Estimation of Catchment Sediment Yield using SWAT Model (Case Study Gelana Reservoir, Rift Valley Basin, Ethiopia)
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Date
2017-11
Authors
Journal Title
Journal ISSN
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Publisher
AAU
Abstract
Sediment particles created from the land by soil erosion processes in the catchment are spread along
with the flow of river. When the flow of river is obstructed and stored in reservoirs, the sediment
settles, deposit and reduces its capacity. Sediment settle in a reservoir is a serious problem that
threatens sustainability of the reservoir. The aim of this study was to estimate sediment yield in the
reservoir, to investigate the spatial and temporal variation of sediment yield and to recommend
appropriate sediment reduction measure. The Soil and Water Assessment Tool physically based semi
distributed hydrological model is utilized for sediment yield estimation in the Gelana catchment (area
of 644.28 km
2
), located in Abaya-Chamo sub-basin, rift valley, Ethiopia. The model was calibrated,
validated and assessed for evaluation to model using Nash–Sutcliffe coefficient and coefficient of
determination at Tore gauged station. Model calibration and validation were done after checking the
performance of sensitive analysis. The first most sensitive parameters were base flow alpha factor
for bank of storage (ALPHA_BNK) for flow calibration and average slop steepness (HRU_SLP) for
sediment calibration. For flow calibration the coefficient of determination and Nash-Sutcliffe
coefficient give as 0.76 and 0.70 respectively. Similarly for flow validation the coefficient of
determination and Nash-Sutcliffe coefficient give as 0.70 and 0.64 respectively. Sediment calibration
the coefficient of determination and Nash-Sutcliffe coefficient give as 0.71 and 0.66 respectively.
Sediment validation the coefficient of determination and Nash-Sutcliffe coefficient give as 0.80 and
0.64 respectively. Both the calibration and validation result indicated that good agreement between
observed and simulated stream flow and sediment yield. The model simulated result shows that the
average annual sediment yield is 89.14 ton/km
2
/year at the dam site. Spatial and temporal variation
of sediment yield were performed. The spatial variation of sediment ranges from 7.58 ton/ha to 53.17
ton/ha. Scenario was developed (S
1
-S
5
) for reduction of sediment yield in the Gelana reservoir.
Description
Keywords
Gelana catchment, Sediment Yield, SWAT, calibration, validation