Determination of nitrogen reduction levels necessary to reach groundwater quality targets in large river basins: the Weser basin case study, Germany

Abstract

We used the interdisciplinary model network REGFLUD to predict the actual mean nitrate concentration in percolation water at the scale of the Weser river basin (Germany) using an area-differentiated (100 m 9 100 m) approach. REGFLUD combines the agro-economic model RAUMIS for estimating nitrogen surpluses and the hydrological models GROWA/DENUZ for assessing the nitrate leaching from the soil. The areas showing predicted nitrate concentrations in percolation water above the EU groundwater quality standard of 50 mg NO 3 /l, have been identified as priority areas for implementing nitrogen reduction measures. For these ''hot spot'' areas a backward modelling approach was used to quantify the maximal permissible nitrogen surplus levels in agriculture to guarantee a mean long-term nitrate concentration in percolation water below 50 mg NO 3 /l. Research work will directly support the implementation of the EU-Water Framework Directive in the Weser basin, e.g. by using the maximal permissible nitrogen surplus levels as a framework for the derivation of regionally adapted and hence effective nitrogen reduction measures.Keywords Catchment modelling Á EU-water framework directive Á Integrative agro-economic-hydrologic model network Á Maximal permissible nitrogen surplus levels Á Nitrate leaching Á Nitrate concentration in percolation water

Model-Based Analysis of Nitrate Concentration in the Leachate—The North Rhine-Westfalia Case Study, Germany

“…Similar considerations are reflected in the groundwater strategies of other countries [29,30]. Against this background, the nitrate concentration in the leachate can be considered as the decisive starting-point to determine the N reduction required [31].…”

“…The co-operation project GROWA+ NRW 2021 initiated by the Federal States' Ministry for Environment, Agriculture, Nature and Consumer Protection started at the end of 2015. In the context of the GROWA+ NRW 2021 project, the coupled agro-economic-hydrologic model network RAUMIS-mGROWA-DENUZ-WEKU-MONERIS [31] is applied and further developed in order to support the implementation process of the EU-Water Framework Directive, the EU Nitrates Directive, and the EU Marine Strategy Framework Directive in the Federal State of North Rhine-Westphalia. The questions to be answered in the GROWA+ NRW 2021 project include;…”

“…Nitrate concentration in the leachate is determined within the framework of an area-differentiated modeling of the diffuse and point source N inputs into groundwater and surface waters. For this purpose, the model system [31,32], which had already proven its suitability in macro-scale applications on the level of States and river basins in Germany, was applied in NRW on the basis of statewide available input data. The individual sub-models and their interplay are documented in the literature [32][33][34][35][36] and will only be briefly described here.…”

Root system-based limits to agricultural productivity and efficiency: the farming systems context

“…7Á5 t ha -1 ), but accompanied by a high risk of nutrient leaching and run-off into groundwater. Farming practices in Denmark and elsewhere in the EU (Larsson et al, 2005;Wendland et al, 2009) have been highly regulated to reduce N losses and, in Denmark, the overall N use in wheat has declined by 40 % with no change in national yields during the last 20 years (Kyllingsbaek and Hansen, 2007;Kronvang et al, 2008;Dalgaard et al, 2014).…”

Simulation of future groundwater recharge using a climate model ensemble and SAR-image based soil parameter distributions — A case study in an intensively-used Mediterranean catchment

“…mGROWA emerged from the water balance model GROWA (Kunkel and Wendland, 2002), which has been used in numerous (large-scale) water balance studies in and outside Germany since the nineties (Herrmann et al, 2009;Kuhr et al, 2013;Panagopoulos et al, 2014;Tetzlaff et al, 2009, accepted for publication;Wendland et al, 2009Wendland et al, , 2003. The ideas and concepts underlying the GROWA/mGROWA modelling approach are described in detail in the references specified above and will thus not be repeated here.…”