Enhancing Small Dam Performance in Wadi Horan: A Hydrological Modelling Study for Rainwater Harvesting

Water resources are a crucial foundation, and their importance increases in dry and semi-arid environments. Given the constraints of water resources, increasing population needs, and the processes of evaporation and infiltration, it is imperative to explore strategies to optimise rainfall, noted for its abruptness and quick accessibility. Constructing small dams is one of the most effective methods for harvesting rainwater in the Iraqi Western Desert. This will conserve water throughout the arid season. The study’s goal was to assess and enhance rainwater harvesting (RWH) performance across diverse design and management scenarios, utilising a novel water-harvesting model (WHCatch) for testing at the sub-catchment level. Rainfall data from two dams in Wadi Horan from 1990 to 2019 were included in the model. This study emphasises the advantages of modelling long-term water balances at the sub-catchment level and proposes strategies for optimising rainwater harvesting to enhance understanding of the hydrological processes inside the rainwater harvesting system. Substantial enhancements in RWH performance were attained by modifying the heights of the spillway (2 m) and the flow directions, yielding 90% and 85% increased storage for the Horan/2 dam and the Horan/3 dam, respectively. In practice, this provides guidelines for creating and implementing low-cost, minor dam modifications as well as for establishing seasonal release schedules that satisfy downstream and storage requirements. The findings are consistent with policy-level support for sustainable development goals in arid regions.