NA - Cold climate modelling

A weakness in the Swat-model is its rather poor ability to simulate water balances during prolonged periods with winter and frozen soils. The data collected through the Agricultural Environmental Monitoring Programme in Norway (JOVA) offers excellent oppo rtunities to do so as they represent agricultural dominated catchments. Discussions will focus on how start research collaboration between Jordforsk and the SWAT development team to improve this aspect in the Swat model. Another weakness in the model is i ts simulation of subsurface routines. Proper subsurface drainage routines for a good simulation are of utmost importance, especially in Norway where the major part of the agricultural land is artificially drained. DRAINMOD is a computer simulation model, developed by the Soil and Water Management Research Group at North Carolina State University, USA (http://www.bae.ncsu.edu/soil_water/drainmod.htm). Discussion between Jordforsk and the developers of DRAINMOD model will focus on how to carry further testi ng of the model under winter condition on data collected the JOVA-project. The Swat team is aware of this weakness in the Swat model and is planning to improve also this part. A realistic alternative was the incorporation of subsurface drainage routines a s developed in the DRAINMOD model. The P index addresses long-term risk, while the SWAT model describes the fluctuations and the influence of variations in runoff volume. The SWAT-model did not reflect the risk of incidental losses from surface applied n utrients and additionally it did not include the distance from field to stream in its estimate. The P index tool did not include the temporal variation of P transfer and for example the importance of high flow events occurring right after soil tillage. Di scussion with Dr. Veith at the USDA Pasture Systems and Watershed Management Research Unit will focus on how to collaborate with Jordforsk to further work on the P-index and its inclusion into the SWAT-model