Modelling water fluxes for the analysis of diffuse pollution at the river basin scale

Diffuse pollution is a significant and sometimes even major component of su rface water pollution. Diffuse inputs of pollutants to the surface water ar e related to runoff of precipitation. This means that the analysis of diffu se pollutant fluxes from the land surface to the surface water requires an analysis of water fluxes. In this paper we have modelled the average long-t erm total runoff, groundwater recharge index and groundwater residence time s for two large European river basins (Rhine and Elbe). We applied and comp ared two independently developed and recently published methods. We found t hat with the available large-scale databases and methods we could simulate successfuly the regional patterns of the average long-term total runoff. Th e reported groundwater recharge indices and groundwater residence times sho uld be interpreted as estimates based on available knowledge and databases. They do not represent absolute values, but illustrate the possible travel times and spatial patterns of the different runoff components that have to be taken into account for the analysis of diffuse pollution at large region al and temporal scales. Copyright (C) 2000 John Wiley gr Sons, Ltd.