Estimation of Stream Flow and Sediment Yield Using HEC-HMS Model (On Rift Valley Basin of Gidabo River, Ethiopia)
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Date
2021-07
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Addis Ababa University
Abstract
Stream flow and sediment yield modeling of watersheds is very essential to solve water associated
problems, and alleviate reservoirs sedimentation problems caused by the soil erosion of the catchment. This
study is intended to estimate the amount of stream flow and sediment yield in Gidabo river catchment,
situated in the rift valley basin of Ethiopia with the help of the Soil Moisture Accounting (SMA) model and
Modified Universal Soil Loss Equation (MUSLE) found in the HEC-HMS model respectively and also to
recommend appropriate sediment yield reduction measures. The catchment land use, land slope, soil and
hydro – meteorological data were used to characterize the hydrology of the study area. The catchment and
river network of GRB have been delineated and its properties were extracted using the Digital Elevation
Model (DEM) of Gidabo basin by using Geographical Information System (GIS). To account for computing
runoff volume, direct runoff, base flow and flow routing, Soil Moisture Accounting (SMA), Clark unit
hydrograph, Recession and Muskingum-cunge methods were used respectively for representing the
hydrological processes of the GRB. The sediment yield of the catchment in this study was estimated by
using the calibrated and validated stream flow with the help of Modified Universal Soil Loss Equation of the
HEC-HMS model. The land cover and soil map have been used to estimate the impervious area, maximum
infiltration rate, surface storage, and MUSLE factors. The HEC-HMS model calibration of this study was
done by using the meteorological and hydrological data of the years from 1997 to 2002 and validation of the
model was done by using the data of the years from 2003-2006 on a daily basis time step for stream flow
and monthly time step for the sediment yield and the performance of the model was from good to very good.
The calibration of the HEC-HMS model of this study at the outlet of the watershed (Maesso station) gives
the Nash-Sutcliffe Efficiency, NSE =0.67, 0.67 and a coefficient of determination R2 = 0.72, 0.76 and
validation test of the model gives NSE =0.69, 0.67 and R2 = 0.79, 0.8 for the estimated stream flow and
sediment yield respectively. Based on these performance results, the computed value of both flow and
sediment yield shows good agreement with the observed value. Due to lack of observed stream flow from
the year 2007, the estimation of the stream flow and sediment yield from 2007 to 2017 was computed by
using the parameters found in the calibration and validation period. In this study, the HEC-HMS model
simulates the average annual stream flow and average annual sediment yield of 12.64 m3/s and 114,317.17
tons/year for the calibration and validation period of 1997 to 2006, 10 m3/s and 115,124.7 tons per year for
the years 2007 to 2017 and 11.32 m3/s and 114,720.93 tons per year for the years 1997 to 2017 respectively
at the outlet of the watershed (Maesso station).
Description
Keywords
Continuous modeling, Calibration and Validation, stream flow, sediment yield, HEC-HMS model