 800 km 2 , approximately 65% of the original 1250 km 2 . Some of them,

including several that have international relevance, are being threatened or degraded by

groundwater abstraction, but in other cases the assumed ecological impact of groundwater

abstraction has been used to justify the construction of large dams for other purposes.

10


Official data on groundwater contamination are scarce and sketchy, even for natural

sources of salinity, which play a significant role in some areas. Aquifer pollution by human

activities may be serious in some areas (Custodio 1992), although fortunately there are large

areas of rural, forest and natural parks in which the risk of pollution is small. Agriculture is a

main contributor through massive use of fertilizers and other agrochemicals for intensive crop

production, mainly along the Mediterranean coast and on the islands. According to DGOH

(1994), the mean rate of nitrogen use in agriculture has increased from 12 kg/ha/a in 1955 to

nearly 60 kg/ha/a in 1988. In parts of some aquifers there are areas in which NO 3 in

groundwater exceeds the 50-mg/L limit for drinking water, in places reaching 200 or even 500

mg/L. Current use of pesticides ranges from 2-12 kg/ha/a, but studies of their impact on

groundwater are scarce. In some areas, intensive raising of livestock causes serious nitrate

problems and reducing conditions in groundwater that increase iron, manganese, and other

heavy-metal concentrations.

A few documented cases exist of groundwater contamination by hydrocarbons, organic

chlorinated solvents, and heavy metals; however, data are scarce. Such cases are not mentioned

in the White Book on Groundwater by the DGOH (1994). New cases are appearing more and

more often, showing that it seems to be a widespread problem. Such industrial contamination

may jeopardize the sustainable use of aquifers as an inexpensive and reliable source of water in

case of drought, emergency, and peak demands in and around urban areas.

MAIN DIFFICULTS WITH SPANISH GROUNDWATER POLICY

Llamas (1997) categorizes the causes of water problems in the Iberian peninsula as

either ethical, aesthetic, or technological. The salient points of his paper in relation to

groundwater are summarized below.

The main reason for the relatively scarce use of groundwater in Spain, and for its poor

management with consequent overexploitation, seawater intrusion, wetland degradation, and

groundwater pollution (several examples of this, will be more in detail show during the field trip

excursions), is the method by which taxpayers' money is allocated to water projects. Most dams

and canals (built for irrigation projects, or for water supply to large towns, during this century)

have been designed and paid by the Ministry of Public Works. Only dams built for hydropower

have been financed by the private or semipublic sectors. In Spain, the lobbies of large

constructors and of farmers have been and still are very successful in draining public funds for

large hydraulic works for urban water supply or irrigation. On the other hand, groundwater

development has been financed primarily by private entities, mainly farmers of modest means,

local water suppliers and factories. It is not easy to alter this situation because of the mental

inertia of many engineers involved in water management who think in terms of "hydraulics"

rather than "water resources and the lobbying power of large construction companies.

Another obstacle to the rational use of groundwater is the poor participation of

groundwater users in the management of aquifers. This situation is in contrast to traditional

social participation of surface-water users in its management. A prime example is the wellknown

"Tribunal de las Aguas" (Water Jury) of Valencia that has been in operation for seven

centuries. The 1985 Water Act attempted to create similar participation among groundwater

users, but thus far, corresponding efforts by Water Authorities have been largely unsuccessful,

with a few exceptions.

Most systematic hydrogeological surveys have been conducted by the Geological

Survey of Spain (IGME). The Ministry of Publics Works had only a small team of

hydrogeologists, some of whom were of excellent professional level but held little authority.

Sixteen years after the 1985 Water Act, the number of hydrogeologists among officials of the

Water Authorities remains pitifully small. This lack of expertise with authority within the

Spanish Water Administration is a major reason for the underexploitation, the overexplotation,

and the general mismanagement of groundwater resources in Spain. This is also why legal and

administrative control of groundwater quality is so weak, despite improved legislation

concerning water supply. Groundwater pollution is seldom mentioned, and when it is referred to

the objective usually is to justify large surface-water or desalination projects to supply potable

water to urban areas formerly supplied with the unpolluted groundwater.

11


As it happens, with a few exceptions groundwater has never been properly investigated

or controlled by Spain's Water Authorities. Instead, hydraulic engineers working for the Water

Authorities are often responsible for man "hydromyths" regarding groundwater that have been

circulating through Spain in recent years. Among these hydromyths, perhaps the most pervasive

is that "the fate of every water well is to become dry or brackish." The logical conclusion of this

wrong philosophy has been the continuation of construction of large dams and canals.

THE BRAND NEW SPANISH NATIONAL HYDROLOGIC PLAN

After more than twenty years (the first documentation involved is dated in 1980), a

brand new and polemic Plan about water has been launched in Spain. Official issue was the 6 th

of July (BOE nº 161, 2001). The Plan want to correct the more dry areas of the peninsula by

mean of one big divertion of water from the Ebro river (the most important river of Spain). But

the problem is that in the mouth of the river there is the Ebro Delta, a very important

ecosystem. The Plan envisages to transfer 1050 Mm 3 of water to de shout basins of the

Mediterranean facade of Spain:

Transferences to be accomplished from the Ebro river:

• 190 Mm 3 to Catalonia

• 315 Mm 3 to Júcar basin

• 450 Mm 3 to Segura basin

• 95 Mm 3 to South (Almería)

………………………………..

1050 Mm 3

Many people from the universities and from other institutions have made efforts against

the Plan because seem to be expensive, antiecologic, hydrosquizofrenic, and deterministic

approach. We expect that finally (fortunately the big (faraonic) construction meaning years

under construction) only one fraction of the dams, channels, and so on, envisaged, will be built.

REFERENCES

BOLETÏN OFICIAL DEL ESTADO (BOE) (2001) "Ley 10/2001 , de 5 de julio, del Plan

Hidrológico Nacional”. Boe nº 161 pp 24228-24250

CUSTODIO, E. (1992) “Groundwater pollution in Spain: general aspects” J, Inst Water

Environ. Management 6 (4): 452-458

CUSTODIO, E.; LLAMAS, M.R. and VILLARROYA, F. (1997) "The role of the Spanish

Committee of the International Association of Hydrogeologists in the management and

protection of Spain´s groundwater resources" Hydrogeology Journal vol, 6 , pp-15-23.

CUSTODIO, E. (1993) Is groundwater overexploitation a new hydrogeological concept?

Groundwater Goengineering, IGEA, Assoc Mineraria Subalpina, Torino, vol 2 pp 5-14

DIRECCIÓN GENERAL DE OBRAS HIDRÁULICAS (DGOH) (1994) “ White book on

groundwater in Spain” Serie Monografías. Servicio de Publicaciones del Ministerio de Obras

Públicas, Transportes y Medio Ambiente. Madrid, 135 pp.

LÓPEZ GETA, J.A.; FORNÉS, J.Mª Y VILLARROYA, F (2001) "Aguas subterráneas. El

inestimable recurso del subsuelo" Edit IGME y Fundación Marcelino Botín 100 pp ( in press)

LLAMAS, M.R. (1985) “Spanish water resources policy: the illogical influence of certain

physical and administrative factors” Mem 18 th Int Congr, Int Association of Hydrogeologists

18(2): 160-168

LLAMAS, M.R.(1997) “Transboundary relations in the Iberian Peninsula, an area with limited

water resources” In: Ghleditsch NP (ed) Conflict and environment. Kluwer, Amsterdam, pp

335-353.

M.E.H and MIMAN (1999) "Spain: a sustainable tourism" Ministry of Economic and Tax and

Ministry of Environment. Madrid, 97 pp

SERVICIO GEOLOGICO DEL MINISTERIO DE OBRAS PÚBLICAS (SGOP) (1990)

"Unidades hidrogeológicas de la España Peninsular e Islas Baleares: sintesis de sus

12


características y mapa a escala 1/1000000 (Groundwater units of Peninsular Spain and Balearic

islands)”. Servicio Geológico. Madrid. Informaciones y Estudios, v 52, 32 pp.

VILLARROYA, F. and ADWELL, C.R.. (1998) "Sustainable development and groundwater

resources exploitation" Environmental Geology 34 (213) May 1998 pp 111-115.

SIMMERS I.; VILLARROYA F. and REBOLLO, L.F. (1993) "Aquifer overexploitation"

Selected Papers Hydrogeology v, 3 1; 392 pp

13


Scientific Fieldtrips

3

2

1

1.- Llanura Manchega and Campo de Montiel

2.- Aragón Region

3.- Lozoya Valley and Peñalara (Madrid)

14


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 14-38

HYDROGEOLOGIC AND ENVIRONMENTAL ISSUES OF THE

LLANURA MANCHEGA AND CAMPO DE MONTIEL AQUIFERS

MONTERO, E.

Department of Geodynamics. Faculty of Geological Sciences. Complutense University. 28040 Madrid (Spain)

INTRODUCTION

The Mancha region, where the Llanura Manchega (Manchega Plain) and the Campo de

Montiel (Field of Montiel) aquifers are sited, has a dry mediterranean climate, with special

geologic and hydrogeologic characteristics, which always have conditioned the access to the

water of the population; this have had a cultural and economic influence.

The aridity that characterizes the area contrast to the big number of existent wetlands:

meandering rivers, flood plains, stepper lakes, carbonate, chloride and sulphate springs,

sometimes with high concentrations. This group of wetlands form the “Mancha Húmeda” (Wet

Mancha) standing out two among them due to its beauty and importance as ecosystems: Las

Tablas de Daimiel and Las Lagunas de Ruidera.

Agriculture, which has been the main source of richness in La Mancha, has broken the

equilibrium which allowed the diversity and stability in the exploitation of hydraulic resources

until the sixties decade. The develop of irrigation from groundwater in the region led to an

exclusive use of the water in the agriculture sector, which has cause among other effects, the

destruction of many wetlands and a serious threat over other (Rueda, 1992).

LLANURA MANCHEGA

1.- GENERAL FEATURES OF THE AREA

At the high catchment of the Guadiana River to El Vicario reservoir is sited the Llanura

Manchega (figure 1). It is a natural region with 16,130 km 2 belonging to the Meridian Castilian

Plateau, sited among the Toledo Mountains, the Iberian Range, the Campo de Montiel and the

Albacete Plain (Llanos de Albacete) (Servicio Geológico, 1988).

The hydrographic boundaries of the catchment are the watershed of the rivers Tajo at

north, Guadalquivir at south and Júcar at east. The most important rivers of this drainage pattern

are: Guadiana, Azuer, Gigüela, Záncara, Córcoles and Bañuelo.

The gentle slope of the rivers and the geologic and rainfall characteristics of the region

give rise to extensive wetlands, being the most important Las Tablas de Daimiel due to its

ecological importance (figure 2).

The area belongs to a temperate climate, dry Mediterranean: mean long-term annual

precipitation is 450 mm with a great seasonal irregularity; mean long-term temperature is 15ºC,

with maximum of about 46ºC and minimum of –19ºC. The mean long-term potential

evapotranspiration is 850 mm/year. These climatic characteristics determine very limited water

resources in the catchment, of about 450 Mm 3 /year. The most singular feature of the region is

the existence of the big underground reservoir of la Llanura Manchega (aquifer 23 or

Hydrologic Unit 04.04), which covers an area of about 5,500 km 2 (figure 2).

Recharge is due to rainfall infiltration, leaking of the rivers (Guadiana, Azuer y

Córcoles) and groundwater from adjacent aquifers (Campo de Montiel). Discharge, in natural

regime takes place through the Ojos del Guadiana (Guadiana Eyes) and close areas (Tablas de

Daimiel).

Due to these peculiarities, the Mancha region is one of the better examples in Spain of

surface and groundwater relationship, representing groundwater the main resources, more than

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70% from the total. The main use of the water is for irrigation being less important industrial

and human supplies.

The water balance of the aquifer shows a budget deficit between inputs and outputs,

which can be understood because of the aquifer empting, which is, estimated around 4,000

Mm 3 .

This empting, due to a heavy pumping of groundwater, produces a drawdown, which

affect to the non-renewable reserves of the aquifer, what put the agriculture development at risk

in the area (this is the first regional source of richness) and, consequently the next links of the

economical chain (Esnaola, et al., 1995).

The consequences of the aquifer overexploitation have influenced the original

hydrogeologic conditions. Regional groundwater level has fallen and natural discharge areas

have disappeared; this is the case of the Tablas de Daimiel and the Guadiana Eyes (dry since

1985).

2.- GEOLOGIC, GEOMORPHOLOGIC AND TECTONIC SETTING

The Llanura Manchega (figure 2) belongs to a morphostructural depression that, with an

ENE-WSW direction, is located in the meridian boundary of the South Plateau. It consists of a

base formed by shales, quartzites, sandstones, conglomerates, clays and gypsum on west area

and limestones, dolomites, marls and sands on centre and east ones (Palaeozoic and Mesozoic).

Over these materials exists a modern continental formation (Miocene) made up of

conglomerates, sands, clays, marls and limestones partially covered by Plioquaternary and

Quaternary detrital materials (figure 3) (Servicio Geológico, 1988). Towards the western of the

Llanura Manchega, at the Campo de Calatrava, remains of volcanic emissions from the upper

Miocene to the lower Pleistocene are frequent. The first lava and volcanic cones have a basicultrabasic

character while the last ones are alkaline and ultrapotasic.

Stratigraphy

The Palaeozoic forms the base of the sedimentary series and close the western boundary

of La Mancha. It is constituted by lower Ordovician shales and quartzites affected by hercinic

folding.

The Triassic is discordant over the Palaeozoic series. Breccias, sandstones, limonites,

clays and some carbonate levels constitute the Triassic. It is the impervious base of the deepest

aquifer.

The Jurassic is sited over the Triassic; it has a calcodolomitc and marly composition,

some of whose levels (Lower and Upper Jurassic) form the deepest aquifers of the area.

The Cretacic is less represented in the area although the most completed series are sited

at the eastern part. It has a detrital composition on the base and a calcareous composition at the

top. The calcareous upper Cretacic is a part of the deep aquifer.

Tertiary and Quaternary materials fill the morphostructural depression. The Tertiary is

discordant with the Mesozoic deposits and is thinner towards the eastern part of the aquifer. It

has a progressive continental makeup with detrital materials at the bottom and a Miocene which

final stretch is composed by sandy limestones that forms the shallow aquifer.

The Plioquaternary has a detrital composition (glacis) and takes part of the shallow

aquifer.

The Quaternary is discordant with many formations in La Mancha. Its litology is varied and it

depends on its origin. It can be distinguished river terraces, alluvial fans and eolian deposits.

Tectonics

The phisiografic and structural unit of the Llanura Manchega takes part of the Iberian

Peninsula foreland area belonging to the Bético-Rifense orogen. It is a depressed area with

heights among 600 and 800 m. The surface and groundwater behaviour shows an asymmetry of

the unit due to a tectonic tilt mainly towards the NW and to a lesser degree to the WSW. Inside

this neotectonic environment of flexural type, the Llanura Manchega depression extends

towards the East towards the Llanos de Albacete unit, and it is surrounded by unites with similar

16


orientations but with a positive character: Campo de Montiel, Montes de Toledo, Mesa de

Ocaña-Altomira y Campo de Calatrava (Rincón et al., 1996).

Tectonics features constitute the northern and southern boundaries of the unit with

ENE-WSW/E-W orientations while the eastern and western limits are related to SE-NW dextral

strike-slip faults. There is a third fracture type towards NNE-SSW. This fracture network has

conditioned the spatial distribution of rivers and streams and the carbonation-karstification

processes of the carbonate units.

3.- GENERAL HYDROGEOLOGY OF THE AQUIFER

In the Llanura Manchega aquifer, there are two hydrogeologic units, among which there

is a detrital unit (Lower Miocene), with an impervious character, which acts as an aquitard

(Servicio Geológico, 1988).

Upper hydrogeologic unit

The shallow aquifer spreads almost all the plain. Limestones and marl limestones

(Upper Miocene) and detrital material (Plioquaternary and Quaternary) constitute the aquifer,

forming a heterogeneous group with a medium thickness of about 35 m and maximum deeps of

about 200 m.

The Pliocene and Quaternary levels have transmissivities among 0 and 500 m 2 /day and

storages capacities among 10 -1 and 10 -2 . At the calcareous levels, the transmisivities vary among

50 and 20,000 m 2 /day and storage capacities among 10 -1 y 10 -2 .

Lower hydrogeologic unit

The deep aquifer spreads on the eastern sector of the plain. It corresponds to limestones

and dolomites Mesozoic formations that constitute the geologic extension of the Campo de

Montiel and Sierra de Altomira aquifers, which with they have a water connection.

There are three different aquifers (Upper Cretacic limestones, Medium Jurassic

limestones and Lower Jurassic dolomites), folded and separated between them by less pervious

layers, which thickness increase towards eastern. The transmissivity of this unit varies among

200 and 6,000 m 2 /day, and its storage capacity is about 4.10 -3 .

System hydrogeologic behaviour

The upper, is a water-table aquifer with parallel flux directions from east to west, in

spite of some areas present NE to SW (Gigüela-Záncara) and SE to NW (south of Manzanares)

directions. The big pumping cones produce local variations as well.

The recharge of this hydrogeologic unit is produced by: rainfall infiltration over the

Llanura Manchega outcrops; stream water infiltration from close systems (Córcoles, Alto

Guadiana, Azuer, Záncara and Gigüela); irrigation excess infiltration; urban spillage infiltration;

and lateral and deep flows (through the basal Miocene) from the Sierra de Altomira and Campo

de Montiel aquifers.

The discharge of this unit is produced by: pumping extractions, mainly for irrigation

uses but for human supply and industrial uses too; Ojos del Guadiana and Tablas de Daimiel

drainage; and direct evapotranspiration from the aquifer on the western area, where the water

table is near to the topographic surface.

The lower hydrogeologic unit is confined or semiconfined. Its recharge is produced by

the rainfall infiltration on the outcrops of Sierra de Altomira and Campo de Montiel aquifers. Its

discharge is done by the pumping wells that exploit the aquifer and through the drainage from

the Miocene aquitard to the upper aquifer.

An intensive exploitation of the western aquifer for irrigation purposes has been carried

out over the last decades, increasing from 30,000 to 125,000 ha the irrigated land from

groundwater, and from 200 Mm 3 /year to 600 Mm 3 /year (more than twice the recharge in a

medium year) between 1974 and 1987. This exploitation gave rise a progressive decline in the

water levels in the wells, which have gone down as far as 30-35 m in some points; the emptying

volume in the aquifer since 1974 is estimated around 4,000 Mm 3 . It has produced the

disappearance of the emergences of the River Guadiana from the Ojos del Guadiana sources to

17


Las Tablas since 1983 and the change of Las Tablas into a recharge pond for the surface waters

of the River Gigüela instead of being a discharge zone of the Llanura Manchega aquifer.

Figure 4 present the evolution of the higher limit of the saturated zone from 1989 to

1994, where is appreciate a general drawdown, which rise 35 m in some areas. As regards the

general flow in the aquifer, in the first date it keeps the original circulation sense, flowing to Los

Ojos del Guadiana and Las Tablas de Daimiel. In 1984 there is a depression towards the north

of Manzanares, the groundwater flow is inverted and the piezometric head keep flat and gentle,

which means a flow diminishment to the outlets. In 1987, the situation is similar, with a

growing E-W of the cone. The situation in 1994 makes worse, with two cones more, one of tem

close to La Tablas, where the drawdown are about 15 m and a change of the flow direction to

the SE.

In February 1987, the aquifer was officially declared overexploited according to the

1985 Spanish Water Law. It implied the banning to carry out new extractions in the aquifer. In

December 1994 was published the definitive declaration.

4.- EXCURSION SITES

OJOS DEL GUADIANA (GUADIANA EYES) (excursion site 1)

The Ojos del Guadiana springs rose in Arenas de San Juan years ago. This point was the

natural water outlet of the Llanura Manchega aquifer (figure 2).

The springs became dry at the end of the seventies and its wide extension was reduced

over the years towards the west area, nearer to Las Tablas de Daimiel.

The enigmatic Guadiana disappearance and reappearance during its flowing through the

Llanura de San Juan is well explained today. The river infiltrated in the Llanura Manchega

downstream the Peñarroya reservoir; there, its waters were mixed up with the aquifer waters

and, 40 km downstream, rose through the Ojos del Guadiana.

The exploitation of the aquifer became intensive at the end of the sixties when pumps

allowed the transformation of unirrigated into irrigation crops. At the end of the seventies the

number of wells have increased so much that the extracted water was much higher than the

recharge one. The exhaustion of some wells increased its number and deep.

A large drought (more than five years) became worse the situation.

The Ojos del Guadiana is one of the natural indicators of the water table in the aquifer

and its worrying drawdown, which affect specially to Las Tablas de Daimiel.

WATER INTERPRETATION CENTRE IN DAIMIEL (excursion site 2)

This museum collect the main natural, social, economic and historic features related to

the water in La Mancha.

It is very interesting the Llanura Manchega aquifer and its relationship with Las Tablas

de Daimiel section.

Models, maps, aerial photographs, satellite images, exhibition panels, dioramas,

aquariums, audiovisuals, etc. show the information.

NATIONAL PARK OF LAS TABLAS DE DAIMIEL (excursion site 3)

Las Tablas de Daimiel (figure 5) is one of the most peculiar ecosystems in the Iberian

Peninsula (Álvarez et al., 1996). This freshwater table is composed of a mixture of shallow,

seasonal waters and deeper, permanent ones. Two decades ago, it arose as a result of the

flooding of the Gigüela and Guadiana rivers together with the upwelling of groundwater

belonging to aquifer nº 23 through many wells, locally called “ojos” (“eyes”). Furthermore,

stagnant areas resulting from human activities (mostly watermill dams) altered the river

landscape. The interplay of surface and groundwater discharges, varying in space, time, quantity

and quality, was the most interesting feature of this ecosystem. Until thirty years ago, the

wetland comprised 6,000 ha but only 1,675 ha remain, which are included in the 1,928-hectare

Las Tablas de Daimiel National Park (Ciudad Real province).

18


Las Tablas de Daimiel are situated 606 m above sea level on La Mancha plain, which is

a geomorphological unit of Miocenic-Pliocenic, continental sediments. Limestones and marls of

lacustrine origin as well as sands, oozes, clays and calcretes are found in Las Tablas’ s area.

These alkaline materials have acted as impermeable substrates and together with the flatness of

the area, have given rise to hydromorphic, and sometimes saline, soils.

There are many solution forms in the surroundings of Daimiel. There are dolines and

uvalas some of which have big dimensions, with mayor axes up to 900 m and deeps of 10-15 m.

Organic limes and clays fill up the flat bottom of these karstic forms. The basins of some

temporal lake (El Escoplillo) still survive.

The river system is little developed and incises less than 20 m in the Llanura

Manchega. The main rivers are Azuer, Guadiana (which rose at the Ojos del Guadiana), Záncara

and Gigüela. This system is not functional today, not only for anthropic causes but because for

climatic reasons. During a recent past and in the Medium and Upper Pleistocene these rivers

drained the Llanura Manchega. An increasing aridity during the Upper Pleistocene reduced the

number of channels and let the fluvial system in the current residual situation.

The climate comes within the cold, temperature continental category with a dry season.

Isotherms range from 12-14ºC whereas the rainfall range is 400-500 mm, with a potential

average evaporation of 778 mm per year. Two dry periods (1895-1954, 1980-1995) and two wet

periods (1875-1894, 1955-1979) have occurred over the last hundred years.

Palynological analyses revealed hydrological changes in the area, reflecting periods of

either riverine or lacustrine dynamics.

Nowadays, flooding levels are markedly variable, albeit decreasing. Twenty years ago,

the usual cyclical pattern was a peak in Spring, decreasing slowly until Autumn when there

were high levels of flooding again. However, Las Tablas have become an infiltration area and,

hence, an area of water loss because of the demand for irrigation over the last decade, and this

has depleted aquifer nº 23.

Over the last ten years, the only water supply to Las Tablas has been through the

Gigüela River from the Tajo-Segura Aqueduct, a facility connecting the Tajo with the Segura

watershed. The Guadiana River has remained dry since 1986. An apparent increase of salinity,

brought about by both the lack of freshwater discharges and hypohaline groundwaters used to

feed the wetland in the worst dry periods of the year, has been recorded.

Nowadays, the potentially flooded surface in the National Park extends from northeast

to southwest. A breakwater dam (Quinto de la Torre), made with compact clays and gabions,

divide the Park in two areas (1147 and 528 ha). Las Tablas are today a great reservoir, which

dam, Puente Navarro, sites at the southwest boundary. Puente Navarro is a concrete and vault

dam; there sites the most extensive and deep (about 4.5 m) area of Las Tablas. There were

another deep areas along the ancient Guadiana stream, but many of them are silted up today.

The shallowest area is at the far end of the Park, at the Gigüela entrance.

There are more than 30 islands in the Park. The biggest ones (such as Isla del Pan and

Isla de Algeciras) site at the northeast area.

Today, remains of the canalisation built before the declaration of Las Tablas as National

Park can be observed in some points

Now, the aquatic environment is markedly irregular, highly turbid with high rates of

sedimentation. The chemical composition of waters is homogeneous, with sulphate and calcium

as the most important ions. There are high nutrient contents, eutrophisation indices (TP, SRP,

COD, inorganic nitrogen) suggesting that Las Tablas is a hypertrophic environment. In other

words, it is an ecosystem experiencing very high organic pollution coming from towns on its

watershed. Pollution from pesticide and heavy metals is, however, negligible.

Hydrochemistry studies show a salinity increase in Las Tablas. The freshwaters of the

Guadiana River diluted the high salt concentration of the water from the rivers Gigüela and its

tributaries, Riánsares and Záncara, which flow through gypsum soils. However, since 1986,

when the Guadiana River disappeared, this situation changed. The increasing drawdowns of the

aquifer and the long drought have been the causes because during the last years the only surface

flow has taken place through the Gigüela River. This stream has been used to transfer the water

from the Tajo-Segura Aqueduct to Las Tablas.

19


Another important aspect is the pumping of groundwaters in order to mitigate the

scarcity of water in the Park. It has increased the water’s salinity in Las Tablas due to the high

salinity of this water. It can be explained as a progressive salinization of the aquifer due to salt

accumulation processes in the sediment and its infiltration.

The maximum salinity levels have been normally measured between September and

November. However, there is a wide salinity variation along the year, which can be explained

because of the big fluctuation of the flooded surface in the Park, due to seasonal effects.

In general terms, phytoplankton and benthic algae comprise widely distributed species,

albeit rarely recorded in Spain in some cases, suggestive of hypertrophic, slightly saline

environments.

Macrophyte vegetation has decreases in terms of species´ richness and plant cover. In

particular, there has been a dramatic substitution of fen sedge formation, which needs a watery

environment for the roots, by reed and tomarisk, which are more tolerant of lack water.

Research into the animal life supports our diagnosis of a stressed environment.

Planktonic crustacea consist of very common species, suggesting an impoverishment of the

community and reflecting poorer water quality. It is important the decreasing number of species

of Mollusca, Tricoptera, Odonata and Plecoptera.

The fish fauna comprised 13 species until the creation of the Natural Park: carp, pike,

two barbel species, Iberian nase, chub, pardilla roach, tench, calandino roach, Moroccan loach,

mosquito fish, black-bass and freshwater blenny. Nowadays, only carp and mosquito fish

maintain stable populations because of pike introduction forty years ago, an increasing pollution

and the reduction in the flooding area.

Waterfowl have always been the distinctive feature of Las Tablas. This environment has

been on the Ramsar List since 1982 and the Spanish Government declared it Special Protection

Area for Birds (SPA) in 1979. The numbers of wintering birds (peak: 26,569 individuals in

1989) and nesting birds (peak: 5,497 pairs in 1988) are related to the size of the flooding area.

Decreases in diversity and population become obvious when one looks at birds censuses of the

latter years.

La Tablas de Daimiel is sited in the municipalities of Daimiel, Fuente el Fresno,

Malagón and Villarrubia de Los Ojos. It is an agricultural area with plots mostly under 20 ha.

Crops are either dry farmed (barley, vine, olive) or under irrigation (barley, maize, oats, beet,

sunflower, alfalfa). Livestock is mainly sheep, cows being used for milk production instead of

meat. The human population decreased in the sixties due to emigration but has increases slightly

in recent years. Per capita income is lower than in Castilla-La Mancha and the Ciudad Real

province.

Historically, the first records of settlements in the area (stone huts called “motillas” or

“morrillas”) go back to 3600-3400 B.P. Since then, there have been continuous human

settlements in the area, its influence being greatest in recent years. The available information

shows how an extensive area, which has experienced many civilisations over 36 centuries, has

been reduced two-thirds within a very short period (1965-1985) because of aquifer

overexploitation, drainage attempt and pollution.

As we have already told, the irrigation surface increasing since the decade of

70s from groundwater’s pumping put in danger the survival of the National Park. At the

beginning of the 90s, groundwater was pumping in order to flood a part of the Park during the

summer. These processes are reflected on the flood levels, which were over the unsaturated

zone until the decade of 80s and sometimes under it since then. The flood surface increased

when the Spanish Government approved a plan for the hydrological regeneration of the National

Park in 1988.

Figure 6 shows the water balance in the area in 1973-1974 and fifteen years later. The

main difference between then is the total quantity of water existing in the system (bigger in the

70´s) and the groundwater flow to Las Tablas. At the end of the 80´s, the sense is reversed and

surface waters recharge the aquifer.

The Spanish Government is committed to conserving Las Tablas de Daimiel National

Park. In order to avoid its environmental degradation, a Water Regeneration Plan has been

implemented with short-, medium- and long-term measures and a final goal of restoring earlier

groundwater levels. In the meantime, artificial management of this wetland must be accepted

20


(many wetlands are managed in this way), thus enabling it to fulfill its ancient role as a refuge

for the biodiversity associated with a wetland type that is threatened all over Europe, i.e.

riverine water tables.

To summarize, nowadays the minimum levels into the Park are artificially supported

through the groundwater pumping and with the sporadic transfers from the Tajo catchment,

which have changed the hydrochemistry of Las Tablas.

PEAT BOG AT THE GUADIANA RIVER IN ZUACORTA (excursion site 4)

PEAT BOG COLLAPSE IN MOLINO DE CHINCHÓN (CHINCHÓN WATERWHEEL)

(excursion site 6)

Limes and clays plenty of soil-organic matter, sands and peats constitute the alluvial

deposits of the Guadiana River between the villages of Daimiel and Villarrubia de los Ojos. In

this area (upstream its meeting with the Azuer River), the Guadiana River seems a karstic

depression more than a river. There are many dolines and uvalas and a great number of springs

which drainage the Llanura Manchega aquifer.

The peats have a Holocene age, probably less than 12,000 years. Periods of flooding,

with very rich waters in limes, calcium and to a lesser extent magnesium and chloride, from the

Llanura Manchega groundwaters, explain the origin of these deposits. The long periods of

flooding have allowed in these areas the formation of peat bogs a long the thalweg. It is frequent

to find calcium carbonate crusts and evaporitic deposits over the peats, probably because of

intensive evaporation processes during the summer and/or drawdown.

The peatland, which covers most of the 20 km of the former thalweg of the Guadiana

River, undergoes a slow process of spontaneous combustion. The configuration and geometry of

the sediments are hence very irregular and change in the time. There are several areas with

different characteristics: limes and very fine sands plenty of organic matter; burnt peats and/or

peats in combustion (at surface or at deeps to 3 m) where peat bog hasn’t been exploited;

vegetal soils sited in narrow belts on the banks of the river, higher than the pet bog; areas

without fires where the pet bog has been well exploited (the extraction has been made to deeps

where there aren’t fires or where the land has been steamrolled; burnt area and/or in combustion

where the peat bog has been exploited without planning (it has produced big holes which help to

the peat oxygenation and it is the most impoverished area because of the fires) (García et

al.,1992).

The biggest peat accumulation areas seem to be associated to ancient “eyes” or to the

lower zones of the valley. The thickness of the peat layers is very variable, from 0,10 to more

than 2 m and present a lenticular shape. The limes associated to the pets have very variable

thickness too, reaching 3 m.

The aquifer drawdown (30-35 m) has caused the lost of the water that saturated the

peats and the other deposits. The total thickness has diminished because of the consolidation,

which produces a general subsidence and local collapses (they use to have a circular shape

because of the collapse of the caves’s roof). A new global subsidence is produced in the burnt

area due to the peat and organic soil’s oxidation and spontaneous combustion.

These materials autoxidize to low temperatures because of its high carbon content. The

peat autocombustión process is due to the formation of pirophoric amorphous compounds of

iron and iron oxides, which act as catalytic of exothermic reactions and initiate the combustion,

causing very toxic ashes and methane gas.

Fires use to produce preferential in greatest organic material thickness areas. They have

a very irregular distribution, probably conditioned by the sedimentary bodies geometry, by the

continuous drawdown and by the air entrance that help its oxidation. Karstic channels and peat

and quaternary porous allow the air entrance to the peat bog.

21


GIGÜELA RIVER IN VILLARRUBIA DE LOS OJOS: STREAM GAUGING STATION

(excursión site 5)

It is a stream gauging station belonging to the SAICA Alert Network (Sistema

Automático de Información de Calidad de Aguas - Water Quality Information Automatic

System). It controls the water entrance to Las Tablas de Daimiel National Park.

This network allows knowing the river condition and detects possible contamination

tops (due to forbidden spillages, contaminated human runoff, etc.) in real time.

In order to obtain the information special equipment and system are installed:

multiparameter analyser (pH, conductivity, temperature, dissolve oxygen); turbidimeters;

ammonium, nitrate, phosphate, total chrome, VI chrome, lead, cadmium and chloride analysers;

level and/or flow sensor; temperature sensor; automatic refrigerated sampler.

There is another auxiliary equipment: data acquisition system; VSAT communications

system; collecting system; microfilter system; water demineralization system.

The stations measure all the parameters constantly and transmit the information

(maximum, minimum, medium) through the satellite to the Catchment and Principal Centres,

where the vigilance is carried out.

These processes allow identifying the contaminated spillages and its author in a short

time, and hence having legal support for later economic sanctions.

CAMPO DE MONTIEL

1. – GENERAL FEATURES OF THE AREA

The high plateau of the Campo de Montiel (Field of Montiel) is located between the

provinces of Ciudad Real and Albacete, south of the Llanura Manchega (Manchega Plain) and

north of Sierra de Alcaraz (figure 7).

A field of limestone and dolomites of the low Jurassic form the plateau. It presents a

tabular structure that sinks by means of fractures towards the north, where is covered by

plioquaternary pediments and by manchego tertiary materials. Its thickness oscillates between

75 and 100 meters, although it can reach the 300 meters to the north and northeast. The Jurassic

assembly lies on an impermeable substrate of Triassic clays, marls and gypsum. The

topographic surface, smoothly undulated, varies from the 700 meters level to the north to the

1000 meters to the south.

The climate is Mediterranean semi-arid, with cold winters. There is little and irregular

rain and long periods of drought are frequent. Annual average precipitation is 460 mm, which is

higher in the southern zone of the aquifer due to the influence of the Sierra of Alcaraz.

Approximately 60% of years rain below the average (Various, 1997). Average temperature is 14

ºC, with a maximum of 34 ºC and a minimum of 1 ºC. As far as the ETP it varies between 700

and 800 mm.

The hydrogeological unit (04-06) that this calcareous field forms corresponds to the

aquifer of the Campo de Montiel (aquifer 24). Several rivers are born in this aquifer, and they

flow into three different hydrographic river basins: Guadiana, Guadalquivir and Júcar.

Generally, the draining network is not well developed and it displays an almost constant fitting

in all valleys because of the presence of an impermeable base. Fitted valleys that resemble

karstic tubes and small karstic heads of little development are observed. Most valleys of the

Campo de Montiel are torrents that take water only as a result of intense rain, especially during

summer storms. Rivers adapt to the jointed and fractured systems showing several main

directions: NW-SE and WSW-ENE; and another one, of less importance, approximately N-S.

This fluvial network, that is born in the field and flows to the river basins of the Guadiana,

Guadalquivir and Júcar, dissects the aquifer in several hydrological units. Finally, there is one

more important exit of water that goes underground to the aquifer of the Llanura Manchega

(Manchega Plain), north of the study zone.

The most important river crossing the Campo de Montiel is the High Guadiana, which is

born in the spring of Pinilla, at 980 meters elevation. It is one of the highest areas of the high

plateau, where it forms a small stream, the Pinilla River, which disappears by infiltration at

some points of its course. Several kilometers downstream the caudal increases suddenly,

22


originating the peculiar ecosystem of the Lagunas de Ruidera, declared Natural Park in 1979

(figure 8).

The economic activity in this region has been historically centered in a precarious

agriculture of dry land (cereals, grapevine and olive tree) until in the eighties a series of

agricultural transformations took place, from dry land farming to others in irrigated land, thanks

to the groundwater exploitation. Due to the limestone and rocky nature of the area, there has

been little development of the soils in the Campo de Montiel. Crops have been mainly

implanted in valleys and “navas”, where the soil layer is slightly thicker. The groundwater

extractions in the head of the Park, along with an intense period of drought that extended from

the end of the eighties to the mid nineties, drastically diminished the levels of the aquifer. Most

of the springs that they fed the assembly of lakes dried, the superficial hydraulic connection

between the lakes was interrupted and many of them dried or were greatly depleted.

Due to this situation, in 1989 the aquifer was declared legally overexploited, being the

first case in Spain.

2. - GEOLOGIC, TECTONIC, AND GEOMORPHOLOGIC SETTING

The Campo de Montiel is located in the southern edge of the Castilian Plateau, between

tertiary and quaternary materials of the Llanura Manchega (to the north) and the mountain range

of intensely folded Jurassic materials of Sierra de Alcaraz (to the south). To the southwest, the

last northeastern spurs of Sierra Morena arise, a group of Paleozoic alignments with hercinic

directions and the volcanic region of the Campo de Calatrava (Field of Calatrava) (figure 9).

Stratigraphy

The geology of this area is integrated by a metamorphic hercinic basement on which

discordant Mesozoic sediments (Triassic and Jurassic) of low thickness are deposited.

The sporadic outcrops of Paleozoic basement in the Campo de Montiel demonstrate (by

its litology and structure) the natural prolongation of the hercinic units of Sierra Morena and of

the Campo de Calatrava towards the east.

Discordant with the Paleozoic quartzite and shales that form the basement of the Campo

de Montiel superposes the Triassic, which arises in great extensions south and west of the unit.

It consists of Germanic facies from the edge of the basin. Its upper section, that consists of

marls and red and green gypsiferous clays in Keuper facies, constitutes the impermeable

substratum where the carbonated materials from the Jurassic that form the aquifer of the Campo

de Montiel lie. From the hydrogeological point of view, the Triassic outcrops in the interior of

the aquifer are of great importance, since they function as dividers and reveal springs associated

to the contrast of permeability between these materials and the calcareous ones. This outcrop

has been related to stratigrafic causes, with diapiric phenomena due to the plasticity of these

materials and, in recent works, to ascents favored by the intense fracturing that affects the cover.

On the impermeable bottom lies a calcodolomitic and marly series that displays a

subhorizontal tabular structure and conforms the Campo de Montiel. Its age has been attributed

to the low Jurassic (Lias) by its position, facies and correlation with neighboring areas, since no

paleontological criteria have been found. Its study presents difficulties due to the existence of

dolomiting and brecciation processes. In addition, the series are not complete because of the

lack of sedimentation and/or erosion. There have been described three litostratigrafic

formations: a) Lower Lias: calcodolomitic formation that constitutes the main aquifer of the

area; it leans directly on the Keuper and its thickness oscillates between 60 and 100 meters; b)

Medium Lias: marl-argillaceous assembly whose thickness is variable and difficult to determine,

considering about 50 meters as an average. Upwards there is a constant lumaquelic level very

dolomitized; and c) Upper Lias: calcareous assembly (about 20-40 meters thick) with some

marl-limestone intercalated sequences, whose main characteristic is the presence of abundant

oolitic levels. Likewise the Medium Lias, it arises east of the area.

The most characteristics tertiary facies in the area correspond to red breccias and limes,

conglomerates and carbonates; very similar in aspect to the Lower Liassic section. The quarcitic

conglomerates are from the plioquaternary age with clay-sandy matrix of intense red color,

23


which can contain cobbles of diabase, granites and shale. Finally, the Quaternary is represented

by diverse travertine and conglomerates and argillaceous alluvial deposits.

Tectonics

Historically it has been considered like a non-tectonic region without hardly any

deformation, that was part of what has been denominated the “Albacete’s stable platform”.

Nevertheless, the last studies demonstrate that its thickness is very variable and that it is

affected by fractures, folds and diapiric processes (bound to the activity of main fractures),

which chamber the aquifer and condition its hydrologic operation (Montero, 1994 and 1995;

Rincón et al., 1996). Folds and fractures were not mapped previously because they were

fossilized by coverings of tertiary and quaternary materials that, in many cases, present similar

lithological characteristics to those of Jurassic materials, with which have been confused (figure

10).

The limits of the aquifer are clearly defined west and south, but not east and north,

although, in the four cases, their directions are related to main tectonic directives: the southern

and northern borders show a WSW-ENE direction, whereas the western and eastern ones have a

NW-SE direction.

The physiografical and hydrogeological unit of the Campo de Montiel has been under a

moderate compressive deformation throughout the neotectonic period, coherent with the last

dynamics of the African and Euro-Asiatic plates. The considerable interrelation between

structural, physiografical and hydrogeological aspects is explained in a flexural litospheric sense

(Rincón et al., 2001b).

The morphology of the hydrogeological unit, its internal hydrogeological subdivisions,

the sense of groundwater flow, the spatial disposition of the springs, or the narrow relationship

existing between superficial and groundwaters, are of clear tectonic conditioning. In addition,

there is a fitting of the fluvial courses in favor of the main structural discontinuities (faults

and/or joints) contemporary with the deformational events or reactivated by these: processes of

karstification clearly conditioned by the tectonic context. Finally, under this flexural proposal

also fits an explanation to the endorheic or semiendorheic character of the High River basin of

the Guadiana, proper of an irregular and immature surface, structured at recent times: successive

antiformal and sinformal flexures (with diverse wavelengths and a fragile surface expression).

The tectonic origin of the division of waters in the Campo de Montiel’s aquifer towards three

different hydrographic river basins seems also evident (Rincón et al., 2001a and b).

3. - GENERAL HYDROGEOLOGY OF THE AQUIFER

The main aquifer of the hydrogeological unit is formed by limestones and dolomites of

the Lower Lias, with a high permeability by fracturing and dissolution, and that presents the

maximum transmissivities in the central zone: head of the Lagunas de Ruidera. Something less

permeable is the oolitic limestone of the Upper Lias that extend to the easternmost zone of the

Campo de Montiel although show a high transmissivity southeast of the aquifer. The limestone

and calcareous breccias from the superior Tertiary, outcropping in the center-western part, also

form small hanged aquifers.

The base of the hydrogeological unit is constituted by impermeable materials from the

Upper Triassic (clays and evaporites in Keuper facies), that arise to the west, south and

southeast. Triassic outcrops within the aquifer are also numerous (figure 9).

The aquifer of Campo de Montiel is a unconfined aquifer, with an extension of 2,575

km 2 . The only recharge of the aquifer is precipitation falling directly on it, since connection

with other units does not exist. The high permeability of the calcareous materials of the Campo

de Montiel allows most of the water coming from precipitations to infiltrates the aquifer, reason

why the surface run-off on the calcareous field is almost null. The discharge of the aquifer takes

place through springs, some located between the carbonated permeable materials and the

impermeable substratum, others originated when the topography cuts at the phreatic level and

others in the contact between permeable limestone with some smaller permeability level within

the calcodolomitic series. Most of the springs show a narrow relationship with fracturing; the

24


ones with higher rates of discharge (Hazadillas, Ossero, Ponzoñón) are associated to

intersections of fractures.

The most important springs give rise to rivers and streams (Pinilla- High Guadiana,

Cañamares, Azuer, Segurilla, Jabalón, Córcoles, Sotuélamos) whose regime is regulated by the

underground reservoir.

The Campo de Montiel can be classified as a diffused flow aquifer. The relatively low

solubility of the dolomites implies little dissolution activity, reason why the flow is not

concentrated in large conduits, there are few caves and these are disconnected among them.

What seems clear is that the framework of fractures that affects the aquifer exerts a control in its

functioning, causing high secondary porosity. This results increased by the phenomena of

dissolution caused by groundwaters when widening the fractures and the original planes of

stratification. Permeability is conditioned by the location of the conduits or fissures, which

depend as well on the lateral changes of facies, the initial permeability or the existence of

fractures widened by dissolution. As a result, the aquifer usually displays great anisotropy.

Thus, obtaining groundwater is difficult, existing great differences as far as the efficiency of

wells located near each other (Montero, 1994).

The transmissivity of the aquifer presents important variations: the highest values occur

in the head of the Lagunas de Ruidera and southeast of Campo de Montiel (500 to 2000 m 2 /day,

reaching 6000 and 7000 m 2 /day occasionally). In the northern, the western and southwestern

areas of the aquifer transmissivity is much lower, between 10 and 100 m 2 /day. The highest

values coincide with those zones where the maximum extractions are conducted, whereas the

lowest occur in areas in which most of wells have been abandoned (Martinez et al., 1992). The

storage coefficient varies between 1 and 5 %.

The study of the aquifer’s geometry by means of the analysis of numerous litologic

columns and of previous geophysical investigations, has detected several Triassic thresholds

that separate the aquifer zones and that create hydrogeological units that behave with almost

total interdependence among them (Montero, 1994; 2000). The impervious Triassic thresholds

of major spread detected in the aquifer are in the strip Villahermosa-Viveros (figure 9), a long

the Lagunas de Ruidera, north and northwest of Ossa de Montiel and surrounding El Bonillo.

All of them can be related to fractures, some by being located in zones of intense fracturing,

others by being circumscribed to large fractures and others by being aligned according to the

main tectonic directives (figure 10).

South of the aquifer the springs are located in contact with permeable materials of the

Jurassic and the impermeable ones of the Upper Triassic. There is an important thickness of

permeable materials below the drainage level in this area, which allows storage of the

groundwater. These characteristics, along with the high transmissivity of the aquifer, allow the

extraction of elevated volumes of water in wells. However, the altitude at which the springs are

located on the impermeable base means that a reduction of a few meters in the water table can

decrease the volume of the springs or dry them (Montero, 1994; 2000).

In the High Guadiana valley, the springs are not associate with the Jurassic-Triassic

contact, but that originate when cutting the topography at the piezometric level. Therefore,

elevated springs dry out when the water level in the aquifer descends, which diminishes the

contributions that in normal conditions the highest lakes receive. When this happens, a

weakening of the hydraulic connection between the lakes takes place, reducing the transferred

discharges to inappreciable values. In certain zones of the aquifer, the geologic structure itself,

the existence of fractures that elevate the impermeable bottom or the erosion of valleys allow

the existence of springs at the impermeable level. This seems to happen in the proximities of the

spring of Pinilla or in the western limit of the aquifer. In these zones, the springs display a

relatively regularized regime, maintaining their volumes practically constant throughout the

year.

Generally, it can be admitted that the aquifer can store great amounts of water, but it has

little capacity of regulation, since natural elements of impermeable nature that retain it do not

exist. A slow unloading of the aquifer takes place if precipitation stop or extractions for

irrigation are increased. On the other hand, it is an aquifer with a great recharging capacity,

recovering its level in less than a year and presenting an overflowing situation a few months

later (like most of the karstic aquifers).

25


4. - EXCURSION SITES

NATURAL PARK OF THE LAGUNAS DE RUIDERA (excursion site 7)

During the Second Spanish Republic (1933) it was declared Natural Site of National

Interest. With the Law of Protected Spaces it received the qualification of Natural Park in 1979.

It is also subject of a Special Plan for Protection approved in 1981. The Junta of Communities

of Castilla La Mancha is the organism in charge of the protection of the Natural Park since

1984.

An assembly of 15 lakes aligned in a NW-SE direction and connected to each other by

channels, gullies, and cascades or springs forms the main valley that constitutes the park. They

appear stepped throughout about 35 kilometers, being the difference of level between the first

and last one 120 meters approximately. Starting from the first ones, upstream, their names are:

Blanca, Concejo, Tomilla, Tinaja, San Pedro, Redondilla, Lengua, Salvadora, Morcilla or Santo

Morcillo, Batana, Colgada, del Rey, Cueva Morenilla, Coladilla and Cenagal or Cenagosa

(figure 8).

They are usually grouped in two assemblies of different characteristics: low and high

lakes. The high lakes, in which the Pinilla river appears again, are located upstream of the town

of Ruidera. In this assembly the largest and deepest lakes are found (some reach 21 meters

deep); each of them is closed by means of a travertine limestone building that acts like a natural

barrier, damming the water which forms a cascade when the system receives sufficient water

from the aquifer. During most of the nineties only the cascade of El Hundimiento remained

active, in the great bar that separates the high from the low lakes. During the summer of 1996,

as a result of the high water levels in the aquifer, the cascades began to appear again, reaching

the lakes the maximum volumes in January of 1997.

The low lakes are short and their travertine barriers are degraded. They are surrounded

by rushes and reeds that practically invade the Cenagal (Quagmire) lake, whose name comes

from the characteristics of its bottom. After this last lake the water continues digressing by a

marshy valley until it is channeled near the tail of the dam of Peñarroya. Downstream of the

dam, the river left the field to enter the Llanura Manchega. Once there, the water disappeared

gradually by evaporation and infiltration in permeable lands of the plain. Nowadays, and

through a network of channels and drains, it is distributed to a large irrigation area in the

municipalities of Argamasilla de Alba and Tomelloso. At times of high rainfall, the spillover of

the dam circulates in the Guadiana River infiltrating a few kilometers ahead in the aquifer of the

Llanura Manchega.

The assembly of lakes represents 300 has. The total volume dammed in 1989 was about

23 Mm 3 (according to the bathymetric study of the lakes made by the HYDROGRAPHIC

CONFEDERATION OF THE GUADIANA). The dam capacity is slightly larger since at this

date the levels in the lakes no longer reached the spill point.

Taking advantage of the unevenness of the water between the different lakes, diverse

hydroelectric power stations were constructed, most of them are no longer used today, with

jumps between 15 and 25 meters and productions between 80 and 1500 kWh.

The described geographic frame serves as habitat for the development of a singular flora

and fauna.

The vegetation is well adapted to the extreme climate existing in this area (great frosts

in winter and warm and dry summers). Two different ecosystems are found: paludal and forest.

Paludal, next to the lakes, is made up of species with submerged roots most of the year or seated

on very humid ground. Several strips of vegetation are distinguished according to their level of

dependency of the water. The halophytic vegetation, that hides some lakes like the Cenagal or

Coladilla by its exuberant development, has undergone enough aggressions in all the Natural

Park and is regretting due to road and beach construction, to the swimming tourism, to

contamination and to periodic burning, reason why it tends to disappear in most of the shoreline.

This type of paludal vegetation has an extraordinary power for purifying water and, in addition,

it is the refuge and place of nest building for all the aquatic birds in the lakes.

The typical perennial vegetation of the plateau, showing the complete series of an oak

forest, characterizes the forest ecosystem. Nowadays, this ecosystem is one of the last remains

of the original vegetation of La Mancha, favored by the influence of the water mass. The aquatic

26


zone of the park has undergone a strong impact in past few years, and the slopes of the valley

have been suffering aggressions for a longer time. The continuous and massive cuttings for

carbon production and the uncontrolled pasturing in the past centuries, along with the

construction of urbanizations and the cuttings to implant new farming areas, have destroyed

great part of the oak forests leaving loose specimens that, in some cases, are millenarian and

extremely large.

Regarding the fauna, it has to be emphasized that noise, pollution of waters and

colonization of adjacent forests (one of the main refuges of the birds) have caused it to back

down towards recondite places outside the park, or towards its left margin which is less

colonized. Among the aquatic birds present in Lagunas de Ruidera are: pochard, tufted duck,

red-crested pochard, mallard, teal, shoveler, gadwall, pintail, coot, great crested grebe, little

grebe, and moorhen. There are also species listed of special interest: osprey, booted eagle, shorttoed

eagle, Bonelli´s eagle, buzzard, goshawk and purple gallinule and, as a species in danger of

extinction, the black stork. In the aquatic ecosystems of the lakes there are common carps,

muskies, green frogs, common toads and white storks.

The forest ecosystem is characterized by the presence of lagomorphs, especially rabbits.

The red-legged partridge is also typical (there are numerous hunting grounds). Other common

birds in the zone are the azure-winged magpie, woodpeckers and swifts.

The Peñarroya swamp gathers most of the water that drains the Lakes. As a result of the

climate, contributions are very variable. Only one every three years they surpass the average of

the last sixty years (90 Mm 3 ). The maximum registered since 1931 was 2,570 Mm 3 in the year

1946-47 and the minimum 15 Mm 3 in 1944-45. Besides the volume and distribution of

precipitations fallen in the year, the unloading of the aquifer is influenced by its loading level,

since after a period of drought part of the water is used to fill up the empty cavities of the

aquifer.

In the period between 1984 and 1987 the transformation in irrigated land (from

groundwaters) of the Campo de Montiel takes place, plowing sometimes forestlands populated

with oaks and “sabinares”. The major exploitations are located in the head of the Natural Park.

This transformation negatively affected the water contributions of the Lagunas de Ruidera, in

the quantity (superficial hydraulic disconnection, dry lakes or with very low levels) and in the

quality of waters due to the percolation of fertilizers and pest-control substances used in

extensive agriculture of irrigated land (increased nitrate content). In 1987 there were 25 Mm 3

extracted from the headstream opposed to the 90 Mm 3 average contributions of the lakes.

The coincidence of lower-than-average precipitations, along with the increment of

extractions from wells for irrigation, triggers a process of generalized decrease of the water

levels of the Lagunas de Ruidera, some of which dried out. Between 1986 and 1995 a slow but

continuous discharge of the lakes took place. In 1986 a gradual decrease of the water levels

begins, reaching a drop of 10 to 15 meters in the level of wells located in the head of the system.

Due to this situation, in 1989, the aquifer is declared legally overexploited, which

implies limiting water for irrigation to an annual maximum and also the determination of an

annual volume of water to be extracted for irrigable in aquifer by means of an annual extraction

planning. The objective of this plan was to diminish the impact of irrigation in the levels of the

lakes and to guarantee irrigation for the lands downstream from the system (by means of the

volume dammed in the reservoir of Peñarroya). Protected by the CEE Nº 2078/92 regulation of

the Council about methods of agro-production compatible with the conservation of the

environment and of natural resources, a compensation program of agrarian rents for farmers was

approved in 1993, so that they would reduce their irrigation dowries to recover the levels of the

Lagunas de Ruidera. The continued drought prevents the increase of the water levels until the

autumn of 1995, when precipitations in the entire region begin to take place. Soon after water

begins to run in streams and fountains that had been dry for several years. After strong storms in

the autumn of 1995 the springs in the head of the Park began to flow, although water infiltrated

again filling up the karstic cavities, beginning to flow regularly once these cavities were full.

Eight months after the precipitations begin the process of filling of the lakes and the aquifer was

completed, obtaining total superficial connection of all the lakes.

27


There is an important thickness of jurassic and quaternary materials in the substrate of

Lagunas de Ruidera that allow the circulation of water underneath, although in some areas the

tectonic and diapiric processes elevate the impermeable threshold of the Upper Triassic

preventing or making difficult the flow (figure 11). In addition, the elevation of the Triassic

materials in the right margin by means of fractures restricts the flow from the aquifer to the

intermediate and low lakes.

The water level at the aquifer, the geometry of the lakes and the geologic characteristics

of its substrate condition the water level in Lagunas de Ruidera. Based on their hydrologic

behavior four assemblies of lakes can be established (Montero, 1994):

The highest, fed by a very transmissive sector of the aquifer, reflect its piezometric

level. For that reason, the topographically elevated points like the Laguna Blanca and its

surrounding springs dry out when the water level in the aquifer descends. The lakes Concejo

and Tomilla continue being "winners" and their levels only descends when the aquifer is very

low, since they are located beneath the phreatic surface. The reductions in the piezometric level

cause superficial water transfer to stop, within this assembly and in the following one.

The second assembly, formed by the intermediate lakes, from Tinaja to Batana, is fed

mainly with superficial contributions from the high lakes and when this is interrupted, it begins

to drain. The high gradient that the piezometry in this section displays indicates a decrease in

transmissivity of the materials that form the base of these lakes. There is a groundwater flow

under the assembly, although it seems to concentrate in conduits and/or more permeable zones.

The lakes Colgada and Rey form the third group. Its feeding is superficial, from transfer

from the second assembly of lakes and from the valley of the Hazadillas (where there are some

of the springs with a higher flow). The elevated position of impermeable materials of the Upper

Triassic makes difficult the groundwater cession from the previous assembly but it allows the

water to remain dammed. This is the reason why the water level does not experience any

variation even if the transfer of superficial water is interrupted.

The impermeability of the bar located between these lakes and those of the fourth

assembly, "low lakes" cause the hydraulic disconnection between both groups. Feeding of the

last lakes takes place, almost exclusively, in a superficial manner.

The system of superficial transfer between the lakes only works in times of very high

phreatic levels. When it is interrupted (what occurred between 1986 and 1996) the lakes of the

intermediate section are the first ones affected, drying later those of headstream; the low lakes

are the less affected (Montero, 1994, 1995 and 2000).

WINERY IN TOMELLOSO (excursion site 8)

Grapevine and wine production in Spain is high and great part of it concentrates in the

Manchega region. This creates a problem, among others, with generation of a significant

volume of wastes from derivatives of the grape from the distilleries. These left over (whatever

the raw material of origin) are called “vinazas” (strong wine) and they were spilled into the

environment, without any previous processing, using several systems (Servicio Geológico,

1988): a) Network of sewage system: the remainder was spilled to superficial waters or green

filters (spilled in surface); b) Caves: vinaza unloading in shallow caves, (spilled in the

unsaturated zone: caves of Tomelloso); c) Old chain dumps: vinazas were spilled in shallow

excavated wells that have dry out (spilled in the unsaturated zone); d) Wells: the spill was

injected in soundings with depths below 100 m (spilled in the saturated zone: deep wells in

Daimiel and Tomelloso); e) Rafts: they were used fundamentally in the spill of vinazas of lias,

since the high concentration of solids in suspension of this effluent makes unviable its

evacuation by other means.

In La Mancha, a traditional method to dispose of urban and industrial residues has been

to introduce them in the subsoil. However, this did not cause any serious problems since urban

residual water volumes were low and they ended up in the sewage network, and industries were

small and familiar.

Growth of population centers and industrial development caused the small wineries to

disappear. Huge factories, which caused a strong increase in the volume of remainders, replaced

them and concentrated the spills in restricted zones.

28


Regarding excursion site 8, there are eight important distilleries in Tomelloso. One of

them spilled in an injection drilling 90 meters deep, five in wells 25 meters deep and two in

caves of vinazas (figure 14).

By the end of 1985, a plant for processing vinazas and producing biogas began to work

in this locality. The biogas function is to accelerate the process of fermentation of vinazas in a

controlled manner and on industrial scale. This is achieved in anaerobic digesters by means of a

bacterial bed, so that their concentration per cubic meter is elevated. The methane produced as a

result of this fermentation is lead to the users by the distilleries.

Vinazas

The industries from La Mancha dedicated to wine distillation process ethyl alcohol like

fundamental product and, in certain cases, generate by-products that they use as raw materials to

make “orujos” (liquor distilled from grape remains), “heces” or “lias” and wines of low

quality.

The main products extracted from the grape are shown in figure 12. In addition to wine,

it can be seen that production of alcohol from the different remainders is very frequent: wines of

low quality, orujos (joint of peels, seeds and floral peduncles of the clusters that stay as

remainders of the obtained juice), heces or lias (sediment in the wine production) and mattocks

(dissolution obtained from the maceration of orujos in water).

From the quantitative point of view, vinazas present important variations based on the

origin of the raw material, the industry that produces them and the harvest. Vinazas of mattocks

display a high content in soluble organic matter, and relatively low and easily biodegradable

suspended matter. Vinazas of lias constitute the most polluting effluent, containing a high load

of suspended solids of organic origin and they are easily biodegradable. Regarding vinazas of

wine they have a high content in biodegradable organic matter and a reduced load of suspended

solids.

The physical and chemical composition of vinazas is very complex. Its main

characteristics are: very low pH, between 3 and 6; a OQD that can exceed 30,000 mg/l; an

organic matter content between 9,000 and 35,000 mg/l; potassium values that surpass the 2,500

mg/l; phenolic compounds to up to 1,000 mg/l; temperatures that can reach 90 ºC, etc. These

characteristics confer the spill a distinct acid and reducing character.

The acidic character causes karstification phenomena, due to the calcareous component

of the land. The reducing character favors the formation of the gases CH 4 and CO 2 in anaerobic

conditions, which can produce explosions if it occurs in a closed environment. Therefore, the

representative parameters of this type of pollution are: potassium, relation SO 4 /CO 3 H - , nitrates,

tannin and lignin, and total organic carbon.

REFERENCES

ÁLVAREZ COBELAS, M. y CIRUJANO, S. (editores) (1996). “Las Tablas de Daimiel.

Ecología acuática y sociedad”. Red de Parques Nacionales. 371 pp.

ESNAOLA, J.M.; MARTÍNEZ ALFARO, P.E. y MONTERO, E. (1995). "Evolución hidrológica,

regadíos y sobreexplotación de la Unidad Hidrogeológica 04.04 "Mancha Occidental" en el marco

legislativo de las aguas subterráneas". Jornadas sobre las Aguas Subterráneas en la Ley de Aguas

española: un decenio de experiencia. Tomo II, pp. 141-149. Murcia, 1995.

GARCÍA RODRÍGUEZ, M. y LLAMAS, M.R. (1992). “Aspectos hidrogeológicos en relación

con la génesis y combustión espontánea de las turbas en los “Ojos” del Guadiana”. III Congreso

Geológico de España y VIII Congreso Latinoamericano de Geología. Actas tomo 2, pp. 285-

289.

MARTÍNEZ ALFARO, P.; MONTERO, E. y LÓPEZ CAMACHO, B. (1992). “The impact of

the overexploitation of the Campo de Montiel aquifer on the Lagunas de Ruidera ecosystem”.

Selected Papers on Hydrogeology, vol.3, pp. 87-91.

MONTERO GONZÁLEZ, E. (1994). “Funcionamiento hidrogeológico del sistema de las

Lagunas de Ruidera”. Tesis Doctoral, U.C.M.; 297 pp.

MONTERO GONZÁLEZ, E. (1995). “Funcionamiento hidrogeológico del sistema de las

Lagunas de Ruidera”. Hidrogeología y Recursos Hidráulicos, Vol. XIX, pp. 373-389.

29


MONTERO GONZÁLEZ, E. (2000). “Contribución al estudio de la geometría y los límites del

acuífero del Campo de Montiel”. Instituto de Estudios Albacetenses “Don Juan Manuel”. 177

pp.

RINCÓN, P.J.; MONTERO, E. y VEGAS, R. (1996). “Condicionamientos estructurales de la

Unidad Hidrogeológica del Campo de Montiel (provincias de Ciudad Real y Albacete)”.

Geogaceta, 20(6), pp. 1274-1276.

RINCÓN, P.J.; MONTERO, E. y VEGAS, R. (2001a). “Contexto tectónico del Parque Natural

de las Lagunas de Ruidera (acuífero del Campo de Montiel)”. Geogaceta (en prensa).

RINCÓN, P.J.; MONTERO, E. y VEGAS, R. (2001b). “Marco tectónico de la Unidad

Hidrogeológica del Campo de Montiel”. (en prensa).

RUEDA SAGASETA, F. (1992). “Las relaciones históricas hombre-agua en La Mancha”. La

Mancha: un espacio del agua. Conferencias organizadas por el Módulo de Promoción y

Desarrollo. Escuela –Taller “Santa Clara”. Alcázar de San Juan, Ciudad Real.

SERVICIO GEOLÓGICO (1988). “El subsuelo como agente depurador de vertidos líquidos

contaminantes”. Informaciones y Estudios nº 49. MOPU.

VARIOS (1997). “Parque Natural Lagunas de Ruidera”. Editorial Cohábitat. 395 pp.

30


Figure 1: Geographic location of the study area (Llanura Manchega) (Source: Servicio Geológico, 1988)

Figure 3: Schematic geologic profiles of the Llanura Manchega. Quaternary - 1: pebbles, sands, silts, etc.

Plioquaternary - 2: conglomerates, pebbles, sands, etc. Pliocene - 3: limestones and limy marls. Miocene - 4:

limestones and marls; 5: red clays. Cretacic - 6: limestones; 7: sands and sandstones. Jurassic - 8: limestones,

dolomites and marls. Triassic - 9: clays, gypsum and sandstones. Palaeozoic - shales and quartzites (Source: Servicio

Geológico, 1988).

31


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 39-

66

FIELDTRIP TO ARAGÓN

Sánchez, J.A.; Pérez, A.; Roc, A.C., and Rubio, J.C.

Department of Earth Sciences. Faculty of Sciences. Zaragoza University. 50009 Zaragoza (Spain)

INTRODUCCIÓN

La Comunidad Autónoma de Aragón está situada al NE de la península Ibérica, su capital

es Zaragoza, que se sitúa a mitad de camino entre las ciudades de Madrid y Barcelona. Desde el

punto de vista geológico, en Aragón existen tres grandes unidades (Figura 1): los Pirineos, la

Cordillera Ibérica, y la Cuenca Terciaria del Ebro.

Figura 1.- Esquema de situación de las zonas de Campo. El número indica el día de visita

En esta guía se presenta un itinerario que atraviesa en dirección Norte-Sur las citadas

unidades geológicas. Este itinerario es principalmente hidrogeológico y está especialmente

referido a las aguas termales. Además se completa con otras zonas de especial interés geológico

o medioambiental.

40


Las zonas y temas seleccionados son los siguientes:

Primer día de campo:

-LAS AGUAS TERMALES DE ALHAMA-JARABA

-LA CUENCA ENDORREICA DE LA LAGUNA DE GALLOCANTA

Segundo día de campo:

-LA UNIDAD ACUÍFERA DE ALFAMEN COMO EJEMPLO DE ACUÍFEROS

MULTICAPA SUPERPUESTOS

-LOS MANANTIALES DE PONTIL COMO EJEMPLO DEL DRENAJE

SUBTERRÁNEO DE LA CORDILLERA IBERICA EN LA DEPRESIÓN TERCIARIA DEL

EBRO

Tercer día de campo:

-LAS AGUAS TERMALES DE PANTICOSA

-EL SINCLINAL DE JACA Y EL MANANTIAL TERMAL DE TIERMAS

PRIMER DÍA DE CAMPO:

LAS AGUAS TERMALES EN ARAGON: DATOS BÁSICOS PREVIOS

El estudio sobre la Aguas Termales de Aragón (Sánchez et al. ) ha permitido inventariar

todos los indicios hidrotermales existentes (manantiales, sondeos...) y cuantificar la energía

geotermal que por convección surge por cada uno de los manantiales. La figura 2 muestra para

todo Aragón, la situación de cada uno de los manantiales termales existentes, junto con un

círculo que es proporcional a la energía termal aportada. La ecuación utilizada para evaluar esta

energía es la de Pfister, M., et al., (1998) que evalúa la energía que cada segundo está saliendo:

E = ∆T x Q x Cx ρ

41


Donde: E es la energía en Megawatios que de forma natural surge por los manantiales. ∆T es la

diferencia entre la temperatura medida en la surgencia y la temperatura media del aire, que sólo

se considera si es mayor de 4ºC. Q es el caudal en l/s. C es el calor específico del agua que tiene

un valor de 4200J/kgºK. Finalmente, ρ es la densidad del agua cuyo valor es 1000 kg/m 3 .

Figura 2.-Situación de los manantiales termales existentes en Aragón

A modo de resumen se acompaña una tabla con los datos básicos de los principales

manantiales inventariados.

42


Este estudio ha permitido también definir las formaciones geotermales de Aragón, que

son los materiales geológicos capaces de almacenar y transmitir agua u otros fluidos a una

temperatura que permitan su aprovechamiento (uso balneario, calentamiento de espacios,

energía eléctrica...) La figura 3 muestra estas formaciones referidas por una parte al Pirineo y

por otra a la Cordillera Ibérica y la cuenca Terciaria del Ebro.

Figura 3.- Columnas estratigráficas y formaciones geotermales de la Cordillera Ibérica y del Pirineo

LAS AGUAS TERMALES DE ALHAMA-JARABA

Los manantiales termales de Alhama y Jaraba se encuentran en la Cordillera Ibérica, en

el contacto entre la parte oriental de la cuenca de Almazán y el borde sur de la Rama Aragonesa

de la Cordillera Ibérica. Son un conjunto de manantiales que se caracterizan por su elevada

temperatura, hasta 35 ºC y su importante caudal, en conjunto superan los mil litros por segundo.

Estos manantiales son la principal alimentación de los río Mesa en Jaraba y Jalón en Alhama.

La figura 4 muestra la situación geológica de estos manantiales y la relación con las

estructuras que condiciona su surgencia. Como puede verse el acuífero principal corresponde a

los materiales carbonatados del Cretácico Superior (Formación Geotermal nº 6, Fig. 3), por ellos

circula el agua subterránea siguiendo su estructura, de manera que en ocasiones desciende a más

de mil metros por debajo de la superficie del terreno (ver cortes 1 y 2), el relleno terciario

constituye un acuitardo de gran superficie y extensión. Destacar que las surgencias se localizan

en estratos carbonatados del Cretácico dispuestos verticalmente, de manera que esa estructura

aflorante (ver fotografía) se continúa varios cientos de metros en profundidad. Es precisamente

43


esa estructura la que permite que el agua, calentada en profundidad, ascienda manteniendo

todavía una temperatura anormalmente alta.

Figura 4.-Situación geológica de estos manantiales en Alhama-Jaraba y la relación con las estructuras que

condiciona su surgencia.

Todo el contacto entre la cuenca terciaria de Almazán y los materiales del Cretácico

superior tiene una disposición similar (ver cortes 1 y 2) de manera que además de los

manantiales de Alhama y Jaraba existen otros en el citado contacto: manantial de Deza con un

caudal de 100 l/s y 19 ºC de temperatura, manantial de Embid de Ariza con 20 l/s y 27ºC, y

manantial de San Roquillo con 20 l/s y 19ºC. Un dato importante es la cota a la que se

encuentran estos manantiales.

La recarga de este acuífero Cretácico se produce en la cabecera del Jalón, a través de

principalmente de materiales calizos del Jurásico. También es importante la recarga que se

produce de forma difusa a través de los extensos depósitos detríticos terciarios de la cuenca de

Almazán. Sobre este tema, y sobre el flujo del agua hacia los manantiales existe una discusión

científica, existiendo una teoría que considera que el agua no circula por debajo de la cuenca

terciaria, sino que sigue la dirección de los afloramientos del Cretácico Superior (ver discusión

de J.A. Sánchez et. al, y la réplica de E. Sanz et al., en Groundwater, vol. 38, nº 3, 324-325 pp.)

Los manantiales termales de Alhama y Jaraba presentan composiciones sulfatadasbicarbonatadas,

cálcicas o cálcico-magnésicas. Las aguas de Alhama son las más mineralizadas,

como un residuo seco entre 650 y 850 mg/l, mientras que las de Jaraba no superan los 650 mg/l.

La figura 5 muestra en un diagrama de Piper la situación de los diferentes manantiales, como

puede verse las aguas termales difieren notablemente de las aguas procedentes de manantiales

no termales.

44


Destacar como los manantiales de mayor caudal (los de Alhama y Jaraba) presenta

composiciones más sulfatado-cloruraras y magnésicas.

Las aguas de estos manantiales tienen un uso balneario, en Alhama existen tres

balnearios y en Jaraba otros tres. Algunos de los manantiales están calificados como mineromedicinales

y además del uso terapéutico, se embotellan para su comercialización, en Jaraba

existen 3 plantas para embotellados de agua. Por otra parte, las aguas de estos manantiales son

recogidas por acequias y con ellas se riegan más de 1000 ha principalmente de frutales.

Figura 5.- Diagrama de Piper-Hill-Langelier de los manantiales de Alhama, Jaraba, San Roquillo y Embid

PARADA 1 (Alhama de Aragón).-

Vista de los estratos carbonatadas del Cretácico Superior, en disposición vertical que

dan lugar a los manantiales termales. Observación del contacto entre el borde de Cuenca

Terciaria y los materiales del Cretácico Superior. Comprobación de la temperatura de uno de los

manantiales termales. Vista del pliegue de Alhama.

PARADA 2 (Jaraba).-

Visita a Baños de Serón y comida. Recorrido a pié hasta el balneario de Sicilia y el lago

termal en Balneario de la Virgen.

Se acompaña plano del itinerario (Fig.6) y diagrama de Piper de todos los manantiales

(Fig. 7).

(Posible visita a la piscina termal).

Después de observar el notable descenso del caudal del río Mesa aguas arriba de Jaraba,

iniciamos el camino hacia la laguna de Gallocanta.

45


Figura 6.- Itinerario de la zona de Jaraba

Figura 7.- Diagrama de Piper-Hill-Langelier de los manantiales de la zona Alhama-Jaraba

46


Figura 8.- Acuífero carbonatado Mesozoico

LA CUENCA ENDORREICA DE LA LAGUNA DE GALLOCANTA

La laguna de Gallocanta es el mayor humedal salino del Noreste de la península Ibérica,

con una superficie de unos 14 km 2 . Presenta una profundidad máxima de 2 metros, llegando a

sequedad total en verano. La composición y caracterización hidroquímica de sus aguas muestra

que Gallocanta es un lago hipersalino de tipo Na-Mg-Cl-(SO4) con una mineralización que

supera los 50 gramos/l y que durante periodos secos presenta un enriquecimiento en sales como

halita, bischofita, epsomita, hexahedrita y mirabilita. Las aguas proceden de flujos subterráneos,

existiendo además cursos torrenciales que aportan aguas superficiales.

Su importancia como lugar de descanso para aves migratorias procedentes del norte de

Europa le han dado un elevado valor medioambiental, está declarada como Zona de Especial

Protección para las Aves, y se está tramitando su transformación en Parque Natural.

La conservación de la laguna, junto con su prados húmedos ha entrado en conflicto con

la explotación de las aguas subterráneas para regadío, provocando problemas entre los

habitantes de la zona y las administraciones públicas. La Comunidad Europea subvenciona una

sobresiembra de semilla de cereal para permitir la alimentación de las aves, especialmente de las

Grullas, pero los agricultores siguen considerándose perjudicados.

47


La laguna de Gallocanta se encuentra en una altiplano a 1050 m. de altitud, rodeado de

montañas de unos 1400 m que constituyen la divisoria de aguas superficiales de su cuenca

endorreica que tiene unos 500 km 2 de extensión.

Son más de 10 barrancos los que confluyen a la laguna, pero sólo dos de ellos llevan

agua casi permanentemente. La precipitación en la zona es escasa, entre 400 y 600 mm/año, y la

evaporación intensa, más 1000 mm, lo que hace que durante la época estival la laguna quede

totalmente seca. Se constata la existencia de una notable aportación de aguas subterráneas a la

laguna, las cuales parece ser que debido a los bombeos han quedado fuertemente reducidas en

los últimos años.

Se han definido dos acuíferos principales, (ver fig. 8 y fig. 9) el acuífero carbonatado

Mesozoico, y el acuífero detrítico de Gallocanta.

Acuífero carbonatado Mesozoico.

Corresponde a calizas y dolomías del Jurásico y Cretácico, como puede verse en la Fig. 8

afloran según una dirección NW-SE, ocupando una extensión de 200 km 2 , de los cuales 160 km 2

se sitúan dentro de la Cuenca de Gallocanta, su espesor medio de unos 140 m.

En este acuífero se han inventariado más de doscientos puntos de agua de los que el 46%

son pozos, el 31% sondeos y el 23% manantiales. A estos puntos habría que añadir la presencia

de varios sumideros. El caudal de explotación y/o drenaje es muy variable, así los manantiales

rara vez superan los 10 l/seg, mientras que los pozos y sondeos suelen tener algo más de caudal,

llegando a superar en algunos casos los 50 l/seg.

La transmisividad de este acuífero oscila entre 100 y 250 m 2 /día, llegando

excepcionalmente a valores de hasta 1000m 2 /día. En cuanto a su coeficiente de almacenamiento

es muy variable, oscilando entre el 0,01 al 3%, considerando un espesor medio saturado de unos

30 m, las reservas de aguas subterráneas se estiman en unos 30 hm 3 .

En la figura 8 se muestran los puntos de agua inventariados y el mapa de isopiezas de

este acuífero; Como puede observarse el flujo dominante es hacia la laguna en el entorno de

ésta, pero tanto hacia el este como hacia el oeste el flujo se dirige hacia las cuenca vecinas,

parece claro por tanto que la divisoria de aguas subterráneas no coincide con la divisoria de las

superficiales. Por otra parte, las variaciones estacionales son muy acusadas, presentando una

respuesta rápida a las precipitaciones. La divisoria de las aguas subterráneas puede ser variable

en el tiempo.

En cuanto a las características físico-químicas de las aguas, predominan las de

composición Bicarbonatadas cálcicas, aunque en algunos casos se observa una fuerte

mineralización, con un alto contenido en SO 4

=

relacionado con los materiales evaporíticos de las

facies Keuper.

Acuífero Detrítico de Gallocanta.

Se trata de materiales terciarias y cuaternarios que rellenan una cubeta alargada de

dirección NO-SE interrumpida por algunos relieves residuales mesozoicos. La extensión de esta

cubeta es de 225 km2 y su espesor medio es de unos 110 m. Esta formado por conglomerados y

lutitas. Los depósitos perilagunares son mas finos. El sustrato de este acuífero lo constituyen

materiales triásicos, jurásicos y cretácicos.

En la zona del entorno de la laguna, la potencia de este acuífero es mínima,

aproximadamente unos 4 a 5 metros. Los bombeos de ensayo realizados junto a la laguna, dan

unos espesores saturados de 2 a 3 m. El coeficiente de almacenamiento sería el 4% y las

reservas serían del orden de 3 hm 3 .

En este acuífero se han inventariado unos 100 puntos de agua, especialmente pozos que

se sitúan en los municipios de Tornos, Gallocanta y Bello, es decir en las proximidades de la

laguna.

En este acuífero existe una clara evolución geoquímica, las aguas bicarbonatadas-cálcicas

y cálcico-magnésicas se disponen en las zonas de borde del acuífero detrítico, donde el agua

procede o bien de cuaternarios de piedemonte (al NE) o bien del acuífero calizo (al SO).

48


Figura 9.- Acuífero Detrítico de Gallocanta

En la zona central las aguas son bicarbonatadas-sulfatadas-cálcicas y bicarbonatadassulfatado-cloruradas

calcio-magnésicas. Ello se corresponde con un mayor tiempo de residencia

en el entorno de la laguna, cuyos materiales de depósito son ricos en sulfatos. El contenido de

sulfatos y cloruros aumenta en las proximidades de la laguna.

Se han detectado elevadas concentraciones de nitratos y nitritos (por encima de niveles

legales de potabilidad, establecidos en 50 mg/l) en la mayoría de los puntos del acuífero sobre

todo en los utilizados para el abastecimiento de Bello, Tornos y Cubel. Estas altas

concentraciones asociadas a un alto contenido de K + sugieren una contaminación relacionada

con el uso masivo de abonos agrícolas.

Asimismo si han reconocido altos contenidos de nitritos entre Tornos y Bello en relación

con aguas residuales. Existen también puntos con altos contenidos en cloruros de sodio,

relacionados con la existencia de explotaciones ganaderas en las proximidades de Bello.

Los vertidos de los núcleos de población se realizan directamente sobre el terreno, sin

existir procesos de depuraciones en la mayoría de los municipios (excepto Tornos).

Varias localidades (Cubel, Santed, Used y Las Cuerlas) disponen de fosas sépticas Estos

vertidos aportan una cantidad significativa de coliformes que generan una cierta contaminación

orgánica en el entorno de la laguna.

49


Teniendo en cuenta que el acuífero detrítico de Gallocanta es un acuífero libre y de

elevada transmisividad, se puede afirmar que presenta un alto grado de vulnerabilidad a la

contaminación.

Funcionamiento Hidrogeológico del conjunto

El conjunto del sistema funciona como en embalse regulador, que recibe la infiltración

del agua de lluvia y la escorrentía de las sierras que lo enmarcan, alimentando a la laguna de

Gallocanta. El esquema que se acompaña es un balance de agua de la cuenca endorreica (ver fig.

10), los balances cierran perfectamente, pero existen grandes dudas sobre la validez de las

cifras. La incertidumbre en determinadas variables es extremadamente grande, por lo que

creemos que el esquema debe servir ante todo como ejemplo de relaciones entre acuíferos,

laguna, explotación de pozos....

La laguna de Gallocanta recibe el agua del flujo subterráneo procedente de los acuíferos,

así como el agua de lluvia que cae sobre ella, además del agua que ocasionalmente aportan los

barrancos. Las perdidas de agua en el vaso de la laguna son exclusivamente por evaporación.

Destacar que debido a su topografía, extremadamente plana, simplemente el balance de agua

(evaporación-precipitación) hace que la laguna esté totalmente inundada o totalmente seca. De

hecho en invierno con una evaporación mínima, aún sin precipitaciones la laguna adquiere una

Figura 10.- Balance de agua de la Laguna de Gallocanta

50


extensa lámina de agua, por el contrario en la época estival, la evaporación es tan intensa (más

de 10 mm/día) que prácticamente es imposible la permanencia de esa lámina de agua. Además

el volumen de agua subterránea que se extrae mediante pozos es pequeña, pero su efecto sobre

la lámina de agua en la laguna puede ser crítico, teniendo en cuenta que las extracciones se

realizan en el borde de la laguna. De hecho puede verse en la figura 11 como desde que se

extraen aguas subterráneas la laguna no responde igual ante la llegada de años húmedos.

Figura 11.- Volumen de agua de lluvia, extracciones y profundidad de la Laguna de Gallocanta

Ambientes sedimentarios de la Laguna de Gallocanta

La forma de la laguna es alargada, con una longitud máxima de 7,5 km y una anchura

media de unos 2,85 km, y en ella se identifican tres sectores bien diferenciados

morfológicamente. En el extremo más noroccidental se sitúa "El Lagunazo de Gallocanta", de

forma subcircular y 1,2 km de diámetro, está separado del resto de la laguna por una barra

conglomerática denominada localmente Los Picos, la cual ha sido posiblemente cortada por la

acción humana para comunicar los diferentes sectores de la laguna. "El Lagunazo grande o

central" es el cuerpo principal de la laguna. Presenta forma alargada de dirección NO-SE con

unos 5 km de longitud y 3 km de anchura. En el sector Suroccidental se localizan "Los ojos de

la laguna", conjunto de manantiales alrededor de los cuales se desarrolla una amplia zona

palustre funcional, en buena parte afectada por la acción antrópica. Por último, en el extremo

oriental se sitúan "Los lagunazos de Tornos" que integran un área palustre funcional de unos 2,9

km de longitud y 4,2 km de anchura.

La distribución de facies sedimentarias ha sido esquematizada en la figura 12. A partir de

los datos obtenidos se han diferenciados tres dominios: lacustre central, lacustre marginal y

palustre. El paso entre el sector central y el marginal puede ser neto, o realizarse a través de una

zona transicional que hemos denominado lacustre marginal/central.

51


Figura 12.- Distribución de ambientes sedimentarios en la Laguna de Gallocanta

El subambiente lacustre central está localizado hacia el NW y SE de los Picos de la

laguna. Ocupa un área de 1x0.5 Km en el Lagunazo y 4.2x1.2 Km en la Laguna grande. Este

sector está caracterizado por el desarrollo de barros negros y el crecimiento de cristales de halita

recubiertos por mallas estromatolíticas. Los barros negros presentan una composición dada por

calcita, dolomita, aragonito, yeso, anhidrita, halitas y blohedita, además de bajas proporciones

en cuarzo y minerales de las arcillas.

El subambiente lacustre marginal ocupa una extensa área y en el ha sido diferenciado un

sector interno y otro externo. El sector más interno ocupa una banda de 0.2 a 0.5 km que se

extiende alrededor del sector central. Presenta muy bajo gradiente topográfico y muestra una

clara asimetría, estando mejor desarrollado en el margen sur de la laguna que en el sector norte.

Los sedimentos característicos consisten en lutitas marrones y margas grises que presentan

oxidaciones y frecuentes bioturbaciones. Es habitual la presencia de costras laminadas

estromatolíticas que atrapan cristales de sales. La composición mineralógica viene dada por

calcita, dolomita, cuarzo minerales de las arcillas y en menor medida halita. En los centímetros

más superficiales hay también yeso, aragonito y hexahedrita. El sector más externo representa

una zona discontinua identificada a lo largo del borde de la laguna. Es un sector cubierto por

Salicornia ramosissima asociada a algas mats. Los sedimentos son lutitas de color marrón y

areniscas de grano grueso entre las que aparecen cantos conglomeráticos de cuarcita.

El subambiente palustres se sitúa alrededor de la laguna y aparece dominantemente

concentrado en dos zonas. La primera de ellas se localiza en el sector NW de la laguna y está

caracterizada por la presencia de manantiales (los ojos de la laguna). La segunda se sitúa al SE y

ocupa el sector denominado Los lagunazos de Tornos. Los sedimentos de este subambiente

están caracterizados por lutitas grises con abundantes gasterópodos, y sobre las que se desarrolla

una densa vegetación de juncos y carrizos. La mayor parte de este subambiente está modificado

por la acción antrópica y son actualmente campos de cultivo.

PARADA 3.-: Panorámica de la Laguna de la Zaida. Esta laguna comprende todos los cauces

procedentes de la sierra de Santa Cruz, formada por materiales paleozoicos, que vierten a esta

52


laguna. La laguna de la Zaida permanece seca de 2 a 3 años seguidos, con el objeto de

cultivarla, y un año con agua. Para ello el hombre realizó un sistema regulador de inundación de

la laguna, que retiene el agua de los barrancos que vierten en ella, en La Parada y La Retuerta.

La represa formada por la Parada encharca la depresión más inmediata a la compuerta y a

continuación la de la Retuerta, desde donde rebosa a la acequia Nueva- Arroyo de la Cañada,

que finalmente vierte el agua a la Laguna de Gallocanta.

PARADA 4.- Panorámica de la Laguna de Gallocanta y observación en detalle de los depósitos

lacustres marginales externos. Se visitará la estación meteorológica situada en los “Picos de la

Laguna” la cual recoge principalmente medidas de precipitaciones, temperatura del aire y del

suelo, velocidad y dirección del viento, evaporación y humedad.

Recorrido de la zona palustre de los Aguanares y observación de los dos manantiales de los que

se abastece el pueblo.

SEGUNDO DÍA DE CAMPO: EL SISTEMA ACUÍFERO DE ALFAMEN

Introducción

El sistema acuífero de Alfamén es un complejo conjunto de acuíferos detríticos y

carbonatados que ha dado lugar a la mayor y más rentable transformación de secano a regadío

con aguas subterráneas de todo Aragón, y posiblemente de la cuenca del Ebro. Este complejo

sistema de acuíferos recibe su nombre de la localidad situada en el centro del mismo, que es

además la que de un modo más evidente ha experimentado el paso de un territorio seco, no

productivo, a una zona regable de frutales, hortalizas...

Actualmente se extraen cerca de 50 hm3/año de aguas subterráneas, los regadíos en la

zona suman unas 15000 ha, de las que 7000 son exclusivamente con aguas subterráneas, 5000

se riegan con aguas del río Jalón derivadas mediante acequias, y unas 3000 ha son de regadío

mixto.

En la zona continúan las transformaciones en regadío, aunque parece evidente un

descenso de los niveles de agua en los acuíferos y comienza a considerarse la existencia de

sobreexplotación, al menos en zona localizadas del sistema acuífero.

Figura 13.- Mapa geológico de la zona de Alfamén, y situación de los cortes.

Unidades acuíferas y su relación

La figura 13 corresponde a un mapa geológico de la zona, como puede verse

predominan los materiales cuaternarios que constituyen un extenso glacis, que desciende desde

53


las sierras paleozoicas situadas al sur, hasta los relieves estructurales que al norte forma las

calizas de La Muela (depósitos lacustres del Mioceno con las que se colmata la cuenca terciaria

del Ebro). En los limites de las sierras aparecen pequeños afloramiento de materiales

carbonatados mesozoicos, al igual que hacia los ríos Jalón y Huerva.

Los ríos Jalón y Huerva constituyen los límites hidráulicos del sistema acuífero, pero el

plano de la figura 13 es poco expresivo de lo que este sistema acuífero encierra. Los datos de

más de 1000 sondeos y pozos han permitido conocer los acuíferos y su relación, así la figura 14

es un corte E-W del Sistema Acuífero, donde puede verse el acuífero carbonatado mesozoico

(calizas del Jurásico especialmente) y los acuíferos detríticos que constituyen las unidades

principalmente explotadas.

Figura 14.- Sección hidrogeológica este-oeste (corte 1)

Siguiendo la misma figura, podemos identificar una unidad detrítica superior, que da

lugar a un acuífero libre, aparece marcada con la letra Q (aunque se sabe que es pliocuaternaria).

Por debajo existe, una formación acuitarda (T/B1), que corresponde a materiales

margosos, que siguiendo la denominación de los sondistas se cita como “marga blanca”. Por

debajo, se encuentra el acuífero terciario que principalmente se explota, es una alternancia de

gravas con cantos y niveles de lutita (arcilla) de edad Mioceno que llega a tener más de 400

metros de espesor, se trata de un acuífero multicapa.

Los caudales que se obtienen en los sondeos, son a veces muy importantes, siendo

frecuentes valores superiores a los 80 l/s, con descensos de 60 a 100 (el acuífero es confinado).

Cuando se explota el acuífero superior (Q), si el espesor saturado es importante, más de 50 m.,

se pueden obtener caudales superiores a los 50 l/s, con descensos de poco más de 20 m.

Destacar que entre el acuífero detrítico terciario (T/B1) y el carbonatado mesozoico existe

un acuitardo formado por lutitas de edad Cretácico (Weald), este acuitardo es efectivo al este de

la carretera Alfamén-Almonacid, independizando ambos acuíferos, al oeste de esa carretera el

acuitardo ha desaparecido o por su reducido espesor no separa ambos acuíferos. Este hecho

queda manifiesto en los niveles piezométricos de cada acuífero.

54


Los cortes 2, 3 y 4 de las figuras 15, 16 y 17 completan la imagen tridimensional de estas

unidades acuíferas y la relación que existe entre ellas.

Figura 15.- Sección hidrogeológica norte-sur (corte2)

El corte 2 es representativo del lugar de la parada, destacando la notable diferencia que

existen en los niveles de agua de los distintos acuíferos. El corte 3 es representativo de la

situación junto a la localidad de Alfamén, si bien al este de la carretera Almonacid-Alfamén,

destacar que el acuífero terciario tiene su nivel por encima del acuífero cuaternario (hasta

tiempos recientes era surgente en todos los sondeos, incluso de forma natural sus aguas

atravesaban el acuitardo y llegaban hasta la superficie, dando lugar a zonas húmedas como las

situadas junto a la ermita de la Virgen de las Lagunas.

Figura 16.- Sección hidrogeológica norte-sur (corte 3).

Finalmente en el corte 4 (ver fig.17), el nivel del acuífero carbonatado es casi coincidente

con el del terciario, no existe el acuitardo (unidad cretácica en facies Weald)

55


Figura 17.- Sección hidrogeológica norte-sur (corte 4)

Piezometría

El elevado número de sondeos existentes, pero sobre todo los datos aportados por unos 20

piezómetros realizados por el Gobierno de Aragón en los que, siempre que es posible, se miden

los niveles por separado de cada unos de los acuíferos (piezómetros en racimo), ha permitido la

elaboración de mapas de isopiezas específicos de cada uno de los acuíferos (planos 1, 2 y 3 de

las fig. 18, 19 y 20).

Figura 18.- Isopiezas del Acuífero detrítico superior (plano 1)

El plano 1 (ver fig. 18) corresponde al mapa de isopiezas del acuífero detrítico superior, el

cuaternario, como puede verse este acuífero tiene una extensión superficial más restringida que

los inferiores, el flujo del agua es claramente hacia el río Jalón. Se acompañan la evolución de

56


los niveles de agua en el piezómetro P-14 situado junto a la localidad de Alfamén (el nivel se

mantiene entre 435-440 m.s.n.m.).

El Plano 2 (fig 19) muestra el mapa de isopiezas del acuífero detrítico inferior

(Mioceno), como puede verse el flujo se dirige también hacia el río Jalón, destacando el fuerte

desnivel piezométrico existente al oeste de Alfamén. La cota de agua en el P-14 (piezómetro

anterior) es inicialmente de 450 m.s.n.m. (condiciones surgentes), pero como puede verse los

bombeos en los últimos quince años le han hecho descender por debajo de los 420m, las

variaciones estacionales relacionadas con los bombeos son muy evidentes.

Figura 19.- Isopiezas del Acuífero detrítico inferior (plano 2)

Figura 20.-Mapa de isopiezas del acuífero carbonatado mesozoico (plano 3).

57


El Plano 3 (fig. 20) muestra el mapa de isopiezas del acuífero carbonatado, como puede

verse los sondeos que lo alcanzan son escasos, pero son suficientes para realizar un mapa que

muestra el drenaje que el río Jalón realiza en toda la unidad acuífera. Destacar que en la zona de

Alfamén la cota del agua en este acuífero se sitúa en unos 380 m.s.n.m., es decir más de 50 m

por debajo de los niveles de los acuíferos detríticos que se encuentran estratigráficamente por

encima.

PARADA 1.-Carretera Cariñena a Longares. El objeto de esta parada es observar la

topografía de la zona y explicar las distintas unidades acuíferas existentes y su relación.

PARADA 2.-Después de un recorrido por diferentes explotaciones de regadío, donde es

posible observar diferentes sistemas de riego (goteo, aspersión, pívot...) se pretende la

observación de un piezómetro en racimo y las bombas de elevación de una explotación

cooperativa (Sociedad Agraria de Transformación).

Los manantiales de Pontil como ejemplo del drenaje subterráneo de la Cordillera Ibérica

en la Depresión Terciaria del Ebro

El acuífero carbonatado mesozoico citado anteriormente constituye un extenso acuífero

que ocupa toda la vertiente norte de la Rama Aragonesa de la Cordillera Ibérica, por este

acuífero carbonatado circula el agua subterránea hasta el contacto con los materiales poco

permeables de la Depresión Terciaria del Ebro (margas y yesos), donde surge dando lugar a una

decena de grandes manantiales que suman un caudal de más de 5000 l/s. El mapa de isopiezas

de la figura 21 muestra la gran extensión de este acuífero carbonatado, gran parte de él cubierto

por materiales del terciario, y como el flujo del agua subterránea se dirige hacia unos pocos

grandes manantiales. El acuífero más importante corresponde a las carniolas del Lías (Jurásico

inferior), por su disposición estratigráfica inmediatamente por encima de una unidad

impermeable (arcillas y yesos del Keuper) constituye el nivel de drenaje regional de toda la

Cordillera Ibérica en este sector, ese drenaje subterráneo es tan efectivo que algunos de los ríos

que descienden de la cordillera pierden totalmente sus aguas, las cuales aparecen en el mismo

río aguas abajo, o bien son transferidas a otros ríos como puede verse en la fig. 21.

Todos los manantiales de este acuífero tiene unos rasgos comunes que los identifican

como de flujo regional según la terminología de Toth.: caudal y composición química constante,

elevada mineralización (1500 mg/l), típica composición sulfatada cálcica, bajo contenido en

tritio, y una temperatura anormalmente alta, unos 25 ºC. Los manantiales más importantes se

sitúan en relación con falla una falla inversa que limita la Cordillera Ibérica con la Depresión

Terciaria del Ebro (falla nordibérica), esta falla sólo es aflorante en La Rioja, mientras que en

Aragón está fosilizada por materiales terciarios del Mioceno. Otros manantiales se sitúan en el

contacto de los materiales carbonatados con las arcillas y yesos del Keuper que forman el

núcleo de estructuras anticlinales.

Los manantiales de Pontil se sitúan en relación con la citada falla nordibérica. La Figura

22 muestra un corte WSW-ENE que sería aproximadamente coincidente con la traza del río

Jalón. Destacar la presencia de anhidrita, su lavado por las aguas subterráneas a lo largo del

tiempo dar lugar a las brechas carbonatadas del Lías. Estas brechas son un acuífero excepcional

por su elevada porosidad y permeabilidad, de hecho los sondeos realizados dan caudales

superiores a los 100 l/s con apenas 5 metros de descenso.

58


Figura 21.- Mapa de isopiezas de los acuíferos carbonatados ibéricos en su

vertiente hacia el Ebro y ubicación de la zona estudiada.

PARADA 3.-Manantiales de Ojos de Pontil: conjunto de pequeñas depresiones por las

que surgen flujos ascendentes de agua que suman casi 500 l/s. Su composición es sulfatada

cálcica y su mineralización de 1400 mg/l, la temperatura de emergencia es de 23 ºC.

Los ojos y su zona húmeda asociada ocupaban hace unas décadas más de 12 ha,

conociéndose el lugar con el nombre de “los prados”. Hasta la reciente intervención del

Ayuntamiento de Rueda de Jalón parte de los terrenos se utilizaban como escombrera ilegal,

también deterioró mucho el humedal el intento de instalar una piscifactoría de anguilas

aprovechando el agua caliente. Actualmente es una zona protegida de gran valor ambiental y

científico, donde aún es posible ver manifestaciones de flujos ascendentes de agua como son los

“volcanes de arena”.

(Después de esta parada, y tras la comida se inicia el recorrido hacia el Pirineo. Según la

disponibilidad de tiempo se realizará alguna parada para explicar la estructura general de la

Cordillera Pirenaica.)

PARADA 4.-Cuenca y abanico aluvial del barranco de Arás en Biescas (Huesca). Se

realiza una parada en el abanico aluvial de este barranco donde el 7 de agosto de 1996 tuvo

lugar una avenida torrencial que arrasó un camping, produciendo 87 muertos y daños estimados

en más de 8000 millones de pesetas. Este desastre ha sido el mayor ocurrido en España, en

términos de vidas humanas, en los últimos 25 años.

Se entrega una publicación de F. Gutiérrez et al. (1998) en la revista de la Soc. Geológica

de España.

TERCER DÍA DE CAMPO: LAS AGUAS TERMALES DE PANTICOSA

Introducción

El balneario de Panticosa se localiza en la denominada zona Axial Pirenaica, se encuentra

59


por tanto en el núcleo de la citada cordillera donde predominan los materiales graníticos,

rodeados por pizarras y calizas fuertemente metamorfizadas.

Figura 22.- Corte hidrogeológico

Panticosa es un centro balneario cuyo mayor auge se produjo a finales del siglo XIX y

primeras décadas del XX, fechas a las que corresponden la mayor parte de los edificios actuales.

Existen indicios de uso del agua termal en la época de los romanos, una excavación en la fuente

de Tiberio, encontró monedas de la época. Actualmente toda la zona está en reconversión, en

invierno es lugar de práctica de sky nórdico y paseo de raquetas, además de lugar de arranque de

numerosas excursiones de alta montaña. De hecho está rodeado de montañas que superan los

3100 m de altitud. El balneario se encuentra a una cota de 1600 m.

La figura 23 muestra la situación de los principales manantiales termales, como puede

verse la mayoría reciben nombre relativos a la supuesta capacidad curativa o paliativa

reconocida, se trata de aguas minero-medicinales. Hay que destacar que la pretensión de

aumentar los caudales en determinados manantiales mediante pequeños taladros horizontales,

ha provocado la desaparición de algunos de ellos y/o la comunicación de aguas de diferente

naturaleza. Este es un hecho grave ya que el carácter minero-medicinal requiere, además de un

historial clínico, la constancia de la composición físico-química de las aguas.

La tabla 1 es un resumen de los datos existentes de todos los manantiales y sondeos:

Temperatura Q (l/s)

Manantial Tiberio 46,7 0,5-4

Manantial Escalar 21,0 0,09

Manantial de la Laguna 23,8 0,15

Fuente San Agustín 27,0 0

Fuente Estomago 31,0 0,15

Fuente del Hígado 25,0 Seca

Sondeo El Carmen 39,5 1,8

Sondeo San Agustín 27,0 0,1

Sondeo Fuente del Hígado 21,0 ?

Tabla 1.- Datos de Temperatura y Caudal de los sondeos

60


T(º) sec/vol Q(l/s) Medición

Manantial

Fuente del Estómago 25,7 2,45 0,204

Taladro Fuente San Agustín 29 5,75 0,087 volumétrico regulado

Taladro del Hígado 23,3 7 0,071 volumétrico regulado

Fuente del Carmen* 11,6 17,25 0,029 volumétrico

Fuente de la Laguna 24,7 3 0,166 volumétrico

Fuente del Escalar 20,7 7 0,071 volumétrico

Datos comparativos (DGA,

1994)

Fuente del Estómago 28,5 0,23

27 0,206

30,5 0,321

31 0,15

0,104

Taladro Fuente San Agustín 27,2 0,11

27 0,104

Taladro del Hígado 21,5

Fuente de la Laguna 23,8 0,126

25 0,29

24,5 0,167

24 0,18

0,16

0,152

Fuente del Escalar 19,6 0,05

21 0,07

21 0,06

20 0,093

Tabla 2.- Datos recogidos durante 1998

Durante el año 1998 se realizó un trabajo de campo con mediciones en los diferentes

puntos, obteniendo los siguientes resultados (ver tabla 2).

Finalmente la tabla 3 muestra las características físico-químicas de los principales

manantiales, como puede observarse se trata de aguas de muy baja mineralización (unos 100

mg/l), valores elevados de pH, sodio como catión dominante y ausencia de un anión

predominante. Destacar el elevado contenido en sílice, y la presencia de desprendimientos de

H 2 S en condiciones de surgencia. En esta tabla se acompañan también datos de las

características del agua del lago, hay que destacar que la mezcla de las aguas termales con las

aguas superficiales frías se produce en casi todos los manantiales.

61


FUENTE DEL

CARMEN

mg/l

meq/ %meq

meq/ %meq

l /l mg/l l /l

LAGO PANTICOSA

Conductividad a 20ºC

78

S/cm Conductividad a 20ºC

43

S/cm

pH 7,69 pH 7,43

SiO2

35,9

3 SiO2 3,03

14,2

Cloruros

0 0,40 36,34 Cloruros 5,70 0,16 27,91

Sulfatos 4,10 0,09 7,66 Sulfatos 4,20 0,09 15,07

36,6

18,3

Bicarbonatos

0 0,60 54,53 Bicarbonatos

0 0,30 52,34

Carbonatos 0,00 0,00 0,00 Carbonatos 0,00 0,00 0,00

Nitratos 1,00 0,02 1,47 Nitratos 1,70 0,03 4,67

11,4

0 0,49 52,43 Sodio 2,30 0,10 18,89

Sodio

Magnesio 1,90 0,16 16,98 Magnesio 1,70 0,14 26,78

Calcio 5,60 0,28 29,72 Calcio 5,60 0,28 53,55

Potasio 0,30 0,01 0,86 Potasio 0,20 0,00 0,78

FUENTE DEL

ESCALAR

MANANTIAL LA

LAGUNA

Conductividad a 20ºC

262

S/cm Conductividad a 20ºC

149

S/cm

pH 8,30 pH 8,72

SiO2

56,9

0 SiO2

43,9

8

36,9

20,6

Cloruros

0 1,04 33,90 Cloruros

0 0,58 35,71

Sulfatos

66,7

0 1,39 45,29 Sulfatos

21,3

0 0,44 27,31

Bicarbonatos

28,1

0 0,46 15,00 Bicarbonatos

24,4

0 0,40 24,63

Carbonatos 4,80 0,16 5,22 Carbonatos 5,40 0,18 11,08

Nitratos 1,10 0,02 0,59 Nitratos 1,30 0,02 1,27

48,1

26,7

Sodio

0 2,09 74,33 Sodio

0 1,16 76,54

Magnesio 4,90 0,40 14,21 Magnesio 1,70 0,14 9,22

Calcio 6,00 0,30 10,66 Calcio 4,00 0,20 13,17

Potasio 0,90 0,02 0,80 Potasio 0,60 0,02 1,07

FUENTE DEL

FUENTE DEL

HIGADO

ESTOMAGO

111

148

Conductividad a 20ºC S/cm Conductividad a 20ºC S/cm

pH 9,11 pH 9,48

44,5

76,5

SiO2

4 SiO2

4

13,5

17,7

Cloruros

0 0,38 24,63 Cloruros

0 0,50 27,08

15,5

20,8

Sulfatos

0 0,32 20,92 Sulfatos

0 0,43 23,46

62


Bicarbonatos

23,2

0 0,38 24,63 Bicarbonatos

23,2

0 0,38 20,58

Carbonatos

13,2

0 0,44 28,52 Carbonatos

15,6

0 0,52 28,17

Nitratos 1,30 0,02 1,31 Nitratos 0,80 0,01 0,72

18,0

30,7

Sodio

0 0,78 54,68 Sodio

0 1,34 80,76

Magnesio 4,90 0,40 27,88 Magnesio 1,70 0,14 8,46

Calcio 4,80 0,24 16,73 Calcio 3,20 0,16 9,67

Potasio 0,40 0,01 0,71 Potasio 0,70 0,02 1,11

Tabla 3.- Características físico-químicas de los principales manantiales

La figura 24 es un modelo conceptual del flujo de agua subterránea en el macizo

granítico, en esencia la zona de recarga se sitúa por encima de los 2000 m.s.n.m., infiltrándose

el agua según un flujo vertical descendente. En profundidad el agua aumenta su temperatura en

función de un gradiente geotérmico normal (1ºC de aumento por cada 33 m), el aumento de

temperatura del agua provoca una disminución de su densidad por lo que se produce un flujo

vertical ascendente. La zona de descarga se localiza en la zona granítica de menor cota (zona del

balneario).

Figura 24..- Modelo conceptual del flujo de agua subterránea en el macizo Granítico.

Destacar que en terrenos no volcánicos, los manantiales termales de mayor temperatura se

localiza siempre en granitos (hasta 70-80 ºC, en Cataluña y en Galicia), el motivo es que estos

terrenos mantienen durante miles de metros de profundidad las mismas características

hidrogeológicas (medios fisurados), incluso la disminución de la permeabilidad en profundidad

se ve compensado por la disminución de la viscosidad al aumentar la temperatura.

En la zona de descarga existe mezcla con aguas frías que se encuentran en los potentes

derrubios existentes, toda la zona es de riesgo de avalanchas, especialmente aludes. Un hecho a

destacar es que las aguas frías del lago (de elevada densidad), condicionan que el flujo termal

disperso se dirija hacia el entorno del mismo, provocando así una cierta concentración.

63


PARADA 1.-En Panticosa se realizará un recorrido por los principales manantiales

existentes.

PARADA 2.-Vista general del Sinclinal de Jaca y del campo de gas del Serrablo

PARADA 3.-Si es posible visita al manantial de Tiermas en el embalse de Yesa. (Sólo

visitable si el citado embalse tiene su nivel de agua por debajo de la cota del manantial)

Figura 23.- Situación de los manantiales del área de Panticosa

La figura 25 corresponde a un mapa geológico simplificado del Sinclinal de Jaca, los

cortes 1 y 2 corresponden a dos transversales de dicho sinclinorio. Como puede observarse en

las figuras citadas, esta gran cuenca sinclinal tiene como sustratos a materiales carbonatados

cretácicos y eocenos, y esta rellena de materiales turbidíticos también eocenos que tienen varios

64


miles de metros de potencia. El campo gasístico se desarrolla en estas turbiditas, siendo la roca

almacén unas capas calizas intercaladas en la serie de lutitas y areniscas (flysh eoceno). Estas

capas calizas se interpretan como “olistostemas”, que serían trozos de plataforma deslizadas por

el talud continental.

Figura 25.- Mapa geológico simplificado del Sinclinal de Jaca. Cortes 1 y 2

corresponden a dos transversales de dicho sinclinorio

65


La figura 26 corresponde a uno de los sondeos en explotación del campo de gas del

Serrablo, como se indica en el tríptico que se acompaña, actualmente el yacimiento de gas se

utiliza como almacén subterráneo, se inyecta gas durante el verano y se extrae durante el

invierno.

Figura 26.- Sondeo en explotación del Campo de Gas del Serrablo

Un hecho a destacar es que los sondeos existentes tienen aguas subterráneas termales (con

valores superiores a los 100ºC), de composición clorurada sódica, tal y como puede verse en la

siguiente tabla:

66


mg/l meq/l

Carbonatos 0 0

Bicarbonatos 486 8,1

Cloruros 9926 280

Sulfatos 620 12,91

Calcio 254 12,7

Magnesio 77 6,3

Sodio 6450 280,43

Potasio 65 1,66

Hierro 0,5 0,01

Tabla 4.- Composición del agua subterránea en el sondeo

El manantial de Tiermas se sitúan en la terminación occidental del sinclinal de Jaca, existe

incertidumbre sobre el origen de sus aguas, pero estimamos que corresponde a la descarga de las

formaciones carbonatadas que constituyen el sustrato del citado sinclinal. El caudal de este

manantial supera los 200 l/s y su temperatura es de unos 39 ºC, se trata por tanto de un auténtico

río de agua termal. La composición de estas aguas es clorurada sódica, tal y como puede verse

en la siguiente tabla 5:

SONDEO TIERMAS mg/l meq/l %meq/l

Conductividad a 20ºC 6240 S/cm

pH 7,48

SiO2 28,40

Cloruros 1907,20 53,79 74,09

Sulfatos 677,50 14,10 19,43

Bicarbonatos 283,10 4,64 6,39

Carbonatos 0,00 0,00 0,00

Nitratos 4,10 0,07 0,09

Sodio 1202,40 52,30 74,69

Magnesio 92,40 7,60 10,85

Calcio 192,40 9,60 13,71

Potasio 20,60 0,53 0,75

Tabla 5.- Composición del agua en el sondo de Tiermas

67


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 67-71

FIELDTRIP TO THE UPPER LOZOYA VALLEY AND

PEÑALARA HANGING GLACIER CIRQUE

CENTENO, J.D. 1 and MOYA, M.E. 2

1 Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain).

2 Departament of Geology. Faculty of Sciences. Alcalá de Henares University.

INTRODUCTION

El Paular basin

The Lozoya river feeded the first water supply

system of Madrid and most of present supply. The upper

Lozoya basin is coincident with the tectonic basin of "El

Paular", surrounded by the two branches of the Guadarrama

range: montes Carpetanos to the North and Cuerda Larga

(long line) to the South. During the Pleistocene, these

mountains developed many glaciers (mainly cirque glaciers

in their SE slopes) among them the Peñalara glacier.

Our fieldtrip will take us to the glacial hanging cirque

of Peñalara (showed ⊕ in the regional map) that was the

Guadarrama

mountains

SPANISH

CENTRAL RANGE

Prehercinian

Prealpine

Postalpine

Figure 1. The Spanish Central range and the Guadarrrama mountains in the context of the Iberian peninsula

geology.

second Spanish natural site to be protected by law in 1930 and is nowadays subject to

increasing preservation measures. While the isolation of the valley -producing an slow rate of

development until today- explains the that few sources of contamination are to be found, present

growing of green tourism is producing an interesting conflict between development and

conservation.

GEOLOGICAL SETTING

The Guadarrama range is an hercinian unit with gneiss's and granites (Precambrian to

Ordovician gneiss's and late Carboniferous granites), although some other rocks can be found

(metasediments, aplite and pegmatite dique, etc.).

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The range is an morphostructural unit uplifted in the Alpine orogeny between the Duero

and Tajo Tertiary basins. Generally speaking, it is a simple morphostructure, with only a main

watershed and one summit line. However, within the range some small secondary basins are

well known, among them the "el Paular" o upper Lozoya basin. As many others, it is a WSW -

ENE fault defined basin traditionally interpreted as a graven but recently explained as a set of

low angle reverse faults.

Within the basin there are upper Cretaceous to Cuaternary sediment as remnants of a

former basin or filling of the present basin. These are the main aquifer units in the area as well

as the base for the few villages of the valley.

CLIMATIC SETTING

The climate in central Spain is mediterranean (dry and warm summer in contrast with a

cold and wetter winter), but many meteo processes do relate to the Central Range. As it extends

WSW-ENE an orographic barrier, rains in the Duero and Tajo basin depends on the storms path.

When storms travel South of the range rain is to be found in the Tajo while northern storms

bring rain to the Duero.

The double summit line of the upper Lozoya produces an increase of average rainfall in

the valley. So Navafría (North of montes Carpetanos) has a year average of 700 mm, Miraflores

(South of Cuerda Larga) 900 mm and Rascafría (within the upper Lozoya valley) 1350 mm.

This local increase in rainfall explains the Lozoya basin outflow and the presence of glaciers

during the Pleistocene.

B

N

N

Figure 2. Storm tracks anf rain in the Guadarrama

mountains.

B

THE GLACIAL HISTORY OF PEÑALARA

Peñalara is the highest summit of the Guadarrama mountains (2430 m) and its glacial

cirque a main reference of the Spanish glacial geomorphology studies. Since the first works by

Obermaier and Carandell (1917) many scientists have studied its landforms, the glacial

processes and the ecology of the area. Until 1959, most models related the deposits and forms to

the classical alpine phases (Riss and Würm). Fränzle (1959) suggested that only Würm

processes had modelled the Spanish Central Range. Since then, most authors have accepted the

lack of evidence of any interphase evidence.

In 1983, Centeno prepared the first accurate mapping of the glaciers of the Guadarrama

mountains and Centeno et al.(1983) formulated a complete evolution model of the Peñalara

glacial cirque. Ultimately we modified this model (Acaso et al., 1998) identifying a rock glacier

(in the upper section) and three retreat moraines.

At the moment, all the recognized elements of the glacier have been drawn in figures 3

and 4:

1. Maximum advance phase. Two parallel stabilization front moraines.

2. Advance and stabilization moraine phase. The biggest moraine complex including

prograding on phase 1 sediments and intra-moraine collapse lakes.

3. Retreat phase. Intra-moraine lake sediments.

4. Advance phase. Deformation till (folded lake sediments destroyed by restoration

works).

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5. Retreat and stabilization phase. Central moraine and disconnection of two cirques in

Peñalara and Dos Hermanas.

6. Progresive retreat. Three moraine arches in Peñalara cirque.

7. Last stabilization with depositional effects. Rock glacier in Dos Hermanas and rock

corridor in Peñalara.

Obermaier y Carandell, 1917 Centeno, Pedraza y Ortega,

1983

Acaso, Centeno y Pedraza,

1998

Recession

C

Rock-glaciers

Recession

moraines

Wür

B

Advance

moraines

Time ⇒

Ris

A

Maximum

Glacial volume ⇒

Figure 3. Classic and recent models of evolution of the glacier (after Acaso el al. 1998)

THE PUBLIC INTEREST ON PEÑALARA AREA

The scientific interest on Peñalara may be considered unusual and difficult to understand.

But some ideas can be put forward to explain it:

1. Its immediacy to Madrid made the area a favourite place for mountain sports and

geologist since the beginning of the XIX century.

2. The Peñalara glacial cirque is the only one to have several phases evidence in the

Guadarrama mountains.

3. Its size and accessibility makes this cirque specially interesting for geology teaching

fieldtrips, a long tradition back to 1883 (Giner y Cossío, 1886) with a benchmark at the

declaration of Site of Natural Interest in 1930.

4. Since the middle 1979’s the area has suffered the struggle between developers (mainly

skiing resorts running since 1969 until 1999) and conservationists.

As a consequence of this general interest, the pressure on the physical and ecological

environment has been very high until the declaration of Natural Park in 1990, when control

have increased progressively.

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Dos Hermanas summit (2380 m)

Rock-glaciers

Laguna Grande

Peñalara summit (2430 m)

Central moraine

Recession Advance moraine

Deformation till

Intramoraine

lake

Advance and

stabilization

Lozoya river

Maximum extension

Figure 4. The main elements of the Peñalara glacier. Modified after Acaso et al., 1998. (modified after a watercolour and

pencil draw by E. Acaso)

At the moment, control of lake eutrophization and native species protection are the main

targets of the Natural Park staff. Erosion control have been set off in the Laguna de Peñalara

shore, but erosion problems may be very important in other points of the area.

OUR FIELDTRIP ITINERARY (Figure 5)

Travel North en route for the “El Paular” basin.

Observation of the basin general aspects and the glaciers setting.

Leave the bus at “Los Cotos” (1) mountain pass to walk headed for the maximum

advance moraines (2).

Then, walk along the glacier forms from the intramoraine “Laguna Chica” (3) to the

“Laguna Grande de Peñalara” (4).

Walk for a panorama at the Zabala refuge (5) and the rock glacier deposits (6).

Back to the bus.

Coffee at the skiing resort of Navacerrada.

If time and allows it, we’ll visit either the “Pepe Hernando” glacier (7) or the “Claveles”

and “Los Pájaros” (8 and 9)

We’ll trek through rough mountain terrain. Boots and warm clothing are indispensable.

Weather changes might be dramatic so the excursion will be always subject to changes.

71


Peñalara, 2430 m

Dos Hermanas

summit, 2380 m

Figure 5. Topographic map and fieldtrip

itinerary.

0 500 m

REFERENCES

ACASO, E.; CENTENO, J.D. y PEDRAZA, J. (1998): Nuevas aportaciones al modelo

evolutivo del glaciar de Peñalara (Sistema Central Español). Aportaciones a la V reunión

nacional de Geomorfología, Granada: 691-695.

CENTENO, J.D. (1983) Sintesis y evolución geomorfológica de la sierra de Guadarrama, Tesis

de Licenciatura, Inedita

CENTENO, J.D; PEDRAZA, J. DE y ORTEGA, L.I. (1983): Estudio geomorfológico,

clasificación del relieve de la sierra de Guadarrama y nuevas aportaciones sobre su morfología

glaciar. Bol. R. Soc. Española Hist. Nat. (Geol) 81 (3-4):153-171.

FRÄNZLE, O. (1959): Glaziale und periglaziale Formbildung im ostlichen Kastilischen

Scheidegebirge (Zentralspanien). Bonner Geographische Abdanlungen, Bonn, 80 pp.

[Traducción española de J. Sagredo en Est. Geogr. 39, 151: 203-231 y 152: 363-419 (1978)]

GINER, F. y COSSÍO, L. (1886) Excursión durante las vacaciones de verano de 1883, Boletín

de la Institución Libre de Enseñanza, nº 237: 384, nº 239: 31-32, nº 240: 95-96, nº 241: 111-

112, nº 242: 127-128, nº 243: 143-144, nº 159-160.

OBERMAIER, H. y CARANDELL, J. (1917): Los glaciares cuaternarios de la sierra de

Guadarrama. Trab. Del Mus. Nac. de Cienc. Nat. Serie Geol., nº 19, Madrid, 95 pp.

72


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001.

Scientific

Sessions

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Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 73-77

EVALUATION OF THE RUNOFF EROSION IN THE DRAINAGE

BASIN OF THE PUENTE ALTA RESERVOIR (SEGOVIA)

JOSÉ MARÍA BODOQUE DEL POZO

Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

SUMMARY

Runoff erosion in the Puente Alta watershed has been evaluated by means of both

direct and indirect (or empirical) methods. Regarding the first group, the quantification of the

reservoir's sediments, accumulated over forty years since the dam was built in 1955, has been

the basis for the evaluation. This information has subsequently been used to validate the

empirical methods and to obtain the sediment yield; in this latter case, a procedure that

combines the sediment delivery ratio (S.D.R.) concept and the Universal Soil Loss Equation

(USLE) has been carried out; besides, the Modified Universal Soil Loss Equation (MUSLE) has

been utilised. A Geographical Information System was built with each of the factors needed for

the evaluation of both equations; eventually they were implemented in the Idrisi 32 software.

STUDY AREA

The drainage basin of the Puente Alta reservoir is located in the north slope of the

Guadarrama Mountains (Spanish Central System, Segovia, Spain). It stores the water of the

Acebeda river, formerly used for the water supply of the city of Segovia. The watershed has an

area of twenty-two square kilometres, with the highest altitude at 2193 m and the lower at

1170m.

METHODOLOGY

When referring runoff erosion, we mean the evaluation of the soil loss in the rill-interrill

locations. Specifically, four procedures have been followed for the evaluation of the runoff

erosion, which can be classified either as direct or indirect.

Among the direct methods, the following were carried out: a) the assessment of the

sediment yield rate (Avendaño et al., 1994), by using the measurement of the sediments trapped

in the Puente Alta Reservoir during the period 1955-1995; b) the determination of erosion rates

from exposed roots, from the information supplied by the differential root’s rings growth pattern

when they are exposed by erosion (Carrara & Carroll, 1978), in order to check the data obtained

from the indirect methods.

The empirical models utilised have been the Universal Soil Loss Equation (USLE)

(Wischmeier & Smith, 1965) and the Modified Universal Soil Loss Equation (MUSLE)

(Williams & Berndt, 1977). A Geographic Information System, implemented in the Idrisi 32

software, was built with each of the factors needed for both evaluations.

The first equation has provided information about the gross erosion rates in t/ha/year

and it has allowed mapping those areas where the erosion processes act with different intensity;

besides, the sediment delivery ratio (S.D.R.) has been calculated (Avendaño et al., 1993). The

second equation has made possible to know the sediment yield in the watershed, on account of

the individual action of the rain amount with a volume of precipitation higher than the average

of the highest precipitation in twenty four hours, always referred to the 1955-1995 period; also,

a 'type' rainstorm defined by means of the average of all precipitation in twenty four hours in the

referred time period has been used in the assessment of sediment yield. Furthermore, its use has

allowed to locate and map the areas inside watershed that are source of sediments to the

reservoir (Figure 1).

74


Finally, it is important to emphasise that by means of the results obtained using the

direct methods, we have been able to validate the use of both experimental procedures, which

could be used in watersheds similar to that of Puente Alta.

EVALUATION OF THE RUNOFF

EROSION IN THE DRAINAGE BASIN OF

THE PUENTE ALTA RESERVOIR

(SEGOVIA).

Studied process

RILL-INTERRILL EROSION

Sediment yield

Gross erosion

Direct Method

(earth dam volume)

Comparison

Gross erosion*S.D.R.

M.U.S.LE

U.S.L.E

BIOINDICATORS

(Exposed roots)

Source areas of

sediments

Cartography

(Erosion grade)

Rate erosion

(mm/year)

Empirical method

validation

Integration

GIS

IDRISI 32

Comparison

Empirical methods

validation

Figure 1. Methodology

75


RESULTS

By using the USLE equation, the obtained average gross erosion for the Puente Alta

watershed is 7/t/ha/year; however, its spatial distribution along the basin is heterogeneous, as a

function of the physiographic conditions, so that the specific results for different land use

classes are: dense forest, 0.4 t/ha/year; grazing land, 0.5 t/ha/year; medium dense forest, 7

t/ha/year; scrub land, 15 t/ha/year; negligible cover, 70 t/ha/year (Figure 2A, 2B)

The sediment yield’s results obtained for the Puente Alta watershed has been: 71

t/km 2 .year, by means of the measure of earth dam volume in Puente Alta Reservoir; 69

t/km 2 .year, using the Universal Soil Loss Equation (USLE) corrected with the sediment delivery

ratio (S.D.R.) coefficient. The deviation of the calculated sediment yield rates by means of an

indirect method is lower than 3 %, with regard the data obtained using the quantification of the

sediments trapped in the Puente Alta Reservoir.

Similarly, the development of the Modified Universal Soil Loss Equation (MUSLE) has

allowed to determine those areas inside the watershed which are potential sources of sediment to

the Puente Alta Reservoir. As well, it has been carried out an estimation of the total sediments

delivered to the reservoir, on account of every downpour during the period 1955-1995, whose

sum is 27,628 tons. This value let us define a sediment yield rate of 84 t/km 2 .year. (Figure 3).

Reservoir and Acebeda river

Dense forest

Medium dense forest

Grazing land

Scrubland

Negigible cover

Vegetati

Soil loss

(t/ha/año)

2200 0

2200 4400 m

Figure2. A) Vegetation cover map; B) Average annual soil loss (t/ha/year) by gross erosion for the drainage basin

to the Puente Alta Reservoir.

76


Reservoir

Reservoir

Reservoir

Septiembre de 1965

(1166 tons)

Septiembre de 1972

(956 tons)

Septiembre de 1976

(879 tons)

Reservoir

Reservoir

Reservoir

Junio de 1977

(607 tons)

Julio de 1970

(465 tons)

Media de las máximas

(118tons)

2500 0

2500 5000 m

Figure 3. Sediment delivery (in tons) in the five downpour with the highest precipitation volume during the period 1965-

1980; also, for a downpour defined by means of the average of the highest precipitation in twenty-four hours during that

same period.

77


REFERENCES

ALLUÉ, M. (en prensa). Mapa Forestal de Segovia, Escala 1:50000. En: Mapa Forestal de

España (J. Sánchez de la Torre, ed.). Dirección General para la Conservación de la Naturaleza

(DGONA), Ministerio de Agricultura Pesca y Alimentación, Madrid.

AVENDAÑO, C.; CALVO, J.P.; COBO, R. & Sanz, M.E. (1993). “La modelización

matemática, ajuste y contraste del coeficiente de entrega de sedimentos a los embalses.

Aplicación al cálculo de la erosión de cuencas fluviales”. Centro de Estudios y Experimentación

de Obras Públicas (CEDEX), Madrid, 1, 210 pp.

AVENDAÑO, C.; CALVO, J.P.; COBO, R. & Sanz, M.E. (1994). “La modelización

matemática, ajuste y contraste del coeficiente de entrega de sedimentos a los embalses.

Aplicación al cálculo de la erosión de cuencas fluviales”. Centro de Estudios y Experimentación

de Obras Públicas (CEDEX), Madrid, 2, 40 pp.

CARRARA, P.E.; CARROLL, T.R., (1979). “The Determination of Erosion Rates from

Exposed Roots in the Piceance Basin, Colorado”. Earth Surface Processes, 4, 307-317 pp.

WILLIAMS, J.R. and BERNDT, H. D. (1977). “Sediment yield prediction based on watershed

hidrology”. Trans. ASAE 20: 1100-1104 pp.

WISCHMEIER, W.H. & SMITH, D.D. (1965). “Predicting rainfall - erosion losses from

cropland east of the Rocky Mountains”. Agr. Handbook No. 282, USDA, Washington, D.C.

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Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 78-81

TERRAIN ANALYSIS IN COASTAL EROSION AND FLUVIAL

MORPHOMETRY

GARROTE, J.

Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

SUMMARY

Two main research areas are presented on this paper, related by the nexus of the terrain

analysis and the use of GIS.

In the coastal field, this analysis will take us to the establishment of erosion and

sedimentation areas that allow to infer morphodynamic patterns. On fluvial studies, terrain

analysis and GIS enables the calculation of morphometric parameters in order to interpret the

tectonic outline of the study area.

INTRODUCTION

The main topic of my current research is the application of terrain analysis, taking as a

tool Terrain Digital Models (DTM) and GIS (Systems of Geographical Information), for the

handling and calculation of morphological data. They are used in two different ways and

environments, coastal erosion and terrain morphometrical anlysis.

Both research fields have been developed in collaboration with Dr. Guillermina Garzón,

and D. Jesús Page collaborated also in the coastal study.

COASTAL EROSION

The study area is located on the Cantabrian sea, between the towns of Comillas and San

Vicente de la Barquera (Cantabria). The beach of Oyambre (Jerra according to the geologic map

1:50.000) with 3 Km. of longitude is developed on the turbidites of the Eocene and Oligocene,

between two more resistant calcareous capes. The ria of the Rabia, constituted in fact by those

of La Rabia and of El Capitan drains at their oriental side. The protection of the W and NW

dominant winds develops an orientation NE in the beach, and a litoral drift towards the E, that

favors the evolution of a sandy spit advancing towards the ría outlet. The ría has a drainage

basin of about 40 Km 2 , but at the present time its solid discharge can be considered practically

absent. To it largely contributes the presence of two man-made dikes that close both creeks, and

that limit the tidal expansion almost in two thirds of their extension. The current feeding of

these Cantabrian beaches is basically autochthonous (Hernández Pacheco and Asensio Amor,

1966). In fact the beach of Oyambre is supplied in this oriental area of the cliff retreat, here

partly formed by a 70000 year-old risen beach (Garzón et al.,).

The following methodology for data collection and management has been repeated in a

systematic way for each campaign (Fig. 1). The head of the profiles, was located in stable points

to generate a profiles net as much perpendicular as possible to the beach and with an

homogeneous separation. 21 topographical profiles were surveyed along 6 field campaigns.

Digital terrain models where carried out from the data to determine the erosion-sedimentation

areas between each campaign and the volume of removed material. Field data interpolation was

performed with the method of Krigging by means of Surfer.

These terrain digital models were implemented in a GIS (Idrisi 32) program and the

areas of beach erosion-sedimentation were established. The removed sands volume was

calculated for each cell of our MDT in order to establish the flow patterns or morphodynamic

trends in the beach.

The interpretation of the obtained results in an annual scale, from April 2000 to March

2001, points out the existence of two differentiated areas (Fig. 2). The West area is dominated

79


y the erosion. It reaches it maximal under a rip-rap seawall built to protect the cliff erosion,

and in it surroundings, what reflects the negative interference that these human works cause on

the coastal dynamics. There is a net lost of material in this area, except for some patches of

scarce sedimentation conditioned by the detachments of cliff material.

Figure 1. Methodological outline

Transport occurs toward the East side of the beach, in which the sedimentation prevails.

Significant deposition occurs from the central part of the beach on. Some areas of erosion on the

East part of the beach could have their origin in the dismantlement of an incipient berm present

in April.

Figure 2. Erosion-sedimentation areas distribution in the period April 2000-March 2001

80


The conditioning factor for this accretion is possibly the material produced by the ría,

which would begin its coastal cycle again in this area. Inside the ría, the accumulation that takes

place in the sandbank, represents the deposit of the materials that the low tide is not able to

transport, due to the ría outlet constriction. This is the result of anthropic changes in the ría that

generates this dead space due to the fact that the energy for transportation is larger on the high

tide.

FLUVIAL MORPHOMETRY AND TERRAIN ANALYSIS

The study area is the oriental part of the Tajo Basin. It consists of an extensional

depression limited by important topographycal feature such as the Central System to the North,

Montes de Toledo to the South and Sierra of Altomira to the East. The basin is very much

conditioned by the tectonic of the area, as it is affected by a series of faults and cortical flexures

(Giner and de Vicente, 1995 and Sánchez Serrano, 2000), that condition rivers morphology and

disposition inside the basin, as well as their morphometric parameters (Garrote et al.,2000 and

Garrote and Garzón, 2001).

The followed research line is based in the calculation of land and fluvial morphometric

parameters in order to relate them to stresses affecting the study area, as well as the generated

structures. On one hand, calculation of fluvial morphometric parameters such as the gradient

index of the main fluvial courses of the basin, allowed us the characterization of the main

structures that affected them at basin scale. Figure 3 shows the results obtained after the gradient

index analysis (Garrote et al., 2000), according to the methodology of Hack() and Masana().

LINES OF SAME GRADIENT INDEX

LINEAMENTS INTERPRETED

HIGHTECTONIC ACTIVITY BOUNDS

Figure 3. Structural linecements interprete from the map of gradient index.

On a further step, some topographical parameters of the basin have been calculated, like

a roughness map, and from it the lineaments were interpreted, which mainly coincided in

direction with those calculated by means of the gradient index. Other new lineaments were

established, that, although not having a direct reflection on the fluvial courses, could be clearly

defined from the roughness map, as shown in figure 4. The followed methodology has ben

developed in Garrote and Garzon (2001) according the previous work of Sánchez Serrano et al.

(1998) or Sánchez Serrano (2000).

On comparing the figures 3 and 4, a similarity of results can be established, from which

we can confirm the utility of these studies in the determination of the lineaments and stress field

81


that condition the basin. It also can be stated, that not all the same lineaments can be interpreted

from both maps, but both methods are supplemented and in this way enables as to define in a

more precise way the group of structural lineaments and cortical flexures that control the

development of the basin of the Tajo River. It opens us a new way to calculate other

morphometric parameters that might contribute with new data and at the same time supplement

those already established.

324375

4339625

533125

Figure 4. Principal structural lineaments as defined from the roughness map

REFERENCES

GARZÓN, G., ALONSO, A., TORRES, T. y LLAMAS, J. (1995). “Edad de las playas colgadas

y de las turberas de Oyambre y Merón (Cantabria)”.Geogaceta. 20 (2). 498-501 pp.

GARROTE, J., FERNÁNDEZ, P. y GARZÓN, G. (2000). “Parámetros morfométricos en la red

de drenaje y sus implicaciones estructurales en la cuenca del Tajo”. VI Congreso

Geomorfológico. Madrid.

GARROTE, J. y GARZÓN, G. (2001). “Respuesta morfológica a los esfuerzos recientes en el

sector oriental de la depresión del Tajo”. V Iberian Quaternary Meeting. Lisboa.

GINER, J.L. y DE VICENTE, G. (1995). “Crisis tectónicas recientes en el sector central de la

cuenca de Madrid”. In Reconstrucción de paleoambientes y cambios climáticos durante el

Cuaternario. 141-162 pp.

HACK, J.T. (1973). “Stream-profile analysis and stream-gradient index”. Jour. Research U.S.

Geol. Survey. Vol. 1 Num. 4. 421-429 pp.

HERNÁNDEZ-PACHECO, F. y ASENSIO, I. (1966). “Fisiografía y sedimentología de la playa

y ría de San Vicente de la Barquera (Santander)”. Estudios Geológicos. 22. 1-23 pp.

MASANA, E. (1994). “El análisis de la red fluvial en el estudio de la neotectónica en las

cadenas costeras catalanas”. Geomorfología en España. 29-41 pp.

SÁNCHEZ SERRANO, F., TEJERO, R. y BERGAMIN, J.F. (1998). “Análisis de la

variabilidad del relieve a partir de modelos digitales del terreno”. Rev. Soc. Geol. España. 11 (1-

2). 139-149 pp.

SANCHEZ SERRANO, F. (2000). “Análisis de la topografía y deformaciones recientes en el

centro de la Península Ibérica”. Tesis Doctoral. 202 p.

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Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 82-89

NATURALLY OCCURRING ARSENIC IN GROUNDWATERS OF

THE MADRID TERTIARY DETRITAL AQUIFER (SPAIN).

HERNÁNDEZ, M.E.

Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

ABSTRACT

High arsenic concentrations (up to 91 µg/L) have been measured in groundwaters from

the Madrid Tertiary Detrital Aquifer. These arsenic contamination phenomena in groundwaters

of the research area respond to natural causes. High arsenic levels appear in groundwaters

with high residence time, that is, they occur in groundwaters characterized by a) high pH values

(values between 8,3 and 9) and the resulting occurrence of CO =

3 anion, b) high sodium

concentrations, and c) low calcium and magnesium concentrations. Furthermore, the

groundwaters which display high concentrations of As show high levels of V, F and B. It´s very

interesting to note that the stable forms of these four constituents in aqueous systems are

anionic complexes. Consequently, it´s really possible that the concentration and mobility of As

could be controlled by anion exchange processes frequently related to evolved groundwaters

characterized by high pH values and tendency to softening. Moreover, arsenic release could be

affected by fluctuating water levels. Nevertheless, although the results of the preliminary

investigations do not confirm this hypothesis, it is not rejected.

INTRODUCTION

The Madrid Tertiary Detrital Aquifer is one of the largest and most important aquifers

in all of Spain. This aquifer was declared a strategic resource for Madrid´s drinking water

supply in the Hydrologic Plan of Tagus Basin (Confederación Hidrográfica del Tajo, 1997).

Previous studies carried out by the the author of this paper revealed high concentrations of

arsenic in some water supply wells located in Madrid city (Hernández García, 1999). The

arsenic concentrations exceeded the maximum contaminant level established by the current

Spanish law for drinking water (50 µg/L). Taking into consideration the high toxicity of this

water constituent and the role of this sedimentary aquifer for the supply of the Madrid region, it

seems necessary to undertake a specific study to assess the magnitude of the problem and to

identify the arsenic sources. Furthermore, in December 2003 the European Directive 98/93/CE

related to the water quality for human consumption will come into effect in Spain. This

Directive will establish a maximum contaminant level for arsenic in drinking water of 10 µg/L;

consequently, the number of water supply wells affected by excessive concentrations of arsenic

will be increased substantially.

OBJECTIVES

The study is focused on the Madrid Tertiary Detrital Aquifer. Four main objectives can

be distinguished: a) to research on the spatial distribution of arsenic in the groundwaters; b) to

assess the variability of the arsenic concentrations according to the groundwaters residence

time; c) to evaluate the correlation between the naturally occurrence of arsenic in groundwaters

and the aquifer mineralogy; d) to research on the most important mechanisms or processes that

control the incorporation of arsenic into the groundwaters.

METHODOLOGY OF RESEARCH

The methodology of research covered the next steps:

83


• Detailed bibliographic compilation related to the geology, the hydrogeology and the

hydrochemistry of the Madrid Tertiary Detrital Aquifer. Detailed bibliographic compilation

about other cases in the whole world of arsenic contamination in groundwaters.

• Detailed water well inventory of the Madrid Tertiary Detrital Aquifer.

• Description and sampling of the soil debris obtained during the execution of water wells to

perform subsequent geochemical analysis in the laboratory of the Geological Survey of

Spain (Instituto Geológico y Minero de España, IGME). 166 samples were obtained from 7

wells in order to analyse: Ag, As, Sb, Ba, Be, Cd, Ce, Co, Cr, Cu, La, Mn, Mo, Nb, Ni, P,

Pb, Se, V, Y, W, Zn, Fe, Al.

• Groundwater sampling to carry out field analysis of unstable parameters (temperature,

electrical conductivity, pH, redox potential and dissolved oxygen) and to perform

subsequent chemical analysis in the laboratory of IGME. 61 samples were obtained in order

to analyse TDS, organic matter, CO 3 = , HCO 3 - , SO 4 = , Cl - , NO 3 - , NO 2 - , NH 4 + , SiO 2 , PO 4 3- ,

Ca 2+ , Na + , Mg 2+ , K + , Al, Ag, As, Sb, Br, Ba, B, Cd, Co, Cr, Cu, Fe, Mn, Hg, Ni, Pb, Se, Sr,

Tl, V, F, Li, Zn. Sampling and preservation in the field were performed by the author

following a specific methodology (UNE-EN ISO 5667-3, 1996; Scalf et al., 1981). The

water was passed trough a 0.45 µm filter before analysis. Water samples were collected in

1L pre-washed polyethylene bottles. Water samples for the determination of cations and

heavy metals were preserved in the field with HNO 3 suprapure. Water samples for the

determination of anions and silica were preserved with refrigeration (4ºC). Table 1 shows

an extract from the analytic results.

• Data processing, data interpretation and securing of the objectives.

THE MADRID AQUIFER

Four main hydrological units can be distinguished in the Madrid region (see figure 1):

a) Central Range (2,500 km 2 ). It is formed mainly by schists and granitic rocks. The

permeability is low; b) Cretaceous limestone (200 km 2 ). They form isolated aquifers. The only

relevant is the one located near Torrelaguna, but its size (200 km 2 ) is small and its connection to

the Jarama river is high; c) Tertiary arkosic sands (2,500 km 2 ). They form the Madrid Tertiary

Detrital Aquifer. Its permeability is medium to low and its connected to the river is poor. The

available fresh ground water stored is at least 20,000 hm 3 . It may constitute the key element for

the future Madrid water supply (Llamas et al. 1996); d) Tertiary evaporite rocks (2,300 km 2 ).

Their permeability is low and the ground water salinity is high.

The sedimentary basin of Madrid is a large tectonic depression (6,000 km 2 ) filled with

continental deposits of Tertiary age. Sediments are detrital (arkosic sands, silts and clays) in the

vicinity of the surrounding mountains. Evaporites and limestones occur towards the centre of

the basin. Between these two types of sediments there is a transition facies, where is common to

find clay, marl, limestone and gypsum. The Madrid Tertiary Detrital Aquifer system is

constituted mainly by quasihorizontal lenses of arkosic sands surrounded by clay and silt. These

deposits are typical of a continental sedimentation of alluvial fans in a dry and warm climate

(López Vera, 1977). The thickness of the Tertiary deposits is usually greater then 1,000 m and

may be up to more than 3,000 m in the deepest parts. Estimated recharge of this aquifer is about

100-200 hm 3 /year. The recharge is mainly produced by infiltration of rainwater falling directly

on the Tertiary interfluves. The discharge occurs at the bottom of the valleys. Local,

intermediate and regional flow systems.

84


Table 1. Extract from the analytic results of groundwaters in the Madrid Tertiary Detrital Aquifer (Spain).

MUNICIPAL TERM REGION WELL TEMP. pH ELEC. COND. O 2 Cl - 2-

SO 4

-

HCO 3

2-

CO 3

-

NO 3 Na + Mg 2+ Ca 2+ K + As V F B Fe Mn

DEPTH (m) (ºC) (µS/cm) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L)

Humanes Madrid 119 19.2 7.61 825 7 93 88 202 0 88 144 15 33 5


according to Toth’s scheme are apparently present. On a local scale hydraulic conductivity

changes sharply in a random fashion, but on a regional scale statistical studies have shown a

pattern in these changes according to the geology. As a first approximation, a homogeneous,

anisotropic, hydraulic conductivity is assumed. Horizontal conductivity is about 0.15 m/day;

vertical conductivity is from 100 to 1,000 times smaller (Martínez Alfaro, 1980).

The public water supply company called Canal de Isabel II (CYII) is responsible for the

water supply of 95% of the Madrid region population (about 5 million inhabitants). The great

majority of the water supplied by CYII come from fifteen surface reservoirs with a total

capacity of 960 hm 3 (see figure 1). The well fields of CYII are only exploited during drought

periods.

Figure 1. Schematic map of the Madrid region geology and the water supply system (Llamas et al., 1996).

HIDROGEOCHEMISTRY. MAIN FACTORS THAT CONTROL THE MOBILITY OF

As IN THESE GROUNDWATERS.

The predominant groundwater types in the Tertiary arkosic sands aquifer are a) Ca 2+ -

HCO - 3 , and b) Na + -HCO - 3 . The calcium bicarbonate type groundwaters represent the recharge

waters in detrital facies with low groundwater residence time. This type of groundwaters can be

captured with shallow wells in the interfluve zones. The sodium bicarbonate type groundwaters

represent high residence time waters within detrital facies. This type of groundwaters can be

captured: a) with shallow and deep wells in the discharge areas, and b) with deep wells (>400

meters depth, approximately) in the interfluve zones. The CO =

3 anion is present since the

hydrogen ion (H + ) undergoes exchange and/or takes part in silicate hydrolisis reactions. Because

of the decrease in the hydrogen ion concentration, pH values tend to increase. In general, pH

values increase gradually from recharge areas (values around 7) to descharge areas (values

between 8,3 and 9). Moreover, there is a tendency toward softening of groundwaters from the

recharge areas to the descharge areas: sodium concentrations tend to increase with the

groundwater flow in parallel with the decrease in calcium and magnesium concentrations,

4


maybe because of divalent/univalent exchange processes (Fernández Uría et al., 1985) and/or

clay minerals neoformation processes (Coleto, 1994).

Likewise, a gradually increase of arsenic concentrations from recharge areas (values


0,1

Figure 2. Scatter plot of total arsenic versus pH

(correlation coefficient: +0.5). Madrid Tertiary Detritic

Aquifer.

As (mg/L)

0,01

6 7 8 9 10

pH

Figure 3. Scatter plot of total arsenic versus cation

exchange ratio (correlation coefficient: +0.4). Madrid

Tertiary Detritic Aquifer.

(rNa + +rK + )/(rCa 2+ +rMg 2+ )

1000

100

10

1

0,1

0,01

0,001 0,01 0,1 1

As (mg/L)

1000

Figure 4. Scatter plot of total arsenic versus depth of

the well (correlation coefficient: -0.1). Madrid Tertiary

Detritic Aquifer.

Well Depth (m)

100

10

0,01 0,1

As (mg/L)

0,1

Figure 5. Scatter plot of total arsenic versus vanadium

(correlation coefficient: +0.6 ). Madrid Tertiary Detritic

Aquifer.

V (mg/L)

0,01

0,001

0,001 0,01 0,1 1

As (mg/L)

6


ACKNOWLEDGEMENTS

This paper has been prepared in the framework of a research grant given by the

Department of Education and Culture of the Community of Madrid (Consejería de Educación y

Cultura de la Comunidad de Madrid) and of a research contract with the Geological Survey of

Spain (Instituto Geológico y Minero de España, IGME).

REFERENCES

BOYLE, D.R. (1992). “Effects of base exchange softening of fluoride uptake in groundwaters

of the Moncton Sub-Basin, New Brunswick, Canada”. In: Y.K. Kharaka and A.S. Maest (eds.),

Proceedings of the 7 th International Symposium on Water-Rock Interaction, Park City, Utah.

A.A. Balkema, Rotterdam: 771-774.

BOYLE, D.R.; TURNER, R.J.W.; HALL, G.E.M. (1998). “Anomalous arsenic concentrations

in groundwaters of an island community, Bowen Island, British Columbia”. Environmental

Geochemistry and Health. Vol. 20: 199-212.

COLETO FIAÑO (1994). “Modelización de la evolución química de las aguas subterráneas en

las Facies de Transición de la Cuenca de Madrid”. Tesis Doctoral. Universidad Complutense de

Madrid. Madrid: 1-200 (aprox.).

CONFEDERACIÓN HIDROGRÁFICA DEL TAJO (1997). “Plan Hidrológico de la Cuenca

del Tajo. Normas”. Ministerio de Medio Ambiente. Dirección General de Obras Hidráulicas y

Calidad de Aguas: 1-135. Difusión limitada.

FERNÁNDEZ URÍA, A.J.; FONTES, J.C.; HERRÁEZ, I. ; LLAMAS, M.R.; RUBIO, P.L.

(1985). “Tridimensional groundwater chemical and isotopic variations as related to the Madrid

aquifer flow system”. Estudios Geológicos. Nº 41: 229-236.

FROST, R.R.; GRIFFIN, R.A. (1977). “Effect of pH on adsorption of arsenic and selenium

from landfill leachate by clay minerals”. Soil Science Society of America Journal. Vol. 41. Nº

1: 53-56.

HEM, J.D. (1989). “Study and interpretation of the chemical characteristics of natural waters”.

U.S. Geological Survey. Water-Supply Paper 2254. Washington: 1-263.

HERNÁNDEZ GARCÍA, Mª E. (1999). “Estudio hidrogeológico, hidrogeoquímico y de

contaminación del Acuífero Detrítico Terciario en las áreas urbana y periurbana de la Villa de

Madrid”. Tesis Doctoral. Facultad de Ciencias Geológicas. Universidad Complutense de

Madrid. Madrid: 1-500 (aprox.).

IGME (1989). “Mineralogía de arcillas. Información complementaria al Mapa Geológico de

España 1/50.000, Hoja de Madrid (559)”. Instituto Geológico y Minero de España. Ministerio

de Industria y Energía. Madrid.

LLAMAS, M.R., VILLARROYA, F.; HERNÁNDEZ GARCÍA, Mª E. (1996). “Causes and

Effects of Water Restrictions in Madrid during the Drought of 1990/93”. Hydrology and

Hydrogeology of Urban and Urbanizing Areas. 1996 AIH Annual Meeting. American Institute

of Hydrology. Boston, Massachusetts. April, 21-26: WQD10-19.

LÓPEZ VERA, F. (1977). “Modelo de sedimentación de los materiales detríticos de la fosa de

Madrid”. XXXII Congreso Luso-Español para el Progreso de la Ciencia. Vol. 42, nº 4: 257-266.

MARTÍNEZ ALFARO, P.E. (1980). “Un primer análisis de la permeabilidad y el grado de

anisotropía de los materiales detríticos de la Fosa del Tajo”. Boletín Geológico y Minero. Vol.

91: 645-648.

PAUL, B.K.; DE, S. (2000). “Arsenic poisoning in Bangladesh: a geographic analysis”. Journal

of the American Water Resources Association. Vol. 36, Nº 4: 799-809.

PIERCE, M.L.; MOORE, C.B. (1982). “Adsorption of arsenite and arsenate on amorphous iron

hydroxide”. Water Research, 16: 1247-1253.

SCALF, M.R.; McNABB, J.F.; DUNLAP, W.J.; COSBY, R.L.; FRYBERGER, J. (1981).

“Manual of groundwater sampling procedures”. NWWA/EPA Series. NWWA. USA: 1-93.

7


UNE-EN ISO 5667-3 (1996). “Calidad del agua. Muestreo. Parte 3: Guía para la conservación y

la manipulación de muestras”. Versión oficial, en español, de la Norma Europea EN-ISO 5667-

3 de fecha diciembre de 1995, que a su vez adopta íntegramente la Norma Internacional ISO

5667-3:1994. AENOR: 1-39.

8


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 90-94

THE ORIGIN AND SIGNIFICANCE OF PHOSPHORUS IN A

PERIURBAN, ALLUVIAL AQUIFER

HIMI, Y. 1 AND ALVAREZ-COBELAS, M. 2

1 Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

2 Centro de Ciencias Medioambientales (CSIC), Serrano 115 dpdo., E-28006 Madrid, Spain

SUMMARY

Phosphorus is the key element in the eutrophication of freshwaters. This study reports

the origin, distribution and significance of phosphorus in diffrent aquatic environments of an

alluvial catchment close to Madrid (Central Spain). Originally as a point-source pollution, local

water fluxes partly drive phosphorus dynamics and its distribution within rivers, lakes and the

aquifer. However, other in-site processes, such as the production of organic matter in lakes and

rivers and the diffuse pollution of P-rich soils, must be considered to account for phosphorus

dynamics in this complex, anthrophogenically-forced landscape.

INTRODUCTION

Nitrate is the preferred freshwater nutrient whose distribution is traced in groundwaters

(Fosters et al., 1986). The reason is the growing concern on the noxius effects of high levels of

nitrate on human health when groundwaters are used up for human consumption (Mirvish,

1991). This has been a research topic for almost twenty years worldwide (Thornton et al., 1999),

arising from the dramatic increase in global fertilizer application in modern agriculture.

Phosphorus, however, is considered the main limiting nutrient of primary productivity in

freshwaters (Vollenweider, 1968), and so its study has been promoted to tackle the

eutrophication problem that affects many surficial water bodies throughout the world (Harper,

1992). Notwithstanding this, phosphorus has seldomly been assessed in groundwater studies up

to date, and the few studies available (e.g. Hidalgo et al., 1997) only report scattered values

without any explanation on either origin, dynamics or relationships with any groundwater and

surficial component of the catchment. This is surprising in view of the many extant, seepage

lakes occurring in catchments which rely mostly on groundwater feeding (Winter, 1999).

Here our aim is to report a study on total phosphorus distribution in a periurban alluvial

aquifer close to Madrid (Spain). We will describe phosphorus concentrations in rivers, gravelpit

lakes and the alluvial aquifer and attempt to relate them with the prevailing water fluxes in

the area.

STUDY SITE

The Jarama alluvial environment is located SE Madrid (Fig. 1). It is now considered a

regional Natural Park (see further information in Díez-Olazábal, 1998, www.elsoto.org,

medioambiente.comadrid.es). The alluvial plain of the Jarama river and its three main tributaries

cover almost 150 km 2 . Pollution of both Madrid city (roughly 3.5 million people with partially

treated wastewaters) and the river Henares industrial belt (roughly 0.4 million people along with

many industries, whose pollution is not entirely treated either) enters the area. Two big and two

much smaller wastewater treatment plants, lacking tertiary treatment, are operating in the area.

More than one hundred gravel-pits have emerged mostly in the lower terrace of the river as a

result of gravel mining in the last thirty years (Roblas and García-Avilés, 1997). Geological and

hydrogeological descriptions of the area can be found in Peláez et al. (1971), Rebollo (1973)

and López-Vera (1977).

9


MATERIALS AND METHODS

Seventeen stagnant water bodies spread throughout the alluvial aquifer were sampled in

1998 and 1999 using standard limnological techniques (Wetzel and Likens, 1991). Total

phosphorus (TP hereafter) was measured in their vertical column seasonally following the

Murphy & Riley method (APHA, 1989). In November 2000, 45 wells were sampled for

phosphorus recording hydraulic head simultaneously (Fig. 2). Data for TP in rivers come from

the Spanish Tajo Water Authority and cover the 1994-1997 hydrological period monthly. We

have carried out some interspersed sampling in river waters since then and found no significant

deviations of total phosphorus from average behaviour of that period.

RESULTS AND DISCUSSION

Water level isopleths in the alluvial catchment suggest that rivers are water importers in

most sites (Fig. 3), and this input comes mostly from groundwaters. Depending upon their

relative position from such isopleths and their location in the valley, gravel-pit lakes may gain

and/or loose water from nearby rivers and the alluvial aquifer. TP ranges 0.56 ± 0.68 (average ±

1 SD), 1.69 ± 3.07 and 3.55 ± 1.91 mg/L for stagnant waterbodies, alluvial groundwaters and

the river Jarama, respectively. A Kruskal-Wallis test suggests that the three data sets of TP

contents vary markedly from each other (p < 0.05), that of groundwaters showing a very high

skewness to the left (Fig. 4). TP content of the alluvial aquifer shows three areas of peak values,

two of them in the vicinity of big wastewater treatment plants and the third one underlying an

irrigation reservoir located downstream of the joint of the Jarama with the organic loads coming

from Madrid city (Fig. 5).

Total Phosphorus (mg/L)

15

12

9

6

3

0

Gravel-pits Jarama river Groundwaters

Figure 5. Box-Whisker plots of total phosphorus content in the rivers, gravel-pit lakes and the

alluvial aquifer.

TP content in lakes is related to that of groundwaters in the following way:

TP lakes = 0.46 * (TP groundwaters ) 0.66 R 2 = 0.46 (p


elt and it is transported to the alluvial catchment through wastewater treatment plants (lacking

tertiary treatment). Despite the hydrologically gaining nature of the rivers, some phosphorus

enters the groundwater aquifer from streams, but the influence of rivers is limited by the

distance to both the sites of the aquifer and the gravel-pit lakes, i.e. the higher the distance the

lower the impact.

This study reveals the close coupling of TP dynamics in a complex hydrologic arena.

TP is primarily produced by nearby cities and factories, and it enters the Regional Park through

rivers from wastewater treatment plants. Then, if a given lake is close to a river, its TP content

arises from both the river and the aquifer, whereas if such a lake is located far away from the

river, then its TP is supplied by the aquifer. However, these results do not account for the whole

variability observed in gravel-pit TP. There are still two further sources of TP. First, in the

southern part of the catchment phosphorus-rich soils contribute TP to lakes via diffuse pollution.

Second, since lakes have no surficial outlet most organic matter (and hence organic phosphorus)

that they produce settles down and remains there, adding up to the phosphorus content of

surficial sediments, thus increasing phosphorus content in the lake through a positive feed-back

mechanism (Sánchez-Carrillo and Alvarez-Cobelas, 2001).

REFERENCES

APHA, (1989). “Standard Methods for the Examination of Waters and Wastewaters”. 17th

edition. Washington D.C.

DÍEZ-OLAZÁBAL, P. (Ed.) (1998). “Parque Regional del Sureste de la Comunidad de

Madrid”. Federación de Amigos de la Tierra. Madrid. 155 pp.

FOSTERS, S.S., BRIDGE, L.R., GEAK, A.K., LAWRENCE, A.R. Y PARKER, J.H. (1986).

“The groundwater nitrate problem: a summary of research on the impact of agricultural land use

practices on groundwater quality between 1976 and 1985”. Hydrological Report of British

Geological Survey, 86/2.

HARPER, D. (1992). “Eutrophication of Freshwaters”. Chapman and Hall. London. 327 pp.

HIDALGO, M.C., CRUZ-SANJULIÁN, J.J. Y AGUSTÍN, C. (1997). “Contaminación difusa

en un acuífero detrítico debida al uso de fertilizantes y plaguicidas (Depresión de Baza,

Granada)”. Hidrogeología y Recursos Hidráulicos, 13: 73-96.

LÓPEZ-VERA, F. (1977). “Hidrogeología regional de la cuenca del río Jarama en los

alrededores de Madrid”. Memoria del Instituto Geológico y Minero de España, 91: 1-227 +

planos.

MIRVISH, S.S. (1991). “The significance for human health of nitrate, nitrite and N-nitroso

compounds”. In: Nitrate contamination (I. Bogárdi y R.D. Kuzelka, eds.), 253-266, Springer

Verlag. Berlin.

PELÁEZ, J.R., PÉREZ-GONZÁLEZ, A., VILAS, L. Y ÁGUEDA, J.A. (1971). “Características

hidrogeológicas del Cuaternario del río Jarama”. Actas del I Congreso Hispano-Luso-

Americano de Geología Económica, Sección de Hidrogeología: 513-526.

REBOLLO, L. 1973. Estudio hidrogeológico del Cuaternario en la cuenca del río Jarama.

Tesina de Licenciatura. Facultad de Geología. Universidad Complutense. Madrid. 52 pp +

anexos.

ROBLAS, N. Y GARCÍA-AVILÉS, J. (1997). “Valoración ambiental y caracterización de los

sistemas acuáticos leníticos del Parque Regional en torno a los ejes de los cursos bajos de los

ríos Manzanares y Jarama”. Documentos nº 24. Centro de Investigación Ambientales de la

Comunidad de Madrid. Consejería de Medio Ambiente y Desarrollo Regional. 128 pp.

SÁNCHEZ-CARRILLO, S. AND ALVAREZ-COBELAS, M. (2001). “Nutrient dynamics and

eutrophication patterns in a semiarid wetland: the effects of fluctuating hydrology”. Water, Air and

Soil Pollution 127: 12-27.

THORNTON, J.A., RAST,W., HOLLAND, M.M., JOLANKAI, G. AND RYDING, S.O.

(Eds.) (1999). “Assessment and control of nonpoint source pollution of aquatic ecosystems Man

and the Biosphere Series, 23. Unesco. Paris.

VOLLENWEIDER, R.A. (1968). “Scientific fundamentals of the eutrophication of lakes and

flowing waters, with particular reference to nitrogen and phosphorus as factors in

eutrophication”. OECD, París. 250 pp.

WETZEL, R.G. & LIKENS, G. (1991). “Limnological analyses”. Springer Verlag. New York.

11


WINTER, T.C. (1999). “Relation of streams, lakes, and wetlands to groundwater flow systems”.

Hydrogeology Journal 7: 28-45.

12


Henares

River

Madrid

2

1

3

Manzanares

River

4

17

9 10

5 7 6

8

11

Gózquez

Dam

Jarama

Channel

Jarama

River

12

13

14

0 5 10 km km

: Exploitation of arid

: Military instalación of " Marañosa"

: Landfill of "Valdemingómez"

: Dump of industrial residuals

: Deposits of hydrocarbons

16

15

0 5 10 km km

: Well

: Wastewater treatment plants (WWTP)

: Gravel-pit lakes

Figure 1. Site location. The main anthropogenic impacts shown. Figure 2.

Sampling sites in the Jarama alluvial catchment.

13


554

November 2000

552

554 556

November 2000

550

548

546

544

542

540

538

536

534

532

530

528

526

524

522

520

518

516

510

514

512

TP (mg /L)

508

12

10

508

504

8

506

502

6

504

500

4

498

496

492

494

504

496 500 502

496

: Ground-water flow line

: Line of equal hydraulic head

2

0

km

0 5 10km

Figure 3. November 2000 isopleths of water level in the Jarama alluvial Catchment. Figure 4.

November 2000 isopleths of total phosphorus content in the Jarama alluvial atchment.

14


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 95-101

HYDROGEOLOGICAL AND HYDROCHEMICAL STUDY OF

LOZOYA RIVER HIGH CATCHMENT (MADRID, SPAIN)

LÓPEZ BAHUT, M. T. 1 ; DE LA LOSA ROMÁN, A. 1 AND

REDONDO ARROYO, C. 1

1 Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

ABSTRACT

This work brings together the researches that are being carried out in the High Valley

of Lozoya. The main points of these researches are the study of the hydrogeological behaviour

in the area by means of a precipitation-runoff model; the surface water and groundwater

chemical quality; and the potential pollution sources. These works are based on the research

project LOWRGREP (Landscape-use Optimization With Regards of the Groundwater Research

Protection on the mountain hard rock areas) financed by the Fifth Framework Programme of

the European Community (Contract: EVK1-1999-00040).

INTRODUCTION

The study area occupies the High Valley of Lozoya, which is located in the Northwest

of the Madrid Region. This valley is within the Guadarrama Sierra, on the eastern side of the

Spanish Central System.

This area covers approximately 250 km 2 and is one of the best conserved natural areas

of the Region, it serves as valuable site for geology (glacial geomorphology) and for ecology

(protected wildlife areas). The Natural Park of Peñalara and an Area of Special Protection for

Birds are located in the study area.

The valley opens towards the NE, forming the Lozoya River, which is the main stream

that crosses the area flowing north-eastward and discharges into the Pinilla Reservoir, which is

one of the twelve reservoirs that supply drinking water to Madrid city.

The climate of this area is Continental Mediterranean type, with long, cold winters, and

short, dry summers. Both temperature and precipitation show a clear variation with altitude. The

average yearly temperature is between 6º and 14ºC. The annual precipitation is between 600 and

900 mm/year in the lowest areas and between 1000 and 1500 mm/year in the areas situated at

more than 2000 m above sea level, searching as much as 2000 mm/year in some places [CAM

1985].

GEOLOGY SETTING

Broadly speaking, there are two lithological units over the high Lozoya catchment. One

is formed by hard rocks, mainly glandular granitic gneisses and, in minor rate, mica schist,

banded gneisses and metamorphosed limestones. They are high-grade metamorphic rocks

deformed by the Hercynian Orogeny forming the basin basement. Only a small plutonic outcrop

appears, which is a post-tectonic granitic intrusion. The other lithological unit is formed by

sedimentary rocks. They fill the basin lying over the metamorphic basement along an angular

erosive unconformity. These are:

- cretaceous sediments: sand, clay and gravel (Utrillas facies); marl and dolomites;

and karstified limestones

- tertiary sediments: polymictic conglomerates and sand cemented with carbonates of

Paleogene age; light ochre arkose type “Madrid facies” of Neogene age.

- Quaternary age sediments as stream alluviums including the lowest terraces of the

river; altered rocks and colluvial deposits on metamorphic rocks; peat deposits;

alluvial fans; glacial moraines; detrital filling in karst cavities.

15


The region suffered from two orogenies. The Hercynian Orogeny is responsible for the

main tectonic events. It has three principal phases of deformation, two light refoldings and two

of later faulting. During the Alpine Orogeny, it was produced the block faulting of the basement

and reworking of Mesozoic, Tertiary and even Quaternary sediments by means of either folds or

faults.

The Lozoya High Valley is an intramontane depression with rhomboidal shape. It is

result of the block dynamics (horst-graben) that occurred along the Miocene as consequence of

the alpine tectonic reactivation. The basic elements that form the valley structure are the slopes

of the mountain massif and its piedmont or valley bottom. Both elements have a clear separation

that generally coincides with the trace of the fault systems.

One of the southernmost glaciated areas during the Pleistocene is found in the Lozoya

High Valley. In this way, the Natural Park of Peñalara is the best example of glacial

geomorphology close to Madrid, where it can be seen morreins, glacial cirques, high mountain

lakes and periglacial process.

HYDROGEOLOGY SETTING

Hard rocks in the area (plutonic and metamorphic rocks) have secondary porosity

originated by alteration processes and joints (mainly of tectonic origin) that allows the

circulation of small amounts of water. At grater depths, the hard rocks are practically

impervious, because of closing fractures produces by the pressure of overlying rocks.

The weathering of hard rocks produces shallow aquifers, which generally have a

thickness of less than 10 m. They are small freatic aquifers that discharge in springs and

streams. The scarce water resources in this aquifers are use to supply water to cattle raising and

some country houses.

The hydrogeological interest in Utrillas facies depends on the clay proportion. Above it,

the marls and dolomites shown low permeability and this units are considered an aquitard. On

the top of the cretaceous series, there is karstified limestone that constituted an unconfined

aquifer of high permeability. The recharge of this cretaceous aquifer is produced by different

mechanisms: direct infiltration of precipitation; infiltration of tributary streams of the Lozoya

River while passing through these permeable rocks; and the recharge from the Pinilla Reservoir.

In a natural flow regime, the discharge is produce towards the Lozoya River and the reservoir.

The tertiary sediments constitute an unconfined aquifer of less importance than the

karstified aquifer.

Except alluvial deposits and the valley bottom which constitute the alluvial aquifer of

the Lozoya River, the rest of quaternary sediments form unimportant unconfined aquifers that

discharge into small spring located along the contact with the impermeable basement.

As a whole, the cretaceous and tertiary sediments, and the alluvial deposits overlap one

another and follow the tectonic fracture structure of Lozoya High Valley. There is a perfect

hydrological connection between the aquifers and rivers that forms a common a continuous

hydraulic system.

HYDROLOGICAL BALANCE. THE USE OF A PRECIPITATION-RUNOFF MODEL.

Methodology

The methodology is summarised in the following steps: 1. Bibliographic compilation;

2. Springs and wells inventory; 3. Monthly stream-gauging in four experimental catchments

during the hydrological year 2000-2001; 4. Meteorological data processing; 5. Unified

cartography with types of soils and their uses.

The precipitation-runoff model will be used in four experimental catchments from the

assessment of the evapotranspiration through the data of precipitation, irrigation and soil

moisture. After the study has been completed, the results will be extrapolated to the rest of the

valley area.

16


HIGH LOZOYA VALLEY

SPAIN

MADRID

Pe ña la ra

Natural Park

Lozoya

Rive r

Pinilla Reservoir

Gauging station

Gauging measures

Rive r

LITHOLOGY

5

3

1

0 2 4 6 8 Km

4

2

Figure 1. Situational geological map. Lithology: 1) glandular granitic gneisses; 2) granitic intrusion 3) Cretaceous

sediments: karstified limestones; marl and dolomites; sand,clay and gravel 4) Tertiary sediments; 5) Quaternary

sediment

Precipitation-runoff model

The computer model chosen for this work is the CHAC 1 , which has been developed by

the CEDEX 2 that belongs to the Ministry of Public Works in Spain. The inputs of the model are:

monthly rainfall data; water level and daily flows data in the stream-gauging stations; average

monthly temperature; humidity; wind rate; and insolation for the assessment of the potential

evapotranspiration; and soil moisture content for the assessment of the real evapotranspiration.

In the study of rainfall, several stations were selected in the area and later, in order to

achieve a more detailed data correlation, other stations located outside the study area were

added. The method of Double Accumulation was applied in the critical analysis of the rainfall

data. This method is based on the comparison of the data of one station with its environment.

The yearly accumulated values of one station are plotted versus either the values of another

reliable close station, or the arithmetic or weighted mean of a group of stations. The data form

on a straight line. From the analysis of these graphs, anomalies in the working order of the

stations were detected and corrected and, consequently, some of the stations were eliminated

from the study.

The CHAC program completed automatically the rainfall data sequence with a tool

based on the CORMUL model. Based on the use of the spatial correlation between the

variables, this random interpolation model was developed in the Centre for Hydrographic

Studies of the CEDEX.

1 CHAC (Cálculo Hidrometeorológico de Aportaciones y Crecidas): Hydrometeorological Assessment of inputs and

flooding.

2 CEDEX (Centro de Estudios y Experimentación de Obras Públicas): Centre for Research and Experimentation of

Public Works.

17


Since the rain-gauge network is not uniform, the isohyetal method will be used. In

drawing the isohyets, such factors as known influence of topography on precipitation can be

taken into account.

There are two stream-gauging stations in the study area. They belong to the Tagus’

Hydrographic Confederation, which has provided us with stream-gauging data for the period

between 1967 and 1995. The determination of a lengthy and reliable sequence of monthly input

data in the Lozoya River will enable the evaluation of the renewable water resources in the

study area. There again, monthly stream-gauging operations are being carried out in four

experimental catchments that have been chosen according to the hydrogeological behaviour of

its materials and the features of the terrain – slope, vegetation, etc. These operations are

performed in the contacts between different materials. The aim is the assessment of the runoff in

every hydrogeological unit.

The potential evapotranspiration will be assessed by means of the Thornthwaite

equation, which is function of the average monthly temperature, relative humidity, wind

rate and insolation. The CHAC program makes the calibration of the maximum soil

moisture to estimate the real evapotranspiration. In order to work with real values, these

data will be validated by a soil sampling campaign.

The rainfall-runoff model is carried out with the Temez rational formula of continuos

simulation [1977]. This model assumes that the terrain is divided in two zones: the upper

unsaturated zone in which the pore spaces contain water, as well as air and other gases; and the

lower zone or aquifer in which the voids in the soil are filled with water. The model also

assumes that one part of rainwater is drained and goes out joining with the water flow of the

river, while the rest of the water is stored in the upper area of the soil, serving later for the

evapotranspiration. One part of the rainwater surplus flows on the surface and the other is

infiltrated into the aquifer. The parameters of this model are: maximum soil moisture; surpluses;

maximum infiltration capacity; and the discharge coefficient. The rainfall-runoff model will be

calibrated with all these parameters.

CHEMICAL QUALITY AND SOURCES OF POLLUTION

The main aim of this study is to achieve the description of the hydrogeochemical

characteristics of the continental water, in order to know what hydrochemical processes

occurred and estimate the possible impact of pollution sources on the quality of water in the

area.

Methodology

The methodology of the hidrochemical study consists of the following stages:

1. Geological and hydrogeological data compilation; 2. Field work in which the springs and

wells inventory was expanded and the potential sources of pollution were identified; 3.

Selection of the most suitable points for the annual control network carried out with monthly

samplings; 4. Samplings with “in situ” measurements of unsettled parameters (pH, temperature,

electrical conductivity and alcalinity); and 5. Sample laboratory analysis and interpretation of

results. The cation analyses were made with ICP-MS, while anions were analysed with ionic

chromatography.

Results and discussion

The results obtained in the monthly samplings so far, shows that, in most cases, the

water shows a very low or low salinity (with conductivity under 200 µS/cm), with pH values

around 6-7, and calcium-bicarbonate hydrogeochemical facies.

E.C.

(µS/cm)

pH T ºC Cl -

mg/L

SO 4

2-

mg/L

CO 3 H -

mg/L

18

NO 3

-

mg/L

Ca 2+

mg/L

Mg 2+

mg/L

Na 2+

mg/L

K +

mg/L

Maximum 1850 8.2 13.5 38 1122 248 13.6 313 98.7 11. 12.6 13.9

Minimun 18 5.7 6.2 0.8 < 0.9 8 0 1.1 0.2 2.1 0 0

SiO 2

mg/L


Average 176 6.5 9 5.4 43 58 4.7 23.4 6.9 4.2 1.7 7.1

Table.1. Summary of the chemical analyses of groundwater and surface water of Lozoya catchtment (29 analyses)

However, as the Schoeller-Berkaloff diagram (Figure 2) shows, there are two types of

water according to the lithology of the terrain where the wells, springs and streams are located.

On the one hand, springs and rivers in hard rocks have water with very low salinity, with

conductivity values between 18 and 95 µS/cm, and less than 40 and 8 mg/L of bicarbonate and

calcium respectively. But on the other hand, springs and wells on the sedimentary aquifer have

bicarbonate and calcium as major ions, reaching values of 35 and l55 mg/L respectively.

meq/l

2+ 2+

Ca Mg Na + Cl - 2- - -

SO 4

HCO 3

NO3

EC

RIVERS AND SPRINGS IN HARD ROCKS

WELLS AND SPRINGS IN SEDIMENTARY ROCKS

FRAGUA WELL (POLLUTED)

Another difference between these

two types of facies is the content on Mg 2+ .

Continental water on hard rocks has

concentrations under 3 mg/L, while

groundwater, circulating across sedimentary

rocks, has concentrations above 3 mg/L until

12 mg/L.

Both hydrogeochemical facies have

in common a low content of chloride and

sodium, with maximum values of 12 y

8 mg/L.

In Figure 2, an analyses of a drilled

well (Well of Fragua) is also represented.

This well is placed on limestones, and the

chemical quality of its water notably differs

from the other springs and wells. It has high

salinity and calcium sulphate

hydrogeochemical facies that appear to have

an anthropic origin.

Figure 2. Scholler-Berkaloff diagram

Besides the major components

shown in Table 1, 60 minor and trace

elements were analysed. Between them,

there are the inorganic contaminants used as

indicators to determine the potability of

water (Ag, Al, As, B, Ba, Be, Cd, Cr, Cu, Fe,

Hg, Mn, Ni, Pb, Sb, Se, etc.). The amount of

these elements are much lower than the

potability limit values established by both

the current Spanish legislation [BOE 1990]

and the more restrictive new European

Directive proposal [OJEC 1998]. Neither

reached the inorganic trace elements limit

values proposed by the Environmental

Protection Agency of USA [EPA 1998].

In only a few cases, the limit values established by the drinking water legislation are

exceeded. This happens in the Well of Fragua where the water has 2,257 µg/L of Zn. Also in

The Eras Fountain whose concentration of Al is 275 µg/L, exceeding the limit value of 200

µg/L established by the European and Spanish legislation.The values of nitrogenous species are

low in every sample. None of the samples have values above 14 mg/L of NO 3

-

, whose origin can

be considered natural rather than anthrophic. As would be hoped, the values of nitrites are the

lowest of the nitrogenous species (never above 0.03 mg/L of NO 2 - ).

19


Figure 3 shows the potential continental-water sources of pollution in the study area.

POLLUTION SOURCES

HIGH LOZOYA VALLEY

Towns

Pic nic Are a s

Ski Re so rt

Municipal Landfill

Spillage

Pe ña la ra

Gas Station Natural Park

Cattle

LITHOLOGY

Lozoya

Rive r

Pinilla Reservoir

5

4

3

2

1

0 2 4 6 8 Km

Figure 3. Potential continental-water source of pollution. Lithology: 1) glandular granitic gneisses 2) granitic

intrusion 3) Cretaceous sediments: karstified limestones; marl and dolomites; sand, clay and gravel 4) Tertiary

sediments: 5) Quaternary sediment

It can be seen that most of the sources occupy a low extension and are located in the

sedimentary aquifer. Outside, on hard rocks, the human presence is only represented by picnic

areas and non-stabled cattle with 5,000 head of cattle. There are more cattle raising activities in

the area, but they are not significant.

The high salinity of its groundwater, rather than by limestone dissolution, in some cases

is produced by the pollution in the sedimentary aquifer. A clear evidence of contamination is

seen in the Fragua Well, which is placed on the limestones of the sedimentary aquifer. Figure 2

shows that its chemical composition is totally different from the results of the other 28 analyses.

The Fragua Well has a very high content of sulfates (1,122 mg/L). Its content of nitrates is only

of 1.2 mg/L, but it has 5.4 mg/L of NH 4+ . The high content of this unstable specie and the

location of the well, close to a population centre, make it possible to think that it is affected by a

leak of the nearby sewer system.

The low concentrations of nitrogenous species in the samples, both in groundwater and

surface water, (excepting the already discussed case of the Fragua Well), show that the cattle

raising in the area does not produce a significant impact in the quality of the continental waters.

However, it is advisable to take into account that precipitation during this winter has been very

important and during this time, (coinciding with the field campaign), the cattle have occupied

the lowest areas of the Lozoya High Valley. During the summer, when the water in rivers and

springs significantly decreases and the cattle are around the slopes of the basin, it is more

probable to detect higher values of nitrogenous species. This hypothesis will be confirmed with

future results of the chemical control network installed in the area.

20


CONCLUDING REMARKS

The different researches carried out in the High Valley of Lozoya will serve a more

detailed knowledge, favourable assessment and sustainable development of the area. They

achieve a great importance due to the purpose of declaring the Guadarrama Sierra Natural Park.

A Geographic System of Information (GIS) will be devise as an answer to the need of a

better territorial organisation.

ACKNOWLEDGMENTS

The translation by Carmen Martínez Pérez-Herrera is fully appreciated and gratefully

acknowledged.

REFERENCES

BOE (BOLETÍN OFICIAL DEL ESTADO – SPANISH OFFICIAL BULLETIN) (1990). Law

1138/1990 of 14 September concerning the technical-sanitary regulation that refers to water

supply and control of potable water quality, pp. 27488-27497

CEDEX ( CENTRE FOR RESEARCH AND EXPERIMENTATION OF PUBLIC WORKS)

“Estudio Hidrológico de la presa de Velillos. Estimación de aportaciones”. Madrid

COMUNIDAD AUTÓNOMA DE MADRID 1985. “Mapa fisiográfico de Madrid”. Escala

1:200.000. Consejería de Agricultura y Ganadería. Memoria 42 pp. Madrid.

ENVIRONMENTAL PROTECTION AGENCY 1998. “National Recommended Water Quality

Criteria; Notice; Republication”. Federal Registre 237 (63): 68354-68364.

INSTITUTO TECNOLÓGICO GEOMINERO DE ESPAÑA 1991. “Mapa Geológico de

España”. Escala 1:50.000. Hoja nº 484 (Buitrago de Lozoya). 105 pp. Madrid.

MARTÍN-LOECHES, M., MUÑOZ, I., SASTRE, A. & VICENTE, R. 1997. “Brackish

groundwater manifestations in the meridional limit of Spanish Central System”. In J.G.

Yélamos & F. Villarroya (ed.), Hydrogeology of Hard Rocks. Some experiences from Iberian

Peninsula and Bohemian Massif; Proc.symp., Madrid, 11-13 September 1997. Madrid: AIH-

GE.

OJEC (OFICIAL JOURNAL OF THE EUROPEAN COMMUNITIES) 1998. Council Directive

98/83/EEC of 3 November 1998, concerning water quality for human consumption. OJEC of 5

December 1998, pp.32-54.

TEMEZ, J.R. (1977). “Modelo matemático de transformación precipitación-aportación”. Asinel,

1977.

VICENTE, R. 1986 “Hidrogeología regional de la Depresión de Campo Arañuelo”. Ph Thesis.

376pp. Department of Geology, University of Alcalá de Henares.

YÉLAMOS, J.G. 1991. “Hidrogeología de las rocas plutónicas y metamórficas en la vertiente

meridional de la Sierra de Guadarrama”. Ph Thesis 334 pp. Department of Q.A. Geology and

Geochemistry, Autonomous Universtity of Madrid.

21


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 102-106

PRELIMINARY SEDIMENTOLOGICAL AND

GEOMORPHOLOGICAL EVOLUTION IN A PART OF THE

GUADIANA BASIN BETWEEN MÉRIDA AND BADAJOZ (SPAIN)

MOYA-PALOMARES, M.E 1,2 ; CENTENO, J.D 2 AND

AZEVEDO, T.M 3

1) Department of Geology. Faculty of Environmental Sciences. Alcalá de Henares University. Madrid (Spain)

2) Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

3 Department of Geology. Faculty of Sciences. Lisboa University. Lisboa (Portugal)

SUMMARY

We are approaching to the sequence of the sedimentary and morphological events

taking place at the Guadiana basin in the Vegas bajas area. The litostratigraphical correlation

with other basins of the western Iberian Peninsula allows to explain the main evolution stages

of the basin.

This work will be the PhD Thesis of M.E. Moya under the suprevision of the other

authors of this article, thas is an advance to the definite version.

RESUMEN

Estamos estableciendo a la secuencia sedimentaria y los procesos morfológicos que se

sucedieron en la cuenca del Guadiana para el tramo de las Vegas bajas. Se destaca las

correlaciones litoestratigráficas con otras cuencas peninsulares que sirven de ayuda para

explicar la evolución de la cuenca.

INTRODUCTION

The study of the morphological and stratigraphical evolution of the Guadiana Basin in

the Extremadura area of Vegas Bajas (VB) is a research program of the Department of

Geodynamic of the Complutense University.

The present work is focused to establish the morpho-sedimentary process since the first

deposit of the Tertiary until the sedimentation of the quaternary deposits into the Guadiana VB.

The main data used to carry out the present work are:

- Bibliografic data.

- Sedimentological data.

- Morphological data.

The sedimentological and geomorphological data of other Iberian Cenozoic basins was

specially contrasted in order to correlate and propose an evolution model to the VB area.

SETTING

The Guadiana crosses Extremadura along a small tertiary basin located at the SW of the

Iberian Peninsula (Fig.1) in wich two separated basins can be defined: Vegas altas and Vegas

bajas ( Hernández- Pacheco, 1932). We are studying the Vegas Bajas (VB) sector that represent

the area from the batholito of Mérida until Badajoz. In this sector of the basin, the Guadiana

River flows E-W. Once the river cross the town of Badajoz, it changes its direction flowing

towards the South, fitted into the Palaeozoic rocks.

22


Fig.1 Location map of the

Guadiana central basin in the

iberian Peninsula. Fig. 2.

Simplified geological map of

the area between Mérida and

Badajoz.

SEDIMENTARY CENOZOIC UNITS IN THE GUADIANA BASIN BETWEEN

MÉRIDA AND BADAJOZ

The sedimentary study allows to define four basin Unconformity Limited Sequences

during the Cenozoic: ULS1, ULS2, ULS3 and ULS4 (Fig.3) .

• The ULS1 unit is formed mainly by clay and sand, with thickness less than 80 meters

(Hernández-Pacheco,1960). This unit is lays discordant on the Iberian Massif substrate.

ULS1 is interpreted as distal alluvial fans of the Oligocene (Hernández-Pacheco, 1932,

1955) or Miocene (Hernández-Pacheco and Crussafont, 1960), being the last idea the most

widely acceted nowadays (Villalobos et al., 1988).

• The ULS2 unit is characterised by sand, conglomerates and, at the top of the unit, a

carbonate deposit (caleño). The units is widely accepted as Miocene (Hernández

Pacheco,1960; Villalobos et al.,1988). The facies analysis shows the characteristic of a

braided system flowing from E to W, related with the present fluvial system. The

palaeocurrent measurements in the sandy bodies revealed a direction very similar than the

actual flow of the Guadiana river with values of 230º to 270º.

Mainly temporary inactive channels and bars composed this fluvial system. Toward the

southern edge of the basin, fans associated to a pre-existing relief prograde rapidly into the main

stream flow.

23


W

E

Caia

Badajoz-La Albuera

Guadajira

Calamonte

Los Pinos

Talavera-La Albuera

Lobón

ULS3/4

USL2

11m

USL2

USL1

Fig.3 Summarised vertical Cenozoic units (ULS1, ULS2, ULS3 and ULS4) between Mérida and Badajoz.

The presence at the top of the unit of 1-2 meters of carbonate lacustrine deposit

(Armenteros et al., 1986), represents the end of sedimentation in the basin during the Miocene.

Other authors considered that this carbonates sheet (caleño) is pedogenic, similar that the

“caliche capro” of New Mexico ( Elbersen, 1982).

After the fill-up of the basin, the fluvial system is reactivated due tectonic processes or the

connection to the Atlantic basin by fluvial captures.

• The ULS3 unit is a deposit of gravel and sand of braided fluvial system, formed by cannel

and bars (fig 4,5). The palaeocurrent measurements in ULS3 revealed an S-W flow

direction (values 225º to 315º). These palaeocurrent ranges indicate that the streamflow

direction is similar than the ULS2 unit. However, to W of the VB the direction of ULS3 is

North–South (180º).

• The ULS4 unit has been identifies as raña 1 deposits in the Vegas area. That deposit was

sedimented in form of aluvian fans of pediment pebble-sheets. They are generally dated as

transitional between the Pliocene and Pleistocene. Most of the stone and gravel, which are

angular, are embedded in a matrix of sand and clay and occur as lenses.

Gm

1 St,

Raña Gt,St is the Spanish and Portuguese name for a conglomarate of quartzite pebbles, poorly rounded and covered by a

ferric patina, into a clayish matrix, very common at the piedmont area of the Iberian massif quartzite ridges. Most

rañas have been deposited in the Pliocene-Pleistocene limit, and their fan-like form is still to be recognised.

– 70 cm

24

St,

Gm


Fig 4, 5: ULS 3 formed by bars ( fig4) and cannels (fig 5)

The block diagram (fig. 6) shows a possible interpretation of the Guadiana Basin from

the Paleogene to the Plio-Pleistocene with the present day data.

The age of the different units is still a question without a solution. There are very few

palaeontological remains and clay minerals have been used to date the deposits by correlation

with other cenozoic basins (Brell, 1975).

ULS1 has paligorskite>montmorillonite>illite. These minerals appear systematically in

other cenozoic basin, toward the west of the Guadiana. The basins of the Tajo, Sado, Moura-

Marmelar and Beira alta (Mondego), are characterised by the same clay mineral association, and

that sediments are paleogene age.

On the other hand, the clay mineral in ULS2 unit is composed by

montmorillonite>illite, while paligoskinte is not present. This clay mineral association is present

in previously mentioned basins and is dated as Miocene.

Finally, ULS3 and ULS4 have kaolinite>illite. In the Portuguese basin (Tajo, Sado,

Moura-Marmelar and Beira Alta) this association are present in Pliocene and Quaternary age.

As a tentative hipothesis, we can consider ULS3 as Pliocene and ULS4 as late Pliocene or early

Pleistocene.

E

(A)

W

(B)

Badajoz

Mérida

(C)

(D)

Fig. 6. Preliminary interpretation of the evolution in the Guadina basin between Mérida and Badajoz during : A)

Paleogene. B) Miocene. C) Pliocuaternary. D) in the present day. Moya et al., (1999, 2000 a,b)

CONCLUSIONS

The Guadiana basin received its first sediment input during the Paleogene with the

sedimentation of ULS1 in a closed basin.

During the Miocene began the fluvial sedimentation in a open basin. The sediments in

this phase are sands of a braided system with palaeocurrents towards for the west (ULS2 unit).

Probably, the fluvial sedimentation continued outside the Vegas bajas towards the west into

Portugual. The fluvial sedimentation was interrupted at the late Miocene when the “caleño” is

deposited.

In the early Pliocene age, a new fluvial system is identified. This system presents

important differences with the miocene fluvial system. It is a gravel and sand braided system

with palaeocurrents towards the west between Mérida and Badajoz and towards the south

around Badajoz city. In this case, the flow of the pliocene system is similar to the present.

25


FURTHER RESEARCH

Once we have done the study and interpretation of the sedimentary filling of the basin,

we proceed to study the geomorpholigical units, their relations with the filling up and the

following stream network entrenchment, and the evolution of the present valley landforms and

dinamycs.

REFERENCES

ARMENTEROS,I.; DABRIO, C.; ALONSO, G.; JORQUERA, A. & VILLALOBOS, M.

(1986) “Laminación y bioturbación en carbonatos lagunares interpretación genética (cuenca del

Guadiana, Badajoz)”. Estudios Geológicos, 42: 271-280 pp.

BRELL, J.M. (1975) “Aplicación de las correlaciones al estudio del terciario continental”.

Congresos y Reuniones Enaddimsa, Serie 7; 2 pp.

ELBERSEN. G.W.W (1982) “Mechanical replacement processes in mobile sofl cacic horizons.,

their role in soil and landscape genesis in an area near Mérida, Spain”. Thesis. Agricultural

Research reports, 919. 1-208 pp.

HERNÁNDEZ PACHECO, E. (1932) “Síntesis fisiográfica y geológica de España”. Trab,

Museo Nacional Ciencias Naturales, 38. 584 pp. Madrid.

HERNÁNDEZ PACHECO, F. (1955) “Fisiografía del solar hispano”, Tomo I. Real Academia

de Ciencias Naturales. Madrid.

HERNÁNDEZ PACHECO, F. (1960). “El terciario continental de Extremadura”. Boletín de la

Real Sociedad Española de Historia Natural, 58. 241-274 pp.

HERNÁNDEZ PACHECO, F. & CRUSAFRONT, M. (1960). “La primera caracterización

paleontológica del Terciario de Extremadura”. Boletín de la Real Sociedad Española de Historia

Natural, 58. 275-282 pp.

MOYA PALOMARES, M.E.; AZEVEDO, M.T. & RODRÍGUEZ-PLAZA, M. (1999).

“Estudio preliminar de los sistemas fluviales Cenozoicos de la cuenca del Guadiana entre

Mérida y Badajoz (España)”. Congresso Nacional Cenozoico de Portugal. Lisboa.

MOYA PALOMARES, M.E.; AZEVEDO, M.T.; CENTENO J.D & RODRÍGUEZ-PLAZA,

M. (2000a). “Interpretación de las facies fluviales de la unidad superior terciaria y

pliocuaternaria en la cuenca del Guadiana”. Congreso Ibérico sobre el Terciario. Barcelona.

MOYA PALOMARES, M.E.; AZEVEDO, M.T. (2000b) “Los sistemas fluviales Cenozoicos

de la cuenca del Guadiana”. Revista Ciencias da Terra, nº12.

VILLALOBOS, M.; JORQUERA, A.; APALATEGUI, I. (1988). “Hoja núm. 802 (La

Albuera)”, 1:50.000 segunda serie.IGME.

26


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 54-

PRESENT AND PAST FLOODS IN THE GUADIANA RIVER

BASIN: HYDRO-AND PALEOHYDROLOGICAL APPROACH

ORTEGA, J.A. 1 AND GARZÓN, G. 2

1 Faculty of Sciences. European University, CEES. Madrid (Spain)

2 Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

SUMMARY

The 1997 Rivillas flood, a tributary of the Guadiana River in the town of Badajoz, was

one of the most catastrophic in the Iberian Peninsula in recent years. This study first

establishes the dynamics of the flood and associated deposits, and from there estimates the

ensuing flow magnitude. In order to establish flood frequency analyses for the Guadiana River,

annual peak discharge estimation on surrounding gauging stations, historical records and

paleostage indicators have been integrated. Using paleohydrological techniques, at least seven

floods, starting from 3260BP, have been identified as slackwater deposits. At least three of these

floods were larger than the greatest on historical record, the one of 1876 AD.

INTRODUCTION

There is a long historical record of flooding in the Guadiana Basin. Unfortunately there

are very few cases in which there are sufficient hydrological data on record for reliable

reconstructions of return periods. In Nov. 1997, one of the most destructive flood disasters in

the Iberian Peninsula in recent years occurred in the Rivillas stream, affecting the town of

Badajoz and causing 23 deaths and material losses estimated at $ 150 M. These figures were

unexpected for a small tributary of the Guadiana river (Fig. 1), only 34 km long with a 314 km 2

lowland watershed, and must rather be related to the flashflood character of the event and the

environmental conditions on the floodplain [Ortega et al., 1998; Moya et al., 1998].

In the Rivillas Stream, on the basis of the flood in 1997, the discharges were estimated

using a variety of methods: first, the rational method (as modified by Temez, 1978) and then

hydraulic calculation programs (HEC-RAS). Paleofloods in the lower basin of the Guadiana

river were studied using paleoflood hydrology techniques in order to estimate peak discharges.

There is a voluminous historical record for the Guadiana, which in some cases made it possible

to establish relations between slackwater deposit-paleostage indicators (SLW-PSI) and

historical floods by dating some of the deposits using the C14 standard and AMS methods.

Verifications were also made by Cs 137. SLW-PSIs produce the most accurate estimates of

paleoflood magnitudes (Baker,

1987) and can be combined with the HEC-RAS hydraulic calculation program to establish

discharge estimates.

ESTIMATIONS OF RIVILLAS STREAM DISCHARGE AND FLOOD RETURN

PERIODS

The Rivillas stream is 34km. long with an average slope of 0.5% and an area of 314

km 2 , formed by tertiary sands and clays with low infiltration rates. Its main tributary, the

Calamón creek, approaches the Rivilla very close to its mouth, so that there are in fact two very

similar subbasins, parallel to each other and with the same orientation (Fig.1). An immediate

survey of the ephemeral flashflood deposits was carried out in order to interpret the resulting

sedimentary features and reconstruct water levels. Hydrologic modeling provided the flood

discharge estimation. The question addressed was the relative importance of this flood in a

historical context and the possibility of establishing a return period for the event. At least 12

floods had been recorded for the Rivillas river since 1700, some of them of even greater

magnitude than the present one. Most of them, however, were produced not by storms at the

27


Rivillas watershed, like this one, but by backwater effect of floods in the Guadiana river that

obstructed the confluence between the two.

Rainfall data for the Rivillas basin given by the INM (1998) reveal figures as high as

130 mm in 24 hours, and an intensity of up to 88mm/h. The rainfall had been the heaviest in the

historical records for the area, which go back nearly 100 years. The closest and most reliable

rain gauge station for the area, at Talavera la Real, registers a record of 117mm/day for the data

series from 1961 to 1990, and this is the figure that was used for the calculations. The SQRT-

ETmax distribution function approach was used as the most suitable for this type of events, both

including and excluding the 1977 event precipitation data. According to this, the return period

for the rainfall in the region was within the range of 500 years.

Return period 24 hours Precipitation 24 hours Precipitation

(without the 1997 event) (including the 1997 event)

25 years 67 mm 71 mm

100 years 84 mm 91 mm

500 years 107 mm 116 mm

A first discharge estimation using the rational formula modified by Temez [1978] gave

discharge for the Rivillas subbasin as 396m 3 /s, calculated for rainfall of 120mm, the figure

obtained for the whole basin from the rainfall isolines map supplied by the INM[1998]. In

another approach, two methods were used to reconstruct the water levels on a selected field

study stretch:

PORTUGAL

SPAIN

Guadiana river

Badajoz

Talavera

Rivillas river

Cansini reach

Ayo. Calamon

La Albuera

Iberian Peninsula

0 5 Km

Valverde

de Leganés

Rivillas river

Atlantic Ocean

Pulo do Lobo

Tagus R.

Guadiana R.

Segura R.

Jucar R

Mediterranean Sea

Figure 1. Location of Rivillas River and studied reaches in the Guadiana Basin

one by means of a detailed field survey of water level marks, and the other based on the storm

hyetograph. The hyetograph was drawn up with the storm rainfall data supplied by the INM,

and from it the flood Unitary Hydrogram (SCS) was obtained using HEC-1 [U.S. Army, 1981].

A flood discharge of 160m 3 /s was calculated for the reach in question. This discharge was used

28


to reconstruct the extension of the flooded area by means of Hec-Ras [U.S. Army, 1997]. These

data were validated by detailed field survey. According to these results, at the outlet from the

Rivillas subbasin, the discharge for the reach would produce a flood peak discharge of 356m 3 /s

calculated by Hec-1. This figure is similar to the official estimation for the flood, that is 375

m 3 /s [CEDEX, 1998] and only a little smaller that the one arrived at by the rational formula, as

is normally expected from this method. However, it was difficult to evaluate these data in an

historical context since there are no available data on discharge in other floods. Historical marks

are related to floods caused by a rise in the waters of the Guadiana and not by water of the

Rivillas itself.

SLACKWATER DEPOSITS AND PALEOHYDROLOGICAL ANALYSIS

Historical flooding on the Guadiana basin was examined in order to understand the

significance of floods in the context of that basin (Ortega & Garzón, 1997). Two populations

can be identified from the distribution of Guadiana floods. Autumn floods are in general

scattered and isolated along the watershed and bear no immediately apparent relationship to

annual rainfall data. Winter floods, on the other hand, are associated with the trunk stream and

fall mainly in wet yearly periods. The Rivillas flood, although belonging to the autumn group

generated in small basins, is also associated with a three-year wet period.

Systematic gauge station records for the Guadiana River, and for most of the Iberian

Peninsula, begin in 1912. However, only a few stations preserve a continuous, reliable record on

which to base detailed hydrological reconstructions. In the towns of Badajoz and Merida, as in

various other riparian towns of Spain and Portugal, there are historical marks defining the height

reached by the waters. All these marks indicate that the highest flood-level on record is that of

1876. With an estimated discharge of 10,000m 3 /sec at Badajoz, this flood is considered a major

point of reference for estimations of return periods.

Since much of the course of the Guadiana runs through deep gullies in the Hercynian

massifs, we decided to look for paleo-flood deposits in these areas. Various sites of such

deposits have been located, although these areas generally present difficulties of access and

excavation. Our goal in this study was to determine low-frequency, high-flow flood peak

discharges. These floods are not recorded at the gauge stations, which were built much more

recently than the sedimentary register that we have compiled. The Guadiana canyon in the Serpa

area (Portugal) was chosen for its good depositional conditions, the possibilities of hydraulic

modeling, and also because there is a gauge station with records going back to 1947. This reach

of the river is enclosed by metamorphic materials forming a steep-sided gorge. The valley is

400m wide. The surface area of the Guadiana in this reach is 60,800 Km 2 .

Most of the slackwater deposits studied are composed of fine to very fine sand and silt.

In some cases these are arranged as couplets or pairs of coarser and finer material which

intercalate as the result of a single impulse in zones favourable to deposition. Both deposits

correspond to the various energy phases that the flood goes through: first, a stronger impulse

with rapid loss of competence and deposition of coarser material, followed by a halt in which

the finer fractions left in suspension are deposited. The various units are separated by coluvial

levels and differences in size and bioturbation.

Two methods have been used to date the SLWs. One is Cs 137 (Ely et al, 1992), used to

determine whether the deposit is earlier or later than 1952, the year in which the nuclear

emissions of this element first began. The other and principal method is C14. Analysis by the

C14 Standard method has shown that results are not always very satisfactory in these cases, and

we therefore separated the organic fraction (charcoal & branches) from the inorganic fraction by

washing and flotation followed by drying, according to the method suggested by House

(personal communication), and samples were dated with C14 AMS technique by BETA Lab.

The hydraulic model was built up following the SWD-PSI methodology (O´Connor &Webb,

1988, House & Pearthree, 1995). The mathematical model used was Hec-Ras version 2.0,

developed by the Hydrologic Engineering Center (Hec-Ras, 1997), with stationary flow and step

backwater flow characteristics.

According to these results, the datings suggest that there have been at least three floods

larger than that of 1876AD, which is considered one of the largest in the area on the basis of the

29


historical records. These floods could be probably related with historical floods recorded

1758AD and 1603AD and a very old one with an approximate age of 3260BP.

DISCUSSION AND CONCLUSIONS

The effects of the flooding of the Rivillas stream in November 1997 were surprising for

the seriousness of the damage and above all for the number of victims. The flow rate data from

field measurements of water levels agree closely with the figures estimated indirectly from the

rainfall recorded at the meteorological stations. The estimated return period for this rainfall is

500 years. While there are records of higher floods on the lower reach of the Rivillas, these

were due not to flash floods like the present case but to floods caused by rising of the Guadiana

River which restricted the drainage capacity of the Rivillas. The seriousness of this event was

due rather to changes of land use in the river basin and occupation of the floodplain.

According to the existing foronomic records, the peak discharge of the largest flood at

the Pulo do Lobo gauge station over a period of 42 years was that of 1947, with a flow

magnitude of 8,127 m 3 /s. This discharge is much smaller than the that of the floods recorded by

us. Also, from the SLW studied in the Tajo River, Benito et al (1998) considered that floods of a

similar or greater magnitude than the 1947AD flood have occurred at least nine times in the last

millennium. Historically, the largest flood for which height levels remain was that of 1876AD,

which devastated several towns and villages along the river basin. Recent estimations suggest

that the flood may have reached 10,600m 3 /s, which places it only in fourth to sixth place in the

range of floods studied.

According to our own findings, there have been at least two higher floods in relatively

recent times: probably those of 1758AD and 1603AD. The latter is the highest in the entire

sedimentary register that we have compiled throughout the studied reach, and these data are not

inconsistent with the conclusions reached previously in the historical record. In addition, there is

a very old record, of 3260BP, with a discharge of almost 12,000m 3 /s, which has been preserved

by the deposition of more recent levels. The data analysed need to be processed further and

compared with interpretations at other points in the basin where work is currently proceeding,

but the offer an example of how the analysis of floods and their return periods are in fact far

more complex than the simple statistical treatment of existing records on dates and water

heights. Such studies need to include preliminary analysis and individualisation of the type of

flood being handled in terms of their significance in the specific physical environment.

REFERENCES

BAKER, V. R., (1987). “Paleoflood hydrology and extraordinary flood events”. Journal of

Hydrology, 96. 79-99pp., Elsevier.

BENITO, G. et al, (1998). “Palaeoflood hydrology of the Tagus river, Central Spain”.

Palaeohydrology and environmental change, edited by G. Benito., V. Baker., & K. J. Gregory.,

John Wiley & Sons. Chichester, 327-333 pp.

HYDROLOGIC ENGINEERING CENTER. (1981). “HEC-1”. Flood Hydrograph Package.

US. Army Corp of Engineers.

HYDROLOGIC ENGINEERING CENTER. (1997) “HEC RAS”. US. Army Corp of

Engineers.

HOUSE, P. K., and PEARTREE, P. A. (1995). “A geomorphologic and hydrologic evaluation

of an extraordinary flood discharge estimate: Bronco Creek, Arizona”. Water Resources

Research, Vol. 31, Nº 12. 3059–3073 pp.

INM. (1998). “El Temporal de los días 5 y 6 de Noviembre de 1997”. Centro Meteorológico

Territorial de Extremadura. (Open File report). Badajoz.

MOYA, M. E.; GARZÓN, G. & ORTEGA, J. A. (1998). “Depósitos de la avenida del arroyo

Rivillas, Badajoz. Noviembre de 1997”. Investigaciones recientes de la geomorfología edited

by A. Gomez & S. Franch. Barcelona, 33-36 pp.

O´CONNOR, J. E. and WEBB, R. H. (1988). “Hydraulic modeling for paleoflood analysis”.

Flood Geomorphology, edited by V. R Baker.; R. C. Kochel., & P. C. Patton.,. Wiley

interscience. New York, 383–482 pp.

30


ORTEGA, J. A. & GARZÓN, G. (1997). “Inundaciones históricas en el Río Guadiana: Sus

implicaciones climáticas”. Cuaternario Ibérico, 365–367 pp. Huelva.

ORTEGA, J. A.; GARZÓN, G. & MOYA, M. E. (1998). “Parámetros climáticos y ambientales

de la avenida del río Rivillas”. Investigaciones recientes de la geomorfología española, edited

by A. Gomez & S. Franch, Barcelona, 237-246 pp.

TEMEZ, J. R. (1978). “Cálculo hidrometeorológico de caudales máximos en pequeñas cuencas

naturales”. MOPU., Madrid, 113 pp.

31


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 112-115

HISTORICAL FLOODS ANALYSIS BETWEEN THE ATLANTIC

AND THE MEDITERRANEAN WATERSHEDS IN CENTRAL-

SOUTH SPAIN

POTENCIANO, A 1 AND GARZÓN, G. 2

1 Geological Institute (IGME), C/ Ríos Rosas 23, 28003 Madrid (Spain)

2 Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

ABSTRACT

Floods evolution since 1500 for the Tagus, Guadiana, Jucar and Segura Rivers basins

show an increase on flood occurrence from late 17th century till nowadays. Two main peaks

around 1890 and 1960 can be stated together with a widespread flooding decay at the begin of

both centuries, on the 1810´and 1920´ decades. The comparative floods analysis between

different river basins presents good correlation between floods peaks on the four studied basins,

but with some differences among them. In spite of the good clustering for flood periods, a

relationship with precipitation data of the different basins could not be been established clearly.

INTRODUCTION

Historical floods on the Tagus, Guadiana, Jucar and Segura river basins have been

compiled, mainly from the data of Comisión Nacional de Protección Civil (1985), and

compared in order to point out differences between the Atlantic and Mediterranean watersheds

of the Southern Iberian Peninsula. A relationship between floods and long historical series of

precipitation, has also been established, in order to establish climatic relationships. The Atlantic

watershed is controlled by the frontal systems related to zonal circulation, whether the

Mediterranean one is mainly affected by Southern flows and cold pools (Capel Molina, 1981;

Olcina, 1994; Benito et al. 1996).

FLOODS COMPARISON BETWEEN ATLANTIC AND MEDITERRANEAN

WATERSHEDS

The comparative floods analysis between different river basins (Fig. 1) shows a good

correlation between floods peaks on the four studied basins, but with some differences among

them. Floods evolution since 1500 shows an increase on the flood occurrence for all the studied

basins from late 18th century till the present one. Although this events increase might be

affected by a more rigorous registration, the recent development of structural regulation works

on the main rivers should also have smoothed the results.

On a further approach, the comparative analysis between Atlantic and Mediterranean

watersheds (Fig.2) confirms a same flooding trend for both. On the Atlantic divide, however,

since the middle of the present century, a significant flood increase is observed in respect to the

ones on the Mediterranean area (Martinez & Garzón, 1996; Ortega & Garzón, 1997). Two main

peaks around 1890 and 1960 (and a smaller on around1920) can be stated together with a

widespread flooding decay at the begin of both centuries, on the 1810´and 1910´ decades.

RELATIONSHIP OF PRECIPITATION AND FLOODS

In spite of the good clustering for flood periods, a relationship with precipitation data of

the different basins could not be been established clearly. This can be justified with a more

detailed approach to floods data on each basin, and on considering separately the floods of

different areas within the basin As en example, several populations can be considered for the

whole Guadiana basin: the ones from the upper basin, the coastal ones, and the ones from the

main river. On considering its yearly distribution, one can observe that the main river ones

32


mainly occur in winter, the upper basin ones are distributed preferentially in autumn, but also

during summer and spring, and that the coastal ones occur in winter, spring and fall (Potenciano

& Garzón, 2001).

60

Floods (Guadiana, Tajo, Segura and Júcar basin)

3 decades running average

50

Floods No.

40

30

20

10

0

1500

1520

1540

1560

1580

1600

1620

1640

1660

1680

1700

1720

1740

1760

1780

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

2000

Decades

Fig. 1. Historical floods and running average for the studied basins since 1500

20

18

16

Fl 14

oo 12

ds 10

No 8

. 6

4

2

0

ATLANTIC

1500 1600 1700 1800 1900

1890

Decades

20

18

16

14

Fl

oo 12

ds 10

No 8

. 6

4

2

0

MEDITERRANEAN

1500 1600 1700 1800 1900

1890

Decades

Fig. 2. Comparison between floods on the Atlantic and Mediterranean watersheds

33


Considering this fact, a further approach has been realized in order to point out the

genetic significance for flooding trends between the different studied basins (Fig. 3). Floods at

the four basins have been considered in relation to its month of occurrence and the part of the

basin to which they correspond and compared to the historical precipitation. It can be stated that

for the Atlantic watershed during the last century floods were registered mainly in the upper

basins. On the other hand, during the last period, an increase in winter floods occurs for the

lower Atlantic basins. Jucar floods are quite homogeneous, whilst for the Segura basin a

significant decay can be noticed since middle of the present century.

DISCUSSION AND CONCLUSIONS

A cyclical flood recurrence can be stated with a remarkable increase since the last

century. Two main peaks are present, the most important one at the end of last century.

There is a good flood correlation on both Atlantic and Mediterranean watersheds , with

a decay of the Segura basin ones for recent years.

Two types of events have been identified, those originated by convective storms,

mainly during the fall months, and the ones controlled by Atlantic frontal systems, restricted to

the winter.

This distribution reinforces the necessity of understanding the causes and mechanisms

of flooding when evaluating recurrence periods, more than a purely statistical approach.

REFERENCES

BENITO, G.; MACHADO, M.J.; PÉREZ-GONZÁLEZ, A. (1996). “Climate change and flood

sensivity in Spain”. Ed. Branson, J., Brown, A.G. & Gregory, K.J. Global Continental Changes:

the context of Palaeohydrology. Londres. Geological Society Special Publication No.115 , 85-

98 pp.

CAPEL MOLINA (1981). “Los climas de España”. Oikos -Tau, Barcelona. 429 p.

COMISIÓN NACIONAL DE PROTECCIÓN CIVIL. (1985). “Estudio de inundaciones

históricas. Cuenca del Guadiana”. Tomo II. Madrid

MARTÍNEZ, J. & GARZÓN, G. (1996). “Análisis de las avenidas históricas en el río Júcar”. 6º

Congreso Nacional y Conferencia Internacional de Geología Ambiental y Ordenación del

Territorio. Volumen 3, 29-41 pp.

OLCINA, J. ( 1994). “Riesgos climáticos en la Península Ibérica”. Penthalon. 438 pp.

ORTEGA, J.A. & GARZÓN, G. (1997). “Inundaciones históricas en el Río Guadiana”. Ed.

Rodriguez, J. Cuaternario Ibérico. AEQUA. Huelva, 365-367 pp.

POTENCIANO, A. & GARZÓN, G. (2001). “Significado paleoclimático de las inundaciones

históricas en las cuencas fluviales atlánticas y mediterráneas del Centro–Sur de España”. 6º

Congreso Español de Geomorfología, Madrid. (en prensa)

34


DISTRIBUTION OF HISTORICAL FLOODS AND PRECI

G U AD IA N A , T A JO , S E G U R A A N D JÚ CAR RIVERS BAS

GUADIANA RIVER BASIN

600

500

GUADIANA UPPER BASIN FLOODS

OTHER FLOODS

GUADIANA LOW BASIN FLOODS

W INTER RAIN IN BADAJO Z

AUTUMNAL RAIN IN BADAJOZ

11Nov

10Oct

9 Sep

800

700

TAJO UPPER BASIN FLOODS

OTHER FLOODS

TAJO RIVER

TAJO LOW BAS

TOTAL RAIN (mm)

400

300

200

8 Aug

Jul

7

6Jun

5May

4Apr

3Mar

MONTH

TOTAL RAIN (mm)

600

500

400

300

100

0

2 Feb

1 Jan

0 Dec

-1

200

100

0

1860

1870

1880

1890

1900

1910

1920

1930

YEAR

SEGUARA RIVER BASIN

1940

1950

1960

1970

1980

1860

1870

1880

1890

1900

1910

1920

YEAR

JÚCAR RIVER BASIN

SEGURA FLOODS

OTHER FLOODS

GUADALENTÍN FLOODS

W INTER R AIN IN ALIC ANTE

AUTUM NAL R AIN IN ALICANTE

TURIA FLOODS

OTHER FLOODS

JUCAR FLOODS

500

Nov 11

1000

TOTAL RAIN (mm)

450

400

350

300

250

200

150

100

50

Oct 10

Sep 9

Aug 8

Jul

7

Jun 6

MONTH

May 5

Apr 4

Mar 3

Feb 2

Jan 1

Dec 0

TOTAL RAIN (mm)

900

800

700

600

500

400

300

200

100

0

1860

1870

1880

1890

1900

1910

1920

YEAR

1930

1940

1950

1960

1970

1980

-1

0

1860

1870

1880

1890

1900

1910

1920

YEAR

Fig. 3. Historical floods and precipitation distribution according to the occurrence month and area of the basin

35


Groundwater and Landscape Sustainable Management. Ed. Department of Geodynamics (UCM), 2001. pp 116

MICROBIOLOGICAL STUDY OF THE INCRUSTATIONS AND

CORROSIONS IN GROUNDWATER WELLS

SENDEROS, A. 1 ; VILLARROYA, F. 1 AND De CASTRO, F. 2

1 Department of Geodynamics. Faculty of Geologic Sciences. Complutense University. 28040 Madrid (Spain)

2 Department of Microbiology, Faculty of Biology Sciences. Complutense University. 28040 Madrid (Spain)

ABSTRACT

A review is made to the mechanisms of the development of incrustations in

groundwater wells, doing special emphasis in the influence that the microorganisms can have in

this development, not only by the direct oxide and hydroxide of iron precipitation, consequence

of their own metabolism, but for the modification of the chemical parameters of the

surroundings or by "passive precipitation". Of most of the samples a shooting of the state of

each well has been made.

Due to the characteristics required by each water sample (sterility for the microbial

study and collection of incrustation at the same point), it has been necessary to design a specific

tool capable to be connected to the video camera. The tool has been patented with the record

number 990012081/1 of the Registry Office of Patents.

Chemical analyses have confirmed the variety of waters tried from the first moment. All

the samples have been imagined in specific diagrams of Pourbaix for the iron, being observed

that most of them falls within the field of stability of Fe(OH) 3 . The incrustations of Hematite and

Goethite predominate, although there are also deposits of the amorphous Fe(OH) 3 .

For the microbiological study, classic laboratory cultures have been made and a system

of detection by colorimetry patented by Dr. D. R. Cullimore of the University of Regina

(Canada) and that has first been used in Spain in this work. After the statistical analyses we

observe that the presence of certain types of micro-organisms is practically independent of the

characteristic of the well, so none is free to undergo alterations of this type. This confirms that

the periodic maintenance of the well is necessary, no matter is chemical characteristics and use.

Finally, there is a review to the most useful systems of regeneration of wells affected by

incrustations.

REFERENCES

SENDEROS, A. (2001). "Estudio microbiológico de las incrustaciones y corrosiones en

captaciones de agua subterránea" Tesis doctoral inédita. Facultad de Ciencias Geológicas.

UCM. 281 pp más anexos. (Microbiological study of the incrustations and corrosions in

groundwater wells).

CULLIMORE, D.R. (1992). "Practical Manual of groundwater microbiology". Lewis Publish.

Michigan, 412 pp.

36

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