Hydrological modeling of the Enguli ephemeral sand river basin using HEC-HMS for sustainable water management in Kenya’s ASALs

Abstract

This research aimed to characterize the hydrological behavior of the Enguli ephemeral sand river in Makueni, Kenya, using simulation modeling to aid sustainable water management in arid and semi-arid areas. The specific objectives were to analyze streamflow patterns and infiltration rates within the basin employing Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS). The Soil Conservation Service Curve Number (SCS-CN) method was used for streamflow simulation, and infiltration modeling was performed using the Green–Ampt method. Model performance for streamflow simulation during calibration was Nash-Sutcliffe Efficiency (NSE) = 0.78, Percent Bias (PBIAS) = 19.83%, and coefficient of determination (R²) = 0.76, while during validation it was NSE = 0.81, PBIAS = -29.28%, and R² = 0.78. In infiltration simulation, model efficiency was NSE = 0.58, PBIAS = -14.32%, and R² = 0.6 after calibration and validation using field measurements from five sampling locations across the study area. Infiltration in the study area was significant, which points towards the reliability of alluvial aquifers as a water source during dry seasons. The study demonstrates the applicability of employing hydrological models in determining the potential of sand rivers as natural water storage reservoirs in arid and semi-arid lands. It forms part of enhanced water resource management approaches and informs climate-resilient, farmer-led irrigation systems.