Abstract
The preservation of water bodies from eutrophication implies accurate estimation of phosphorusand nitrogen loads and the control of nutrient production on a catchment scale. In this paper, a simple tool forthe modelling of annual nutrient loads is presented. It is implemented in ARC/INFO GIS using Arc MacroLanguage (AML). The use of a GIS is justified as the spatial characteristics of the catchment area (land use,industrial wastewater location) dictate water quality. The annual nutrient loads are worked out on thecatchment scale, using existing GIS routines together with specific routines developed in AML forhydrological and water quality modelling purposes. The catchment area is divided into hydrologicalsubcatchments with relatively homogeneous spatial characteristics. Each subcatchment is linked to aspecific nutrient export potential. These nutrient loads, calculated on a subcatchment-by-subcatchmentbasis, are conveyed to the outlet of the catchment and allow annual nutrient load estimation. A comparisonwith a water monitoring study is conducted to verify the adequation of modelling results for phosphorus andnitrogen loads.