Evaluation and Application of Environmental Flows in Running Waters in Slovenia

Water use invariably results in major impacts on river flows. Environmental Flows (EF) are defined as the quantity and quality of water that is needed to preserve the structure and the function of the river and riparian zone ecosystem and sufficient quantity of water to enable the survival and reproduction of aquatic organisms in different hydraulic habitats. This paper describes the criteria and methods used to determine EF and experiences with their application in Slovenia. The diversity of running waters of Slovenia demand special treatment and determination of EF for each individual section of the river system. Using hydrological, morphological and ecological criteria, two different approaches are used for the determination of EF in Slovenia, a rapid assessment method and a detailed assessment method. For both methods, data are then analyzed by an expert panel in order to determine an EF. Since 1994, more than 180 study sites have been examined for research and application of EF in Slovenia. Determination of EF for existing users has prioritized their water requirements so they can remain economically viable. Where new schemes are proposed, there has been much greater scope to prioritize ecosystem requirements. EF determination is receiving growing attention and will continue to increase in importance, driven by research that aids our understanding of flow-biota relationships and recent environmental policy and legislation at both the national and European level.