Integration of MONERIS and GREAT-ER in the decision support system for the German Elbe river basin

The Elbe-DSS is a tool for integrated river basin management of the German part of River Elbe basin. Various simulation models are used to assess the impact of measures such as reforestation, changes of agro-practices or efficiency of wastewater treatment plants and of external scenarios on a set of management objectives. For the assessment of nutrient and pollutant loads and impacts, MONERIS and GREAT-ER are integrated in the Elbe-DSS. MONERIS calculates nutrient inputs from diffuse and point sources on a sub catchment scale of about 1,000 km2. GREAT-ER was developed as a tool for exposure assessment of point source emissions considering fate in sewage treatment plants as well as degradation and transport in rivers. Both models work on long-term scale but results are calculated for different spatial entities. GREAT-ER divides the whole river network into small segments that are linked through a routing algorithm. To integrate both models, diffuse nutrient inputs for the sub-catchments calculated from MONERIS were distributed to the river network in GREAT-ER, where further elimination and transport processes are calculated together with inputs from point sources. As an example for measures the effects of reforestation on phosphate loads and concentrations in the river network were simulated. Results show a spatial heterogenic effect mainly influenced by the erosion pathway.