Model-based evaluation of agri-environmental measures in the Federal State of Brandenburg (Germany) concerning N pollution of groundwater and surface water

GIS-based modeling of soil-crop interactions and hydrological processes is a valuable instrument to assess land-use effects on N pollution of water resources from the agricultural sector. A case study is presented using spatial information on soils, climatic zones, land use, and distribution of agri-environmental measures within the federal State of Brandenburg (Germany) to assess the reduction effect of EU-funded measures on N pollution of water resources. In a first step, the area was classified concerning the risk for groundwater and surface-water pollution. For this, spatially distributed model calculations of the soil-solution exchange frequency were intersected to a vulnerability map for groundwater derived from geological data and zones of different transit times from the root zone into surface waters. In a second step, model calculations of water and N dynamics in the soil-crop system for different crop and management systems were performed to calculate nitrate leaching from the root zone and to estimate the effect of present agri-environmental measures to reduce N pollution on groundwater and surface waters. The results indicated that 75% of the agri-environmental measures were placed in areas with low impact on groundwater and surface waters. Therefore, the effectiveness of the agri-environmental measures concerning water-protection aims was moderate.