Abstract
The water storage in Shika dam, Zaria-Nigeria is often adversely affected by sedimentation because of severe soil erosion in headwater catchments. The HEC-HMS model is a commonly used tool to simulate streamflow and sedimentation of various processes of the hydrological cycle, depending majorly on their characteristics. The objective of this study is to apply HEC-HMS model for simulation of sedimentation in shika dam, Zaria-Nigeria. The required rainfall-runoff, flood discharge and sediment data were collected from Zaria Dam guage station for two years (1st January 2019–31st December, 2020). The geographical parameters of the study area were extracted from digital elevation model (DEM), soil map and land use map using geographic information system (GIS) and Remote Sensing techniques. Total Suspended Solute (TSS) and Particle grading were determined from the laboratory analysis of the soil sample. The study revealed that sedimentation from soil erosion in the catchment area significantly reduced the dam's capacity from its original 16,000,000 m³ to 3,543,700.8 m³. This sediment accumulation also reduced the dam’s height (15 to 2.82 m), surface area (3,200 to 1,563 km2), crest length (640 to 160 m), and discharge capacity (707.9 to 542.8 m3/s).
The HEC-HMS model successfully simulated streamflow and sediment transport processes using rainfall-runoff data, topography, and land use characteristics. The results estimates that 12,655,412.9 tonnes of sediment were transported and deposited into the dam over the study period. The study identified that sub-catchments SC1 and SC2 contributed significantly to sediment deposition, mainly due to agricultural and fishing activities in these areas.

Key words: HEC-HMS Model, Sedimentation, Rainfall-runoff, Zaria Dam, Hydrological modeling, Total Suspended Solids (TSS), Sediment transport, Watershed delineation, Digital Elevation Model (DEM), Streamflow simulation, Remote Sensing, Soil erosion, Geographic Information System (GIS), Water storage,