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

Contents Introduction to the Danube Basin Pilot Area  Geographical and socio-economic aspects  Hydrogeological overview  Geothermal Overview  Utilization of geothermal water Present and future hydrogeothermal resources  Modeling results  Evaluation of sustainability of current use of thermal ground water  Recommendations for monitoring areas

Geographical and socio-economic aspects  Total investigated area: cca km² (HU:40%, SK:51%, AT: 9%)  Moderate population density: 50 – 300 inhab. per km 2  High share of agricultural activities  Mayor cities (inhabitants): Bratislava – Trnava – Komárno – Nové Zámky – Dunajská Streda – Győr – Mosonmagyaróvár – Komárom– Sopron – Pápa – Neusiedl am See  Industrial zones: Bratislava, Komárno, Komárom, Győr

Geological overview - Danube Basin 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 m Gabcikovo depression

Hydrogeological conditions - Danube Basin 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.

Hydrogeological conditions - Danube Basin 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

Geothermal conditions Influence by the surrounding mountains and basin subsindence Moderate HFD conditions – 70 – 100 mW/m 2 Temperatures at the depth 2500 m – 75 °C – 120 °C

utilization of geothermal water - pumping + natural overflow form wells average yield of utilized geothermal water on Hungarian side of the Danube basin m 3 /year, 78 wells utilized, average well utilization m 3 /year/well average yield of utilized geothermal water on Slovak side of the Danube basin m 3 /year, 33 wells utilized, average well utilization m 3 /year/well active user of geothermal water on Austrian side of the Danube basin (Frauenkirchen) – no data available use: bathing and balneology, heating (greenhouse and district) Utilization of geothermal water

For the evaluation in the project TRANSENERGY – geoscientific modelling on supraregion and pilot areas with different scales Tasks for the Hydogeological and Geothermal models or the Danube basin :  Evaluation of sustainability of current use of thermal ground water  Calculate the water budgets in transboundary flows  Estimate the power and energy stored  Show the potential transboundary areas that might be affected in future and give monitoring recomnedations  Give the recomendation for future utization Source of information: Common databases compiled for the purpose of the project Geological model of the supraregion and pilot areas Hydogeological and Geothermal model supra region  Description of the overall hydraulic conditions and regional flow systems  Description of the overall geothermal conditions  Estimation of existing geothermal potentials Reservoir delineation

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 extractions reported - years The vertical extent - 10,000 m a.s.l. Vertical resolution The model adopted a geological model consisting of 8 hydrostratigraphic units: Quaternary - phreatic Upper Pannonian Lower Pannonian Sarmatian Badenian Badenian volcanites Cenozoic Mesozoic, Paleozoic and Crystalline basement

Flow boundary conditions 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 Hydraulic and geothermal models 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

-1000 m a.s.l m a.s.l m a.s.l-5000 m a.s.l Pressure differences (Pa) caused by steady pumping at different depth levels 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

 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 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 ground water (high permeability) across the whole thickness of the quaternary gravels and sands cooling propagates to large depths over 3 km m a.s.l m a.s.l m a.s.l Difference in temperature - pre-utilization state vs. steady pumping scenario at the basement of Upper Pannonian Hydraulic and geothermal models - RESULTS

Transboundary aspects evaluation Hydraulic and geothermal models - RESULTS 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

Balance of the renewable thermal enegy Actual utilization in geothemal wells is small in comparision to thermal power of the Danube basin model Still potential for sustainable geothermal energy utilization amount of thermal energy contained in porous rock and pore water filling (Specific Identified Resources) of upper Pannonian hydraulic unit (including aqiufers and aquicludes) portion of heat stored that can be theoreticay excavated raising from the egde of the basin to the centre, reaching up to 140 GJ/m 2 Hydraulic and geothermal models - RESULTS

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, effective water management both quantitative and chemical (quality) monitoring proposed monitoring areas (red) 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 km 2 ) 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

of upper Pannonian thermal aquifer between Gyõr and Veľký Meder used for bathing proposed extend of monitoring Area 2 Gyõr – Veľký Meder (315 km 2 ) 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 Proposal for transboundary monitoring in Danube Basin

Thank You for attention! ŠGÚDŠ ŠVASTA Jaromír REMŠÍK Anton ČERNÁK Radovan MFGITÓTH Gyuri SZALKAI Ágnes Rotár GBAGOETZL Gregor