Available groundwater resources in fresh/salt water transition zones of Lithuania.

Abstract:European Union Directives 2000/60/EC and 2006/118/EC oblige member states to assess groundwater quantitative and chemical status on the territory of their countries. Groundwater resources in Lithuania are much larger than present or future drinking water demands. Therefore all drinking water supply in the country is and will be based exceptionally on groundwater. The favourable hydrogeological and economic situation assures relatively good groundwater chemical status, only locally and slightly affected by pollution. Considerably more serious is the problem of salt water encroachment into fresh groundwater bodies. Some wellfields, located in fresh/salt water transition zones demonstrate significant and sustained upward trends of chlorides and sulphates concentrations, sometimes exceeding drinking water standards. Simulation results show that even more serious changes of groundwater chemical status of this kind are possible in the future. Therefore we suggest that those changes are taken into account when assessing available groundwater resources in fresh/salt water transition zones.