1Aquatic Environments Research Centre, Department of Geography, University of Reading, Reading, RG6 6AB, UK
2USARQ-Institut National de la Recherche Agronomique, Centre de Rennes, 65 rue de St Brieuc, CS 84215, 35042 Rennes, France
3Universiteit van Amsterdam, IBED - Physical Geography, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
4Finnish Environment Institute, Impacts Research Division, PO Box 140, Kesäkatu 6, FIN-00251, Helsinki, Finland
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Abstract. A new version of the Integrated Nitrogen in Catchments model (INCA) was developed and tested using flow and streamwater nitrate concentration data collected from the River Kennet during 1998. INCA is a process-based model of the nitrogen cycle in the plant/soil and in-stream systems. The model simulates the nitrogen export from different land-use types within a river system, and the in-stream nitrate and ammonium concentrations at a daily time-step. The structure of the new version differs from the original, in that soil-water retention volumes have been added and the interface adapted to permit multiple crop and vegetation growth periods and fertiliser applications. The process equations are now written in terms of loads rather than concentrations allowing a more robust tracking of mass conservation when using numerical integration. The new version is able to reproduce the seasonal dynamics observed in the streamwater nitrogen concentration data, and the loads associated with plant/soil system nitrogen processes reported in the literature. As such, the model results suggest that the new structure is appropriate for the simulation of nitrogen in the River Kennet and an improvement on the original model. The utility of the INCA model is discussed in terms of improving scientific understanding and catchment management.
Keywords: modelling, water quality, nitrogen, nitrate, River Kennet, River Thames
Wade, A. J., Durand, P., Beaujouan, V., Wessel, W. W., Raat, K. J., Whitehead, P. G., Butterfield, D., Rankinen, K., and Lepisto, A.: A nitrogen model for European catchments: INCA, new model structure and equations, Hydrol. Earth Syst. Sci., 6, 559-582, doi:10.5194/hess-6-559-2002, 2002.