HEC-HMS Based Estimation of Rainfall Runoff Relationship in Central Highlands of Ethiopia, a Case Study in Beressa Watershed

Bantideru Fenta Tawu

Abstract

Rainfall and runoff are the most frequently used events in hydrology. Calculating of a flow at the outlet of river is vigorous for a number of hydrologic studies like water resource management and flood forecasting. This study supported out to estimate rainfall-runoff relation in Beressa watershed. HEC-HMS model is used to pretend rainfall-runoff process and to apply the rainfall-runoff analysis by using SCS_CN method in Beressa Watershed. A physical based semi-distributed hydrological model (HEC-HMS) is applied to simulate hydrological. Model sensitivity analysis of the physical parameters, calibration and validation of the model were successfully carried out. The HEC-HMS model was run 1989 to 1999 for calibration and 2003– 2008 for validation purposes. The calibrated and validated results showed good match between measured and simulated daily stream flow data with the Nash-Sutcliffe efficiency (NSE) coefficient of determination (R2) and of 0.65 and 0.67 for the calibration and 0.69 and 0.72 for validation respectively. The land use change changing aspects of the watershed observed for the time span 1989 to 2014 indicates that the cultivated and built-up areas are increasing with 44.45% and 31.04% respectively at the same time as decreasing of grass and forest land by 46.41 and 44.79 percent change. For the periods of 1989 and 2014 significant land use changes occurred. The result of this analysis showed that the mean monthly stream flow increased from 18.16 mm to 23.16 mm. from the result of the model the stream flow faces changed due to the land use land cover change during the study period.