Section “Groundwater in Sedimentary Basins” - Latvijas Universitāte

Section “Groundwater in Sedimentary Basins” - Latvijas Universitāte

Section “Groundwater in Sedimentary Basins” - Latvijas Universitāte


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The 70 th Scientific Conference of the University of LatviaSession of Geology<strong>Section</strong>„Groundwater<strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s”ABSTRACT BOOK

The 70 th Scientific Conference of the University of LatviaSession of Geology<strong>Section</strong>“Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s”ABSTRACT BOOKFaculty of Geography and Earth Sciences,Alberta street 10, room 313, RigaJanuary 30, 2012Riga, 2012

CONTENTSRe<strong>in</strong> VaikmäeThe state of art and new trends <strong>in</strong> the application of isotope-geochemistry forgroundwater research 5Oļģerts AleksānsThe specifics of determ<strong>in</strong><strong>in</strong>g hydrogeological parameters for two-phase liquid flows<strong>in</strong> porous media 5Jonas Kley, Alexander Malz, Stephan DonndorfTowards “realistic” fault zones <strong>in</strong> a 3D structure model of the Thur<strong>in</strong>gian Bas<strong>in</strong>,Germany 8Aivars SpalviņšLimits and presuppositions on creat<strong>in</strong>g and use of the regional hydrogeologicalmodel of Latvia 10Eleonora Pērkone, Jānis Bikše, Jānis Jātnieks, Ilze Kl<strong>in</strong>ts, Aija Dēliņa,Tomas Saks, Baiba Raga, Inga RetiķeStudies and projections of hydraulic conductivity of Devonian and Cambrian clasticsediments 13Juris Seņņikovs, Andrejs Timuh<strong>in</strong>s, Jānis VirbulisSensitivity of hydrogeological model to the surface roughness and spatial variabilityof hydraulic conductivity 14Jānis Virbulis, Juris SeņņikovsTransient modell<strong>in</strong>g of groundwater dynamics <strong>in</strong> the Baltic Artesian Bas<strong>in</strong> 15Albertas Bit<strong>in</strong>asFormation of groundwater <strong>in</strong> sedimentary bas<strong>in</strong>s: traditional and alternative models 16Veiko Karu, Jana PavlenkovaWater filled underground oil shale m<strong>in</strong>es as a heat source 19Tomas Saks, Juris Seņņikovs, Andrejs Timuh<strong>in</strong>s, Andis KalvānsReconstruct<strong>in</strong>g the groundwater flow <strong>in</strong> the Baltic Bas<strong>in</strong> dur<strong>in</strong>g the last glaciation 21Didzis Lauva, Inga Grīnfelde, Artūrs Ve<strong>in</strong>bergs, Kaspars Abramenko,Valdis Vircavs, Zane Dimanta, Ilva Vītola, Agnese GailumaThe uncerta<strong>in</strong>ty of the future annual long-term groundwater table fluctuation regime<strong>in</strong> Latvia 22Baiba Raga, Andis Kalvāns, Aija Dēliņa, Eleonora Pērkone, Inga RetiķeEvolution of groundwater composition <strong>in</strong> the depression cone of the Riga region 24Alise Babre, Aija DēliņaApplication of stable isotope content <strong>in</strong> groundwater to validate the results of thehydrogeological model of the Baltic Artesian Bas<strong>in</strong> 25Valdis Vircavs, Zane Dimanta, Didzis Lauva, Kaspars Abramenko,Artūrs Ve<strong>in</strong>bergs, Agnese Gailuma, Ilva VītolaThe analysis of groundwater quality problems <strong>in</strong> Baltic Sea region countries 27Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 3

Andis KalvānsThe visualisation of groundwater chemical composition us<strong>in</strong>g the RGB scale.An example from the D12 aquifer, Latvia 28Jānis Teterovskis, Andis KalvānsCredibility criteria of the results of underground water analysis 29Inga Retiķe, Andis Kalvāns, Aija Dēliņa, Alise Babre, Baiba Raga,Eleonora PērkoneTrace elements <strong>in</strong> groundwater <strong>in</strong> Latvia: exist<strong>in</strong>g data and first new results 32Agnese Gailuma, Ilva VītolaRecession curve analysis approach for groundwater 33Ilze Kl<strong>in</strong>ts, Jānis Virbulis, Aija DēliņaInfluence of water abstraction on groundwater flow <strong>in</strong> the BAB 34Jānis Jātnieks, Konrāds Popovs, Jānis Ukass, Tomas Saks, Aija DēliņaUseful statistics for describ<strong>in</strong>g hydraulic conductivity of the quaternary stratafrom the Latvian borehole log data 35Juris Burlakovs, Armands RuskulisEnvironmental situation <strong>in</strong> the area around Inčukalns ponds and threatsto groundwater 37Juris Burlakovs, Dz<strong>in</strong>tars LācisThe development trends of Mūru-Žagares and Jonišķi-Akmenes groundwaterhorizon surface depression and sea water <strong>in</strong>trusion impact <strong>in</strong> Liepāja city 38Jānis Bikše, Aija Dēliņa, Alise BabreAdditional data on the CFC concentration and correspond<strong>in</strong>g ground water age<strong>in</strong> the fresh groundwater of Latvia 40Aija Dēliņa, Jānis Virbulis, Ilze Kl<strong>in</strong>tsGroundwater abstraction dynamics <strong>in</strong> the Baltic Artesian Bas<strong>in</strong> 42Jānis Ukass, Konrāds Popovs, Tomas SaksReconstruct<strong>in</strong>g the Caledonian structural complex deformationthrough thickness analysis 43Konrāds Popovs, Jānis Ukass, Jānis Jātnieks, Tomas SaksBAB V1 geometrical model: <strong>in</strong>tegrat<strong>in</strong>g heterogeneous and uneven density data <strong>in</strong>toa 3D geological model 45Oļegs Grigorjevs, Andis KalvānsThe sensibility analysis of Cl - and SO 42-titration <strong>in</strong> groundwater samples 474 The 70 th Scientific Conference of the University of Latvia

THE STATE OF ART AND NEW TRENDSIN THE APPLICATION OF ISOTOPE-GEOCHEMISTRYFOR GROUNDWATER RESEARCHRe<strong>in</strong> VAIKMÄEInstitute of Geology at Tall<strong>in</strong>n University of Technology, e-mail: Re<strong>in</strong>.Vaikmae@ttu.eeEnvironmental isotopes are now almost rout<strong>in</strong>ely applied <strong>in</strong> studies of groundwaterresources.Tritium, radiocarbon and stable isotope ratios of D/H and 18 O/ 16 O havebeen most widely used, and <strong>in</strong>creas<strong>in</strong>g use is be<strong>in</strong>g made of <strong>in</strong>ert gases.In the past decade, aquifers have <strong>in</strong>creas<strong>in</strong>gly become palaeoclimatic archives<strong>in</strong> their own right alongside ice cores, sediments and other proxy records. The ma<strong>in</strong>tool for this task has been the noble gas palaeo-thermometer <strong>in</strong> comb<strong>in</strong>ation withquantitative groundwater dat<strong>in</strong>g us<strong>in</strong>g radionuclides. Noble gas radionuclides playa unique role as tracers <strong>in</strong> environmental studies due to their chemical <strong>in</strong>ertnessand low concentration, mak<strong>in</strong>g them ideal tracers. The same properties on the otherhand make them difficult to measure on natural concentration levels. Therefore, fordecades, low level count<strong>in</strong>g (LLC) was the only method for detect<strong>in</strong>g radioisotopesof argon and krypton at an atmospheric level. In recent times and with the <strong>in</strong>crease<strong>in</strong> <strong>in</strong>terest and potential applications, analytical efforts with novel detection methodshave been <strong>in</strong>tensified. In this talk, noble gas groundwater dat<strong>in</strong>g techniques overtime scales from decades to millions of years are also discussed <strong>in</strong> relation to noblegas palaeo records at different locations <strong>in</strong> Europe.THE SPECIFICS OF DETERMININGHYDROGEOLOGICAL PARAMETERSFOR TWO-PHASE LIQUID FLOWS IN POROUS MEDIAOļģerts ALEKSĀNSGeoExpert Ltd., e-mail: olgerts.aleksans@geoexpert.lvThe two-phase fluid vertical distribution <strong>in</strong> the groundwater aquifer concept hasbeen repeatedly changed and hydro geological calculation methodology has changed aswell. Yet, <strong>in</strong> the 1950’s-1960’s, it was based on a standard (API-Publication, 2004), buterroneous impression, that the free-phase liquid layer <strong>in</strong> a ground-water aquifer formsa lens that is strictly separated from the water and floats above it. It was consideredthat <strong>in</strong> this lens, 100% from the pore volume is filled with free-phase liquid.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 5

TOWARDS “REALISTIC” FAULT ZONESIN A 3D STRUCTURE MODELOF THE THURINGIAN BASIN, GERMANYJonas KLEY, Alexander MALZ, Stephan DONNDORFINFLUINS – Integrated Fluid Dynamics <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s,Friedrich Schiller University Jena, Institute of Geosciences, Burgweg 11, 07749 Jena,Germany, e-mail: jonas.kley@uni-jena.de3D computer models of geological architecture are presently evolv<strong>in</strong>g <strong>in</strong>to astandard tool for visualization and analysis. Such models typically comprise thebound<strong>in</strong>g surfaces of stratigraphic layers or stratigraphic volumes, and faults.Faults are ubiquitous <strong>in</strong> the Earth´s crust; they are shear fractures across whichthe stratigraphic layers are offset. Faults thus affect the cont<strong>in</strong>uity of aquifersand can themselves act as fluid conduits or barriers. This is one reason why a“realistic” representation of faults <strong>in</strong> 3D models is desirable. Still, many exist<strong>in</strong>gmodels treat faults <strong>in</strong> a simplistic fashion, e.g. as vertical downward projections offault traces observed at the surface. Besides be<strong>in</strong>g geologically and mechanicallyunreasonable, this also causes technical difficulties <strong>in</strong> the modell<strong>in</strong>g workflow.Boreholes located close to a fault at the surface can cross dipp<strong>in</strong>g fractures atdepth, result<strong>in</strong>g <strong>in</strong> stratigraphic control po<strong>in</strong>ts be<strong>in</strong>g allocated to the wrong block.Most natural faults are <strong>in</strong>cl<strong>in</strong>ed and may change dips accord<strong>in</strong>g to rock type orflatten <strong>in</strong>to mechanically weak layers. Also, faults tend to split up <strong>in</strong>to severalbranches, form<strong>in</strong>g fault zones. Obta<strong>in</strong><strong>in</strong>g a more accurate representation of faultsand fault zones is therefore challeng<strong>in</strong>g.Here we present work-<strong>in</strong>-progress from the Thur<strong>in</strong>gian Bas<strong>in</strong> where we attemptto <strong>in</strong>tegrate complex fault zones <strong>in</strong> both a 3D architecture model and a numericalflow model. The Thur<strong>in</strong>gian Bas<strong>in</strong> is a doubly-plung<strong>in</strong>g, NW-trend<strong>in</strong>g syncl<strong>in</strong>esome 150 km long and 75 km wide. Its mostly Triassic strata <strong>in</strong>cludes sandstone,limestone, shale and evaporite. The Thur<strong>in</strong>gian Bas<strong>in</strong> became separated fromthe much larger North German Bas<strong>in</strong> only <strong>in</strong> the Late Cretaceous time, whencontractional tectonics created its syncl<strong>in</strong>al geometry. The syncl<strong>in</strong>e is dissectedby several longitud<strong>in</strong>al fault zones. For some of these, a history of early normalfault<strong>in</strong>g followed by reverse reactivation has been demonstrated. Wholesaleuplift <strong>in</strong> the latest Cretaceous and early Paleogene time led to exhumation of theThur<strong>in</strong>gian Bas<strong>in</strong>. Deposition is presently restricted to its north-eastern corner.The uplifted Thur<strong>in</strong>gian Bas<strong>in</strong> grants access to strata deeply buried <strong>in</strong> the NorthGerman Bas<strong>in</strong>, Germany’s most important hydrocarbon prov<strong>in</strong>ce. It can thus beviewed as a very large outcrop analogue of a geologic situation that has been<strong>in</strong>tensely <strong>in</strong>vestigated by seismics and drill<strong>in</strong>g <strong>in</strong> the North German Bas<strong>in</strong>. The TBis geologically mapped at the 1 : 25.000 scale. Subsurface data is much scarcer.8 The 70 th Scientific Conference of the University of Latvia

There are a number of boreholes penetrat<strong>in</strong>g the basement and many more thathave reached the Zechste<strong>in</strong>. Localized <strong>in</strong>formation is available from a few deepsalt m<strong>in</strong>es. Modern seismic data is limited to a few 2D l<strong>in</strong>es, <strong>in</strong>clud<strong>in</strong>g two, newlyacquired by the INFLUINS project. Away from the fault zones, extrapolation todepth is facilitated by the relatively constant thickness of most stratigraphic units.In the fault zones, there is never enough data to fully constra<strong>in</strong> the geometries,so we need to make educated guesses as to how the faults cont<strong>in</strong>ue to depth.We use balanc<strong>in</strong>g of serial, parallel cross-sections as a method of constra<strong>in</strong><strong>in</strong>gsubsurface extrapolations. The fundamental assumption is that rock volume doesnot change dur<strong>in</strong>g deformation. Under plane stra<strong>in</strong> conditions, i.e. with all particlesmov<strong>in</strong>g <strong>in</strong> the cross-section plane, this translates <strong>in</strong>to constant cross-section areasbefore and after deformation. The structure sections are checked for consistencyby restor<strong>in</strong>g them to an undeformed state with orig<strong>in</strong>al layer thicknesses. If this ispossible without produc<strong>in</strong>g any gaps or overlaps between strata, the <strong>in</strong>terpretationis considered valid (but not unique) for a s<strong>in</strong>gle cross-section. Such valid solutionsare found <strong>in</strong> a computer-aided yet <strong>in</strong>tuitive, trial-and-error procedure us<strong>in</strong>g MidlandValley´s 2DMove program.Additional constra<strong>in</strong>ts are provided by comparison of adjacent cross-sections.Structures should change cont<strong>in</strong>uously from one section to another unless there areobvious cross-faults. Also, from the deformed and restored cross-sections, we canmeasure the length change (stra<strong>in</strong>) <strong>in</strong>curred dur<strong>in</strong>g deformation. The stra<strong>in</strong> shouldbe compatible among the cross-sections: If at all, it should vary smoothly andsystematically along a given fault zone.Fig. 1. High resolution model of a graben structure <strong>in</strong> the north-western Thur<strong>in</strong>gian Bas<strong>in</strong>,show<strong>in</strong>g serial cross-sections and triangulated surfaces represent<strong>in</strong>g stratigraphic boundariesand faults. Notice short-wavelength fold<strong>in</strong>g close to the fault visible <strong>in</strong> some cross-sections.The stratigraphic contacts and faults <strong>in</strong> the result<strong>in</strong>g grid of parallel balancedsections are then <strong>in</strong>terpolated <strong>in</strong>to a model conta<strong>in</strong><strong>in</strong>g stratigraphic boundaries andfaults as triangulated surfaces <strong>in</strong> gOcad (Fig. 1). The <strong>in</strong>terpolation is also controlledSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 9

y borehole data located off the sections and the traces of stratigraphic boundariesat the surface. We have written customized scripts to largely automatize this step,with particular attention to a seamless fit between stratigraphic boundary surfacesand fault planes which share the same nodes along their contacts. Additionalattention was paid to the creation of a uniform triangulated grid with maximizedangles. This ensures that uniform triangulated volumes can be created from themodel for further use <strong>in</strong> numerical flow modell<strong>in</strong>g. A 3D balanc<strong>in</strong>g of the structuremodel is also planned, to check and <strong>in</strong>crease the accuracy.An, as yet, unsolved problem is the implementation of the fault zones and theirhydraulic properties <strong>in</strong> a large-scale model of the entire bas<strong>in</strong>. Short-wavelengthfolds and subsidiary faults control which aquifers and seals are juxtaposed acrossthe fault zones. It is impossible to <strong>in</strong>clude these structures <strong>in</strong> the regional model,but neglect<strong>in</strong>g them would result <strong>in</strong> <strong>in</strong>correct assessments of hydraulic l<strong>in</strong>ks orbarriers. We presently plan to test and calibrate the hydraulic properties of thefault zones <strong>in</strong> smaller, high-resolution models and then to implement geometricallysimple “equivalent” fault zones with appropriate, variable transmissivities betweenspecific aquifers.LIMITS AND PRESUPPOSITIONS ON CREATING ANDUSE OF THE REGIONAL HYDROGEOLOGICAL MODELOF LATVIAAivars SPALVIŅŠRiga Technical University, Faculty of Computer Science and Information Technology,Environment Modell<strong>in</strong>g Centre, e-mail: emc@cs.rtu.lvThe ma<strong>in</strong> limits regard<strong>in</strong>g the regional hydrogeological model (HM) of Latvia(see Fig. 1) are, as follows:• The HM will be used for the management of dr<strong>in</strong>k<strong>in</strong>g groundwater resourcesof Latvia;• The HM is created by the Environment Modell<strong>in</strong>g Centre team of the RigaTechnical University (RTU); the project is co-f<strong>in</strong>anced by the European Fundof Regional Development;• The duration of the project is 24 months; the HM must be established <strong>in</strong> 2013;• The geological and hydrogeological <strong>in</strong>formation required for establish<strong>in</strong>gthe HM, is provided by the Latvian Environment, Geology and MeteorologyCentre (LEGMC);10 The 70 th Scientific Conference of the University of Latvia

• The pr<strong>in</strong>cipal parameters of the HM must be agreed between RTU andLEGMC;• Data carried by the HM must be publicly available as a part of Latvia’senvironment <strong>in</strong>formation system; the system is supported by LEGMC;• Dur<strong>in</strong>g the five years (till 2017), RTU and LEGMC cannot use the HMcommercially.Fig. 1. Location of Latvia’s HM.The HM of Latvia will generalize geological and hydrogeological <strong>in</strong>formationaccumulated by LEGMC. The HM will also serve as the base for creat<strong>in</strong>g moredetailed local HM’s.It is not possible to <strong>in</strong>corporate all the data that can be provided by LEGMC<strong>in</strong>to regional HM’s. A reasonable reduction <strong>in</strong> HM complexity can be achieved byimplement<strong>in</strong>g the follow<strong>in</strong>g presuppositions:• The complexity and dimensions of the HM must not exceed the feasibilityof a modern personal computer used to run the HM; The HM simulates thesteady state average regimes of the groundwater flow; the HM area size is475 km × 300 km; the HM volume is approximated by the f<strong>in</strong>ite differencemethod; its plane approximation step is 500 meters; the spatial HM grid conta<strong>in</strong>s25 planes; therefore, the grid consists of 951 × 601 × 25 = 14.86 × 10 6 nodes;the HM volume represents the active groundwater zone that is bedded by theregional Narva aquitard;Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 11

• To ensure compatibility with the models and software tools of other countries,the “Groundwater Vistas” (GV) commercial program is used for the runn<strong>in</strong>gof the HM; the program is be<strong>in</strong>g regularly updated (GV-6 version is available);it conta<strong>in</strong>s the MODFLOW, MODPATH and MT3D software tools applied forgroundwater modell<strong>in</strong>g worldwide;• At the present, the HM consists of its active and passive parts; the active part<strong>in</strong>cludes the land territory of Latvia and the Gulf of Riga; the passive partrepresents the border areas of neighbour<strong>in</strong>g countries. However, the HM isopen for trans-boundary modell<strong>in</strong>g projects; a neighbour<strong>in</strong>g country wouldthen provide data for activat<strong>in</strong>g the HM area <strong>in</strong>volved;• Although buried valleys may be of considerable importance, they arenot accounted for by the current HM version; it is difficult to create themgeometrically as the fill<strong>in</strong>g material of valleys may be unknown;• In the HM, only the Narva aquitard is cont<strong>in</strong>uous; the other geological layersare discont<strong>in</strong>uous, because they <strong>in</strong>clude areas with a zero thickness; for themodel, these areas have a thickness of 0.02 meters and their permeability is1.0 m/day;• Three elevation surfaces of the HM are especially important:- the hydrogeological relief relh that represents the ground surface wherethe hydrographical network is <strong>in</strong>corporated;- the geological relief relg that gives land surface elevations;- the sub-Quaternary surface subQ that covers the system of basicgeological layers.The difference m w= relh-relg is the thickness of surface water bodies. (<strong>in</strong> theHM, m w> 0 for the sea area and for the Daugava river with its three lakes withhydroelectric power stations); for other water bodies (lakes, rivers), m w= 0.The difference ∆ = relg-subQ is used for obta<strong>in</strong><strong>in</strong>g the Quarternary systemthickness m Q: m Q= ∆ if ∆ > 1.0; m Q= 1.0 if ∆ ≤ 1.0 and relg = subQ + 1; by correct<strong>in</strong>grelg, along the river valleys where ∆ < 0, the subQ surface rema<strong>in</strong>s unchanged (nodeep valleys are cut <strong>in</strong>to it); otherwise, the grid nodes will be lost where river longl<strong>in</strong>es elevations must be connected (option River of GV):• The relh map serves as the piezometric boundary condition, on the HM top;due to this condition, the HM automatically creates a feasible <strong>in</strong>filtration flowdistribution;• No real thicknesses of bogs, of the aeration zone and of the unconf<strong>in</strong>edQuaternary aquifer are used dur<strong>in</strong>g the HM calibration; the aeration zoneof the thickness of 0.02 meters acts as a formal aquitard that controls the<strong>in</strong>tensity of the <strong>in</strong>filtration flow; the bogs are located with<strong>in</strong> this formallayer; if necessary, the real thicknesses of the abovementioned layers can berestored;• In HM, real thicknesses are used for layers (bogs, the aeration zone and thequaternary unconf<strong>in</strong>ed layer are exceptions); to account for admixtures thatexist <strong>in</strong> the layers, the maps of their permeability are corrected;12 The 70 th Scientific Conference of the University of Latvia

• For aquifers, along the borderl<strong>in</strong>e of the HM active part, piezometric boundaryconditions (heads) are applied; an impervious border surface cannot be used,because the cross border groundwater flow is notable everywhere;• As the piezometric boundary condition, on the HM bottom, the Pernavaaquifer map of its head distribution is used.Most of the abovedescribed measures can be used, if complex hydrogeologicalmodels have to be created.STUDIES AND PROJECTIONS OF HYDRAULICCONDUCTIVITY OF DEVONIAN AND CAMBRIANCLASTIC SEDIMENTSEleonora PĒRKONE 1 , Jānis BIKŠE 1 , Jānis JĀTNIEKS 1 , Ilze KLINTS 2 ,Aija DĒLIŅA 1 , Tomas Saks 1 , Baiba RAGA 1 , Inga RETIĶE 1University of Latvia, 1 Faculty of Geography and Earth Sciences, 2 VTPMML,e-mail: eleonora.perkone@lu.lvAquifer fluid conductivity properties describe the ability of sediments to transmitgroundwater, and consequently govern the groundwater flow. Hydraulic conductivitymostly depends on the different physical properties of the sediments and theirliquid filter<strong>in</strong>g properties. Studies and knowledge of hydraulic conductivity (K),transmissivity, storativity and aquifer properties for the particular aquifer are veryimportant for the hydrogeological problem solv<strong>in</strong>g process.This study presents the results of the comparative study between hydraulicconductivity, gra<strong>in</strong> size distribution and sediment lithology of the lower DevonianEmsian stage, the middle Devonian Eifelian and Givetian stage, the upper DevonianFrasnian stage, and Cambrian clastic sediments <strong>in</strong> the central part of the BalticBas<strong>in</strong>. The aim of this study was to f<strong>in</strong>d characteristic hydraulic conductivity valuesfor each aquifer based on aquifer gra<strong>in</strong> size distribution and lithology on the onehand and pump<strong>in</strong>g test results on the other.For the calculation of the hydraulic conductivity, one has to take <strong>in</strong>to accountnot only gra<strong>in</strong> size distribution, but effective porosity, temperature and k<strong>in</strong>ematicviscosity of the fluid as well, which are lack<strong>in</strong>g <strong>in</strong> this study.Pump<strong>in</strong>g test results provide a range of at least two orders of hydraulicconductivity values for each aquifer. To characterize the typical values for eachaquifer and further subdivide each aquifer <strong>in</strong>to regions of different hydraulicconductivities, the pump<strong>in</strong>g test results were correlated with gra<strong>in</strong> size distribution.A fraction of f<strong>in</strong>e particles, with a size less than 0.05 mm, was chosen as aSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 13

limit<strong>in</strong>g factor for the hydraulic conductivity <strong>in</strong> the sandstones. The correlation ofhydraulic conductivity and gra<strong>in</strong> size distribution was carried out by compar<strong>in</strong>gthe

were perturbed and the sensitivity of the model to the surface roughness and spatialvariability of hydraulic conductivity was calculated. Additional attention was paidto the estimation of the impact of subgrid scales of the topological surface to thecalculated hydraulic head distribution.This study is supported by the European Social Fund ProjectNo. 2009/0212/1DP/ MODELLING OF GROUNDWATERDYNAMICS IN THE BALTIC ARTESIAN BASINJānis VIRBULIS, Juris SEŅŅIKOVSVTPMML, University of Latvia, e-mail: janis@modlab.lvThe transient solver of groundwater flow for the model of the Baltic ArtesianBas<strong>in</strong> (BAB) was developed us<strong>in</strong>g the f<strong>in</strong>ite volume OpenFOAM libraries. SolverpotentialFoam was employed as a basis for the development, add<strong>in</strong>g the transientand water abstraction terms, as well as the management of the unconf<strong>in</strong>ed zone.The geometry of the model consists of a subsequent comb<strong>in</strong>ation of aquifers andaquitards with enormous differences of conductivities by 9 orders and thicknesses by2 orders between them. Due to the large area of the BAB and the complex structure ofsediments only one element per layer is tolerable. Therefore, high accuracy schemeswith the ability to handle large pressure gradients should be used. Investigationsshow that Monotone Upstream-centred Schemes for Conservation Laws (MUSCL)are best suited for such typical hydrogeological structures.Mesh structure, conductivity and boundary conditions are prepared <strong>in</strong> the preprocess<strong>in</strong>grout<strong>in</strong>es of HiFiGeo software and exported to the OpenFOAM fileformats.A method for the consideration of the unconf<strong>in</strong>ed zone has been developed. Thestorativity and conductivity of the unconf<strong>in</strong>ed volume elements are reduced thusexclud<strong>in</strong>g the unconf<strong>in</strong>ed zone from the flow field.The <strong>in</strong>fluence of storativity and conductivity on the transient solutions has beendemonstrated for typical ranges of material properties <strong>in</strong> the BAB.Dist<strong>in</strong>ct time dependence of the groundwater abstraction is typical for theBAB over the last 50 years with a maximum <strong>in</strong> the 1980’s. The result<strong>in</strong>g transientbehaviour of the groundwater flow, the piezometric head and the development anddisappear<strong>in</strong>g of the cones of depression has been calculated.This study is supported by the European Social Fund ProjectNo. 2009/0212/1DP/ of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 15

FORMATION OF GROUNDWATERIN SEDIMENTARY BASINS:TRADITIONAL AND ALTERNATIVE MODELSAlbertas BITINASCoastal Research and Plann<strong>in</strong>g Institute, Klaipėda University, 84 H. Manto Str., LT-92294Klaipėda, Lithuania, e-mail: albertas.bit<strong>in</strong>as@corpi.ku.ltAccord<strong>in</strong>g to the accepted “classical” model of the Baltic Artesian Bas<strong>in</strong>groundwater dynamics, currently acknowledged and widely used by researchers,groundwater recharge is the most <strong>in</strong>tensive <strong>in</strong> the heights, and groundwater runoffmov<strong>in</strong>g towards the periphery of the artesian bas<strong>in</strong>, i.e. to the central part of theBaltic Syneclise <strong>in</strong> the area of the Baltic Sea, where its submar<strong>in</strong>e dischargetakes place (Juodkazis, 1979; Региональная..., 1989; Mokrik, 2003; and others).The greatest thickness of the fresh groundwater layer <strong>in</strong> the Eastern Baltic regionreaches 500 meters, and this has been determ<strong>in</strong>ed <strong>in</strong> the northwestern part ofLithuania (Mokrik, 2003). However, an alternative model of fresh groundwaterformation – meltwater <strong>in</strong>jections <strong>in</strong>to aquifers – is also possible. It has beenestablished that the oxygen isotopic composition of fresh groundwater of theCambrian-Vendian aquifer <strong>in</strong> the Estonian Monocl<strong>in</strong>e is abnormally light andthat δ 18 O values reach -20‰ – -22‰, i.e. the groundwater is of glacigenousorig<strong>in</strong> (Vaikmäe, 1999; Mokrik, 2003). Referr<strong>in</strong>g to these data, the researchersexpla<strong>in</strong> the formation of fresh water resources by meltwater <strong>in</strong>jections <strong>in</strong>to theaquifers dur<strong>in</strong>g the degradation of the ice sheet and deglaciation of the area(Vaikmäe et al., 2001; Mokrik, 2003; Zuzevičius, 2010; and others).Accord<strong>in</strong>g to other researchers, ways for fresh groundwater to form could beexpla<strong>in</strong>ed by the mechanism of meltwater with high hydrostatic head circulationunder the cont<strong>in</strong>ental ice sheet dur<strong>in</strong>g the transgressive phase of glaciation(Boulton et al., 1995, 1996; and others). A great amount of water was <strong>in</strong>filtrated<strong>in</strong>to aquifers of the subglacial substratum <strong>in</strong> this way. We th<strong>in</strong>k that the model of<strong>in</strong>filtration mentioned has been proved by the results of groundwater (dissolvedcarbonates) radiocarbon dat<strong>in</strong>g. A few hundred groundwater dat<strong>in</strong>g results fromdifferent aquifers <strong>in</strong> Lithuania and the surround<strong>in</strong>g regions show that the entireamount of fresh groundwater was formed only commenc<strong>in</strong>g from the second halfof the Last Glacial (Middle and Late Weichselian), i.e. there is practically nowater older than 34-35 kyrs (Bit<strong>in</strong>as, 1999, 2011). It is important to note thatthe results of groundwater radiocarbon dat<strong>in</strong>g are not accurate (they are usually“aged”), and that is why it is necessary to make correspond<strong>in</strong>g corrections <strong>in</strong> their<strong>in</strong>terpretation (Mokrik and Mažeika, 2006; Mokrik et al., 2008). The distribution ofgroundwater dat<strong>in</strong>g results of the Upper Permian aquifer <strong>in</strong> the Western Lithuaniais presented (Fig.) as an example. Accord<strong>in</strong>g to the traditional (“classical”) model,16 The 70 th Scientific Conference of the University of Latvia

Fig. Geological occurrence of the Upper Permian aquifer <strong>in</strong> Western Lithuania and theradiocarbon age of groundwater (dissolved carbonates) of this layer.1 – Quaternary deposits; 2 – clay; 3 – sand; 4 – fractured limestone; 5 – clayey marl andlimestone. Age of deposits: D 3– Upper Devonian; P 2– Upper Permian; T 1– Lower Triassic;J 3– Upper JurassicSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 17

the formation of fresh water <strong>in</strong> the Upper Permian aquifer took place more orless regularly dur<strong>in</strong>g the Middle and Late Weichselian, despite the fact that thearea before glaciation had been frozen over, so any water <strong>in</strong>filtration was hardlypossible. Another model of fresh groundwater formation – meltwater <strong>in</strong>jectionswith high hydrostatic head – gives a better explanation of fresh groundwaterdistribution and the reason why freshwater <strong>in</strong>jections reach such depths.A different <strong>in</strong>terpretation of groundwater dat<strong>in</strong>g results, as well as a newperception of cont<strong>in</strong>ental glacier dynamics and the mechanism of its meltwatercirculation, enable one to change the attitude not only of the almost dogmaticapproach to glacial geology, but also to modify the already settled viewpo<strong>in</strong>tson groundwater dynamics <strong>in</strong> aquifers dur<strong>in</strong>g ice ages and the formation of freshgroundwater resources. Thus, we have to answer a number of new questions:suppos<strong>in</strong>g that part of the fresh groundwater resources <strong>in</strong> the Eastern Baltic regionhave been formed due to meltwater <strong>in</strong>jections, what are their real exploitationresources? Are they possibly much smaller than we imag<strong>in</strong>e? Can most of them bereasonably considered as the renew<strong>in</strong>g ones?ReferencesBit<strong>in</strong>as, A. 1999. Paleoįrėžių genezė. Geologijos akiračiai 1, 24–34.Bit<strong>in</strong>as, A. 2011. Paskut<strong>in</strong>ysis ledynmetis ryt<strong>in</strong>ės Baltijos regione. Klaipėdos universitetoleidykla. 154 p.Boulton, G. S., Caban, P. E., Gijssel van K. 1995. Groundwater flow beneath ice sheets:part I – large scale patterns. Quaternary Science Reviews 14, 545–562.Boulton, G. S., Caban, P. E., Gijssel van K., Leij<strong>in</strong>se, A., Punkari, M., 1996. The impact ofglaciation on the groundwater regime of Northwest Europe. Global and Planetary Change12, 397–413.Juodkazis, V. 1979. Pabaltijo hidrogeologijos pagr<strong>in</strong>dai.Vilnius: Mokslas. 144 p.Mokrik, R. 2003. Baltijos base<strong>in</strong>o paleohidrogeologija. Neoproterozojus ir fanerozojus.Vilnius: Vilniaus universiteto leidykla. 333 p.Mokrik, R., Mažeika, J. 2006. Hidrogeochemija. Vilnius: Vilniaus universiteto leidykla.244 p.Mokrik, R., Bičkauskienė, A., Mažeika, J. 2008.Vidurio Lietuvos žemumos tekton<strong>in</strong>ių lūžiųzonos nustatymas izotop<strong>in</strong>iais metodais devono vanden<strong>in</strong>gajame komplekse. Geologijosakiračiai 3-4, 51–59.Vaikmäe, R. 1999. The <strong>in</strong>fluence of Scand<strong>in</strong>avian Ice Sheet on the formation of Estoniangroundwater. In: INQUA International Congress „The environmental background to hom<strong>in</strong>idevolution <strong>in</strong> Africa”, 3-11 August 1999, Durban, South Africa: Book of Abstracts, p. 185.Vaikmäe, R., Vallner, L., Loosli, H. H., Blaser, P. C., Juillard-Tardent, M. 2001. Paleogroundwater of glacial orig<strong>in</strong> <strong>in</strong> the Cambrian-Vendian aquifer of northern Estonia. In: W. M. Edmundsand C. J Milne (Eds.), Palaeowaters <strong>in</strong> coastal Europe: evolution of groundwater s<strong>in</strong>ce the latePleistocene. Geological Society, London, Special Publications 189, 17–27.Zuzevičius, A. 2010. The groundwater dynamics <strong>in</strong> the southern part of the Baltic ArtesianBas<strong>in</strong> dur<strong>in</strong>g the Late Pleistocene. Baltica 23 (1), 1–12.Региональная геология Прибалтики, 1989. В. И. Иодказис (Ред.). Вильнюс: Мокслас.220 с.18 The 70 th Scientific Conference of the University of Latvia

WATER FILLED UNDERGROUND OIL SHALE MINESAS A HEAT SOURCEVeiko KARU 1 , Jana PAVLENKOVA 21Tall<strong>in</strong>n University of Technology, Department of M<strong>in</strong><strong>in</strong>g, 2 Development Manager, MäetaguseMunicipality, Estonia, e-mail: veiko.karu@ttu.ee, jana.pavlenkova@maetagusevv.eeUnderground oil shale has been m<strong>in</strong>ed for 90 years <strong>in</strong> the middle-north partof the Baltic oil shale deposit, <strong>in</strong> the Estonian deposit. After the closure of them<strong>in</strong>e, the m<strong>in</strong>e works filled with water. Underground oil shale m<strong>in</strong><strong>in</strong>g createsunderground water pools called technogenic water bodies (Figure 1). The Estonianoil shale deposit is comprised of ten closed m<strong>in</strong>es that are fully or partly filledwith water. Eight m<strong>in</strong>es <strong>in</strong> the central part of the deposit: Ahtme, Kohtla, Kukruse,Käva, Sompa, Tammiku, m<strong>in</strong>e No. 2 and m<strong>in</strong>e No. 4 form one water body. Ubjam<strong>in</strong>e and Kiviõli m<strong>in</strong>es are located <strong>in</strong> the western part of the deposit, away fromthe other m<strong>in</strong>es.Fig. 1. North-South cross section of underground m<strong>in</strong><strong>in</strong>g area and heat pump <strong>in</strong>stallationexample.The ma<strong>in</strong> aim of this paper is to analyze the feasibility of us<strong>in</strong>g m<strong>in</strong>e water as aheat source for heat pumps and to f<strong>in</strong>d suitable places to set up such systems. It wouldbe useful to use this m<strong>in</strong>e water as a heat source for heat pumps to produce heat.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 19

Technologies have to be created and evaluated for def<strong>in</strong><strong>in</strong>g hydro geologicalparameters to def<strong>in</strong>e underground space, properties and classification of used m<strong>in</strong>es.Classification helps to def<strong>in</strong>e the space that is available for water <strong>in</strong> abandoned m<strong>in</strong>es.A 3D model was built with geometrical data from m<strong>in</strong>e plans, m<strong>in</strong>e clos<strong>in</strong>g acts andborehole data and from land survey data. The ma<strong>in</strong> tools chosen for spatial modell<strong>in</strong>gwere spreadsheets and MS Access databases for systemis<strong>in</strong>g and query<strong>in</strong>g data,MapInfo for georeferenc<strong>in</strong>g, Vertical Mapper for <strong>in</strong>terpolat<strong>in</strong>g and grid calculationsand Modflow for the pump<strong>in</strong>g simulation. With the help of <strong>in</strong>terpolated grids, thesurface elevations, layer thicknesses and required properties were calculated.The best possible technical solution for us<strong>in</strong>g m<strong>in</strong>e water <strong>in</strong> heat pumps is:1) pump<strong>in</strong>g the water through the drill hole onto the ground surface2) water goes to the heat exchanger unit3) m<strong>in</strong>e water temperature will be lowered <strong>in</strong> the heat pump heat exchanger byabout 1...4 degrees,4) after that, the m<strong>in</strong>e water is directed back to the m<strong>in</strong>e.Table 1. COP values for Ahtme 10MW heat pump complexTable 2. Kiikla 500kW heat pump20 The 70 th Scientific Conference of the University of Latvia

If we use underground water pool water, then the recommended temperaturereduction must be more then one degree. It depends on how large a heat exchangeris economical. When the temperature is lowered less, we have to use large volumesof m<strong>in</strong>e water.The best location for the heat pump complex is near Ahtme Power Plant. The heatpump complex <strong>in</strong> Ahtme will need water pumps and heat pumps. By build<strong>in</strong>g thisunit at Ahtme, the water requirement and the COP values are as shown <strong>in</strong> Table 1.M<strong>in</strong>e water usage for a heat pump complex is unique <strong>in</strong> the world. The firstpilot pump <strong>in</strong> Estonia was opened <strong>in</strong> 2011 at Kiikla settlement <strong>in</strong> Estonia. At Kiiklasettlement the <strong>in</strong>stalled heat pump is like a pilot unit for us<strong>in</strong>g m<strong>in</strong>e water as a heatsource and the COP values and other parameters are shown <strong>in</strong> Table 2.RECONSTRUCTING THE GROUNDWATER FLOW INTHE BALTIC BASIN DURING THE LAST GLACIATIONTomas SAKS 1 , Juris SEŅŅIKOVS 2 , Andrejs TIMUHINS 2 ,Andis KALVĀNS 1University of Latvia, 1 Faculty of Geography and Earth Sciences, 2 VTPMML,e-mail: tomas.saks@lu.lvGroundwater flow beneath the ice sheets has caught the imag<strong>in</strong>ation of scientistsrelatively recently. The groundwater <strong>in</strong> the Baltic bas<strong>in</strong> can be subdivided <strong>in</strong>tothree identifiable groups accord<strong>in</strong>g to its chemical and isotopic composition: waterof the Quaternary age of either the warm (1) or cold (2) stages, or Pre-Quaternarybr<strong>in</strong>e (3). The first two are readily identified by the stable isotope values andchemical composition (Radla, 2010), while the last is characterised by highconcentrations of dissolved salts and is found <strong>in</strong> the deeper part of the bas<strong>in</strong>.The aim of this study is to test the assumption that the groundwater body ofglacial orig<strong>in</strong> found <strong>in</strong> the Cambrian–Vendian aquifer <strong>in</strong> Northern Estonia orig<strong>in</strong>atedas a result of sub-glacial meltwater <strong>in</strong>filtration dur<strong>in</strong>g the reoccurr<strong>in</strong>g glaciations.In the last decades it has been proved that most large ice sheets tend to reside onwarm beds even <strong>in</strong> harsh climatic conditions and that sub-glacial melt<strong>in</strong>g due togeothermal heat flow and deformation heat from the ice flow is tak<strong>in</strong>g place.A steady state regional groundwater flow model of the Baltic bas<strong>in</strong> was usedto simulate the groundwater flow dur<strong>in</strong>g the last glaciations with model geometryadjusted to reflect the sub-glacial topography. Ice thickness model data (Argus andPeltier, 2010) was set as a constant head boundary condition on the topographicalsurface. In total, 19 calculation scenarios from 28 ka BP to 10 ka BP were chosen.The meltwater pressure at the ice sole was assumed to be equal to the ice pressure.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 21

The modell<strong>in</strong>g results suggest two ma<strong>in</strong> recharge areas of the Cm-V aquifersystem, and a reversed groundwater flow that persisted for at least 14 thousandyears. Modell<strong>in</strong>g suggests that the groundwater flow velocities <strong>in</strong> the Cm-V beneaththe ice sheet exceeded the present velocities by a factor of 10 on average. Thevolume recharged dur<strong>in</strong>g the reversed groundwater flow amounts to ~ 2*10 12 m 3 .Assum<strong>in</strong>g mean porosity of the Cm-V to be around 25% (Brangulis, 1995) thisvolume corresponds to approximately 200 km of the <strong>in</strong>trusion length, which is anobvious overestimation.It is likely that the sub-glacial groundwater recharge operated on shorter timescales than modelled, perhaps due to the slow degradation of the permafrost whichdeveloped <strong>in</strong> front of the advanc<strong>in</strong>g ice marg<strong>in</strong>, or pore water pressure at the icesole less than that of the ice weight due to meltwater evacuation by the englacialdra<strong>in</strong>age system. However, the most difficulty <strong>in</strong> quantify<strong>in</strong>g the parameter is thedevelopment of a rather th<strong>in</strong> but cont<strong>in</strong>uous till layer that could effectively hamperthe sub-glacial meltwater <strong>in</strong>filtration.This study is f<strong>in</strong>anced by the European Social Fund ProjectNo. 2009/0212/1DP/, D. F., Peltier, R. W. 2010. Constra<strong>in</strong><strong>in</strong>g models of postglacial rebound us<strong>in</strong>g spacegeodesy: a detailed assessment of model ICE-5G (VM2) and its relatives. GeophysicalJournal International. 181, 697–723.Brangulis, A. P. 1985. Vend I Kembrij Latvii. Riga, Z<strong>in</strong>atne, 134 pp. (In Russian).Raidla, V. 2010. Chemical and isotope evolution of groundwater <strong>in</strong> the Cambrian-Vendianaquifer system <strong>in</strong> Estonia., Dissertationes Geologicae Universitatis Tartuensis 28, Tartu: TartuÜlikooli KirjastusTHE UNCERTAINTY OF THE FUTURE ANNUALLONG-TERM GROUNDWATER TABLE FLUCTUATIONREGIME IN LATVIADidzis LAUVA, Inga GRĪNFELDE, Artūrs VEINBERGS,Kaspars ABRAMENKO, Valdis VIRCAVS, Zane DIMANTA,Ilva VĪTOLA, Agnese GAILUMALatvia University of Agriculture, e-mail: didzis@lauvadidzis.comVary<strong>in</strong>g annual regimes of shallow groundwater levels affect the overallhydrological system significantly and <strong>in</strong> differ<strong>in</strong>g ways, as do related causes suchas agricultural and forestry production. These regimes can be constructed and22 The 70 th Scientific Conference of the University of Latvia

compiled if groundwater level monitor<strong>in</strong>g is used and the groundwater levels areknown. The primary objective of ground water regime monitor<strong>in</strong>g is to record<strong>in</strong>formation on ground water levels <strong>in</strong> space and time. Measurements of waterlevels <strong>in</strong> wells provide the most fundamental <strong>in</strong>dicator of the status of this resourceand are critical to a mean<strong>in</strong>gful evaluation of the effects it causes. Modell<strong>in</strong>ggroundwater levels us<strong>in</strong>g future daily climate data allows the prediction of futuregroundwater table fluctuations. The ability to adapt to changes depends on know<strong>in</strong>gthe possible alterations of the groundwater level regime. Such knowledge couldform the basis for different and flexible approaches to susta<strong>in</strong>able development <strong>in</strong>the future. The classical Latvian long-term groundwater level fluctuation regimecan be described as an M-shaped function which represents two groundwaterlevel maximums (<strong>in</strong> spr<strong>in</strong>g and late autumn) and two m<strong>in</strong>imums (<strong>in</strong> w<strong>in</strong>ter andlate summer). The aim of this paper is to model the long-term annual regimeof relatively shallow groundwater levels us<strong>in</strong>g 14 climate scenario group<strong>in</strong>gsand <strong>in</strong> addition, to analyze them accord<strong>in</strong>g to the dom<strong>in</strong>ance of cont<strong>in</strong>entality<strong>in</strong> Latvia (Draveniece, 2007). Us<strong>in</strong>g relative groundwater levels allows one tocompare wells with different absolute amplitude and average levels, as wellas remov<strong>in</strong>g <strong>in</strong>ter-annual trends. Such a method has been successfully used <strong>in</strong>Poland (Chelmicki, 1993). The mathematical model METUL was chosen asthe best known and most appropriate model for Latvian climatic conditions formodell<strong>in</strong>g future daily groundwater levels, us<strong>in</strong>g daily temperature, precipitationand humidity. To characterize how the variability of different climate scenariosaffects the annual regime of shallow groundwater levels, statistical methodsfocus<strong>in</strong>g on percentile analyses were applied. Results from one freely chosenmodel were used to analyze the differences and similarities between the s<strong>in</strong>gleclimate scenario model and the multiple climate scenarios model ensemble.Results show def<strong>in</strong>ite annual long-term groundwater regime changes <strong>in</strong> the futureperiod (2070-2100) compared to the reference period (1961-1990) over all ofLatvia. The future Latvian long-term groundwater level fluctuation regime canbe described as an A-shaped function with one maximum and one m<strong>in</strong>imum.Spatiotemporal differences are similar <strong>in</strong> both periods with a gradual transitionadjusted for cont<strong>in</strong>entality, be<strong>in</strong>g most apparent <strong>in</strong> the spr<strong>in</strong>g months.This study is f<strong>in</strong>anced by the European Social Fund ProjectNo. 2009/0212/1DP/ Chelmicki, W. 1993. The annual regime of shallow groundwater levels <strong>in</strong> Poland. GroundWater. 31(3), 383-388.2. Draveniece, A. 2007. Okeāniskās un kont<strong>in</strong>entālās gaisa masas Latvijā. <strong>Latvijas</strong> Veģetācija,14, 135.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 23

EVOLUTION OF GROUNDWATER COMPOSITIONIN THE DEPRESSION CONE OF THE RIGA REGIONBaiba RAGA, Andis KALVĀNS, Aija DĒLIŅA, Eleonora PĒRKONE,Inga RETIĶEUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: baiba.raga@lu.lvGroundwater is one of the major sources of dr<strong>in</strong>k<strong>in</strong>g water, but its effectiveusage is very important, otherwise problems related to water quality and the quantityof the resource can arise. An example of <strong>in</strong>effective groundwater usage has beenobservable from 1950 to 1990 <strong>in</strong> Riga, where <strong>in</strong>tensive groundwater extractionfrom the Arukilas-Amatas multi-aquifer system has caused a sharp and significantlower<strong>in</strong>g of piezometric surfaces.Riga is the capital of Latvia, a city where the ma<strong>in</strong> water supply is both centralizedand decentralized, mostly from groundwater sources, that is, from the Arukilas-Amatas multi-aquifer system, which consists of sandstones and siltstone. Theserocks belong to the middle and upper Devonian and have good properties for theextraction of groundwater: they have high permeability and are widely spread. Thissystem covers the upper Devonian Plav<strong>in</strong>as formation which consists of dolomite,but above it lies the Salaspils formation which consists of marl and gypsum, and islocated <strong>in</strong> the southern and western part of Riga. Below this system lies the middleDevonian Narvas aquitard which consists of marl and clay.Initially, the lower<strong>in</strong>g of the water table was quick and the maximum decl<strong>in</strong>eof the piezometric surface was observed <strong>in</strong> 1972, when it was about 16 m lowerthan the average. Regeneration of the water table began at the end of the 1980’s,when groundwater usage decreased. Nowadays, the piezometric surface is be<strong>in</strong>grenewed, and fluctuations are <strong>in</strong>significant and described as natural. The area wherethe natural groundwater regime has changed, <strong>in</strong>duced by the anthropogenic effect,is called “Large Riga”.In the study, long–term monitor<strong>in</strong>g data has been used to track groundwaterchemical changes and evolution <strong>in</strong> the Arukila-Amatas multi-aquifer system.Data on piezometric surfaces and major ions from 45 monitor<strong>in</strong>g wells have beenanalysed. Before the data was analyzed, statistical analysis was done to excludevalues which may be <strong>in</strong>correct. Based on a map that shows the piezometric surfacedifference between two periods: 1949-1951 (which describes the natural situation),and 1970-1972 (where the m<strong>in</strong>imal groundwater level <strong>in</strong> the Gauja aquifer wasobserved), the territory was divided <strong>in</strong>to three zones – the central, middle andperiphery, which differ from each other by the volume of decl<strong>in</strong>e <strong>in</strong> the piezometricsurfaces. The map was created us<strong>in</strong>g Surfer 9 software. Changes <strong>in</strong> groundwaterflow <strong>in</strong> the “Large Riga” area were studied us<strong>in</strong>g a hydrogeological model. Us<strong>in</strong>gthis as a basis, the speed with which changes <strong>in</strong> water chemical composition <strong>in</strong>aquifers shows up and how these trends change <strong>in</strong> time were studied.24 The 70 th Scientific Conference of the University of Latvia

2-It was discovered that the sources of water with high SO 4which worsen thequality of water <strong>in</strong> deeper aquifers, come from the Salaspils aquifer, because thefirst signs were observed <strong>in</strong> the Plav<strong>in</strong>as aquifer, which lies below the Salaspilsformation. The same changes <strong>in</strong> water composition <strong>in</strong> deeper aquifers can beobserved with a time lag.Significant changes <strong>in</strong> water composition were observed <strong>in</strong> the central part,where the greatest lower<strong>in</strong>g <strong>in</strong> the piezometric surface is found, and was sufficientto cause stronger downward flow from upper aquifers, which <strong>in</strong>duced the mix<strong>in</strong>gof water from different aquifers <strong>in</strong> this territory. As a result, there are greatchanges <strong>in</strong> water composition <strong>in</strong> this zone. In addition, the first signs of changes<strong>in</strong> water composition show up very quickly, but the return to a natural situation isrelatively slow.The fact was also observed, that when the piezometric surface rose up at theend of the 1980’s, the mix<strong>in</strong>g from different aquifers decl<strong>in</strong>ed. This can be clearlyobserved <strong>in</strong> the upper Devonian Plav<strong>in</strong>as aquifer <strong>in</strong> the central part, where there is-an <strong>in</strong>creas<strong>in</strong>g concentration of the HCO 3ion <strong>in</strong> the latest samples. These are thefirst signs that the situation <strong>in</strong> this multi-aquifer system is beg<strong>in</strong>n<strong>in</strong>g to return to itsnatural condition.Despite the fact that Riga lies near the sea, the lower<strong>in</strong>g of the water table <strong>in</strong>the Arukilas-Amatas multi-aquifer system hasn’t <strong>in</strong>duced an <strong>in</strong>tensive <strong>in</strong>trusion ofsea water. This process has only been observed <strong>in</strong> some areas, where the <strong>in</strong>trusionhas occurred through the bed of the River Daugava, where the Plav<strong>in</strong>as aquiferdolomites are situated.This study is supported by the European Social Fund projectNo. 2009/0212/1DP/ OF STABLE ISOTOPE CONTENTIN GROUNDWATER TO VALIDATE THE RESULTSOF THE HYDROGEOLOGICAL MODELOF THE BALTIC ARTESIAN BASINAlise BABRE, Aija DĒLIŅAUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: alise.babre@lu.lvGroundwater levels and their fluctuations are most commonly used to calibratethe developed numerical groundwater models. However, environmental waterisotopes and groundwater chemistry, especially, trace elements and conservativeions such as chlor<strong>in</strong>e can also be used <strong>in</strong> this validation process. Isotope andSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 25

geochemical data are ma<strong>in</strong>ly used to calibrate transient flow or mix<strong>in</strong>g modelsbackwards, for <strong>in</strong>stance if paleoreconstructions are performed. Isotope or chemicaltracers are used <strong>in</strong> a small scale surface or subsurface hydrological models. Theycan also be used <strong>in</strong> large scale models if a large set of data is obta<strong>in</strong>ed and differentisotope ratios occur, thus different end members can be dist<strong>in</strong>guished and mix<strong>in</strong>gl<strong>in</strong>es can be detected.Theoretically, <strong>in</strong> a case of relatively stable groundwater and a constant climateregime, stable water isotope ratios as well as chlor<strong>in</strong>e concentrations shouldn’tchange much along the flow paths to the groundwater discharge areas. If rechargeoccurred <strong>in</strong> the same conditions as observed nowadays, then oxygen and hydrogenstable isotope composition should be more or less around the mean values <strong>in</strong>precipitation. Aga<strong>in</strong>, the TDS values should <strong>in</strong>crease from recharge to dischargedue to more or less <strong>in</strong>tensive groundwater/rock <strong>in</strong>teraction. Hydraulic connectionthus mix<strong>in</strong>g between deeper and shallower aquifers as well as <strong>in</strong> the case of<strong>in</strong>teraction between aquifer and surface water bodies can change the chemical aswell as the isotopic values, although if such <strong>in</strong>teraction is significant <strong>in</strong> well builtnumerical models, it should be apparent.In this study we tried to apply isotopes and major ion chemistry to verify theresponse of the developed and calibrated Baltic Artesian Bas<strong>in</strong> numerical model.The developed large scale steady state model has a total area of approximately480,000 km 3 .The stable isotope ratios from more than 200 samples covered a large rangeand no consequences could be observed when the chemical or isotopic data wastreated alone. Due to this, smaller places for model verification were chosen and<strong>in</strong> those areas, where hydrogeological conditions were previously <strong>in</strong>vestigated withhigh accuracy. One of the chosen sites was the Upper Devonian Gauja aquifer<strong>in</strong> the Riga district. The Quaternary and Middle Devonian Pernava aquifers wereother study areas analyzed <strong>in</strong> almost all of the territory of the Baltic Artesian Bas<strong>in</strong>where new data was collected or old data was available.Modelled and observed piezometric levels <strong>in</strong> most aquifers above the regionalaquitard which consists of Middle Devonian Narva clayey sediments are very closeand the ma<strong>in</strong> flow paths are almost equal. Despite a f<strong>in</strong>e match<strong>in</strong>g level above theNarva aquitard, below it, neither levels nor flow paths were modelled to a satisfactorylevel. In some cases piezometric level mismatch can <strong>in</strong>crease up to 80 m. In theseaquifers where modelled piezometric levels differ, such a great distribution ofisotopic and chemical values can’t be expla<strong>in</strong>ed with the developed model.The great mismatch <strong>in</strong> the model can be expla<strong>in</strong>ed <strong>in</strong> two controversial ways.One is that the problem is <strong>in</strong> the model, which can be expla<strong>in</strong>ed by an <strong>in</strong>accuratemodel structure or the <strong>in</strong>correctly def<strong>in</strong>ed permeability properties of materials.Another problem could be the rema<strong>in</strong>s of the Quaternary evolution, which with therapid climate changes and hydrogeological conditions dur<strong>in</strong>g the Quaternary periodmay still have an impact on subsurface hydrology nowadays.26 The 70 th Scientific Conference of the University of Latvia

If we assume that the model was built properly and that the structure calculatespiezometric levels very well <strong>in</strong> aquifers with faster water exchange, it is morelikely that the problem occurred due to not tak<strong>in</strong>g <strong>in</strong>to account the evolutionof groundwater hydrology dur<strong>in</strong>g the Quaternary period, especially the LatePleistocene and the Holocene.The present work has been funded by the European Social Fund Project “Establishmentof <strong>in</strong>terdiscipl<strong>in</strong>ary scientist group and modell<strong>in</strong>g system for groundwater research”(Project Nr. 2009/0212/1DP/ ANALYSIS OF GROUNDWATER QUALITYPROBLEMS IN BALTIC SEA REGION COUNTRIESValdis VIRCAVS, Zane DIMANTA, Didzis LAUVA,Kaspars ABRAMENKO, Artūrs VEINBERGS, Agnese GAILUMA,Ilva VĪTOLALatvia University of Agriculture, Faculty of Rural Eng<strong>in</strong>eer<strong>in</strong>g, Department of EnvironmentalEng<strong>in</strong>eer<strong>in</strong>g and Water Management, e-mail: valdis.vircavs@llu.lvGroundwater resource quality and availability is a world wide problem andresearch field. Groundwater is the largest reservoir of freshwater <strong>in</strong> countries <strong>in</strong>the the Baltic Sea region. One of the current problems <strong>in</strong> the region is agriculturalactivity. The use of nitrogen fertilizers <strong>in</strong> agriculture is one of the ma<strong>in</strong> factorscontribut<strong>in</strong>g to the contam<strong>in</strong>ation of surface water and groundwater, from varioustypes of nitrogen.The aim of the study presented is to analyze the current agricultural impacton groundwater quality <strong>in</strong> the Baltic Sea region and to give guidance andrecommendations for better <strong>in</strong>ternational cooperation based on EU directives. Thema<strong>in</strong> task is to compare the current situation of groundwater quality <strong>in</strong> three groupsof Baltic Sea region countries and to def<strong>in</strong>e development scenarios.The study presents general <strong>in</strong>formation about groundwater quality <strong>in</strong> thefollow<strong>in</strong>g Baltic Sea region countries: Denmark, Sweden, F<strong>in</strong>land, Estonia, Latvia,Lithuania, Poland and Germany. The countries from the region are divided <strong>in</strong>to threegroups based on similar geographical, agro climatic and agro historical conditionsand applied methods. The first group is the Baltic States – Estonia, Latvia andLithuania, the second is the Northern European countries – F<strong>in</strong>land and Sweden,and the third group is Denmark, Germany and Poland.The major contam<strong>in</strong>ation <strong>in</strong> the Baltic Sea region is from agricultural chemicals,for example, fertilizers (nitrate, phosphorus) and pesticides. The role of diffuseSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 27

source pollution <strong>in</strong> agriculture is a common problem <strong>in</strong> the region and is solved <strong>in</strong>a different way <strong>in</strong> each country. All of the countries <strong>in</strong> the region, except Russia,are subject to European Union (EU) groundwater directive restrictions. EuropeanEnvironmental Agency (EEA) EUROWATERNET data bases are available for abetter understand<strong>in</strong>g of the quality of groundwater and its contam<strong>in</strong>ation <strong>in</strong> theregion.In the research, the present situation is analyzed and advice and conclusionshave been provided for future groundwater quality scenarios for the Baltic Searegion. A monitor<strong>in</strong>g system has been established <strong>in</strong> all Baltic region countries <strong>in</strong>accordance with EU directives to determ<strong>in</strong>e and forecast groundwater quality.This study is supported by the European Social Fund project “Establishment of<strong>in</strong>terdiscipl<strong>in</strong>ary scientists group and modell<strong>in</strong>g system for groundwater research”.No. 2009/0212/1DP/ VISUALISATION OF GROUNDWATER CHEMICALCOMPOSITION USING THE RGB SCALE.AN EXAMPLE FROM THE D12 AQUIFER, LATVIAAndis KALVĀNSUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: andis.kalvans@lu.lvGroundwater composition is traditionally visualised us<strong>in</strong>g the Piper diagramwhere the relative concentration of all major <strong>in</strong>organic components are plotted <strong>in</strong>ternary diagrams. This is a convenient approach to identify different water typesor, for example, to study the evolution of water composition along the flow l<strong>in</strong>es.However, it is not easy to exam<strong>in</strong>e more complex spatial variations of watercomposition us<strong>in</strong>g ternary diagrams.The ternary diagrams where the relative concentration of anions (or cations) isplotted are remarkably similar to the RGB colour scale which is usually used forcolour cod<strong>in</strong>g <strong>in</strong> colour photography. In digital images, the RGB colour scale iscomposed of three bands – red, green and blue (RGB) – where simple numbers<strong>in</strong>dicate the relative <strong>in</strong>tensity of each of the bands. The colour values <strong>in</strong> theRGB scale can be substituted by the relative concentrations of the three desiredchemical components, thus allow<strong>in</strong>g the visualisation of three parameters witha s<strong>in</strong>gle colour code. The conversion of relative concentrations of the dom<strong>in</strong>antanions to RGB colour is straightforward: calculate the proportion of each anion(e.g. <strong>in</strong> %) and convert theses values to the respective colour <strong>in</strong>tensities <strong>in</strong> the RGBscale. Thus, the spatial variation of concentrations of the three chemical componentscan be visualised with a colour code on the map or a cross section.28 The 70 th Scientific Conference of the University of Latvia

But there is more: the absolute concentration values can be converted tothe RGB colour values, thus represent<strong>in</strong>g the absolute and not only the relativeconcentrations of given chemical compounds. To do this, arbitrary m<strong>in</strong>imumand maximum concentrations of all desired compounds need to be def<strong>in</strong>ed.The m<strong>in</strong>imum value <strong>in</strong> most cases obviously will be 0, but the maximum valuepossibly needs to be specified for each compound and for each case <strong>in</strong>dividually.-For example, the HCO 3concentration rarely exceeds 8 mmol/l <strong>in</strong> groundwater,while the Cl - can exceed 2,500 mmol/l. Actually the problem of def<strong>in</strong><strong>in</strong>g theconversion criterions is a secondary one. The primary problem is how to visualisethe scale for colour cod<strong>in</strong>g where the summary colour <strong>in</strong>tensity (the sum of allthree colour band values) is the fourth parameter or dimension, besides therelative values of three colour bands.The most significant disadvantage of the presented colour cod<strong>in</strong>g scheme isthat the ability to dist<strong>in</strong>guish colour is not the same for everyone. The ability of aperson to discrim<strong>in</strong>ate between similar colours depends on the person’s physicalabilities and even from the person’s cultural background.In the territory of Latvia, the lower-middle Devonian aquifer system, conf<strong>in</strong>ed-by the Narva formation’s regional aquiclude, hosts fresh, HCO 3dom<strong>in</strong>ated water<strong>in</strong> the NE of the territory and Cl - 2-and SO 4dom<strong>in</strong>ated water with downward<strong>in</strong>creas<strong>in</strong>g Cl - concentration <strong>in</strong> the rest of the territory. Cl dom<strong>in</strong>ated br<strong>in</strong>e<strong>in</strong>trusions from below, freshwater <strong>in</strong>filtration from above and dissolutionof gypsum that is often found as an accessory m<strong>in</strong>eral are dom<strong>in</strong>ant factorscontroll<strong>in</strong>g groundwater composition <strong>in</strong> the horizon. Thus, the lower and middleDevonian sub-Narva water horizon complex is a good example for us<strong>in</strong>g theRGB scale to visualise the water composition and <strong>in</strong> identify<strong>in</strong>g the distributionof different water types.This study is supported by the European Social Fund projectNo. 2009/0212/1DP/ CRITERIA OF THE RESULTS OFUNDERGROUND WATER ANALYSISJānis TETEROVSKIS, Andis KALVĀNSUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: teterovskis@<strong>in</strong>box.lvThe wells data base compiled by the LVGMC <strong>in</strong>cludes the results of severalthousand groundwater sample analyses made as early as the 1960’s. As the data hasbeen accumulated dur<strong>in</strong>g a period of more than 50 years, which <strong>in</strong>cludes progressSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 29

<strong>in</strong> analytical technologies and turmoil <strong>in</strong> the political system, the credibility of dataneeds to be evaluated before it can be used for scientific research.Infiltration of precipitation water is the force mov<strong>in</strong>g groundwater flow, whilethe shape of the flow is determ<strong>in</strong>ed by geological structures and earth surfaceelevation. As none of these factors has changed significantly dur<strong>in</strong>g the last 10,000years s<strong>in</strong>ce the end of the ice age (Mokrik and Mazeika, 2002), it can be concludedthat the configuration of groundwater flow has not substantially changed andthe dynamic equilibrium of water composition has been ma<strong>in</strong>ta<strong>in</strong>ed. The steadygroundwater flow means that any systematic changes <strong>in</strong> composition will happengradually over a long period of time, determ<strong>in</strong>ed by gradual disarrangement offlow patterns smoothed out by flow dispersion and diffusion (Ingebritsen et al.,2008). The measured variations <strong>in</strong> groundwater composition will have the characterof an un<strong>in</strong>tentional fluctuation which could even be <strong>in</strong>duced by perturbationscreated dur<strong>in</strong>g water sample collection. An exception is regions with <strong>in</strong>tensivewater extraction such as the surround<strong>in</strong>gs of Riga and Jelgava, where dur<strong>in</strong>g the1960’s, 1970’s and 1980’s huge depressions <strong>in</strong> the groundwater level developed(Lev<strong>in</strong>a and Lev<strong>in</strong>s, 2005). But, even here gradual rather than abrupt groundwatercomposition changes will be tak<strong>in</strong>g place.In order to identify analytical mistakes, we suggest the use of total validationcriterion (TVC) which is calculated by divid<strong>in</strong>g the concentration of Ca 2+ ion(mgekv/l) with the sum of the concentration of anions (mgekv/l). The TVC iscalculated from the only chemical components that were determ<strong>in</strong>ed directly, even<strong>in</strong> the early days of systematic groundwater composition exploration, that is HCO 3-, SO 42-, Cl - and Ca 2+ . The rest of the major components – Na + , K + , Mg 2+ – accord<strong>in</strong>gto GOST standards, were calculated from the ion balance (Na + and K + ) or from<strong>in</strong>direct measurements (Mg 2+ ).The TVC can be used to validate long term series of groundwater monitor<strong>in</strong>gdata <strong>in</strong> observation po<strong>in</strong>ts where short term variations caused by climatic andmeteorological or human factors can be excluded. Divergences from the generaltrend at each monitor<strong>in</strong>g spot should be considered bad measurements and dismissed(Fig. 1.).Fig. 1. TVC value of monitor<strong>in</strong>g well No. 1508 at Baldone. There is no feasible geologicalexplanation for the four divergences from the general trend and these analyses should beregarded as wrong.30 The 70 th Scientific Conference of the University of Latvia

In order to identify sample spoil<strong>in</strong>g dur<strong>in</strong>g storage due to freez<strong>in</strong>g or aerationwhich can result <strong>in</strong> calcium carbonate precipitation, the results need to be checkedfor consistency of concentration of Ca 2+ and HCO 3-ion concentrations <strong>in</strong> (mgekv/l).If the changes are severe and correlate for both ions, then the results should beconsidered as a bad mistake. It’s possible that TVC won’t spot this deviation(Fig. 2. and 3.).Fig. 2. TVC value of monitor<strong>in</strong>g well No. 1492 at Inčukalns. Only one bad measurementcan be identified us<strong>in</strong>g TVC.Fig. 3. Cl - , HCO 3-and Ca 2+ concentration (mg/L) at monitor<strong>in</strong>g well No. 1492 at Inčukalns.Two coherent drops <strong>in</strong> the Ca2+ and HCO3- concentrations suggest that CaCO3 precipitatedfrom the sample dur<strong>in</strong>g the storage possibly due to sample freez<strong>in</strong>g or loss of CO 2gas.We speculate that the proportion of <strong>in</strong>correct analyses <strong>in</strong> the data base are similarfor the monitor<strong>in</strong>g wells where long term series of observations are available andother well types where only one or a few groundwater samples have been collectedand analysed. If this is so, the overall quality of the groundwater composition database can be quantified and considered when perform<strong>in</strong>g statistical or <strong>in</strong>dividualanalyses of water composition data.References1. Mokrik, R., Mazeika, J. 2002. Palaeohydrogeological reconstruction of groundwaterrecharge dur<strong>in</strong>g Late Weichselian <strong>in</strong> the Baltic bas<strong>in</strong>. Geologija, 39, 49-572. Ingebritsen, S. E., Sanford, W. E., Neuzil, C. E. 2008. Groundwater <strong>in</strong> geologic processes,2nd ed. Cambridge. Cambridge University Press, 5363. Lev<strong>in</strong>a, N., Lev<strong>in</strong>s, I. 2005. Pazemes ūdeņu pamatmonitor<strong>in</strong>gs, 2004, Rīga. <strong>Latvijas</strong> Vides,ģeoloģijas un meteoroloģijas aģentūra, 345Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 31

TRACE ELEMENTS IN GROUNDWATER IN LATVIA:EXISTING DATA AND FIRST NEW RESULTSInga RETIĶE, Andis KALVĀNS, Aija DĒLIŅA, Alise BABRE,Baiba RAGA, Eleonora PĒRKONEUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: <strong>in</strong>ga.retike@gmail.comThe territory of Latvia is a part of the Baltic Artesian (<strong>Sedimentary</strong>) Bas<strong>in</strong> whichcan be subdivided <strong>in</strong>to three major water exchange zones: freshwater (active waterexchange), sal<strong>in</strong>e (delayed exchange), and br<strong>in</strong>e (stagnant) hydrogeological zones,<strong>in</strong> consider<strong>in</strong>g the water chemistry and <strong>in</strong>tensity of water connection betweenaquifers. The occurrence of trace elements <strong>in</strong> groundwater can be due to naturalsources such as dilution of water bear<strong>in</strong>g rocks, surface impact or anthropogenic<strong>in</strong>fluence.An extensive set of data about groundwater <strong>in</strong> Latvia is available from thebeg<strong>in</strong>n<strong>in</strong>g of the 1960’s and conta<strong>in</strong>s ma<strong>in</strong>ly <strong>in</strong>formation about groundwaterlevels, major ion chemistry and physical parameters. It is impossible to test thequality of the old data on trace element concentration from geological mapp<strong>in</strong>g andhydrogeological exploration dur<strong>in</strong>g Soviet times. The more recent studies conta<strong>in</strong>ma<strong>in</strong>ly data about the Quaternary sedimentary aquifer and are limited to the activewater exchange zone. A lack of available trace element data <strong>in</strong> the deeper strata ledto the implementation of this study.The aim of this study is to determ<strong>in</strong>e the distribution and sources of traceelements <strong>in</strong> groundwater <strong>in</strong> Latvia and compare the results with the major ionchemistry data and WHO and EU potable water standards. At the end of this studythere will be new data about approximately two hundred groundwater samples.Groundwater samples from monitor<strong>in</strong>g and supply wells, as well as boreholes andspr<strong>in</strong>gs, were analyzed by total x-ray fluorescence (TXRF) and atomic absorptionspectroscopy (AAS) techniques to determ<strong>in</strong>e the concentration of trace and somemajor elements. The contents of cations and anions, pH, electrical conductivity(EC), redox potential (ORP), TDS and dissolved oxygen were analysed to assessthe quality of groundwater.Generally, the concentration of trace elements <strong>in</strong> uncontam<strong>in</strong>ated shallowgroundwater samples is bellow WHO and EU potable water standards. Previousstudies suggest that uranium, arsenic, cobalt, and copper <strong>in</strong> groundwater can oftenbe derived from agricultural fertilizers and due to the high flux of nitrate present<strong>in</strong> <strong>in</strong>filtrat<strong>in</strong>g water, some metals can be released from deposits (Gosk et al.,2006). The <strong>in</strong>fluence of the lithology of aquifer deposits on concentrations of traceelements is statistically significant only <strong>in</strong> cases where aquifer deposits are rich<strong>in</strong> organic matter or conta<strong>in</strong> well-soluble m<strong>in</strong>erals. Some exceed<strong>in</strong>g trace elementconcentrations are associated with gypsum dissolution <strong>in</strong> shallow groundwater32 The 70 th Scientific Conference of the University of Latvia

samples. Studies show that the concentration of barium, iron, lithium and strontium<strong>in</strong>creases with <strong>in</strong>creas<strong>in</strong>g residence time and the conf<strong>in</strong>ement degree of an aquifer(Lev<strong>in</strong>s and Gosk, 2007).Due to <strong>in</strong>complete studies, it is essential to determ<strong>in</strong>e the trace element basel<strong>in</strong>evalues <strong>in</strong> Latvian conf<strong>in</strong>ed aquifers, to avoid migration of pollutants to loweraquifers.This study is supported by the European Social Fund ProjectNo. 2009/0212/1DP/, E., Lev<strong>in</strong>s, I., Jorgensen, L. F. 2006. Agricultural Infl uence on Groundwater <strong>in</strong> Latvia.DANMARKS OG GRØNLANDS GEOLOGISKE UNDERSØGELSE RAPPORT 2006/85.Lev<strong>in</strong>s, I., Gosk, E. 2007. Trace elements <strong>in</strong> groundwater as <strong>in</strong>dicators of anthropogenicimpact. Environmental Geology, 55, 285–290.RECESSION CURVE ANALYSIS APPROACH FORGROUNDWATERAgnese GAILUMA, Ilva VĪTOLALatvia University of Agriculture, Dept. of Environmental Eng<strong>in</strong>eer<strong>in</strong>g and WaterManagement,e-mail: agnese.gailuma@<strong>in</strong>box.lv, ilva.anisimova@gmail.comRecession curve analysis is a powerful and effective analysis technique <strong>in</strong> manyresearch areas related to hydrogeology, where observations have to be made, suchas water filtration and absorption of moisture, irrigation and dra<strong>in</strong>age, plann<strong>in</strong>gof hydroelectric power production and chemical leach<strong>in</strong>g (elution of chemicalsubstances), as well as <strong>in</strong> other areas.Upward areas were cut out from the <strong>in</strong>itial curve with<strong>in</strong> the process of decreasedrecession curve analysis, leav<strong>in</strong>g only the drops of the curve. Consequently, thecurve is transformed more closely to the groundwater flow, <strong>in</strong> an attempt to removethe impact of ra<strong>in</strong> or drought periods from the curve. Respectively, the drop-downcurve is part of the data, collected with a hydrograph, where data with the dischargedom<strong>in</strong>ates, without consider<strong>in</strong>g the impact of precipitation.There are manually prepared hydrographs for the analysis of recession curves forobservation wells (MG2, BG2 and AG1) <strong>in</strong> agricultural monitor<strong>in</strong>g sites <strong>in</strong> Latvia.Data of decl<strong>in</strong><strong>in</strong>g periods, split by month, was extracted with<strong>in</strong> this study fromthe available monitored data of groundwater levels. The drop-down curves weremanually (by chang<strong>in</strong>g the date) moved together to f<strong>in</strong>d the best match, therebySession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 33

obta<strong>in</strong><strong>in</strong>g monthly drop-down curves, represent<strong>in</strong>g each month separately. Monthlycurves were comb<strong>in</strong>ed and manually jo<strong>in</strong>ed to obta<strong>in</strong> characteristic drop-downcurves for the year for each well. The mathematical model of data equalization wasused for display<strong>in</strong>g data, f<strong>in</strong>d<strong>in</strong>g the correspond<strong>in</strong>g or closest logarithmic functionof the recession for the graph. Us<strong>in</strong>g recession curve analysis theory, a readymadetool – “A Visual Basic Spreadsheet Macro for Recession Curve Analysis” (Posavecet al., 2006) was also used to prepare similar curves with superior accuracy <strong>in</strong> theselection of data and match<strong>in</strong>g of logarithmic functions, than the functions whichwere developed by the manual process<strong>in</strong>g of data. The recession curves obta<strong>in</strong>edwere similar but not identical.With a full knowledge of the fluctuations of ground water levels, it is possibleto <strong>in</strong>directly (without tak<strong>in</strong>g soil samples) determ<strong>in</strong>e the filtration coefficient: amore rapid decl<strong>in</strong>e <strong>in</strong> the recession curve corresponds to better filtration conditions.This research could be very useful <strong>in</strong> construction plann<strong>in</strong>g, road constructions,agriculture etc.The authors gratefully acknowledge the fund<strong>in</strong>g from the ESF Project “Establishmentof <strong>in</strong>terdiscipl<strong>in</strong>ary scientist group and modell<strong>in</strong>g system for groundwater research”(Agreement No. 2009/0212/1DP/, K et al., 2006. A Visual Basic Spreadsheet Macro for Recession Curve Analysis.Ground water, Vol. 44, No. 5: 764–767.INFLUENCE OF WATER ABSTRACTIONON GROUNDWATER FLOW IN THE BABIlze KLINTS 1 , Jānis VIRBULIS 1 , Aija DĒLIŅA 2University of Latvia, 1 VTPMML , 2 Faculty of Geography and Earth Sciences,e-mail: ilzestankevica@<strong>in</strong>box.lvThere have been 3 different scenarios of groundwater abstraction trends <strong>in</strong> theregion of the Baltic Artesian Bas<strong>in</strong> start<strong>in</strong>g from 1950 until the present day:1. Natural scenario of groundwater abstraction – m<strong>in</strong>imal water extraction,almost unnoticeable compared to natural processes of water circulation;2. Wasteful scenario of groundwater abstraction – significant water usage lead<strong>in</strong>gto reveal <strong>in</strong>fluence to the groundwater resources;3. Medium scenario of groundwater abstraction – reasonable water extraction,m<strong>in</strong>imal <strong>in</strong>fluence to groundwater resources, ma<strong>in</strong>ta<strong>in</strong><strong>in</strong>g natural groundwaterresource restoration.34 The 70 th Scientific Conference of the University of Latvia

The groundwater extraction trend <strong>in</strong> all the Baltic countries is similar – start<strong>in</strong>gfrom 1950 until about 1965, the representative trend was m<strong>in</strong>imal water extraction(natural scenario of groundwater extraction); from 1965 until 1990, the characteristictrend was an <strong>in</strong>creas<strong>in</strong>g amount of groundwater extraction, which led to the wastefulscenario of groundwater extraction at the end of the given time period; after 1990, arapid decrease <strong>in</strong> the amount of extracted groundwater was observed, referr<strong>in</strong>g to themedium scenario of groundwater extraction which exists presently.The groundwater extraction sources have a non-homogeneous distributionthroughout the Baltic Artesian Bas<strong>in</strong>, where most of the wells are concentratedaround the biggest cities and <strong>in</strong>dustrial regions (<strong>in</strong> the territory of Latvia this meansthe largest cities: Riga, Liepaja, Daugavpils, Jurmala etc.). The spatial localizationof groundwater wells leads to vulnerability <strong>in</strong> local groundwater resources, as wellas a limitation on groundwater resource usage.Stationary calculations us<strong>in</strong>g the BAB version 1 hydrogeological model showsthat <strong>in</strong>creased groundwater extraction causes areas of depression. In Latvia, the areasof depression are observed <strong>in</strong> aquifers D3 gj, D3 am, and D2 br near Riga, as wellas <strong>in</strong> the Cambrian aquifer <strong>in</strong> Estonia near Tall<strong>in</strong>n and are cases of the medium andwasteful scenario of groundwater abstraction.The preferred future mode of groundwater extraction should ma<strong>in</strong>ta<strong>in</strong> the balancebetween the extraction and restoration of groundwater resources. In cases where an<strong>in</strong>crease <strong>in</strong> the volume of groundwater extraction is necessary, one must consider the<strong>in</strong>fluence on the potentially available groundwater resources.This study is supported by the European Social Fund ProjectNo. 2009/0212/1DP/ STATISTICS FOR DESCRIBING HYDRAULICCONDUCTIVITY OF THE QUATERNARY STRATA FROMTHE LATVIAN BOREHOLE LOG DATAJānis JĀTNIEKS, Konrāds POPOVS, Jānis UKASS, Tomas SAKS,Aija DĒLIŅAUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: janis.jatnieks@lu.lvBorehole log data <strong>in</strong> the territory of Latvia is highly variable <strong>in</strong> quality, spatialdistribution and accuracy of georeferenc<strong>in</strong>g, mak<strong>in</strong>g direct comparisons betweendifferent boreholes difficult. (It is, however, useful to compile some globalstatistics describ<strong>in</strong>g the broader geological characteristics present <strong>in</strong> the Quaternarylithology.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 35

The regional groundwater modell<strong>in</strong>g system for the Baltic Artesian Bas<strong>in</strong> –MOSYS V1 required hydraulic conductivities for the Quaternary strata. To derivethis, we started by look<strong>in</strong>g at the ways to compare the quality of the boreholelog data available. To make the log structures comparable <strong>in</strong> a universal form,useful for f<strong>in</strong>d<strong>in</strong>g structural patterns, a range normalization for all layer depthentries <strong>in</strong> all boreholes was performed. This range-normalized borehole log datais used to generate 1000 b<strong>in</strong> histograms for boreholes that have at least 2 layers<strong>in</strong> the Quaternary part of the log data. A 1000 b<strong>in</strong> histogram was selected because1 unit of normalized depth represents, on average, ~5 cm of the log depth <strong>in</strong> theQuaternary sequence, thus provid<strong>in</strong>g an adequate precision for this analysis aswell as allow<strong>in</strong>g for an amount of “noise” <strong>in</strong> the log data precision.For generalization of the lithology structure <strong>in</strong> the Quaternary sediments, asimplified 4 layer model was used <strong>in</strong> MOSYS V1. This was based on the results ofgeneralized aquifer-aquiclude transition statistics of the borehole logs as <strong>in</strong>ferredfrom the lithology. There are two such transitions for 88% of boreholes <strong>in</strong> Latvia,suggest<strong>in</strong>g that a simplified yet representative version of the Quaternary sequencecan be made out of 4 layers – 2 aquitards and 2 aquifers respectively.To further improve this model, another set of layer transition counts wereperformed. Us<strong>in</strong>g the lithology classifier for aggregation of lithological codes<strong>in</strong>to more general groups of sedimentary rock types, a global count of alltransitions between rock type classes was performed us<strong>in</strong>g the SQL databaselanguage. The most common layer transitions are sand-loam, loam-sand andsand-silt, siltstone.These results have been generated for use <strong>in</strong> different experiments dur<strong>in</strong>gour work on the development of a regional groundwater model. The normalizedlayer transition histograms show that some transitions are particularly numerous,such as the 0.500, 0.333 and 0.250 normalized depth transitions <strong>in</strong> the Quaternarysediments, po<strong>in</strong>t<strong>in</strong>g perhaps towards a requirement for borehole log qualitycontrol. The aquifer-aquiclude counts allow for a coarse generalization ofhydraulic conductivity <strong>in</strong> a simplified 4 layer model of the Quaternary strata.The layer transition counts for aggregate lithology types served as a reference forimplement<strong>in</strong>g a sequence based <strong>in</strong>terpolation of <strong>in</strong>ter-cluster boundary transitiongradients for spatial clusters of similar lithological structure <strong>in</strong> the Quaternarypart of the borehole logs. This <strong>in</strong>formation has been gradually complied dur<strong>in</strong>gthe PUMa project. It may, however, be possible for other studies to benefit directlyfrom these results.This study is supported by the European Social Fund ProjectNo. 2009/0212/1DP/ Environment, Geology and Meteorology Centre, [s.a], Data base “Urbumi” (LatvianBorehole Data Base).36 The 70 th Scientific Conference of the University of Latvia

ENVIRONMENTAL SITUATION IN THE AREA AROUNDINČUKALNS PONDS AND THREATS TO GROUNDWATERJuris BURLAKOVS 1 , Armands RUSKULIS 21University of Latvia, Faculty of Geography and Earth Sciences, e-mail: jurisb@vkb.lv2Latvian Environment, Geology and Meteorology Centre, e-mail: armands.ruskulis@<strong>in</strong>box.lvThe Southern and Northern acid tar ponds at Inčukalns are historicalcontam<strong>in</strong>ated sites located 30-35 km from Riga. Dur<strong>in</strong>g the period from 1950-1980,acid tar was generated as waste from the production of medical and perfumeryoil. With a disregard for environmental protection measures, acid tar and otherchemical waste was dumped <strong>in</strong> sandy pits <strong>in</strong> this forested area. The dump site wasclosed <strong>in</strong> 1986.The geological conditions <strong>in</strong> Latvia are such that the surficial sediment layersoften have good filtration characteristics, mean<strong>in</strong>g that potential contam<strong>in</strong>ation canmigrate to the deeper horizons of groundwater (artesian waters). This means thatsurface waters as well as soils must be protected from different k<strong>in</strong>ds of pollution.Studies and comparisons <strong>in</strong> the Inčukalns area are slightly complicated becauseof the many factors <strong>in</strong>fluenc<strong>in</strong>g groundwater. Therefore, monitor<strong>in</strong>g has beendone here more or less regularly for at least a decade. Groundwater analysis hasbeen conducted mostly us<strong>in</strong>g the methodological approaches used <strong>in</strong> geology, notsurface water analysis. The results from monitor<strong>in</strong>g show that the area around bothacid tar ponds – the Northern and Southern are contam<strong>in</strong>ated at both levels – theupper groundwater and the deeper Gauja horizon. The complexity arises because ofthe differentiation of the contam<strong>in</strong>ation layers. In addition, the parameters for theupper groundwater and the deeper Gauja horizon are not completely understood.The contam<strong>in</strong>ation plumes are migrat<strong>in</strong>g <strong>in</strong> the horizontal as well as the verticalplane, and thus the pollut<strong>in</strong>g substances from the Northern and Southern ponds aregett<strong>in</strong>g closer to the Gauja River and also threat<strong>in</strong>g the groundwater resources ofthe Riga City. Considerable contam<strong>in</strong>ation <strong>in</strong> the permeable and percolation sandylayers has reached groundwater and artesian waters at a depth of 70-90 m by wayof <strong>in</strong>filtration.In 2010, a remediation project for the Inčukalns acid tar ponds began, the ma<strong>in</strong>task be<strong>in</strong>g to prevent contam<strong>in</strong>ation of the territories next to the acid tar ponds.Project implementation tasks will <strong>in</strong>clude treatment with lime and the replacement,excavation and disposal to landfill (with or without treatment) and un-eng<strong>in</strong>eeredcapp<strong>in</strong>g, as well as the pump<strong>in</strong>g out of contam<strong>in</strong>ated water, then its treatmentand <strong>in</strong>jection back <strong>in</strong>to the subterranean level <strong>in</strong> order to stop the mobility ofthe contam<strong>in</strong>ated plume. The sandy layers, <strong>in</strong> which the acid tar is located, arepermeable and have good filtration properties. This means that there is a potentialhazard to be dealt with <strong>in</strong> the next 25 years, if the movement of the contam<strong>in</strong>ationSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 37

plume <strong>in</strong> the groundwater is not stopped before the Gauja River. The ma<strong>in</strong> idea isto stop the plume by pump<strong>in</strong>g, then treat<strong>in</strong>g and <strong>in</strong>ject<strong>in</strong>g the groundwater back<strong>in</strong>to the subterranean. Environmental impact and monitor<strong>in</strong>g should be undertakenus<strong>in</strong>g previous knowledge from other case studies. Air emissions, as well as thebehaviour of acid tar and its <strong>in</strong>gredients <strong>in</strong> soil and groundwater dur<strong>in</strong>g excavationand neutralization works, must be strongly taken <strong>in</strong> account. Legislation and fund<strong>in</strong>gshould be considered <strong>in</strong> the plann<strong>in</strong>g of any remediation activities. Emissions andresiduals dur<strong>in</strong>g the works must also be strongly controlled.The opportunity to collaborate with<strong>in</strong> the EU remediation framework of historicallycontam<strong>in</strong>ated territories provides an opportunity to carry out environmental researchand follow-up with remediation projects <strong>in</strong> problematic areas. The remediation <strong>in</strong>Inčukalns will demand a multidiscipl<strong>in</strong>ary approach <strong>in</strong> order to have a successfulresult. The acid tar <strong>in</strong> the ponds and <strong>in</strong> the soil has complicated chemical propertiesand therefore, similar case studies on acid tar lagoon remediation should be used <strong>in</strong>the plann<strong>in</strong>g of such activities <strong>in</strong> the Republic of Latvia.THE DEVELOPMENT TRENDS OF MŪRU-ŽAGARESAND JONIŠĶI-AKMENES GROUNDWATER HORIZONSURFACE DEPRESSION AND SEA WATER INTRUSIONIMPACT IN LIEPĀJA CITYJuris BURLAKOVS, Dz<strong>in</strong>tars LĀCISUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: jurisb@vkb.lvIn ancient times, Quaternary groundwater was used as the source of water supply<strong>in</strong> Liepāja City. It was only <strong>in</strong> the middle of the 19 th century, that water supply wellswere first drilled deeper – <strong>in</strong>to bedrock. The Žagare horizon of the Upper Devonian(D 3 žg) was mostly exploited and a more extensive use of it commenced <strong>in</strong> the 1930’sand 1940’s. At this time Liepāja’s <strong>in</strong>dustrial development was <strong>in</strong>creas<strong>in</strong>g, the volumeof exploited water resources was grow<strong>in</strong>g and the first reports were appear<strong>in</strong>g on thedevelopment of sea water <strong>in</strong>trusion, which was percolat<strong>in</strong>g the horizons of artesiangroundwater. Laboratory tests showed that water quality dim<strong>in</strong>ished due to this andno longer met the standard for dr<strong>in</strong>k<strong>in</strong>g water.Hydrogeological mapp<strong>in</strong>g on a scale of 1:100 000 was done for Liepāja City andsurround<strong>in</strong>gs <strong>in</strong> 1947, and the authors <strong>in</strong>sisted that only the Naujoji Akmene-MiddleKetleri and Mūru-Žagare artesian horizons of the Upper Devonian could be used as auseful source of dr<strong>in</strong>k<strong>in</strong>g water. It was recommended that a system of dr<strong>in</strong>k<strong>in</strong>g waterextraction wells be developed to the east of the Liepāja Lake between Grobiņa and38 The 70 th Scientific Conference of the University of Latvia

Otaņķi. The first two experimental research-exploitation wells were drilled <strong>in</strong> thisarea <strong>in</strong> 1953, with the depths of these wells be<strong>in</strong>g 102.8 m and 117.0 m respectively.Research was carried out on water supply needs <strong>in</strong> the artesian horizons of LowerCarboniferous and Upper Devonian (Žagare Formation). Further analysis showedthat the capacity of these horizons was sufficient for use as the water supply forLiepāja City. Two additional dr<strong>in</strong>k<strong>in</strong>g water wells were drilled <strong>in</strong> 1959 <strong>in</strong> Otaņķi,with their construction be<strong>in</strong>g the same as for the previous two. Water quality results<strong>in</strong> 1960 already showed that the content of dry matter and chlorides <strong>in</strong> the waterhorizons of the Lower Carboniferous and Upper Devonian Žagare Formation <strong>in</strong> thecentre of Liepāja City were 2-3 g/l and 1.6 g/l respectively.In the period from 1960-1970, the size of the groundwater horizon surfacedepression <strong>in</strong> the centre of Liepāja City grew because of the <strong>in</strong>creas<strong>in</strong>g <strong>in</strong>tensity ofwater extraction. Thus, dur<strong>in</strong>g that time, this surface depression had already startedto fulfil a particular protective function from the <strong>in</strong>tensive sea water <strong>in</strong>trusion <strong>in</strong>tothe Otaņķi water supply prospect. In order to improve the situation <strong>in</strong> the watersupply to Liepāja City, several research-exploitation wells were drilled <strong>in</strong> the Aistereprospect. Dur<strong>in</strong>g the 1983-1985 research <strong>in</strong> Liepāja City, it was observed that thepiezometric surfaces of the Upper Devonian Mūru-Žagares and Jonišķi-Kursasgroundwater horizons were almost the same (around -7 m). Both of these horizonsare separated by up to 20 m thick sedimentary rocks of the Akmene Formation withlow filtration properties.The <strong>in</strong>tensive and long-term exploitation of the Upper Devonian Mūru-Žagaregroundwater horizon <strong>in</strong> Liepāja City and surround<strong>in</strong>gs has caused, and furtherdeveloped, a complicated hydrodynamic and hydrochemical situation: the <strong>in</strong>trusionof sea water (enriched with chlorides) and the shift<strong>in</strong>g of the lower situated Eleja-Pļaviņas water horizons (with sulphates). As a result of the mentioned obstacles,the concentration of chlorides <strong>in</strong> the groundwater of Mūru-Žagare horizon hadalready risen, <strong>in</strong> 1944, from 10-20 mg/l to 245 mg/l, but the concentration ofsulphates averagely from 100 mg/l to 200 mg/l. The piezometric surface of thishorizon <strong>in</strong> 1944 was 2-3 m, while ten years later it was 3-4 m below sea level,but the concentration of chlorides <strong>in</strong> wells rose up to 600 mg/l. From 1976 it wasobserved that the eastern part of the sea water (and chloride) <strong>in</strong>trusion zone hadstarted to move <strong>in</strong> the direction of the groundwater prospect Otaņķi, with the ma<strong>in</strong>reason for this process be<strong>in</strong>g the <strong>in</strong>tensive exploitation of wells <strong>in</strong> this prospect.The lowest levels of the piezometric surface <strong>in</strong> Liepāja City were observedfrom 1985-1990 (-14 m), when the exploitation of the Mūru-Žagare horizon wasthe most <strong>in</strong>tense. If we compare the development trends of the surface depression<strong>in</strong> Liepāja City territory and Otaņķi groundwater prospect, accord<strong>in</strong>g data fromlast year from “Liepājas ūdens” Ltd., static groundwater level <strong>in</strong> Otaņķi prospectfor the Mūru-Žagares horizon surface is systematically lower<strong>in</strong>g and <strong>in</strong> 2008reached -9.0 to -16.5 m. At the beg<strong>in</strong>n<strong>in</strong>g of the exploitation of the Otaņķiprospect from 1961-1976, the piezometric surface of the Mūru-Žagares horizonwas fixed at a level of -5.0 to -5.5 m.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 39

The lower<strong>in</strong>g of the piezometric surface of the Mūru-Žagares groundwaterhorizon is the reason for the <strong>in</strong>crease <strong>in</strong> the concentration of chlorides <strong>in</strong> water.The maximum concentration (up to 2000 mg/l) can be observed <strong>in</strong> wells <strong>in</strong> LiepājaCity, which is the centre of the depression, but the results of groundwater chemicalanalysis from observation wells <strong>in</strong> Liepāja City (DB 2642, Zemnieku St. 28) show achloride concentration of up to 1200 mg/l.The results from the “Liepājas ūdens” Ltd. central test<strong>in</strong>g laboratory for the period2007-2011 from Otaņķi groundwater prospect are show<strong>in</strong>g chloride concentrations,which do not exceed water quality norms (250 mg/l). A problematic issue is that,accord<strong>in</strong>g to some evaluations, sea water <strong>in</strong>trusion is shift<strong>in</strong>g frontally with a speedof 50 m/yr. A possible solution to this problem could be more <strong>in</strong>tensive pump<strong>in</strong>g <strong>in</strong>the Liepāja City area <strong>in</strong> order to generate an artificially bigger surface depression forthe groundwater surface <strong>in</strong> order to stop migration of the sea water <strong>in</strong>trusion further<strong>in</strong>land, for example, to Otaņķi prospect.ADDITIONAL DATA ON THE CFC CONCENTRATIONAND CORRESPONDING GROUND WATER AGE IN THEFRESH GROUNDWATER OF LATVIAJānis BIKŠE, Aija DĒLIŅA, Alise BABREFaculty of Geography and Earth Sciences, University of Latvia, e-mail: janis.bikse@lu.lvOne of the ma<strong>in</strong> issues <strong>in</strong> groundwater studies is groundwater age, also known asresidence time. This is important for <strong>in</strong>vestigat<strong>in</strong>g the groundwater filtration rate andto solve various issues such as groundwater use, management and protection.The concentration of tritium will be determ<strong>in</strong>ed <strong>in</strong> about 60 samples, but theCFC concentration has now been analyzed <strong>in</strong> 39 samples – 19 samples <strong>in</strong> year2010 and 20 new samples <strong>in</strong> 2011 (Fig. 1.). Previous studies have shown that theLatvian CFC method is appropriate for aquifers to an average depth of 30-50 m(Gosk et al., 2006). Therefore, new samples for the year 2011 were taken froman average depth of 37 m, although the depth varies from 6 m to 128 m and onesample was taken from surface water (Baltezers bas<strong>in</strong>). CFCs concentrations wereanalyzed <strong>in</strong> the laboratory at GEUS after Busenberg and Plummer (Busenbergand Plummer, 1992) described a method us<strong>in</strong>g gas chromatography equippedwith an EDC detector. Interpretation of the results was carried out by laboratoryexpert, Troels Laier. Many samples were taken from one place at different depthsto obta<strong>in</strong> a better view of residence time distribution and these new samples from20 wells were located <strong>in</strong> 8 places (Fig. 1.).40 The 70 th Scientific Conference of the University of Latvia

Fig. 1. Sites of new samples for CFC analysis.New samples were taken both from the unconf<strong>in</strong>ed aquifer and the first conf<strong>in</strong>edaquifer. The sampl<strong>in</strong>g <strong>in</strong>terval for CFC analysis varies from 6-14 m up to 108-128m. It was found that most of the groundwater determ<strong>in</strong>ed from both – the conf<strong>in</strong>edand the unconf<strong>in</strong>ed aquifer – had a residence time of 35-60 years (Fig. 2.).0time <strong>in</strong> years20 25 30 35 40 45 50 55 60 6520sample depth, m406080100120Fig. 2. Water residence time at different depths.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 41

An <strong>in</strong>terest<strong>in</strong>g situation was found at the Ēvarži wells, where water residencetime at a depth of 24 – 29 m was ~63 years but at a depth of 48 – 53 m, the waterage was 43 years (the distance between these 2 wells is only 10 meters). In such asituation, the major role <strong>in</strong> water age distribution is from water horizontal flow.This study is supported by the European Social Fund projectNo. 2009/0212/1DP/, E., Plummer, L. N. 1992. Use of chlorofluorocarbons (CCl3F and CCl2F2) ashydrologic tracers and age-dat<strong>in</strong>g tools: The alluvium and terrace system of central Oklahoma.Water Resources Research, 28, pp. 2257-2283.Gosk, E., Lev<strong>in</strong>s, I., Jorgensen, L. F. 2006. Agricultural Influence on Groundwater <strong>in</strong> Latvia.Danmarks og Grønlands geologiske undersøgelse rapport 2006/85. Geological Survey ofDenmark and Greenland, Copenhagen, 95 p.GROUNDWATER ABSTRACTION DYNAMICSIN THE BALTIC ARTESIAN BASINAija DĒLIŅA 1 , Jānis VIRBULIS 2 , Ilze KLINTS 2University of Latvia, 1 Faculty of Geography and Earth Sciences, 2 VTPMML,e-mail: aija.del<strong>in</strong>a@lu.lvThe Baltic Artesian Bas<strong>in</strong> consists of a number of multi-aquifer systems thatconta<strong>in</strong> fresh groundwater. The fresh groundwater is the ma<strong>in</strong> dr<strong>in</strong>k<strong>in</strong>g water sourcefor the centralised and decentralised water supply <strong>in</strong> Estonia, Latvia and Lithuania.The fresh groundwater resources <strong>in</strong> the Baltic Artesian Bas<strong>in</strong> are pretty large,roughly about 4.1 million m³, which is 10-15 times more than is abstracted fordr<strong>in</strong>k<strong>in</strong>g water supply needs (Jodkazis, 1980). However, the groundwater abstractionis distributed unevenly spatially and <strong>in</strong> time. In order to model groundwater flow<strong>in</strong> the transient conditions, one has to know the changes <strong>in</strong> groundwater abstraction<strong>in</strong> time and space.The ma<strong>in</strong> task of the study was to provide knowledge on groundwater abstractiondynamics <strong>in</strong> order to develop different scenarios for the model calculations. The dataon groundwater abstraction was collected from the geological surveys of Estoniaand Lithuania and the Latvian Environment, Geology and Meteorology Centre.Groundwater has already been used <strong>in</strong> water supply for several centuries, tak<strong>in</strong>gwater from spr<strong>in</strong>gs or from shallow dug wells. The first deeper wells drilled forgroundwater abstraction were already <strong>in</strong>stalled at the end of the 19 th century, butthese were just a few, and did not cause any impact on groundwater resources. Withthe development of drill<strong>in</strong>g techniques, the number of wells and abstracted water42 The 70 th Scientific Conference of the University of Latvia

amount <strong>in</strong>creased cont<strong>in</strong>uously. The most wells were drilled from 1955-1970’s. Forexample, dur<strong>in</strong>g this period 10-30 wells were <strong>in</strong>stalled <strong>in</strong> Riga every year, and theamount of abstracted groundwater <strong>in</strong>creased to 5,000-6,000 m³/day per year. Thedevelopment of a centralised water supply was typical for this period, and a lot ofwell fields for public water supply were <strong>in</strong>stalled. The maximum water abstractionwas reached at the end of the 1970’s – beg<strong>in</strong>n<strong>in</strong>g of the 1980’s after which more orless stable water abstraction cont<strong>in</strong>ued until the beg<strong>in</strong>n<strong>in</strong>g of the 1990’s. With thecollapse of <strong>in</strong>dustry, water abstraction dropped sharply and the volume of abstractedwater decreased about two times. Today, water abstraction has <strong>in</strong>creased comparedto the 1990’s, but below the overexploitation dur<strong>in</strong>g the 1970-1980’s.It is typical that the amount of water abstracted for the centralised anddecentralised water supply is rather similar, a little more for the centralised watersupply, but the number of wells is 5–10 times more <strong>in</strong> the decentralised watersupply. For the model calculations, this means that it is most important to take <strong>in</strong>toaccount the centralised water supply, where a large amount of water abstraction isconcentrated <strong>in</strong> one spot (cell), but the <strong>in</strong>dividual locations of decentralised watersupply wells could be omitted for the regional studies, because the yield of eachwell is very low (100-200 m³/day <strong>in</strong> average). The only exception is large <strong>in</strong>dustrialenterprises hav<strong>in</strong>g local semi-centralised water supply systems.For model calculations, it is assumed that the natural conditions could be assumedfor the time period before year 1950, which is followed by the disturbed groundwaterregime due to the overexploitation of the groundwater resources until 1992, and thechange back to semi-natural conditions after the year 2000.This study is supported by the European Social Fund ProjectNo. 2009/0212/1DP/, V.I. 1980. Formirovanije I osvoenije ekspluatacionnyh resursov podzemnyh vodPribaltiki. Vilius, Mokslas; 176 p. (<strong>in</strong> Russian).RECONSTRUCTING THE CALEDONIAN STRUCTURALCOMPLEX DEFORMATION THROUGH THICKNESSANALYSISJānis UKASS, Konrāds POPOVS, Tomas SAKSUniversity of Latvia, Faculty of Geography and Earth Sciences, e-mail: Janis.Ukass@gmail.comIn this study we attempt to <strong>in</strong>terpret the deformation that occurred <strong>in</strong> the EarlyPaleozoic time, known as the Caledonian tectonic event, which compared to otherSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 43

tectonic events had the most significant impact. Theoretical material was collectedand analyzed from previous studies dur<strong>in</strong>g this research, and a considerable amountof published material was gathered about tectonic structures with<strong>in</strong> the territoryof Latvia. Based on this data, a rough resolution 3D geological tectonic blockmodel was developed. Although geophysical research has previously been carriedout by Geological Survey, the studies offer <strong>in</strong>sight of structures <strong>in</strong> general, but donot determ<strong>in</strong>e their k<strong>in</strong>ematics or possible evolution, except for some local scalestructures (Brangulis and Kaņevs, 2002).To reach the goal, the MOSYS modell<strong>in</strong>g system which was developed with<strong>in</strong>the PUMA project was used for the geological structure modell<strong>in</strong>g (Seņņikovs et al.,2011). An algorithmic genetic approach was applied to <strong>in</strong>terpolate the data of welllogs as strata volume and to sequentially reconstruct the post-deformation situation.This approach allows for the modification of the model construction at any stepand all processes are fully documented and are repeatable. The geometrical modelconsists of 33 tectonic blocks bordered by the faults, which were distributed by<strong>in</strong>terpret<strong>in</strong>g the displacement volume of the blocks along the faults, provid<strong>in</strong>g anopportunity to characterize the common tectonic evolution.Thickness analysis was performed to determ<strong>in</strong>e the tectonic events which led todef<strong>in</strong>ed uplift or s<strong>in</strong>k<strong>in</strong>g events, by compar<strong>in</strong>g the volume <strong>in</strong> each tectonic block andthe eroded amount of strata. This method showed that the smallest strata thicknesschange was <strong>in</strong> the Ordovician and Llandovery, Wenlock epochs of the Silurianbut the largest changes of strata thickness and erosion occurred at the end of theSilurian and <strong>in</strong> the Early Devonian. Both thickness changes and erosion show thatprocesses occurred very rapidly and that there was a major compression event at theCaledonian orogeny and should be l<strong>in</strong>ked to Scandian orogeny.The methodology applied allowed us to reach good model strata surfaces andcompatibility of well logs which was no larger than 3 meters and <strong>in</strong>dicated that themodel is reliable for strata thickness analyses. The constructed model is respectivefor the studied region, which is confirmed by the analysis that strata thickness iswell ma<strong>in</strong>ta<strong>in</strong>ed and strata thickness does not vary radically <strong>in</strong> each tectonic block.Although research data is sparse, the dip angles of fault structures are unknown andthe fault planes <strong>in</strong> the model are vertical, it still <strong>in</strong>dicates major characteristics ofdeformation and strata thickness changes which, as a prelim<strong>in</strong>ary study <strong>in</strong> tectonicevolution, is enough to draw the first major conclusions.This Project was supported by ESF project “Establishment of <strong>in</strong>terdiscipl<strong>in</strong>ary scientistgroup and modell<strong>in</strong>g system for Groundwater research”(Project Nr. 2009/0212/1DP/, A. J., Kaņevs, S. 2002. Tectonics of Latvia. Riga, State Geology Survey (<strong>in</strong> Latvian).Seņņikovs, J., Virbulis J., Bethers, U. 2011. Mathematical model of the Baltic Artesian Bas<strong>in</strong>.Geophysical Research Abstracts, Vol. 13, EGU2011-8155, EGU General Assembly 201144 The 70 th Scientific Conference of the University of Latvia

BAB V1 GEOMETRICAL MODEL:INTEGRATING HETEROGENEOUS AND UNEVENDENSITY DATA INTO A 3D GEOLOGICAL MODELKonrāds POPOVS, Jānis UKASS, Jānis JĀTNIEKS, Tomas SAKSUniversity of Latvia, Faculty of Geography and Earth Sciences,e-mail: konrads.popovs@lu.lvAlthough specialized tools allow one to model complex geological bodies<strong>in</strong> 3D us<strong>in</strong>g geological maps, survey records and borehole data, the build<strong>in</strong>g ofa viable geological model is still a challenge. One of the ma<strong>in</strong> difficulties <strong>in</strong>3D reconstructions lies <strong>in</strong> the heterogeneity of the data and its <strong>in</strong>terpretation,where there is a need for accuracy, representation at the scale of <strong>in</strong>terest andreliability.A 3D regional geological model was created for the Baltic Artesian Bas<strong>in</strong>(BB) – for modell<strong>in</strong>g the groundwater flow. A large volume of geological datadescrib<strong>in</strong>g the geological structure of the BB was available; however, the datacoverage is very uneven.In previous studies a number of problems have been solved associated withthe collection, harmonization and post-production of cartographic data <strong>in</strong> differentresolutions and various formats, which <strong>in</strong>cludes the control of various data<strong>in</strong>put, generalization and topological issues (Dēliņa et al., 2011). Mathematicalalgorithms have also been created that consider the priority, importance andplausibility of each data source <strong>in</strong> <strong>in</strong>tegrat<strong>in</strong>g topography and lithology dataas well as borehole data (Seņņikovs et al., 2011). However, there is a need touse low resolution data and <strong>in</strong>terpretations from <strong>in</strong>formation <strong>in</strong> the literature forcerta<strong>in</strong> areas, mak<strong>in</strong>g geological generalizations and <strong>in</strong>terpretations that are basedon knowledge about the geological evolution of the territory.Geological reconstruction is subord<strong>in</strong>ated to geological preconditions, wherestructure generation is based on an assumption that post-depositional deformationproduces no significant change <strong>in</strong> the sedimentary strata volume – strata thicknessand its length <strong>in</strong> a cross sectional plane rema<strong>in</strong>s unchanged, except as a result oferosion (Dahlstrom, 1969). In the case of the BB, tectonic deformation occurred<strong>in</strong> sequential cycles where subsequent tectonic stage strata was separated byregional unconformities (Brangulis and Kanevs, 2002), provid<strong>in</strong>g an opportunityfor an algorithmic approach <strong>in</strong> the reconstruction of these conditions for thewhole BB territory.The methodology for the model reconstruction <strong>in</strong>cludes several steps, <strong>in</strong>clud<strong>in</strong>g3D reconstruction of the structural surfaces with known tectonic structures,determ<strong>in</strong>ation and reconstruction of the unconformities, which together withSession of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 45

structural surfaces form an ensemble of base surfaces which are further used toreconstruct sedimentary layer distribution and thickness variations.The 3D reconstruction of the base surfaces: known tectonic structures andamount of slip along the faults and unconformities, are reconstructed us<strong>in</strong>g allavailable data after consider<strong>in</strong>g the priority of each data source. For areas withoutdata, surfaces are reconstructed us<strong>in</strong>g extrapolation of thickness data between thebase surfaces.All depositional layers <strong>in</strong> the territory of Latvia and Estonia are reconstructedus<strong>in</strong>g <strong>in</strong>itial thickness data from the boreholes, add<strong>in</strong>g additional surface datafrom cartographic and published cross sections, while the thickness between thecurrent and underly<strong>in</strong>g surface is extrapolated to the territories for which there isno data.The topography of each model layer was obta<strong>in</strong>ed by sequentially summ<strong>in</strong>gthickness to the <strong>in</strong>itial base surfaces. Thereby, each layer reflects the topographyand amount of slip along the fault of the underly<strong>in</strong>g layer. An overly<strong>in</strong>g tectoniccycle sequence is implemented <strong>in</strong>to the model structure by us<strong>in</strong>g an unconformitysurface as an <strong>in</strong>itial reference surface.Applied techniques made it possible to reliably reconstruct the 3D geologicalstructure of the BB and allowed the prediction of the surface geometry of thelayers <strong>in</strong> areas with sparse data. Modell<strong>in</strong>g results allows the quantify<strong>in</strong>g of areas<strong>in</strong> the model where additional data is necessary for geological reconstruction.The approach used has good potential for the development of regional geologicalmodels of sedimentary bas<strong>in</strong>s and is valid for the spatial <strong>in</strong>terpretation of geologicalstructures from heterogeneous and sparse data, subord<strong>in</strong>at<strong>in</strong>g this process to theprerequisites of geological evolution.The present work has been funded by the European Social Fund Project “Establishmentof <strong>in</strong>terdiscipl<strong>in</strong>ary scientist group and modell<strong>in</strong>g system for groundwater research”(Project Nr. 2009/0212/1DP/, A. J., Kaņevs, S., 2002. Tectonics of Latvia. Riga, State Geology Survey (<strong>in</strong> Latvian).Dahlstrom, C. D., 1969. Balanced cross sections. Canadian Journal of Earth Sciences, 6,743-757Dēliņa, A., Saks, T., Jātnieks, J., Popovs, K., 2011.Baltijas artēziskā base<strong>in</strong>a ģeoloģiskāuzbūve hidroģeoloģiskajam modelim – pieejamo datu implementācija un problēmas. <strong>Latvijas</strong>universitātes 69. z<strong>in</strong>ātniskā conference. Ģeoloģijas sekcijas apakšsekcija “Baltijas artēziskābase<strong>in</strong>a pazemes ūdeņi.” Referātu tēzes. Rīga, <strong>Latvijas</strong> Universitāte, 30.-32. (<strong>in</strong> Latvian).Seņņikovs J., Virbulis J., Bethers, U., 2011. Mathematical model of the Baltic Artesian Bas<strong>in</strong>.EGU General Assembly, Vienna, Austria, April 2011.46 The 70 th Scientific Conference of the University of Latvia

THE SENSIBILITY ANALYSIS OF CL - ANDSO 42-TITRATION IN GROUNDWATER SAMPLESOļegs GRIGORJEVS, Andis KALVĀNSUniversity of Latvia, Faculty of Geography and Earth Sciences,e-mail: gregoryev.oleg@gmail.comThe dom<strong>in</strong>ant cations <strong>in</strong> groundwater are K + , Na + , Ca 2+ , Mg 2+ and the anionsare HCO 3-, Cl - and SO 42-. The method for determ<strong>in</strong><strong>in</strong>g the concentration of anionsused <strong>in</strong> the “Establishment of <strong>in</strong>terdiscipl<strong>in</strong>ary scientist group and modell<strong>in</strong>gsystem for groundwater research” Project is described here. The concentrationof ions <strong>in</strong> groundwater can vary across several orders of magnitude, e.g. <strong>in</strong> thecase of Cl - from several mg/L to more than 100 g/L. The measurement of lowconcentrations of SO 42-and Cl - can be particularly difficult.The turbidimetric method is used to measure the concentration of the sulphate ion.By add<strong>in</strong>g barium chloride, barium sulphate is obta<strong>in</strong>ed. BaSO 4solubility is about1 mg/L and it def<strong>in</strong>es the determ<strong>in</strong>ation limit of the method. If SO 42-concentrationis lower than 5 mg/L, it cannot be measured, because <strong>in</strong> it the l<strong>in</strong>ear dependence oflight absorption to SO 42-concentration is break<strong>in</strong>g down.Cl - concentration is measured us<strong>in</strong>g the argentometric method. Potassiumchromate is used to <strong>in</strong>dicate the end po<strong>in</strong>t of the silver nitrate titration of chloride(Eaton et al., 2005). In measur<strong>in</strong>g chloride with a low concentration, the solutioncolour changes later. The accuracy of both methods <strong>in</strong> a low concentration rangewas tested and procedures were developed to improve it.Us<strong>in</strong>g test solutions it has been found that <strong>in</strong> the solutions with chlorideconcentration less than about 40 mg/L, the measured results are higher than thetheoretical concentration known for the test solutions (Fig. 1.).50Concentration obta<strong>in</strong>ed mg/L45403530252015105y = 0,00195x 2 + 0,83677x + 3,35979R 2 = 0,99986y=xResults obta<strong>in</strong>edPoly. (Resultsobta<strong>in</strong>ed)00 10 20 30 40 50Theoretical concentration mg/LFig. 1. Comparison of measured and theoretical Cl - concentration.Session of Geology – <strong>Section</strong> “Groundwater <strong>in</strong> <strong>Sedimentary</strong> Bas<strong>in</strong>s” 47

Us<strong>in</strong>g mathematical regression the best fit curve can be found which is describedby the equation:(1)Solv<strong>in</strong>g equation (1) the Cl - concentration corrected value can be found by theequation:, (2)where, γ Obt.– measured result and γ Cl– corrected value, which should represent thereality more closely. Equation (2) can be used to correct the measurement accuracyif the Cl - concentration is less than 35 mg/L.Sulphates cannot be measured if the concentration is less than 5 mg/L, asthere is no l<strong>in</strong>ear dependence of light absorption by the precipitated BaSO 4. It ispossible to add Na 2SO 4to a shift<strong>in</strong>g sulphate concentration <strong>in</strong> the range of l<strong>in</strong>earabsorption. In know<strong>in</strong>g exactly the amount of extra SO 42-ions <strong>in</strong>troduced <strong>in</strong> thesolution, it is possible to calculate the <strong>in</strong>itial SO 42-concentration. This approachcan be used if the SO 42-concentration is lower than 10 mg/L. The offset of theresults is demonstrated <strong>in</strong> Fig. 2.1,61,4Absorption1,210,80,6y = 0,0536x + 0,7535R 2 = 0,9956y = 0,05220x - 0,09825R 2 = 0,99925Without additivesWith additiveL<strong>in</strong>ear (Without additives)L<strong>in</strong>ear (With additive)0,40,200 5 10 15 20 25 30 35Concentration, mg/LFig. 2. Calibration curves for SO 42-measurement with and without additivesor extra added Na 2SO 4.This study is supported by the European Social Fund projectNo.2009/0212/1DP/ Eaton, A. D., Clescerl, L. S., Rice, E. W., Greenberg, A. H. (eds.) 2005. Standard methodsfor the exam<strong>in</strong>ation of water & wastewater. American Public Health Association, AmericanWater Works Association, Water Environment Federation, Wash<strong>in</strong>gton.48 The 70 th Scientific Conference of the University of Latvia

INVESTING IN YOUR FUTUREThe session is organised <strong>in</strong> the scope of the European Social Fund project „Establishment of<strong>in</strong>terdiscipl<strong>in</strong>ary scientist group and modell<strong>in</strong>g system for groundwater research” (Project contractNr. 2009/0212/1DP/ Project is implemented by University of Latvia,Faculty of Geography and Earth sciences and Faculty of Physics and Mathematics <strong>in</strong> collaborationwith Latvia University of Agriculture, Faculty of Rural Eng<strong>in</strong>eer<strong>in</strong>g, Department of EnvironmentalEng<strong>in</strong>eer<strong>in</strong>g and Water Management.www.puma.lu.lvISBN 978-9984-45-443-69 789984 454436

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