Nutrients are substances or combinations that are essential for plant growth. In rivers the growth of algae and aquatic plants is limited by the amount of solved nutrients. But this natural balance is disturbed by anthropogenic activities. The most nutrient inputs are from diffuse discharges from agriculture and sewage and industrial effluents, most of all phosphorous compounds (phosphates and organically bonded phosphorous) and nitrogen compounds (ammonia and nitrate).

This increases the growth of aquatic plants. The algae carpet clouds the water and because of the lack of light many plants in the depth die off. The dead plant matter is decomposed by oxygen cosumption. Therefore there is often oxigen deficiency in the dammed sections because of low flow rate and long resting time of the water body. High nutrient loads from the river waters are also responsible for the eutrophication in coastal waters.

The reduction of nutrients is one of the significant water management issues in the Weser river basin. To reduce the nutrient inputs, measures have been developed and implemented for years in the agricultural sector. But not only environmental issues, also social and economic consequences have to be considered. To do this, for the Weser river basin district a network of three models was developed within the framework of the modelling project AGRUM to describe the nutrient situation using a basin wide coherent methodology and to assess the impact of agricultural and environmental measures for the reduction of nutrients.

Data nutrients
in the (in German)