Radovan Černák, Jaromír Švasta ŠGÚDŠ, Mlynská dolina 1, Bratislava

1. Radovan Černák, Jaromír Švasta ŠGÚDŠ, Mlynská dolina 1, Bratislava The Danube Basin (Austria-Hungary-Slovakia)Recommendations for sustainable management of transboundary hydrogeothermal resources at cross-border pilot areas

2. Contents • Introduction to the DanubeBasin Pilot Area • Geographical and socio-economic aspects • Hydrogeological overview • Geothermal Overview • Utilizationofgeothermalwater • Present and future hydrogeothermal resources • Modeling results • Evaluation of sustainability of current use of thermal ground water • Recommendationsfor monitoring areas

3. Geographical and socio-economic aspects • Total investigated area: • cca 12 400 km² (HU:40%, SK:51%, AT: 9%) • Moderatepopulationdensity: • 50 – 300 inhab. per km2 • Mayorcities (inhabitants): Bratislava – 420 000 Trnava – 66 000 Komárno – 35 000 Nové Zámky – 40 000 Dunajská Streda – 23 000 Győr – 132 000 Mosonmagyaróvár – 35 000 Komárom– 20 000 Sopron – 56 000 Pápa – 35 000 Neusiedl am See - 10 000 • Industrialzones:Bratislava, Komárno, Komárom, Győr • Highshareofagriculturalactivities

4. Geologicaloverview - DanubeBasin • several depocenters / various age - depressions surrounded by mountains • the depth of the basin > 8500 m - central part of the basin - Gabcikovo depression • The Pre-Tertiary basement - crystalline and mainly late Paleozoic and Mesozoic (dominantly Triassic – Jurassic) sedimentary seqences • Tertiary rocks - sandstones, marls and clays as well as coal or bauxite occurrences • Badenian, Sarmatian sediments - clays, siltstones, conglomerates, sandstones • Lower Pannonian - shallow water to lacustrine sediments -clays, sands, gravels • Upper Pannonian and Pliocene sediments - deltaic and fluvial facies • parts of the Upper Pannonian also basaltic volcanism • Quaternary deposits - Fluvial deposits +loess - thickness - 600 m Gabcikovo depression

5. Hydrogeologicalconditions- DanubeBasin • The crystalline basement has no significant - groundwater flow system • Mesozoic aquifer system of the Danube Range blocks of carboniferous basement – limestones/dolomites – favourable hydraulic conditions, sometimes in connection of overlying sedimentary fill of the basin (Badenian sediments) • The Miocene sedimentary aquifers (Badenian or Sarmatian sands and limestones) are connected to the basement aquifers and form a single flow system. They content fossil waters with high salinity • The Upper Miocene and Lower Pannonian - low permeable and thick marl and clay sequences = regional aquicludes • separate the flow system of the basement from the deep (usually thermal water) flow system of the porous formations characterized the Pannonian reservoir.

6. Hydrogeologicalconditions- DanubeBasin • Upper Pannonian formation - interlayer leakage, intergranular permeability and confined groundwater level, thermal waters 42–92 °C, sands to sandstones aquifers. • towards the center of the basin the number of sandstone aquifer layers and thickness increases • towards the center of the basin porosity and permeability decrease • the sandy aquifer layers vary with aquitard clay, sandy clay layers • Quaternary sediments - unconfined reservoir, cold groundwater with hydraulic connection with the Pannonian flow systems, groundwater regime depends on the Danube river • With respect to lithology, the aquifer and overlying beds have been divided into six hydrogeological complexes. Each represents a complex with different ratio of aquifers and aquicludes. The waters in the Central depression are either marinogenic or petrogenic and are divided into five chemical types

7. Geothermal conditions • Influence by thesurroundingmountains and basinsubsindence • Moderate HFD conditions – 70 – 100 mW/m2 • Temperaturesatthedepth 2500 m – 75 °C – 120 °C

8. Utilizationofgeothermalwater • utilization of geothermal water - pumping + natural overflow form wells • average yield of utilized geothermal water on Hungarian side of the Danube basin 4 005 221 m3/year, 78 wellsutilized, averagewellutilization51 349 m3/year/well • average yield of utilized geothermal water on Slovak side of the Danube basin 2 891 818 m3/year, 33 wellsutilized, averagewellutilization87 631 m3/year/well • activeuserof geothermal water on Austrian sideof the Danube basin (Frauenkirchen)– no dataavailable • use: bathing and balneology, heating (greenhouse and district)

9. Fortheevaluation in theproject TRANSENERGY • – geoscientificmodelling on supraregion and pilot areaswithdifferentscales • TasksfortheHydogeological and Geothermalmodels or theDanubebasin : • Evaluationofsustainabilityofcurrentuseofthermalgroundwater • Calculatethewaterbudgets in transboundaryflows • Estimatethepower and energystored • Show thepotentialtransboundaryareasthatmightbeaffected in future and give monitoring recomnedations • Givetherecomendationforfutureutization • Sourceofinformation: • Commondatabasescompiledforthepurposeoftheproject • Geological model ofthesupraregion and pilot areas • Hydogeological and Geothermal model supraregion • Description of the overall hydraulic conditions and regionalflowsystems • Description of the overall geothermal conditions • Estimation of existing geothermal potentials • Reservoirdelineation

10. Evaluation of sustainability of current use of thermal ground water by hydraulic and geothermal models • simulate the hydrogeological and geothermal conditions (steady state model) - pre-Neogene and Neogene fill of the Danube basin - focused on Upper Pannonian geothermal aquifers • compared in the model • pre-utilization reflecting “natural conditions” with no pumping assumption • assumption considering influence of the production wells based on geothermal water extractionsreported - years 2007-2010 The vertical extent -10,000 m a.s.l. • Vertical resolution • The model adopted a geological model consisting of 8hydrostratigraphic units: • Quaternary - phreatic • Upper Pannonian • Lower Pannonian • Sarmatian • Badenian • Badenian volcanites • Cenozoic • Mesozoic, Paleozoic and Crystalline basement

11. Hydraulic and geothermal models Flow boundary conditions • outer limit of the model follows natural hydrogeological boundaries - defined by extend of thermal water bearing horizons or by groundwater divides - no-flow boundary • all across the top surface constant groundwater head - groundwater potential of cold water Quaternary aquifers laying on top of thermal aquifers • utilization variant - average reported well yields from 2007 – 2010 assigned as pumping rates Heat boundary conditions • at the base of the model - constant heat flux (mW/m2), Lenkey, 2012 • at the ground surface uniform temperature 10 °C • radiogenic heat production in rocks

12. Hydraulic and geothermal models - RESULTS model - numerical representation of hydrological and geothermal characteristics of the pilot area • model effects of wells utilization – pressure changes • theoretical infinite pumping of all existing operating geothermal wells • decrease of the pressures caused by pumping of the rates (as reported for the years 2007 – 2011) is negligible on regional scale • Decrease of the pressures is on pumped wells and has local efect • Changes in pressures in deeper horizons are subtle and are caused by change of water density as a decrease of water temperature casued by pumping -1000 m a.s.l -2000 m a.s.l -3000 m a.s.l -5000 m a.s.l Pressure differences (Pa) caused by steady pumping at different depth levels

13. Hydraulic and geothermal models - RESULTS • model effects of wells utilization –Temperature distribution • convection - high importance for heat transport • in karstified Mesozoic carbonate - Komárno elevated block • relatively intensive water interchange between recharge and discharge zones in Quaternary sediments - 1000 m a.s.l • considerable cooling of the whole carbonate massive in Komarno elevated block • cooling effect of thick quaternary aquifer in the central part, large depth (up to 600 m), rapid circulation of 10˚C groundwater (high permeability) across the whole thicknessof the quaternary gravels and sands • cooling propagates to large depths over 3 km Difference in temperature - pre-utilization state vs. steady pumping scenario at the basement of Upper Pannonian -2000 m a.s.l - 3000 m a.s.l

14. Hydraulic and geothermal models - RESULTS Transboundary aspects evaluation • computed flow trajectories with travel times, induced by pumping in utilized thermal wells • significant amounts of water and energy moving either naturally or by forced convection from state to state • international cooperation in managing geothermal resources needed • lateral extend of well capture zones may be underestimated, in model homogeneous aquifers, in reality predominantly from more permeable layers

15. Hydraulic and geothermal models - RESULTS • amount of thermal energy contained in porous rock and porewater filling (SpecificIdentifiedResources) ofupperPannonianhydraulicunit (includingaqiufers and aquicludes) • portion of heat stored thatcanbetheoreticayexcavatedraisingfromtheegdeofthebasin to the centre, reachingup to 140 GJ/m2 • Balanceoftherenewablethermalenegy • Actualutilization in geothemalwellsissmallincomparision to thermalpoweroftheDanubebasin model • Stillpotentialforsustainablegeothermalenergyutilization

16. Proposal for transboundary monitoring in Danube Basin • the main reservoir of Danube Basin represents the Upper Pannonian formation,the dish-like shape and brachysynclinal structure of depression, • contains thermal waters 42–92 °C warm which are bound mainly to sands to sandstones aquifers • possibility decrease of temperature due to infinite pumping (color) and piesometric head contours at the base of upper Pannonian at natural state (black, m a.s.l.) • recommendations for establishment of groundwater monitoring - necessary for a long-term, effectivewater management both quantitative and chemical (quality) monitoring • proposed monitoring areas (red)

17. Proposal for transboundary monitoring in Danube Basin • thermal waters are bound to upper Pannonian aquifer, extending on both sides of the border river Danube at depths from 1000 to 2500 m • thermal waters are utilized by a number wells, almost solely for recreational purposes • proposed extend of monitoring Mosonmagyaróvár – Lipót – Šamorín (310 km2) • advisable to set up at least 2 new monitoring wells between Mosonmagyaróvár and Šamorín, use existing currently non operated wells FGČ-1, BL-1 and FGGa-1 • monitored parameters - minimum well head pressure and reservoir temperature, sampled on weekly basis

18. Proposal for transboundary monitoring in Danube Basin • of upper Pannonian thermal aquifer between Gyõr and Veľký Meder used for bathing • proposed extend of monitoring Area 2 Gyõr – Veľký Meder (315 km2) • area close to river Danube – no hydrogeological boreholes - recommended 2 monitoring boreholes • currently unused wells VZO-14 and VČR-16 can be easily converted into monitoring boreholes • monitored parameters - minimum well head pressure and reservoir temperature, sampled on weekly basis

19. Thank You for attention! ŠGÚDŠ ŠVASTA Jaromír REMŠÍK Anton ČERNÁK Radovan MFGI TÓTH Gyuri SZALKAI Ágnes Rotár GBA GOETZL Gregor