Assessment of the influence of rainfall intensity on sediment yield and surface runoff.

Abstract

Surface runoff and sediment yield measurements are usually essential for understanding the primary productivity and ecosystem functioning of water bodies. Sediment yield is commonly attributed to the magnitudes of soil erosion in a given area which highly influences the transportation of sediments to various water bodies leading to water pollution. This implies that regular measurement of sediment yield and surface runoff is relevant to reduce water pollution. However, sediment yield measurements are scarce and if measured they cover small areas of study which reduces the effectiveness of managing the environment. Thus employing methods that cover larger areas in estimating sediment yield can be so essential in improving environmental management towards water pollution. In this study, SWAT model was employed to estimate sediment yield and surface runoff in Bukora sub-catchment area. This was done using soil data from National Agriculture Research Organization., Landsat 8 and SRTM data from the USGS program and precipitation data. Supervised image classification using the maximum likelihood classifier algorithm was employed to do land cover mapping of the area. The results show that the model has potential of estimating sediment yield and surface runoff. Surface runoff and sediment yield values were generally observed to be highest in sub-basin 26, 27 and 28 among the 31 sub-basins. The results from this study can be utilized by the National Environment Management Authority to manage various water resources. Policy makers can also use the provided information to make policies that reduce sediment yield through addressing soil erosion in the Lake Victoria basin.