| dc.description.abstract | Water as a natural resource is becoming under pressure because of the increasing population and other global drivers such as climate change and land-use change. Kenya is classified as a water scarce country because a large part of the country lies under semi-arid climatic conditions, with variable rainfall patterns. Therefore, it is important to manage this scarce resource for sustainability. Hydrological models are becoming important tools that are used by water resource managers to assess and predict hydrological processes that intern help in decision making. Soil erosion is universally recognized as a major problem to the water resources because it leads to increased sediments yield. Therefore, it is important model sediment yield at the catchment level for easy intervention. I this study soil and water assessment tool was selected to simulate flows and sediment yield. The main aim of the study was to determine if the SWAT model could be used to simulate and reasonably estimate sediment yield in the upper Nzoia catchment.
The model was set up using the following data; a 30 by 30m digital elevation model (DEM), a 1 km spatial resolution of land use dataset and 10 km spatial resolution of soil dataset. Daily precipitation data for 5 stations from 1999 to 2009 was available but the maximum and minimum temperature was only available for one station. Monthly flow data obtained from gauging station 1DA02 was used for calibration and validation, and model performance result showed an ENS of 0.7 and R2 of 0.73 for calibration while validation produced ENS of 0.66 and R2 of0.68. Both the calibration and validation results are within the acceptable range.
Simulation of sediment yield established four subbasins that yielded higher sediments. They were subbasin 8,1,17 and 21. All of them showed sediment yield above the maximum allowable soil loss. A 20 m filter strip was found to be the best management practice that was most effective for reduction of sediment yield with 69.97% reduction when applied to the entire catchment and 89% when applied to subbasins producing high sediment yields | en_US |
