Grid-based modelling of nutrient inputs from diffuse and point sources for the state of North Rhine-Westphalia (Germany) as a tool for river basin management according to EU-WFD
Tetzlaff, Björn; Haider⊃, J.; Kreins, P.; Kuhr, Petra; Kunkel, Ralf; Wendland, Frank
An integrated model network, consisting of the agro-economical model RAUMIS, the water balance model GROWA, the nitrogen transport models DENUZ and WeKu and the phosphorus transport model MEPhos was applied to the state of North Rhine-Westphalia (34,000 km²) in Germany. The aim was to describe the actual state of nitrogen and phosphorus pollution in surface waters, originating from point and diffuse source inputs. The transport models considered diffuse inputs on a grid basis (10-100 m cell size), i.e. groundwater, wash-off, erosion and artificial drainage. Point sources were quantified either on a plant basis (waste water treatment) or for river sub-basins (rainwater sewers and combined sewers overflows). The model results showed annual inputs of approx. 117,000 tons/yr nitrogen and approx. 3,800 tons/yr phosphorus, which correspond well with mean annual loads es- timated from measured water quality and discharge data. Distributed model results allowed for the delineation of priority areas for management options within the state. The results achieved to support the development of river basin management plans, required by the implementation process of the European Water Framework Directive.