Understanding the hydrological impacts of climate change in the Tana River Basin, Kenya.
Seven Regional Circulation Models (RCMs), simulating two Representative Concentration Pathways (i.e., RCPs 4.5 and 8.5), were used as input to the Soil and Water Assessment Tool (SWAT) model to determine the possible impacts of climate change on the hydrology of the Tana River Basin in Kenya. Four hydrological characteristics - water yield, groundwater recharge, baseflow and flow regulation - were determined and mapped throughout the basin for three 30-year time periods: 2020-2049, 2040-2069 and 2070-2099. Results show a spatial heterogeneity with clear differences between the upper, middle and lower basins. Simulation of both RCPs indicate an increase in mean annual rainfall for all three time periods, with an earlier onset of rainfall in some model simulations. The majority of models indicate an increase in extreme climate events under both RCPs. The response of the basin to the increase in rainfall is not linear, and the simulated increases in water yield, groundwater recharge and baseflow are much higher (in percentage terms) than the changes in rainfall. The impacts of climate change will be superimposed onto a basin with complex land use, built infrastructure and an intricate sociopolitical history. The results have important implications for the management of both built and natural infrastructure in the basin.