Sediment Management in Reservoir (Case study of Gilgel Gibe-I Dam)
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Date
2016-10
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Addis Ababa University
Abstract
Reservoir sedimentation is a gradual accumulation of the incoming sediment load from a river; it is important to predict sediment inflow at Gilgel Gibe I and evaluate its consequences on the reservoir and sustain the reservoir through long term optimum sediment management program.
The overall goal of this study focuses on predicting sediment yield and its sustainability and identification of most appropriate sediment management strategy are under the scope of this study and applying SWAT model interface with GIS in predicting sediment yield in the Omo Basin Gilgel Gibe-I Reservoir is the major.
The proposed hydroelectric power project (designated as Gilgel Gibe I Reservoir) is located on Gilgel Gibe River (Omo Basin) approximately at 7.8314 degree N and 37.1918 degree E, and Most components of the project is situated in the Jimma zone of the Oromia regional state, more specifically in Asendabo, Sekoru and Saja Weredas.
The main objective of this study is to predict the sediment yield to Gilgel Gibe-I Watershed. The model is calibrated and validated taking the Asendabo station found in the catchment by transferring the gagged data to the outlet of Gilgel Gibe-I watershed.
The model is calibrated and validated for both flow and sediment concentration at Asendabos station (2966km2) and run at Gilgel Gibe-I dam reservoir outlet (3602km2 ) to estimate the sediment yield.
Flow calibration gives coefficient of determination (R2) and Nash-Sutcliffe simulation efficiency (ENS) 0.68 and 0.67 respectively. Flow validation gives 0.58 and 0.57 for R2 and ENS values respectively. Sediment calibration gives R2and ENS 0.79 and 0.78 respectively and validation test gives R2and ENS 0.76 and 0.48 respectively. This result indicates that the observed values show good agreement with simulated value for both flow and sediment yield.
In this study the SWAT model yields average annual sediment of 106.178 ton/km2/yr or (10617.8 ton/ha/yr) at Gilgel Gibe-I outlet dam site.
Identifying erosion prone areas in the watershed enables the watershed management to be applied to the proper areas to reduce the sediment yield.
Applying filter strip and terracing (stone bunds) in low slope areas of the catchment could give potential effect of best management practice.
Key words
Arc SWAT, Spatial and Temporal data, sediment Yield, Gilgel Gibe-I Watershed, simulation, calibration, validation, SWAT CUP, Erosion prone area ,strategic management practice
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Keywords
Arc SWAT, Spatial and Temporal data, Sediment Yield, Gilgel Gibe-I Watershed, Simulation, Calibration, Validation, SWAT CUP, Erosion prone area, Strategic management practice