Climate change impact on SWAT simulated streamflow in western Kenya
International Journal of Climatology
Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium; Department of Meteorology, University of Nairobi, Nairobi, Kenya; Centre de Recherches de Climatologie, Université de Bourgogne, 6 Bd Gabriel, 21000 Dijon, France
Weather and climate extremes such as droughts and floods have far reaching impacts in Kenya. They have had implications in a variety of sectors including agriculture, water resources, health, energy, and disaster management among others. Lake Victoria and its catchment support millions of people and any impact on its ability to support the livelihoods of the communities in this region is of major concern. Thus, the main objective of this study was to assess the potential 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 spatial 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 monthly basis. All - but one - global circulation models (GCMs) showed consistency in the monthly rainfall amounts. Rainfall was higher in the 2050s than in the 2020s. According to climate change scenarios, temperature will increase in this 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 of 2.4-23.2% corresponded to a change in streamflow of about 6-115%. The analysis revealed important rainfall-runoff linear relationships for certain months that could be extrapolated to estimate amounts of streamflow under various scenarios of change in rainfall. Streamflow response was not sensitive to changes in temperature. If all other variables, e.g. land cover, population growth etc., were held constant, a significant increase in streamflow may be expected in the coming decades as a consequence of increased rainfall amounts. © 2008 Royal Meteorological Society.
Annual rainfall; Climate change impact; Climate change scenarios; Climatic changes; Disaster management; General circulation model; General circulation models; Global circulation model; Lake Victoria; Land cover; Linear relationships; Modelling; Population growth; Rainfall runoff; Soil and Water assessment tools; Study areas; Temperature changes; Temporal Data; Catchments; Disaster prevention; Drought; Rain; Runoff; Stream flow; Thermal effects; Water; Water resources; Climate change; climate change; climate effect; computer simulation; general circulation model; hydrological modeling; rainfall-runoff modeling; streamflow; temperature anomaly; Africa; East Africa; East African Lakes; Kenya; Lake Victoria; Sub-Saharan Africa