The assessment of the required groundwater quantity for the conservation of ecosystems and the achievement of a good ecological status of surface waters

Abstract

Assessment of the available quantity of groundwater is of essential importance for its sustainable use. Modern approaches for estimation of groundwater availability take into account all potential impacts of abstractions, including impacts on groundwater dependent ecosystems and impacts on surface waters ecological status. Groundwater body is in good quantitative status if groundwater abstractions do not cause significant damages to groundwater dependent ecosystems and significant diminution in the ecological status of surface water bodies. The methodology presented in this paper was developed as an integral part of the assessment of the quantitative status of groundwater bodies in Slovenia and is tailored to the characteristics of the groundwater dependent ecosystems as well as hydrological and hydrogeological conditions in the Slovenian territory. Two different approaches were implemented; for forest habitats on alluvial aquifers, and habitats of amphibians and molluscs in karst areas. Estimates of the required quantity of groundwater for groundwater dependent ecosystems conservation were performed at the level of groundwater bodies and annual averages of temporal variables of the water balance, calculated with the regional water balance model GROWA-SI. In the areas of groundwater bodies with groundwater dependent ecosystems estimated quantity present 0.1 % - 12.4 % of the groundwater recharge. The estimated share of annual renewable quantity of groundwater to maintain the ecological status of surface waters for the entire territory of Slovenia is 23.2 %. The largest share, 30 % is in north-eastern Slovenia and the lowest in the north-west part of Slovenia with a 16.6 % average annual renewable quantity.