The significance of hydrological criteria for the assessment of the ecological quality in river basins

Abstract

With the implementation of the European Water Framework Directive (WFD) the achievement of a good ecological status of surface waters and a good quantitative and qualitative status of groundwater has become obligatory. The ecological status is defined by biological, chemical and physical criteria. In the River Basin Management Plans required by the WFD, all human impacts on the aquatic environment shall be quantified and evaluated. For this purpose catchment related assessment methods which describe the physical and chemical predictors of the ecological status in surface waters and the status of groundwater are needed. They will have to be combined with monitoring programs and assessments of the water bodies themselves. To complete the existing biological, chemical and morphological assessment methods a spatially orientated assessment procedure for the hydrological quality of meso-scale river basins was developed. In this procedure human impacts on hydrology, river morphology and water quality are quantified and assessed. The procedure is divided into the three assessment units “ catchment properties”, “ runoff dynamics” and “ nutrient budget, water quality and solute dynamics”. It was applied to 22 meso-scale river basins in South-West Germany. The assessment results enable a quantification of the level of human impact on the aquatic environment.