Impacts of Land Use Land Cover Change on Sediment Yield and Stream Flow: A Case of Finchaa Hydropower Reservoir, Ethiopia

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Author(s) Megersa K. Leta | Tamene A. Demissie | Sifan A. Koriche
Pages 763-781
Volume 6
Issue 4
Date April, 2017
Keywords Finchaa Watershed, Hydrological Modelling, Land use land cover, Sediment yield, SWAT

Changes in land use land cover (LULC) are a fundamental variable that have great impacts influencing many environmental aspects. LULC changes coupled with faulty management systems may result in high rate of soil erosion and increased sediment transport by changing the magnitude and pattern of runoff, peak flow, sediment yield and ground water levels, thus adversely affecting the life expectancy of hydropower reservoirs. Geographic Information System (GIS) version based Soil and Water Assessment Tool (SWAT) has been used to evaluate sensitivities and patterns of LULC changes in the Finchaa River basin located in western part of Oromia state, Ethiopia. Remote sensing products and ancillary data used in the study are SRTM Digital Elevation Model, LULC map, soil characteristics map, and hydro-meteorological variables. Calibration and validation of the SWAT against stream flow in the Finchaa reservoir attained a coefficient of determination and Nash- Sutcliffe were used to evaluate the performance of the model monthly and gives simulation efficiency 0.83 & 0.74 and 0.86 & 0.83 respectively. Four LULC change scenarios were tested based on socio-economic data and physical factors influencing the LULC. The Scenarios developed were: Scenario-1. Conversion to Agriculture Partially. Scenario- 2. Conversion to Grassland. Scenario- 3. Complete afforestation. Scenario-4. Complete deforestation and the base Scenario. Among the scenarios examined afforestation scenario reduce the soil erosion, runoff and sediment yield at the sub-basin level. The simulated average annual sediment yield and surface runoff were 56.041 T/Ha and 227.89 mm respectively. The simulated average annual sediment yield and surface runoff were 105.243 T/Ha and 366.14 mm respectively for the conversion of land use to agriculture where as the simulated average annual sediment yield and surface runoff were 66.88 T/Ha and 271.23 mm respectively for base scenario. The results of the evaluation of LULC changes in Finchaa watershed show that land use changes can have significant impacts on the Finchaa reservoir warranting further detail investigation to come up with appropriate watershed management practices.

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