Quantifizierung aktueller und zukünftiger Nährstoffeinträge und Handlungsbedarfe für ein deutschlandweites Nährstoffmanagement – AGRUM-DE

The aim of the project was to create a nationwide, uniform, spatially high- resolution nutrient model together with agricultural and water management authorities of the federal states in order to create information bases that can contribute to fulfilling the reporting obligations of the Water Framework Directive (WFD), among other things. The aim was to map inputs of nitrogen and phosphorus from agriculture, the wastewater sector and the air pathway into groundwater, surface waters and the tributaries in the North Sea and Baltic Sea or the transfer levels to neighbouring countries, taking into account the respective most important conversion and degradation processes. The AGRUM-DE model network consists of the agricultural-economic model RAUMIS (operated at the Thünen Institute) and the hydrological models mGROWA-DENUZ- WEKU-MePhos (Jülich Research Centre, FZJ) and the model MONERIS (Institute of Freshwater Ecology and Inland Fisheries, IGB): • Using the RAUMIS model, the Thünen Institute calculated nitrogen balances of agriculture on municipal areas and an analysis of the effect of the amended Fertiliser Ordinance (DüV) on achieving the management objectives for groundwater, inland waters and coastal waters. • Using the mGROWA-WEKU-DENUZ-MEPhos models of the Jülich Research Centre, the water balance and diffuse nutrient inputs into groundwater and surface waters were determined separately according to the most important input pathways. The model calculations were carried out for the entire area of Germany in a grid of 100 m × 100 m. • The MONERIS model was developed and applied by the IGB in Berlin to calculate N and P inputs from point sources and urban systems into surface waters at the municipal level and the retention and degradation of N and P compounds in surface waters at the sub-basin level. Through an as-is analysis, the different origins and levels of nutrient inputs were first determined. This made it possible to spatially identify pollution hot-spots and thus priority areas for the implementation of measures. Based on this, the regional N and P action requirement to achieve the protection goals for groundwater and surface waters to achieve the marine protection goals was determined and the effects of the amended Fertiliser Ordinance on nutrient inputs were analyzed. The project was accompanied by a working group of around 50 experts from the federal states in the field of agriculture and water management, in which all project steps – from the definition of the data basis to the presentation of the results – were presented, discussed and agreed in detail.