Development of the WEISS Water Emission Inventory Support System (Dutch) designed to estimate, through a bottom-up approach, all pollutants from all sources to the surface waters. WEISS tackles this problem in a geographically-explicit manner and on a high resolution (+/- 1 ha). Both point and diffuse sources are included in WEISS. The pathway of the pollutants from the source to the surface waters via intermediate nodes is calculated. VITO took care of the conceptual development, the modelling and the software-technical implementation of the WEISS system, as well as its documentation and application to Flanders.