Runoff and Sediment Yield Estimation under Land Use Land Cover Dynamics (A Case Study of Genale Dawa Dam-3) A Thesis in Hydraulic Engineering Stream
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Date
2020-09
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Addis Ababa University
Abstract
The study of stream flow patterns with respect to LULC changes helps the assessment of sustainability of land use/cover systems. The dynamics of Land use/cover is one of the causing factor to change the hydrologic response of the Ganale sub-basin resulting for soil erosion and over producing of runoff and sediment yield. Therefore this thesis is attempted to access the effects of land use/cover changes on Genale Dawa Dam-3 reservoir sedimentation for the year of 1994, 2000, and 2017.
The land use/cover was generated from satellite image using ERDAS Imagine 2014 software. Using the three land use/cover and the same other input data (DEM, climate data and soil map) for all, three independent model were delineated. The delineated Genale sub-basin was divided into 286 sub-basins and 2632 HRU‘s for 1994 and 2000, 2449 HRU for 2017. Model calibration and validation was done successfully at Chenemesa gauging station. Calibration and validation of the SWAT model was done under sensitivity analysis by means of using SWAT-CUP software SUFI2 program. Hence calibration and validation of flow and sediment yield for each model is conducted from 1990-2005 and 2006-2015 respectively.
Accordingly the R2 and NSE were found to be in the acceptable range (0.66 to 0.71 for R2 and 0.51 to 0.65 for NSE). The evaluation of land use/cover result showed that the average annual Sediment load and runoff at upper Genale Dam-3 site is found that 14.1 ton per ha per year, 77.8mm for land use/cover in 1994 was 16.4 ton per ha/year, 102.2mm for land use/cover in 2000 and 24.3 ton per ha per year, 130.6mm for land use/cover in 2017 respectively. Variability of sediment yield in Genale sub basin are fluctuates between 0.1ton per ha per year to 129 ton/ha/yr. in 1994 of LULC, 0.1ton/ha/yr. up to 111 ton/ha/yr. in 2000 LULC and 1 per ha per year to 162 1ton per ha per year in 2017LULC in annually average during the period from (1990-2017) respectively. The model prediction results indicated that in 1994, 2000, and 6.7%, 5.2%, and 11.9% of Genale sub-basin area were highly eroded by producing greater than 50 ton/ha/yr.
Therefore, the result of the study shall be supports different concerned party to plan and implement suitable soil and water conservation approaches.
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Keywords
Genale sub-basin, land use/cover change, runoff, sediment yield, SWAT model, ERDAS, SWAT-CUP, calibration, validation, streamflow