Model-based analysis of agricultural and environmental actions to reduce the nitrogen load in groundwater and surface waters in the Weser river basin district

In the framework of the project "AGRUM - Weser" a model instrument was developed to assess the regionally differentiated nitrogen pollution of groundwater and surface waters and to predict the effects of nitrogen-reducing practices in agriculture. For this purpose the agro-economic model RAUMIS was coupled with the hydrological models GROWA-DENUZ/WEKU and MONERIS. By combining approaches to quantify the inputs from point sources and from diffuse sources with economic profitability analyses, the model instrument was able to consider simultaneously the complex socio-economic and hydrological / hydrogeological interdependences. The focus was on integrative model analyses to evaluate the consequences of agricultural and ecopolitical nitrogen-reduction measures aiming to reach quality targets in the context of the implementation of the EU Water Framework Directive. Initially the actual nitrogen surpluses in agriculture (2003) and the nitrogen inputs into groundwater and surface waters were assessed. Based on this status-quo analysis, the effects were predicted that will result from agricultural and environmental measures to be implemented by the year 2015 at EU level (baseline scenario) to reduce diffuse nitrogen surpluses on farmland and nitrogen inputs into groundwater and surface waters. Then, the additional need for action to reach the good-quality status of groundwater and surface waters was identified. Finally, an option and the resulting costs of combining nitrogen-reduction measures to achieve good groundwater quality are presented.Original Abstract: Im Rahmen des Modellvorhabens AGRUM Weser wurde ein Modellinstrument entwickelt, mit dem die Stickstoffbelastung von Grundwasser und Oberflaechengewaessem regional differenziert abgeschaetzt werden kann, und welches darueber hinaus in der Lage ist, die Wirkung von Minderungsmassnahmen der Landwirtschaft zu prognostizieren. Hierzu wurde das agraroekonomische Modell RAUMIS mit den hydrologischen Modellen GROWA-DENUZ/WEKU und MONERIS gekoppelt Das Modellinstrument war durch eine Kombination von Ansaetzen zur Quantifizierung der Eintraege aus punktfoermigen und diffusen Quellen mit Wirtschaftlichkeitsanalysen dazu in der Lage, die vielfaltigen, komplexen soziooekonomischen sowie hydrologischen und hydrogeologischen Wechselwirkungen und Zusammenhaenge simultan zu beruecksichtigen. Im Vordergrund standen hierbei integrative Modellanalysen zur Bewertung von Agrar- und agrarumweltpolitischen Stickstoff-Minderungsma