The application of a GIS-based decision support system to predict nitrate leaching to groundwater in southern Germany

A decision support system has been developed in New Zealand which links nat ional databases with a physically-based, basin-scale surface water quality model within a geographical information system (GIS) interface. In this stu dy, the system is applied to a drainage basin in southern Germany, pan of w hich is underlain by an aquifer which provides water for potable supply. Th e contamination of the groundwater resource by nitrate is of much concern i n this area, and to aid in the prediction of groundwater contamination, the system is modified so that it can predict the concentrations of nitrate le ached to groundwater. Model predictions over a six year period are compared with measured flow and concentration data from the river and concentration data from numerous boreholes. Model output in terms of nitrate leaching is displayed as a map over the extent of the aquifer so that areas particular ly susceptible to nitrate leaching can be identified.