Modelling regional climate change and the impact on surface and sub-surface hydrology in the Volta Basin (West Africa)

In order to estimate the effect of an anthropogenic influence on the water balance in the Volta Basin, located in West Africa, joint regional climate–hydrology simulations were performed using the mesoscale meteorological model MM5 and the hydrological model WaSiM. The regional climate simulations show a decrease in rainfall at the beginning of the rainy season, an increase at the height of the rainy season and a clear increase in temperature. A mean delay in the onset of the rainy season accompanied with an increase in inter-annual variability of precipitation in the early stage of the rainy season was delineated. Due to the increase in potential evaporation, following the increase in temperature, most of the surplus rainfall evaporates. The highest sensitivity of the hydrological model to changing meteorological input conditions is found for direct runoff. Changes in the components of the hydrological cycle only seldom exceed the simulated present-day inter-annual variability.