Climate Change and the European Water Dimension - Agri ...

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ack to the oceans via transport in streams, rivers, lakes, reservoirs, wetlands and groundwater bodies, to begin its cycle anew. Approximately 42,000 km 3 of precipitation flows each year to the oceans through the world’s rivers. Some of the precipitation will seep down into the Earth’s surface and become groundwater. Some of it will be taken up by plants and subsequently released in gaseous form back into the atmosphere via transpiration. A substantial quantity of water is returned to the atmosphere in this manner, thereby shortcircuiting the full hydrologic cycle. It is estimated, for example, that a hectare of corn can transpire about 30-40 m 3 of water into the atmosphere each day. Nevertheless, because of their enormous surface area, the most important source of water in the atmosphere is evaporation from the oceans, which comprises nearly 90% of the total global evaporation. Indeed, more water evaporates from the oceans than is directly precipitated back, thus creating the driving force for the hydrologic cycle. III.2. HYDROLOGIC CYCLE COMPONENTS AND CLIMATE CHANGE Geographical Distribution of Resources The magnitude of each component of the hydrologic cycle in a region or country is determined by a number of factors, including the amount of water received from precipitation, inflow and outflow in rivers and aquifers (this factor is particularly important in transnational water bodies) and the amount lost by evaporation and evapotranspiration (influenced to a large extent by local land use/land cover). Human activities also greatly affect individual components of the hydrological cycle, through actions such as water abstraction from ground and surface water bodies, through irrigation, and morphological changes. Methods for calculating the availability of freshwater resources vary considerably from country to country, making comparison difficult. Rees and Cole (1997) have developed a method of estimating the renewable freshwater resources across the EU. The method uses data from hydrometric (river gauging) networks, supplemented by an empirical freshwater balance model that relates runoff to precipitation and potential evaporation. Freshwater resources vary considerably across the European Region: annual runoff ranges from over 3000 mm in western Norway, to 100 mm over large areas of Eastern Europe, and to less than 25 mm in inland Spain (figure III.3). The average annual runoff for the member countries of the European Environment Agency (EEA, 1998) is estimated to be about 3100 km 3 per year. This is equivalent to 4500 m 3 per capita per year for a population of 680 million (Stanners and Bourdeau, 1995). The population of the WHO European Region is some 870 million, but figures for total runoff are not available. Specific processes govern the generation of each individual component in the hydrologic cycle. The following paragraphs offer a description of each component, and how each could be possibly affected by climate change. 36
Figure III.2. Long-term average annual runoff in the European Union and nearby areas (EEA, 1998). Precipitation Precipitation is the primary mechanism for transporting water from the atmosphere to the surface of the earth. Dominant variables in precipitation dynamics are temperature, density and pressure. The starting point for precipitation formation is atmospheric moisture content, expressed as the mixing ratio (ratio between mass of water vapor and mass of dry air) or specific humidity (ratio between water vapor mass and total mass). Clouds form when air becomes supersaturated with water vapor, i.e. when moisture content is higher that corresponding to saturation vapor pressure. Supersaturation is associated with the rapid cooling of ascending air masses, where water vapor condenses forming hydrometeors. Aerosol particles in turn act as seeds for the formation of water droplets, which fall to the ground when their weights exceed the carrying capacity of atmospheric currents. Because of atmospheric circulation, water vapor can move over large distances; thus precipitation, in any of its forms (rain, hail, snow, sleet, and freezing rain), happens at locations that are different from those where atmospheric water vapor was generated. For a complete review on precipitation processes and related atmospheric dynamics see Smith (1993). Precipitation is characterized by a high variability in space and time. Striking differences can be observed in precipitation intensity even at small space and time ranges, sometimes giving birth to extreme occurrences of high precipitation (floods) or no precipitation (droughts). For a review 37
Page 1 and 2: Climate Change and the European Wat
Page 3 and 4: European Commission- Joint Research
Page 7 and 8: At the 2003 Rome Informal Meeting o
Page 11 and 12: Changes in the diurnal variation of
Page 13 and 14: Fugure I.2. (a) Maximum grid covera
Page 15 and 16: century. This corresponds to a sea
Page 17 and 18: Other causes Other causes of climat
Page 19 and 20: tropospheric ozone are photochemica
Page 21 and 22: Figure. I.4. Radiative forcings and
Page 23 and 24: There are two indirect effects of a
Page 25 and 26: The projected warming is not unifor
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Page 31 and 32: Aerosols and climate change in the
Page 33 and 34: precipitation intensities have been
Page 35: Chapter III. The Hydrologic Cycle I
Page 39 and 40: Figure III.4. Projected change in s
Page 41 and 42: eduction in the rate of evaporation
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Page 45 and 46: temperatures potentially lead to hi
Page 47 and 48: Chapter IV.A. Proxy indicators of C
Page 49 and 50: Mean Air Temperature (Dec.-March) [
Page 51 and 52: correlation coefficient -0.4 -0.3 -
Page 53 and 54: Chapter IV. B. The Impact of Climat
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Page 59 and 60: quality degradation and meet the in
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Box # 1: The North Sea The North Se
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and organic material more rapidly t
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suggesting that climate rather than
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CO2 2- ). In turn, the alkalinity i
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looms are often associated with tox
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events of dense water through the D
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(1) Are we already observing a resp
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eastern and western side of the Nor
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system, their physiology and intern
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each coastal element be studied and
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IV.D.1. Introduction Coastal lagoon
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In the last decade, a general model
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topics in coastal lagoons (de Wit e
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Po River Delta lagoons, the long dr
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esilient to environmental changes a
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Chapter V.A. Climate Change and Ext
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It is realized that adaptation to c
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Climate Change and the European Wat
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member states. Moreover some agenci
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Large, global scale climatic driver
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V.B.5. Climate change and droughts
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Evacuation from forest fires at Mas
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In European forest policy, water is
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Drought mitigation and the involvem
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DSS-DROUGHT A Decision Support Syst
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Chapter V .C. Climate Change, Ecolo
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The quality class boundaries within
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An example of this kind of relation
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Regions 1 to 5 represent mainly a m
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een observed in southwestern countr
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Table V.D.2: Percentage area affect
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Lake Surface Temperature [°C] Desc
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Case Study: Esthwaite Water, Cumbri
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Residence time (days) Chlorophyll (
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Case Study: Lake Erken, Sweden ►
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TP (µg l -1 ) Modelling To analyse
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Data availability and investigation
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smaller volume of water. The warmer
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Chapter VI.B. Climate Change and th
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Concerning the flora of the lagoon
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Figure VI.B.2: Frequency of “bora
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Figure VI.C.2. Daily flows in Ebro
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Figure VI.C.4. Mean temperature inc
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factors including an appropriate su
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with the lower limit range indicate
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Chapter VI.C. The Effects of Climat
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the main carrier of nutrients to gr
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system pathway shows an increase of
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Table-VI.C.7: Main factors and cons
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Chapter VI.D. Climate Change and th
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Atmospheric deposition to marine wa
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Many studies during the 90’s have
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severe flooding were investigated (
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Table VI.E.1. Waterborne pathogens
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Chapter VI.F. Climate Change, Extre
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Areas behind the dikes broken in 20
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Second, the chemical is transported
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POPs exist in the atmosphere in the
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and ice have quite a low capacity t
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Table VI.F.1. Priority substances i
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22. Monteith, J.L., 1965. Evaporati
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31. Rodionov, S.N. 1994. Global and
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28. Dokulil, M.T., 2003. Algae as e
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63. Hejzlar, J., Dubrovský, M. Buc
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99. Melack, J.M., J. Dozier, C.R. G
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136. Straile, D. & Adrian, R. 2000.
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14. Blaas, M., Kerkhoven, D., and d
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60. McCleery, R. H. and Perrins, C.
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105. UNESCO 2003. The integrated st
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ecosystems and the landscape and de
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2. Carter, T.R., Saarikko, R.A., an
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24. Hydrographisches Zentralbüro 1
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European Coastal Lagoons: The Influ
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4. Bouma MJ, Sondrop HE, van der Ka
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variable trophic status: a paired l
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France GIANMARCO GIORDANI Departmen
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Chapter VI.E. Climate Change and Wa
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