Use of the DRAINMOD and MIKE 11 Models in Combination with GIS for Simulating at Catchment Scale the Nitrate Load

The main objective of this paper is modeling of the nitrate load in the river outlet of a dominantly rural catchment using the simulation models DRAINMOD and MIKE 11 in combination with a regional GIS, containing major data layers of the catchment. In addition to describing the DRAINMOD-GIS approach in combination with the MIKE 11 model, for simulating the NO₃-N fluxes in the land phase and the river draining the catchment, the methodology is tested using data of the Molenbeek river catchment situated in the Flemish region of Belgium. The sensitivity analysis indicates that the nutrient load at the catchment outlet is most sensitive to the nitrification rate (K₄) and mildly sensitive to the denitrification rate (K₆) in the nitrification process and insensitive to the dispersion coefficient (D) in the one-dimensional advection-dispersion equation.