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Ute Kuhn

Weser River Basin Commission, Hildesheim, Germany

“Can the nitrogen management goals for the Weser river basin area be achieved? Nutrient management by the Weser River Basin Commission“

© Ute KuhnUte Kuhn
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In 2007, as in all other German river areas, the pollution of the waters with the relevant nutrients nitrogen and phosphorus was also identified as a significant water management issue for the river basin district Weser. The investigations into the reporting for the second cycle confirmed this. In transitional and coastal waters as well as in the North Sea the available nitrogen determines the extent of algae growth. Only under certain environmental conditions, phosphorus is the limiting factor in these areas. For river waters and lakes, phosphorus is mostly responsible for algae growth. As a further important difference to river water bodies, lakes and groundwater bodies, the stress of the transitional and coastal water bodies results from the sum of the diffuse and point nutrient inputs from the entire river catchment area. Consequently, only a joint action of the agriculture and water management of all neighboring countries is constructive. Furthermore, only a combination of adapted administrative law and voluntary measures sufficiently reduces the nutrient inputs. The amendment of the Ordinance has been made with an amendment to the Fertilizer Ordinance (DüV). Furthermore, the supplementary voluntary measures are also being implemented in the second management plan. In addition to the technical requirements, the program package of the voluntary measures mainly depends on the acceptance of all parties involved (primarily agriculture). In order to promote water-conserving land management, the federal states offer financial incentive programs to promote the application of so-called agri-environmental measures. These programs build on the good experiences of cooperation in drinking water protection areas. An important part of these programs is the agricultural advisory instrument. This serves to strengthen farmers' awareness of water pollution, also in the light of business considerations. In addition, synergy effects in the area of near-natural water bodies are also being used. For example, bank edge strips to improve the water structure reduce erosion-induced phosphorus deposits. In areas exposed to erosion, measures have also been included in the program of measures aimed at reducing nutrient and fine material entries. To reduce the number of phosphorus inputs from sewage treatment plants, extensive measures were included in the program of measures.

A necessary jointly coordinated approach to reduce nutrient pollutions is one of the main task the RBC Weser. The results of the model project AGRUM Weser and the follow-up project AGRUM+ are an important basis. There numerical models simulated the nutrient situation across the entire catchment area of the River Basin District Weser. Forecasts for the Baseline (implementation of basic measures) and further measures scenarios were simulated and estimated. For the federal states, these results were the foundations for the reduction of nutrient inputs for each waterbody. The results of the analyzes confirm the assessment of the Bund/Länder-Arbeitsgemeinschaft Wasser (LAWA) that the management objectives with regard to the nutrients cannot be achieved with voluntary agri-environmental measures and that a further tightening of the ordinance is necessary. In some hot-spot areas, not even the observance of the good agricultural practice (implementation of the DüV) is sufficient to meet the groundwater protection targets. In approximately 80 communities the nutrient balance surpluses are to be reduced to <40 kgN / ha LF and in 30 communities even to <30 kgN / ha LF.