ADGEO Advances in Geosciences ADGEO Adv. Geosci. 1680-7359 Copernicus Publications Göttingen, Germany 10.5194/adgeo-5-7-2005 Modelling of point and non-point source pollution of nitrate with SWAT in the river Dill, Germany Pohlert T. 1 Huisman J. A. 1 Breuer L. 1 Frede H.-G. 1 Institute for Landscape Ecology and Resources Management, University of Giessen, Heinrich-Buff-Ring 26, 35392 Giessen, Germany 16 12 2005 5 7 12 Copyright: © 2005 T. Pohlert et al. 2005 This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/ This article is available from https://adgeo.copernicus.org/articles/5/7/2005/adgeo-5-7-2005.html The full text article is available as a PDF file from https://adgeo.copernicus.org/articles/5/7/2005/adgeo-5-7-2005.pdf

We used the Soil and Water Assessment Tool (SWAT) to simulate point and non-point source pollution of nitrate in a mesoscale mountainous catchment. The results show that the model efficiency for daily discharge is 0.81 for the calibration period (November 1990 to December 1993) and 0.56 for the validation period (April 2000 to January 2003). The model efficiency for monthly nitrate load is 0.66 and 0.77 for the calibration period (April 2000 to March 2002) and validation period (April 2002 to January 2003), respectively. However, the model efficiency for daily loads is low (0.15), which cannot only be attributed to the quality of input data of point source effluents. An analysis of the internal fluxes and cycles of nitrogen pointed out considerable weaknesses in the models conceptualisation of the nitrogen modules which will be improved in future research.