Koech et al. (2025) Hydrological modeling of the Enguli ephemeral sand river basin using HEC-HMS for sustainable water management in Kenya’s ASALs

Identification

• Journal: International Journal of Hydrology Research
• Year: 2025
• Date: 2025-12-31
• Authors: Innocent Chepngeno Koech, Kevin O. Achieng, Njenga Mburu, Kahsay N. Zeraebruk
• DOI: 10.18488/ijhr.v10i1.4678

Research Groups

• Department of Civil Engineering, Dedan Kimathi University of Technology, Nyeri, Kenya
• Department of Civil Engineering, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya

Short Summary

This research characterized the hydrological behavior of the Enguli ephemeral sand river basin in Makueni, Kenya, using HEC-HMS to aid sustainable water management in arid and semi-arid areas. The study successfully simulated streamflow patterns and infiltration rates, demonstrating the potential of sand rivers as natural water storage reservoirs and informing climate-resilient irrigation systems.

Objective

• To characterize the hydrological behavior of the Enguli ephemeral sand river basin in Makueni, Kenya, using simulation modeling for sustainable water management in arid and semi-arid lands (ASALs).
• To analyze streamflow patterns of the Enguli River using the HEC-HMS model.
• To assess infiltration rates across the Enguli basin using the Green–Ampt infiltration model within HEC-HMS.

Study Configuration

• Spatial Scale: Enguli River watershed (46.774 km²) within Makueni County, Kenya (approximately 8,176.7 km²).
• Temporal Scale: Rainfall data from 2010 to 2024; Streamflow data from 2018 to 2023. Model calibration period: March 27, 2018, to December 31, 2021. Model validation period: January 1, 2022, to December 31, 2023.

Methodology and Data

• Models used: Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) version 4.12.
  • Soil Conservation Service Curve Number (SCS-CN) method for streamflow simulation.
  • Green–Ampt method for infiltration modeling.
  • Soil Conservation Service Unit Hydrograph (SCS-UH) model for converting excess rainfall into runoff.
  • Muskingum routing method for channel flow simulation.
• Data sources:
  • Digital Elevation Model (DEM): Alos Palsar (12.5 m spatial resolution).
  • Land Use Land Cover (LULC): Sentinel-2 (10 m spatial resolution).
  • Soil data: Soil and Terrain Database for Kenya (KENSOTER).
  • Rainfall data (2010-2024): Kenya Meteorological Department (KMD) and Trans-African Hydro-Meteorological Observatory (TAHMO) (daily temporal resolution).
  • Streamflow data (2018-2023): Water Resources Authority (WRA) (daily temporal resolution).
  • Soil hydraulic properties, infiltration data, and soil moisture content: Field measurements using a double-ring infiltrometer (ASTM D3385-03 standard) at five sampling locations.

Main Results

• Streamflow Simulation:
  • Model performance during calibration (2018-2021): Nash-Sutcliffe Efficiency (NSE) = 0.78, Percent Bias (PBIAS) = 19.83%, Coefficient of determination (R²) = 0.76.
  • Model performance during validation (2022-2023): NSE = 0.81, PBIAS = -29.28%, R² = 0.78.
  • Significant streamflow events were concentrated during the rainy seasons (March–May and October–December), confirming the ephemeral nature of the Enguli River.
  • Simulated hydrographs showed rapid rises and short-lived peaks, characteristic of quick surface runoff in semi-arid catchments.
• Infiltration Simulation:
  • Model performance (calibrated and validated): NSE = 0.58, PBIAS = -14.32%, R² = 0.60.
  • Significant spatial variability in infiltration rates was observed across the sub-basins.
  • Monthly average infiltration values (2010–2024) ranged from approximately 110.79 mm/day to 255.51 mm/day.
  • High infiltration rates (up to 255.51 mm/day) were recorded in central and southeastern sub-basins, attributed to flatter topography, sandy soils, and permeable geological layers.
  • The significant infiltration in the study area indicates the reliability of alluvial aquifers as a potential water source during dry seasons.

Contributions

• Explores streamflow and infiltration simulation modeling in ephemeral sand river systems, addressing a significant knowledge gap in hydrological characterization in data-scarce dryland areas.
• Provides insights into the role and impact of sand rivers as natural aquifers, enhancing understanding of their potential to support climate-resilient and farmer-led irrigation systems.
• Contributes field-based infiltration data as input for a calibrated hydrological model, a crucial step toward understanding groundwater recharge potential for sand river basins.
• Informs sustainable water resource management, increases agricultural resilience in ASALs, and promotes climate-adaptive water storage technologies, aligning with Sustainable Development Goals (SDGs) 2 (Zero Hunger), 6 (Clean Water and Sanitation), and 13 (Climate Action).

Funding

• IHE Delft, Netherlands under the project “Smallholder farming families Adapt African Alluvial Aquifers to Strengthen Their Own Resilience (A4Store)” (Grant number: 111363).

Citation

@article{Koech2025Hydrological,
  author = {Koech, Innocent Chepngeno and Achieng, Kevin O. and Mburu, Njenga and Zeraebruk, Kahsay N.},
  title = {Hydrological modeling of the Enguli ephemeral sand river basin using HEC-HMS for sustainable water management in Kenya’s ASALs},
  journal = {International Journal of Hydrology Research},
  year = {2025},
  doi = {10.18488/ijhr.v10i1.4678},
  url = {https://doi.org/10.18488/ijhr.v10i1.4678}
}