EFFECTS OF INCREASED LAND USE CHANGES ON RUNOFF AND SEDIMENT YIELD IN THE UPPER RIVER NZOIA CATCHMENT

River Nzoia originates from three water towers namely Nandi hills, Cherengany Hills and Mount Elgon. With increased anthropogenic activities in Nzoia river catchments, land cover has continuously been altered. This scenario has resulted into increased quantity of physical parameters in runoff among them, sediment load and turbidity, during rainy season. This study modelled effects of increased land use changes on runoff and sediment loads. Digital Elevation Model, spatial soil data, sediment loads and meteorological data for the year 2000 to 2012 were the main input into the Soil Water Assessment Tool (SWAT 2012) model for calibration and validation. Data from 1990 to 2014 was as well collected for comparison purposes. Arc GIS 10.1 was used for spatial data analysis. Supervised Land classes were processed from satellite images for the year 2000 and 2010 using ENVI 4.7 software. The upper river catchment had an area of 10, 859km2 compared to 12,904km2 for entire watershed, has 27 catchments, and 36 Hydrologic Response Units.