Modeling of Sediment Yield at Kesem Dam and Identifying Soil and Water Conservation Measures
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Date
2019-04
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Addis Ababa University
Abstract
Soil erosion reduces not only soil productivity of the area but also reservoir capacity. The
information on sources of sediment yield within a catchment can be used as a perspective on the
rate of soil erosion occurring within that catchment. The objective of this study was to model and
analyze the potential soil erosion of the catchment, to estimate the sediment yield of the
watershed, and recommend appropriate soil and water conservation measures regarded as the
best management activities of the watershed. A SWAT 2012 (Soil and Water Assessment Tool)
model was selected for the simulation of the soil erosion and sediment yield of Kesem watershed
which is located in Middle Awash sub basin, Ethiopia. Model calibration and validation were
done after checking the performance of sensitive analysis. Twenty one parameters were
identified for flow calibration and of which the Initial Soil Conservation Service (SCS) runoff
curve number for moisture condition II (CN2) was the most sensitive one and twelve parameters
were selected for sediment calibration of which an effective hydraulic conductivity (CH_K2)
was the most sensitive for sediment. During flow calibration the R2 and NS give as value of 0.68
and 0.67 respectively, and similarly for validation the R2 and NS give as value of 0.65 and 0.60,
respectively. For sediment calibration the R2 and NS coefficient give as 0.77 and 0.64,
respectively and sediment validation R2 and NS give as 0.65 and 0.54, respectively. The
calibration and validation results found were good and satisfactory for both flow and sediment.
The total observed flow for study area at gauged station was 15.52m3/s and the simulated flow
by SWAT model was 14.15m3/s and observed annual sediment yield generated from rating curve
at selected gauging station was found 29.62ton/ha/yr and the simulated yield by SWAT model
was 25.75ton/ha/yr. From the model simulated output, sub-basins 2, 7, 5, and 18 were found to
be the severely eroded sub-basins with annual average sediment yield of 22.01t/ha, 19.29t/ha,
19.09t/ha and 18.93t/ha, respectively. While, sub-basins 12 and 13 were found to be the least
sediment sources with annual average sediment yield of 0.03 t/ha and 0.06t/ha respectively. Six
scenarios were developed to decrease sediment yield in the catchment and sediment management
approach were proposed in the Kesem catchment.
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Keywords
Kesem watersheds, Soil erosion, Sediment yield, SWAT model, Scenarios