Modelling seasonal nitrate concentrations in runoff of a heathland catchment in SW Norway using the MAGIC model: I. Calibration and specification of nitrogen processes

摘要

MAGIC (the Model of Acidification of Groundwater In Catchments) has been widely applied onncatchments all over the world. The model has been used with annual time resolution to simulatenthe long-term effects of acidic deposition on surface water chemistry. Here MAGIC was appliednusing a monthly time step. The purpose was to simulate observed seasonal nitrate (NO3)nconcentrations and fluxes at an upland heathland catchment in southwestern Norway during thenperiod 1993–2004. The rates of the key ecosystem nitrogen (N) processes (mineralization, plantnuptake, litterfall and immobilization) were assumed to be governed by temperature. A snownaccumulation and melt routine was used. The rates were calibrated to obtain the best matchnbetween the observed and simulated NO3 patterns. The best fit was obtained with standardnyearly cycles for deposition and N parameters. The results show that MAGIC can explain 68 andn88% of the variation in seasonal NO3 concentrations and fluxes, respectively. The calibratednmodel provides a tool for exploring the effects of future scenarios of climate change and Nndeposition on NO3 in streamwater.