Source areas and mixing of runoff components at the hillslope scale : a multi-technical approach

Abstract Hillslope processes (i.e. water flow pathways, source areas and residence times) are essential for predicting water quantities and water quality. A multi-technical approach using classical hydrometry, natural and artificial tracers and electrical resistivity tomography (ERT) was applied to two adjacent steep hillslopes in the Black Forest Mountains, Germany. The differences in the hydrological and hydrochemical responses during three floods were larger than expected based on previously available information of topography, land use and geology. At one site a very dynamic shallow groundwater system dominated the flood generation, which could not be observed at the other site. The reasons for the heterogeneity of hillslope processes are the different soils and structures of the periglacial drift (first-order control); this is augmented by the different land use (pasture vs forest) and its effects on the near-surface processes (second-order control). The multi-technical approach proved very useful: t...