Determination of Rainfall-Runoff Relationship for Wadi Dayqah Catchment

Abstract

The aim of this study is to investigate the rainfall-runoff relationship for the Wadi Dayqah catchment, Oman. HEC-GeoHMS software was used to delineate catchment boundaries and to determine the sub-catchment areas and their centroids, while HEC-HMS and Excel sheets were used for event modeling and calibration. Three storm events from eight different rain gauge stations, with one Wadi gauge, were used in the study. Phi-index and Green-Ampt infiltration methods were used to model the losses, while the SCS unit hydrograph method, Snyder (Tulsa) unit hydrograph method, and a derived unit hydrograph were used for modeling the transformation process. The inverse-distance method was used for modeling meteorological processes. The developed models using the standard methods did not give reasonable results. Therefore, an empirical relationship between rainfall and runoff volume was developed. The data showed that there is a reasonable exponential relationship between the rainfall depth and the runoff volume of the Wadi Dayqah Catchment. The new relationship was verified by analyzing two storm events and using the observed water level and volume of water in the reservoir, and good agreement was found between the observed and computed runoff volumes. The results of this study will be useful for reservoir management during storm events.