Sensitivity of the INCA model to N process parameters and hydrological input

The Integrated Nitrogen in CAtchments (INCA) model simulates nitrogen transport and processes within catchments. It was applied to the Simojoki river basin in northern Finland where major human impacts are forest management and atmospheric nitrogen deposition. In this work the main emphasis is to evaluate the sensitivity of the INCA model to hydrological input. Parameters defining vegetation nitrogen uptake and denitrification rate were also studied. A simple univariate parametric (one-at-a-time) sensitivity analysis was conducted for NO3-N leaching, NH4-N leaching and denitrification in forest cut areas. Mineral nitrogen leaching was mainly influenced by hydrologically effective rainfall (HER). The parameter that controls denitrification rate had more influence than hydrological input parameters on the total amount of N that has been denitrified. There were only minor differences in parameter ranking between land use classes studied.