Evaluation of hydrological model parameter transferability for simulating the impact of land use on catchment hydrology

During the past decades, the use of hydrological models for predicting the impact of land use on catchment hydrology increased considerably. The performance of those models is often judged by a simple split-sample test using historical discharge series. The derived parameter values are then assumed to be identical for the new land use scenario, apart from the crop and management characteristics that are adapted to the land use under study. This paper checks the validity of this assumption in an indirect way, by evaluating the transferability of the main controlling parameters of the semi-distributed SWAT model in a stepwise fashion: within the catchment, a neighbouring catchment and a catchment under a different environmental setting. The results indicate that there is a decline in model performance when parameters are transferred in time and space. Transfer within the catchment and to a neighbouring catchment gives for the case study still a reasonable performance, yet one should be careful when exchanging parameter values between regions with a different topography, soil and land use. These factors might influence the infiltration and percolation of water and so affect the associated model parameters. (C) 2004 Elsevier Ltd. All rights reserved.