Advances in Hydrological Modelling used in River Basins: A Comprehensive Review of HEC-HMS and SWAT

Water is considered as most valuable resource for human existence on the earth and in order to simulate, optimise, and distribute hydrological data for various purposes in different sectors, hydrological models are very convenient to attain this aim for water resources management and as a decision support tool. A hydrologic model is a simplification of a real-world system that aids in understanding, predicting, and managing water resources. Both the flow and quality of water are commonly studied using hydrologic models. In the present study, two hydrological models are reviewed and studied in view of their effectiveness and performance in water resource allocation and management in river basins. The first model was considered “The Hydrologic Modelling System (HEC-HMS)”, developed by the Hydrologic Engineering Centre of the U.S. Army Corps of Engineers, which is a widely used tool for simulating the precipitation-runoff processes of dendritic watershed systems. Designed to support both natural and engineered hydrologic systems, HEC-HMS is capable of modelling complex rainfall-runoff events and continuous hydrologic processes such as baseflow and snowmelt. The model is versatile and integrates various hydrologic methods for loss estimation, runoff transformation, channel routing, and reservoir modelling. The other model considered in this study was “the Soil and Water Assessment Tool (SWAT)’’ is a comprehensive, semi-distributed, process-based watershed model developed by the USDA to predict the impact of land management practices on water, sediment, and agricultural chemical yields in large and complex watersheds. Designed to operate over long periods and at large spatial scales, SWAT integrates climate, hydrology, soil properties, land use, and management practices to simulate water balance and pollutant transport. The model divides a watershed into multiple sub-basins and hydrologic response units (HRUs), enabling detailed representation of spatial variability in land cover and soil characteristics. SWAT is widely used for evaluating conservation practices, water quality assessments, climate change impacts, and sustainable watershed management strategies.