Rainfall-Runoff Modelling for Sustainable Water Resources Management: The Case of Gumara Watershed, Ethiopia
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Date
2008-07
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Addis Ababa Universty
Abstract
Flow estimation at a point in a river is vital for a number of hydrologic applications including
flood forecasting, water resource management, and for development applications. This paper
presents the result of a watershed scale rainfall-runoff modeling on gaged part of Gumara
watershed using the hydrologic model HEC-HMS in a GIS environment.
The model in combination with GIS extension HEC-GeoHMS, was used to convert the
precipitation excess to overland flow and channel runoff. Rainfall data used gaged precipitation
alone from nine meteorological stations. The simulation was done for a period of 5 years. The
predicted hydrograph was calibrated against observed one and the model parameters were
optimized for good simulation. The predicted peak discharge, using rain gage data, was close to
the observed value and the smaller discharges followed the observed trend. But the simulated
peak value was very far apart .The simulated peak discharge has a value of 578.9 m3/s while the
observed discharge is 256.9 m3/s, which has a difference of 322 m3/s.
The model framework developed in the study considered the spatial variation in the runoff
response of the watershed through the use of curve numbers based on soil type and land use, and
the spatial distribution of the rainfall in the watershed by using rainfall data from a number of
rain gage stations located in different parts of the basin.
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Keywords
Gumara Watershed