Climate Change Impact on SWAT Simulated Streamflow in Western Kenya

Githui F, Gitau W, Mutua F, Bauwens W. "Climate Change Impact on SWAT Simulated Streamflow in Western Kenya." International Journal of Climatology. 2009;29(12):1823-1834.


Weather and climate extremes such as droughts and floods have far reaching impacts in Kenya. They havehad implications in a variety of sectors including agriculture, water resources, health, energy, and disaster managementamong others. Lake Victoria and its catchment support millions of people and any impact on its ability to support thelivelihoods of the communities in this region is of major concern. Thus, the main objective of this study was to assess thepotential future climatic changes on the Nzoia catchment in the Lake Victoria basin, and how they might affect streamflow.The Soil and Water Assessment Tool was used to investigate the impact of climatic change on streamflow of the study area.The model was set up using readily available s patial and temporal data, and calibrated against measured daily streamflow.Climate change scenarios were obtained from general circulation models.Results obtained showed increased amounts of annual rainfall for all the scenarios but with variations on a monthlybasis. All – but one – global circulation models (GCMs) showed consistency in the monthly rainfall amounts. Rainfall washigher in the 2050s than in the 2020s. According to climate change scenarios, temperature will increase i n t his region,with the 2050s experiencing much higher increases than the 2020s with a monthly temperature change range of 0–1.7°C.The range of change in mean annual rainfall o f 2.4–23.2% corresponded to a change in streamflow of about 6–115%. Theanalysis revealed important rainfall–runoff linear relationships for certain months that could be extrapolated to estimateamounts of streamflow under various scenarios of change in rainfall. Streamflow response was not sensitive to changesin temperature. If all other variables, e.g. land cover, population growth etc., were held constant, a significant increase instreamflow may be expected in the coming decades as a consequence of increased rainfall amounts. Copyright 2008Royal Meteorological SocietyKEY WORDS climate change; streamflow; runoff; general circulation models; hydrology; modelling

Royal Meteorological Society

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