Impact of Land-Use Changes on Sediment Load and Capacity Reduction of Lake Ziway, Ethiopia

Document pages: 13 pages

Abstract: Land-use change has been afactor that alters the hydrologic response of the watersheds leading toinfluencing on sediment yield changes. This study is mainly focusing on theassessment of the impacts of the land-use changes on sediment load and lakedepth reduction on Lake Ziway, Ethiopia using an integrated approach of RemoteSensing (RS), GIS and SWAT model. ERDAS IMAGINE 14 model was used to generateland-use maps from Landsat TM, ETM+, and Ls8 acquired, in 1988, 2002 and 2015as representative for the periods of (1988-1998), (1998-2008) and (2008-2018), respectively. The maximum likelihoodalgorithm of supervised classification applied to classify the basin land-use into seven land-use classes. TheSWAT hydrological model with ArcGIS interface setup for the basin toevaluate the flow and sediment load with calibration and validation performanceof the model range R2 (0.71 - 0.89) and NSE (0.57 - 0.87). As a result, the total average annualsediment yield from the sub-basins estimated as 3.59 t ha yr, 4.36 t ha yr, and 4.89 t ha yr for three consecutivedecadal periods 1988-1998, 1998-2008, and 2008-2018 respectively. The increasing trend of sediment yield in the LakeZiway watershed through one period to another justified as due to land-use.Similarly, the net sediment volume deposited in the lake also showedincremental trained with the land-use changesas 1.5 mcm yr, 1.81 mcm yr, and 2.033 mcm yr for the period of1988-1998, 1999-2008, and 2009-2018, respectively. The depth and water holdingcapacity of the lake reduced by 4.3 m and 25.76 mcm, respectively, from the depth and capacityrecorded on the 2006 bathymetric survey,which was the effect of deposited sediment over the last 12 years.