Abstract:
Rainfall runoff modeling is one of the most complex hydrological modeling due to the involvement of
different watershed physical parameters. It is essential for the analysis of watershed hydrological response
toward the received precipitation under the influence of watershed parameters. As it is a replica of watershed
hydrological response, rainfall runoff modeling is essential to evaluate the general characteristics of total
surface runoff at catchment’s outlet. The main objective of this study was rainfall runoff modeling using
HEC-HMS for Awash Bello sub-catchment. Hydro-meteorological data collected from the National
Meteorological Agency and Ministry of Water Resource, Irrigation and Electricity were used for model
calibration and validation. SCS-CN, SCS-UH, Muskingum and monthly constant method were used for
precipitation loss modeling, transform modeling, flood routing and base flow modeling respectively. Nash
Sutcliff Efficiency and coefficient of determination have been selected for model performance evaluation.
The model had shown good performance both during calibration and validation with (NSE = 0.855, R2=
0.867) for calibration and (NSE = 0.739, R2 = 0.863) for validation respectively. PBIAS for calibration and
validation were checked and they were within the acceptable range with a value of 4.59% and 5.67%
respectively. By the successful accomplishing of calibration and validation, the peak flood from the model
(573.7m3
/s) was compared with direct observed flow (546.4m3
/s) and model provided nearly the same result
with the direct observed flow.
