Abstract
The land and water resources of the Lake Tana Sub Basin basin is in danger due to soil erosion, sediment transport, land degradation and storage capacity reduction. There is a need for sediment transport research of this basin that can improve catchment’s management programs. This study assesses the impact of land use and land cover change effects on reservoir sedimentation using SWAT model in Upper Ribb watershed. The land use and land cover change analyses for three different years of 1973, 1995 and 2016 were performed using ERDAS Imagine 2014 which was in turn used for estimation of sediment yield. In this study the bush/shrub land were changed to grazing and cultivated land. An increase of cultivated land by 29.947% over 43 years (1973 – 2016) period resulted in an increase of sediment yield by 343.25 t/km 2 /year respectively. Model calibration and validation for sediment yield were done at Abo Bahir. The performance of the model was also checked at this station. Both the monthly calibration and validation results showed good match between measured and simulated sediment yield data with the coefficient of determination (R 2 ) of 0.857, Nash-Sutcliffe efficiency (NSE) 0.832 for the calibration, and R 2 of 0.834 and NSE of 0.796 of the validation period. Spatial sediment distribution was done using the calibrated and validated sediment yield results of 2016 land use. High potential source areas were found at north-eastern part of the watershed which was a combined result of highly cultivated land, steep slope and erosive soil (Eutric Leptosols). Therefore, these critical sub- watersheds should preserve from further exposing of soil erosion through either forest resource development or uncultivated the steeply slope areas. And also the increasing/expanding bushes/shrub land should also be encouraged in the watershed first by applying for those most erosion prone sub watersheds. Keywords : Upper Ribb watershed, SWAT, sediment yield, spatial sediment distribution. DOI: 10.7176/CER/12-5-01 Publication date: May 31 st 2020
Highlights
The total environmental effects such as change in vegetation cover, soil characteristics, flora and fauna population and hydrological cycle have been strongly influenced by the conversion of land and forest resources (Hurni et al, 2010)
The key intention of this study aims application of soil and water assessment tool (SWAT) for the assessment of land use and cover change effects on sediment yield of the Upper Ribb watershed
The classification of 1995 land sat satellite image in Upper Ribb Watershed (Figure 4.2 and Table 4.1) revealed that the proportion of land allocated for cultivation expanded to 55.405%
Summary
The total environmental effects such as change in vegetation cover, soil characteristics, flora and fauna population and hydrological cycle have been strongly influenced by the conversion of land and forest resources (Hurni et al, 2010). Population growth causes degradation of resources forests that rely on the available land. This increases the run off volume by decreasing infiltration as well as increase the amount of sediment or erosion content that is transported by the run off in the catchment. An understanding of the quantity of sediment deposition in a reservoir is necessary for effective reservoir and basin management. Sedimentation affects both the useful life of a reservoir for such important purposes as water supply and flood control as well as its aesthetic quality
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