A comparison of hydrological models for assessing the impact of land use and climate change on discharge in a tropical catchment

This study assesses the suitability of different model types for simulating scenarios of future discharge behaviour in a West African catchment (2344 km2) in the context of climate and land use change. The comparison of models enables the identification of possible sources of uncertainty in hydrological modelling of a tropical catchment. All models were calibrated and validated for the period from 1998 to 2005 with reasonable quality. The simulation of climate and land use change impacts on discharge behaviour results in substantial differences caused by model structure and calibration strategy. The semi-distributed conceptual model UHP-HRU is shown to be the most suitable for the simulation of current discharge dynamics because the simulated runoff components most closely match the current perception of hydrological processes based on field data interpretation. In addition, the model does not introduce new uncertainties into the simulation by imposing high data demands. All models simulate an increase in surface runoff due to land use change. The application of climate change scenarios resulted in considerable variation between the models and points not only to uncertainties in climate change scenarios but also gives an idea of the possible range of future developments. Overall, this study indicates that the major weakness of all hydrological models is their poor representation of the catchment’s soil characteristics and flow processes.