Influence of Infiltration Methods on Runoff Estimation for Sustainable Rainwater Harvesting in Arid Regions

ABSTRACT Arid regions face severe water stress due to limited rainfall and growing water demand, making accurate runoff estimation essential for sustainable water management. Infiltration processes strongly influence both hydrograph volume and peak discharge, and their accurate estimation is critical for hydrological modelling. This study applies the Watershed Modelling System (WMS) to evaluate rainwater harvesting potential in the Wadi El‐Aawag watershed, southwestern Sinai, Egypt, using four infiltration loss estimation methods: Uniform Loss (LU), Green–Ampt (LGA), Holtan (LH) and the Soil Conservation Service (SCS) curve number method. Each method accounts for soil type, land cover and infiltration characteristics, enabling assessment across recurrence intervals of 5, 10, 25, 50 and 100 years. The results indicate considerable variation in runoff response across the selected methods. The estimated runoff volumes were 35.11, 24.10, 31.65 and 23.57 million m 3 for LU, LGA, LH and SCS, respectively, for recurrence intervals of 100 years. Among the tested approaches, the SCS method provided the most reliable and realistic estimates for the study area. These findings emphasise the importance of method selection when modelling infiltration losses and highlight the role of robust hydrological assessment in optimising rainwater harvesting, mitigating drought risks and enhancing long‐term water security in arid regions.