Groundwater model calibration for the Amsterdam Water Supply dune area

The groundwater model of the 36-km(2) dune area of the Amsterdam Water Supply has been calibrated in steady-state mode using MODINV. The calibration of the four parameters took two months work and 67 optimization runs. The optimizing code facilitated the elimination of many model errors by allowing us to focus on the hydrological causes of spatial error correlation, which has to be removed before optimized parameters can be accepted for further use. Throughout the process, the model has been greatly improved, finally yielding an ever low root mean square error of 0.17 m in the two topmost aquifers, and 0.15 m in the third aquifer. This result would not have been possible without the optimization.