Modelling the effectiveness of agricultural measures to reduce the amount of pesticides entering surface waters

In agricultural areas, pesticide concentrations in rivers can show a highly dynamic course frequently exceeding the standards. In order to diminish these high concentration peaks and to reduce their negative impacts on the receiving ecosystem, different measures can be taken. The objective of this study is to evaluate the impact of implementation of best management practices on pesticide fluxes entering surface waters using a modelling approach. We focus on the Nil catchment, a small basin situated in the centre of Belgium. From previous studies, the SWAT model (Soil and Water Assessment Tool) was calibrated and validated for hydrology and pesticide input for this basin. Different management scenarios were simulated and compared to the initial situation. The results revealed that strip cropping seems to be more efficient than the implementation of cover crops, than buffer strips, than a 25% reduction of point losses and plough management respectively. The study showed that a modelling approach can be used to estimate the impacts of water quality management programs in river basins. Such an approach allows to rank different mitigation measures for pesticide fluxes towards surface waters.