Reichenbach et al. (2026) Soil and Water Assessment Tool reveals dominant baseflow in semi-arid catchment with sand dams in Kenya

Identification

• Journal: Frontiers in Water
• Year: 2026
• Date: 2026-09-17
• Authors: Jana Reichenbach, Andreas Braun, Volker Hochschild
• DOI: 10.3389/frwa.2026.1922866

Research Groups

• Geoinformatics Group, Geography Research Area, Department of Geosciences, University of Tübingen, Tübingen, Germany

Short Summary

This study applies the Soil and Water Assessment Tool (SWAT+) to a 22.35 km2 ungauged ephemeral catchment in Makueni County, Kenya, containing 22 sand dams, to characterize baseline hydrology for 1990–2024 and explore projected hydrological changes under RCP 4.5 climate scenario through 2099.

Objective

• To establish a baseline characterisation of the catchment water balance and dominant hydrological processes under current conditions.
• To assess projected hydrological changes under the RCP 4.5 scenario through 2099 using statistically downscaled climate projections.
• To evaluate the feasibility of representing sand dams as reservoir objects within SWAT+ and to quantify their modelled contribution to the catchment water balance.

Study Configuration

• Spatial Scale: Catchment scale (22.35 km2)
• Temporal Scale: Daily time step, with a warm-up period of 7 years and outputs generated for the period from 1990 to 2024

Methodology and Data

• Models used: Soil and Water Assessment Tool (SWAT+), version 61.0.1
• Data sources:
  • Topography: TanDEM-X 30 m Edited DEM dataset
  • Soils: SOTWIS/KENSOTER v2.0/Harmonized World Soil Database (HWSD v2.0)
  • Land use and land cover: OpenLandMap (OLMglcfcs30d)
  • Climate data: CHIRPS, ERA5, AgERA5
  • Evapotranspiration: GLEAM
  • Sand dams location data: Global Sand Dams Database

Main Results

• The baseline simulation indicates an evapotranspiration-dominated catchment with strong subsurface flow contributions.
• Modeled baseflow accounts for approximately 70% of total streamflow under current conditions.
• Under RCP4.5, increased precipitation is partitioned predominantly into enhanced percolation and subsurface flow, strengthening the modeled baseflow contribution while also increasing localized surface-runoff peaks.

Contributions

• This study contributes methodological and empirical knowledge to support the design, upscaling, and climate-proofing of sand dam systems across semi-arid East Africa.
• The results demonstrate the potential of open-data-supported hydrological modeling for characterizing ungauged semi-arid catchments and exploring sand-dam networks at the catchment scale.

Funding

• This study was funded by [insert funding agency or project name].

Citation

@article{Reichenbach2026Soil,
  author = {Reichenbach, Jana and Braun, Andreas and Hochschild, Volker},
  title = {Soil and Water Assessment Tool reveals dominant baseflow in semi-arid catchment with sand dams in Kenya},
  journal = {Frontiers in Water},
  year = {2026},
  doi = {10.3389/frwa.2026.1922866},
  url = {https://doi.org/10.3389/frwa.2026.1922866}
}