Abstract

In Germany, the runoff volume, peak flow rate, sediment and phosphorus yield were calculated with modified Agricultural Non-Point Source Pollution Model (AGNPS) in the Weiherbach Watershed (size: 3.5 km²), Germany. Measures of the MEKA Program, which is a governmental instrument in order to reduce agricultural overproduction and protect the environment, were calculated with AGNPSm to compare simulation output to actual output from current land use (base values). MEKA-measures assumed for simulations were mulch-seeding and cover crops to reduce soil erosion on 201.8 ha. The modeling framework comprised a geographic information system (GIS), an interface, and AGNPSm. In 1994, average sediment delivery with MEKA measures were reduced to 36.5% (49.4 t) and phosphorus yield to 24.1 % (41.9 kg). Maximum reduction rates in sediment yield by MEKA Program were achieved in fall. The corresponding amount of governmental subsidies to pay to farmers were DM 36,362.