Rainfall-runoff Modelling For Sustainable Water Resources Management The Case Of Gumara Watershed Ethiopia

Flow estimation at a point in a river is vital for a number of hydrologic applications includingrnflood forecasting, water resource management, and for development applications. This paperrnpresents the result of a watershed scale rainfall-runoff modeling on gaged part of Gumararnwatershed using the hydrologic model HEC-HMS in a GIS environment.rnThe model in combination with GIS extension HEC-GeoHMS, was used to convert thernprecipitation excess to overland flow and channel runoff. Rainfall data used gaged precipitationrnalone from nine meteorological stations. The simulation was done for a period of 5 years. Thernpredicted hydrograph was calibrated against observed one and the model parameters werernoptimized for good simulation. The predicted peak discharge, using rain gage data, was close tornthe observed value and the smaller discharges followed the observed trend. But the simulatedrnpeak value was very far apart .The simulated peak discharge has a value of 578.9 m3/s while thernobserved discharge is 256.9 m3/s, which has a difference of 322 m3/s.rnThe model framework developed in the study considered the spatial variation in the runoffrnresponse of the watershed through the use of curve numbers based on soil type and land use, andrnthe spatial distribution of the rainfall in the watershed by using rainfall data from a number ofrnrain gage stations located in different parts of the basin.

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