Modelling scenarios to assess the effects of different agricultural management and land use options to reduce diffuse nitrogen pollution into the river Elbe

Abstract

The European Water Framework Directive requires the development of measure programs, management plans and strategies to avoid the water pollution with nutrients and other harmful matters. In a case study model calculations were used to evaluate different options of land use, agricultural and water management to reduce nitrogen immissions and enhance water and nutrient retardation in the Elbe river basin. The model scenarios consider measures which are recommended to reduce nitrogen pollution like organic farming, conversion of arable land into pasture, extensivation of grassland production and set aside. Additionally the re-wetting of formerly drained areas by water management is considered where applicable. Although there are distinct differences in nitrogen leaching between the different agricultural land use and management options, the regional effects of the scenarios on the emissions from the root zone are only fair (max. 13%) because of their limited extent of application. But the targeted application of the measures in zones of high river impact risk derived from groundwater residence times and decay calculations lead to a distinct reduction of the nitrogen input into the river flow system. The combination of water management and extensivation of agricultural production can achieve a reduction of 22% (4.400 t/a) of the nitrogen immissions originated from agriculture. Areas with a high reduction potential for nitrogen immission can be identified. This can be a relevant information for the development of measure programs within the water framework directive.