Large transboundary Upper Miocene geothermal sandy aquifers which are widely utilized by both countries for balneological and direct heat purposes exist in the Slovenian-Hungarian border region. In NE Slovenia the total direct heat use was 382 TJ in 2010, while in SW Hungary it was 648 TJ, including utilization from basement reservoirs. The total installed capacity of the 13 Slovenian users was 38.8 MW t , while that of the 29 Hungarian users was 70.6 MW t . Utilisation takes place without harmonized management strategies which might endanger the longterm sustainability of these systems. We aimed to overcome this by delineating a transboundary thermal groundwater body (TTGWB) Mura-Zala with an aerial extent of 4,974 km 2 and with vertical extent between depths 500-2,200 m, which was done based on detailed geological, hydrological, geochemical and geothermal models as well as numerical modelling. The regional groundwater flow in the Mura-Zala TTGWB is from west to east in general, the modeled cross-border flow is approximately 50 l/s. At present, thermal water abstraction rates from the Mura/ Újfalu Fm. (61.8 l/s in the Slovenian and 67.3 l/s in the Hungarian part of the TTGWB) does not endanger the good regional quantity status of the water body, and this should be maintained by allowing a maximum increase of thermal water abstraction 3.5 times higher than today. However, to achieve target numbers for an increased proportion of geothermal energy in the total energy mix in both countries, we suggest that increase of thermal efficiency and re-injection should be prioritized apart from the higher thermal water abstraction with setting up limit of the maximum allowable drawdown. Izvle~ekNa mejnem obmo~ju med Slovenijo in Madžarsko so razprostranjeni obsežni, prekomejni zgornjemiocenski geotermalni pe{~eni vodonosniki, ki se v obeh državah uporabljajo predvsem v balneolo{ke namene in za direktno rabo toplote. V severovzhodni Sloveniji je skupna direktna raba toplote v letu 2010 dosegla 382 TJ, v jugovzhodnem delu Madžarske pa 648 TJ, vklju~no z rabo vodonosnikov v podlagi neogenskih kamnin. Celotna in{talirana kapaciteta 13 slovenskih uporabnikov je zna{ala 38,8 MW t , medtem ko je in{talirana kapaciteta pri 29 madžarskih uporabnikih dosegla 70,6 MW t . Uporaba poteka brez usklajene strategije upravljanja, kar lahko ogrozi dolgoro~no vzdržnost teh sistemov. To smo želeli prese~i z opredelitvijo prekomejnega Mursko-Zalskega telesa termalne podzemne vode (VTPodV Mura-Zala) s povr{ino 4.974 km 2 in vertikalnim razponom globine 500-2200 m, dolo~enega na podlagi podrobnih geolo{kih, hidrogeolo{kih, geokemi~nih in geotermalnih modelov, kot tudi numeri~nega modela podzemne vode. Tok podzemne vode v VTPodV Mura-Zala je usmerjen pretežno v smeri zahod-vzhod, pri ~emer je prekomejni tok ocenjen na približno 50 l/s. Pri trenutni koli~ini odvzema termalne vode (~ 61,8 l/s iz slovenskega ter ~ 67,3 l/s iz madžarskega dela VTPodV Mura-Zala) koli~insko stanje telesa ni ogroženo, a njegovo dobro stanje je potrebno ohranjati ...

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The assurance of drinking water supply is one of the biggest emerging global challenges, especially in urban areas. In this respect, groundwater and its management in the urban environment are gaining importance. This paper presents the modeling of nitrogen load from the leaky sewer system and from agriculture and the impact of this pressure on the groundwater quality (nitrate concentration) in the urban aquifer located beneath the City of Ljubljana. The estimated total nitrogen load in the model area of 58 km2 is 334 ton/year, 38% arising from the leaky sewer system and 62% from agriculture. This load was used as input into the groundwater solute transport model to simulate the distribution of nitrate concentration in the aquifer. The modeled nitrate concentrations at the observation locations were found to be on average slightly lower (2.7 mg/L) than observed, and in general reflected the observed contamination pattern. The ability of the presented model to relate and quantify the impact of pressures from different contamination sources on groundwater quality can be beneficially used for the planning and optimization of groundwater management measures for the improvement of groundwater quality.

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