Hydrologic Response to land use changes on the catchment scale

Regional land use changes due to European market policy have far reaching consequences for various landscape functions. Among others land use change influences the local water balance. Simulation models are mostly used to analyse the effect of management practices on water quality but they can also be a useful tool to quantify the hydrologic response of a catchment to different land use options. In this study the physically based, continuous time step model SWAT mod has been applied within the joint research project SFB 299 at the Giessen University to support the development of sustainable land use concepts. In a first step the model has been calibrated and validated for four mesoscale watersheds with differing land use distributions. Then the model performance for changing land use has been tested in an artificial watershed with a single crop at one time and one underlying soil type to eliminate the complex interactions of natural watersheds. In relation to forest barley produced the strongest response of the water balance components. Finally a case study for the Dietzholze watershed with two land use scenarios derived with the ProLand model has been carried out. The impact of land use change on the annual water balance was relatively small due to compensating effects in a complex catchment. The decrease of forest due to a grassland bonus amplifies the peak flow rate and thus increases the risk of flooding.