Weather and climate extremes such its droughts and flood,; have far reaching Impacts in Kenya. They have had implications :11 it variety of sectors including, agriculture, water resources, health, energy. and disaster management among, others. Law Victoria and Its catchment support Millions of people and any impact oil its ability to support the livelihood 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 oil 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 oil streamflow of the Study area The model was set Lip using readily available spatial and temporal data, and calibrated against measured daily streamflow. Climate change. scenarios were obtained from general circulation loll models Results obtained showed Increased amounts of, annual rainfall for all the scenarios but With variations on a monthly basis. All - but are - global circulation models (GCMS) showed consistency in the monthly rainfall amounts Rainfall was hi-her in the 2050s than in the 2020s. According to climate change scenarios. temperature, Will increase in this region, with the 2050s ex)cnencin- much lii,her increases [hall the 2020s wall a nlOIltIllV lCIIIpCI-dtUI-C Lhalloc range of 0- 1 7 degrees C The range of, chan,e in mean annual rainfall of 2 4-23.2% corresponded to I 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 ill rainfall Streamflow response was not sensitive to changes in temperature. If all other variables. c g. land cover. population growth etc, were held constant. I significant increase in streamflow may be expected in the coming, decades as a consequence of increased rainfall amounts Copyright (C) 2008 Royal Meteorological Society