Legislative effects on the development of surface water quality in rural areas in Northern Germany

The objective of this study was to document the development of the water quality in a rural catchment in Northern Germany as a result of the change of environmental legislation designed to achieve protection of water bodies. The selected lowland catchment ‘Honigau’ (14 km²) was extensively investigated during two monitoring campaigns from 1972 to 1974 and 1996 to 1998, respectively. The anthropogenically caused pollution level of the brook draining the study area was greatly reduced over time, because the number of households connected to waste water treatment plants was increased. In addition, new and improved wastewater treatment plants ensured a more efficient treatment. Furthermore, state-of-the-art storage capacities for manure at the farms reduced nutrient losses. The results showed that technical progress and an improved legislative framework have a greater effect on the reduction of nutrient losses from point than from diffuse sources resulting in much lower phosphorus concentrations, but there were still elevated nitrate concentrations, particularly caused by the tile-drainage of organic soils.