Modeling pesticide losses from diffuse sources in Germany

A GIS-based model estimates the losses from diffuse sources in surface wate rs in Germany for 42 active ingredients applied to 11 field crops, vineyard s and orchards. For the following pathways of entry: tile drainage, runoff and spray drift, the calculated mean pesticide input amounts to 1490 kg/yea r, 9060 kg/year and 3350 kg/year, respectively, in 1994. The model results are highly sensitive to the model parameters, primarily the chemical proper ties of the active ingredients. The modeled water inputs were compared with measured pesticide loads in smaller catchments and large river basins to v alidate model results. Both datasets agree as to the order of magnitude, ne vertheless due to the scale of the study the results should be addressed ma inly to comparative interpretations with the focus on the proportions betwe en different active ingredients, soil regions, climates and application per iods.