Input pathways and river load of pesticides in Germany - a national scale modeling assessment

A model has been developed which estimates the magnitude and the spatial di stribution of pesticide losses from diffuse sources (surface run-off, tile drains and spraydrift) into surface waters for the entire area of Germany. The cumulative annual losses of 42 active ingredients applied to 11 field c rops, orchards and vineyards are calculated for river basins in Germany bas ed on grid maps with a resolution of 1 x 1 km(2). The model validation show ed a sufficient degree of accuracy of the model results compared to measure d pesticide loads in 13 small catchments. According to the model results th e pesticide input from diffuse sources into surface waters amounted to 13.8 t in 1994 aggregated for the entire area of Germany. Input via surface run off contributed 9.1 t while tile drainage was 1.4 t and spraydrift 3.4 t re spectively. Alongside the model calculations empirical data of the pesticid e load of rivers in Germany are presented. A comparison of the measured riv er loads with the modeled inputs from non-point sources leads to the conclu sion that in most regions of Germany the largest portion of the load is due to the input from farm effluents.