Technical Note: Alternative in-stream denitrification equation for the INCA-N model

摘要

The Integrated Catchment model for Nitrogen (INCA-N) is a semi-distributed,process based model that has been used to model the impacts of land use,climate, and land management changes on hydrology and nitrogen loading. Anobserved problem with the INCA-N model is reproducing low nitrate–nitrogenconcentrations during the summer growing season in some catchments. In thisstudy, the current equation used to simulate the rate of in-streamdenitrification was replaced with an alternate equation that uses a masstransfer coefficient and the stream bottom area. The results of simulatingin-stream denitrification using the two different methods were compared for aone year simulation period of the Yl?neenjoki catchment in Finland. Thealternate equation (Nash–Sutcliffe efficiency = 0.61) simulatedconcentrations during the periods of the growing season with the lowest flowthat were closer to the observed concentrations than the current equation(Nash–Sutcliffe efficiency = 0.60), but the results were mixed duringother portions of the year. The results of the calibration and validation ofthe model using the two equations show that the alternate equation willsimulate lower nitrate–nitrogen concentrations during the growing seasonwhen compared to the current equation, but promote investigation into othererrors in the model that may be causing inaccuracies in the modeledconcentrations.