T-JAM

The final goal of the T-JAM project was to establish a common, harmonized thermal water management strategy for the area of the Mura-Zala basin, which promotes the sustainable utilization of thermal groundwater body (divided by the Slovenian-Hungarian border but officially not delineated yet) and geothermal energy in the region.

The project intends to contribute to the solution of the problem of sustainable use of natural resources shared by neighbouring countries. The main carrying medium of geothermal energy is thermal groundwater, which flows along regional flow paths determined by geological structures independently of state borders. Possible negative effects (depression, decrease in yield and temperature) due to (over)exploitation in a given country may arise in the neighbouring country leading to political-economical tensions. Thus only a joint, cross-border, harmonized management strategy can lead to the sustainable utilization of hydrogeothermal resources.

To understand the hydrogeothermal system of the cross-border region of north-east Slovenia and south-west Hungary, several conceptual models had to be established first, which are based on harmonized datasets. Borehole data from Slovenian and Hungarian project area were gathered first, joined and harmonized in an expert database (792 Hungarian and 404 Slovenian boreholes) which contains all available technical, geological, hydrogeological, geothermal, geochemical and utilization data on each well separately. Most of this data are owned by borehole managers and are not public, and were used only by project partners for various geoscientific interpretations. However, the most representative data interesting also for the thermal water users and the wider public were published in a public database (containing data of 158 Hungarian and 99 Slovenian boreholes) in the form of a user friendly web application, which is available from the project website (www.t-jam.eu). Results of databases are summarized in the report “Joint three-lingual geothermal database”.

The report on “Geological conceptual model” gives a detailed description of the geology of the area, its main structural units and tectonics, as well as the sedimentary basin fill complex. The geological buildup is best represented on 9 regional geological cross sections: 3 WSW-ENE from Slovenia to Hungary crossing the border, and 6 NW-SE ones. The sections have a uniform geological legend which reflects a common understanding of geological formations. Furthermore, the geological model provided the bounding surfaces / depth contour maps of the main hydrostratigraphic units (input for the hydrogeological model), such as the pre-tertiary basement, bottom and top of the Upper Miocene turbidites (Szolnok / Lower Lendava formations), bottom and top of the Upper Miocene-Pliocene delta front sands (Újfalu / Lower Mura formations) for the entire project area. A harmonized surface geological map with uniform legend was also edited for the project area.

The report on the “Hydrogeological conceptual model” summarizes the current knowledge about the hydrogeological buildup of the investigated area and provided a theoretical background for the numerical models. It overviewed the main parts of the regional groundwater flow systems, such as gravity- and density-driven cold and thermal systems, the overpressured zones and closed thermal convections forming the regional-, intermediate and shallow flow systems. It delineated the (hydraulic) boundaries of the model, and gave a short description of the main hydrostratigraphic units and their hydrogeological parameters, such as porosity, transmissivity and hydraulic conductivity. It was concluded that the deepest tertiary aquifers probably contain stagnant, fossil groundwater and are identified as the ‘Miocene’ and ‘Lower Pannonian’ aquifers on the Hungarian side and as the Špilje and Haloze Formation aquifers on the Slovenian side. They have a very limited extent, or isolated from their surroundings, and therefore a transboundary flow is less possible. The covering Szolnok / Lendava formation aquifers may locally be a part of the active regional groundwater flow systems but more probably they are also rather isolated. The deep regional groundwater flow system developed in the Újfalu and Mura formation aquifers, which represent the best and the most exploited geothermal aquifers in the T-JAM project region. The overlying Ptuj-Grad, Zagyva and Somló&Tihany Formations formation aquifers are a part of the intermediate flow system, and contain thermal water in the deeper parts while from the shallower parts drinking and industrial water is produced. This system recharges in the north lying Goričko hills in Slovenia and the flow direction is assumed to be from Slovenia to Hungary. The uppermost (shallow) Quaternary aquifers extend over the whole research area.

The report on the “Hydrogeochemical conceptual model” overviewed the main hydrogeochemical processes of the T-JAM area and discussed the major factors related to the origin of the groundwaters and dissolved gases. An interpretation of the archived hydrogeochemical data and the newly sampled thermal and cold waters (12 Hungarian and 12 Slovenian wells) made it possible to prove the existence of joint transboundary geothermal aquifers between Slovenia and Hungary based on hydrogeochemical characters. The Ptuj-Grad, Zagyva and Somló&Tihany Formations have a low TDS content and a high cation ratio. Carbon dioxide is often the main dissolved gas in the Ptuj-Grad Formation water, while in the Zagyva and Somló&Tihany Formations mainly nitrogen gas is present. The groundwater stored in the Mura and Újfalu Formation has higher TDS values, but they have lower cation ratio compared to the overlying intermediate flow system. They are enriched locally in carbon dioxide or methane, but mostly air is dissolved in the groundwater. The Lendava and Szolnok Formations contain similar groundwater which is probably not a part of the active regional groundwater flow system. Water is now more or less stagnant and isolated from the surroundings; therefore it has a high TDS content, similar to the middle and lower Miocene formations aquifers. The Mesozoic aquifers investigated in Hungary and Slovenia on the T-JAM project area are not comparable, due to very scarce data. The Mesozoic carbonate aquifers in Slovenia mostly store diluted brines, while in Hungary slightly mineralized water with a combination of multiple ions is observed.

The report on the “Geothermal conceptual model” overviewed the available data background for geothermal models. In both countries necessary data have been collected from boreholes and water wells, such as temperatures and temperature gradients, thermal conductivities of lithologically different rocks, and calculated heat-flow densities. The values of thermal conductivity of rocks are comparable; those from Slovenian boreholes are in the range 0.92 to 4.6 W/(m•K), while those in the Hungarian part fall in the range 1.3 to 4.4 W/(m•K). The mean geothermal gradients in the Slovenian side are in the range 27 (Mesozoic) to 75 °C/km (Miocene), showing especially large range in younger sediments, which is similar also in Hungarian part. However, the mean geothermal gradients are very similar in different specific depths (500, 1000, 2000 and 4000 m) on both sides; for Hungarian part roughly 42 to 50 °C/km, and for Slovenian part 38 to 50 °C/km. The presented geothermal conceptual model provided the picture of the actual temperature field which is reflected from the 3D geological distribution and some locally confined hydrogeological effects. To represent initial temperature distribution, four maps were edited for the entire project area to show temperature distribution at depth of 500, 1000, 2000 and 4000 m below the surface. Common characteristics of temperature maps are few discernible anomalies at shallow depths (500 to 2000 m) connected with local phenomenon, such as convection zone in the faulted metamorphic basement (Slovenia) and upwelling of thermal karstic water (Hungary). In the mid depths (2 to 4 km) the reasons for anomalies may be thermal convection along the deep faults in the pre-Tertiary basement and regional forced convection in the thermal karst.

The report on the “Numerical flow model” integrated all results of the conceptual models and made it possible to quantify hydrogeological processes. The numerical modeling was performed in Visual MODFLOW. The rectangular model-area is 143 × 122 km, grid size is 500×500 m. The modeled hydrostratigraphic units are: (1) Quaternary and Pliocene unconfined drinking water aquifers in gravelly alluvium and fluvial terraces, (2) Pliocene and Pannonian delta plain and alluvial system with lukewarm water (upper zone of Mura, and Zagyva Formation) and (3) Pliocene and Pannonian delta front sediments with thermal water (lower zone of Mura, and Újfalu Formation). Calibration targets of the model were observed heads, permanent surface flows, groundwater age and budget of the Lake Hévíz mixing zone. With the numerical model the groundwater table map, hydraulic potentials and drawdowns for different aquifers were assessed. Different modeling scenarios were applied, investigating depressions caused by various production of cold and thermal water separately and together, in one country and both of them, and zone budgets were calculated. The model shows that depressions in the cold aquifer are local, caused mainly by water abstraction in Radenci, Szombathey and Zalaegerszeg, and can be neglected along the state border. On contrary, a major depression is noticed in the geothermal aquifer in NE Slovenia, reaching 6-8 m along the border, which reflects the joint effects of the cold and thermal water production in both countries. If solely thermal water abstraction in both countries is modeled (cold water abstraction is neglected), the depression is 5-7 m. The thermal groundwater body is recharged from north and west (NE Slovenia) and the flow direction is from west to east. The model also showed that the thermal water abstraction on the Slovenian side has much bigger effect on the size and depth of hydraulic depression along the state border than abstractions in Hungary. However, it was estimated that thermal water abstraction has not caused dramatic changes in the regional flow directions so far. Based on the modeling results, the transboundary Mura-Zala thermal groundwater body was also delineated.

The project also intended to overview the current situation on geothermal energy utilization in the T-JAM area, including ground source heat pumps. The report on “Geothermal heat pumps manual” gave a comprehensive overview on the principles of heat pumps and shallow geothermal systems, comparing ground-coupled and water-source heat pumps, their advantages and disadvantages. An overview on the EU, Slovenian and Hungarian legislation framework was also provided, as well as financial incentive schemes and burdens in both countries.

The report on the “Review of geothermal energy utilization in north-eastern Slovenia and south-western Hungary” summarized the state of direct geothermal energy utilization till the first half of 2010 based on an internationally accepted questionnaire, which was sent to all direct heat users of geothermal energy in the T-JAM project area. On the Slovenian area the 13 users at 11 locations use geothermal energy for individual space heating, district heating, air conditioning, greenhouse heating, and bathing and swimming (including balneology). In Hungary 29 users on 20 locations use the overwhelming majority for bathing and swimming (including balneology) and district heating exists only at one location. In NE Slovenia the total direct heat use is 382 TJ/year, excluding heat-pumps, in Hungary it is 648 TJ/year. The total installed capacity of the 13 Slovenian users is 38.8 MWt, while that of the 29 Hungarian users is 70.6 MWt. The rate of utilization of ground source heat pumps is hard to assess in both countries, due to the lack of information. In Slovenia (Prekmurje and Podravje regions) it is estimated to have about 600 installed units representing both closed and open looped types with capacity about 8 MWt which extract about 40 TJ/year energy from the shallow subsurface. In Hungary part of the project area heat pumps extract about 18 TJ of energy every year. Both on the Slovenian and Hungarian sides the average flow rate is about 40-50% of the flow rate at maximum utilization, which shows that wells do not operate efficiently. The capacity factor is about 0,3 in both countries.

The report on “Screening of EU and national legislations” gives a comprehensive overview on the legal background of geothermal energy utilization comprising mining-, environment- and water management legislations in both countries, and at EU level (including international conventions and bilateral agreements).

The wide common knowledge platform that was built up during the T-JAM project enabled the partners to transforms all scientific results into everyday practice and formulate recommendations for a joint and harmonized cross-border groundwater management strategy in line with the EU Water Framework Directive. The report on “Cross-border management recommendations” phrases these suggestions to all decision-makers, especially to the Permanent Bilateral Slovenian – Hungarian Water Management Commission, i.e. to officially determine the joint thermal groundwater body Mura-Zala, which was delineated on the basis of the numerical modelling, and implement proposed measures to reach the environmental and geothermal energy objectives. The extent of the TTGWB Mura-Zala is greater than 4,000 km2 which means that this transboundary groundwater body is certainly significant also in Danube River Basin Management scale. Following the renewable energy goals from Directive (2009/28/EC) and also the future development of the transboundary socio-economic development of the area, TTGWB Mura-Zala (especially agriculture and tourism) will highly increase thermal water demand. This has certainly to be encouraged via possible increase of current rate of thermal water abstraction to a maximum amount of 3.5 higher than present, but most of all by the promotion of best available technology including re-injection and increment of thermal efficiency. The proposed measures of information exchange and common monitoring system are probably the crucial step in the implementation process of common water management.