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Radovica - Metlika / Zumberak Aquifer - 98

Croatia - Slovenia

Aquifer type 2

In Slovenia: Surface water and groundwater divides separate from state border, recharge in one country, discharge in adjacent.

The Radovica - Metlika / Zumberak Aquifer is made up of Upper Triassic dolomites, Upper Jurassic limestones, Cretaceous predominantly carbonate flysch, karstic limestones. Pressure condition is partly confined, partly unconfined. Recharge area is both in Croatia and Slovenia; the discharge area is in Slovenia. There is possible drainage to surface water systems/ Groundwater covers the total of the water used in the Slovenian part and flows from Croatia to Slovenia.


Radovica - Metlika / Zumberak AquiferCroatiaSlovenia
Area (sq. km) 158 27
Thickness: mean, max (m) N/A >1000
Groundwater uses and functions Dominantly drinking water supply; supports ecosystems. Drinking water supply (town of Metlika; minimum yield of the Obrh spring discharge is
about 50 l/s, maximum yield > 1000 l/s).
Pressure factors None Agricultural activities, lack of sewerage in the spring recharge area, illegal dump sites. Spring water quantity fluctuates significantly due to the karstic geomorphology; water scarcity in summer; possible problem regarding the surface stream hydrological minimum during drought. Excessive pesticide content, possible microbiological pollution; turbidity of water is observed during the rainy season.
Groundwater management measures Groundwater management measures Wastewater treatment infrastructure and septic tank systems being developed in the recharge area (in progress);
uncontrolled dump site inventory and appropriate addressing of the issue is planned for the future.
Other information Border length 12 km. Agreed delineation of transboundary groundwaters, and development of monitoring programmes
are needed. No transboundary impact. Transboundary aquifer under consideration, but not approved.
Border length 12 km. Population ~2 500 (density 95 inhabitants/ No transboundary impact. Possible additional and more frequent discharge reduction in drought seasons as a consequence of climate change.
It is unclear which groundwater systems in the two countries correspond to each other; delineation of transboundary groundwater systems needs common research and a bilateral expert group decision to propose a transboundary groundwater, if appropriate.
Establishment of transboundary water protection areas is needed; the bilateral water commission will discuss this issue.