GIS-based application of hydrological modelling in the Borkena Catchment, Ethiopia

Hydrologic models have been used in different river basins across the world for a better understanding of the hydrological cycle and the water resource availability. This study tested the applicability of the Hydraulic Engineering Center Hydrologic Modelling System (HEC-HMS) in the Borkena Catchment of Awash Basin. The HEC-HMS system is used to estimate peak flood, time to peak, and runoff volume. Model calibration and validation were carried out using the observed streamflow data from 1989 to1997 and from 1998 to 2002, respectively. The observed and simulated peak streamflows for calibration were 165.3 and 122.6 m3/s and for validation were 197.3 and 155.2 m3/s, respectively, whereas the average volumes were 1,223 and 1,380 mm for calibration and 1,647 and 1,847 mm for validation, respectively. From these results, it is observed that HEC-HMS slightly underestimated peak flow and overestimated runoff volume in both calibration and validation periods. Nash-Sutcliffe Efficiency values of 0.65 and 0.70, Coefficient of Determination values of 0.69 and 0.71, and Percent Bias of 12.84 and 12.16% for calibration and validation, respectively, were obtained. It can be concluded that in areas with limited water resources and ungauged watersheds like Borkena Catchment, simulated results of this study can be used for the design of different infrastructures for flood control and prevention in the study area and adjacent catchments.