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<p>Soil erosion and reservoir sedimentation are major environmental challenges in Ethiopian highland watersheds, contributing to land degradation and increased sediment loads in downstream reservoirs. However, spatially explicit assessments that jointly evaluate soil erosion, sediment delivery, and conservation priority areas remain limited in data-scarce mountainous environments. This study applied an integrated geospatial framework to assess soil erosion, sediment delivery, and conservation priority areas in the Genale Dawa-3 Hydropower Watershed, southeastern Ethiopia. Google Earth Engine (GEE) was used to derive land-use/land-cover and vegetation information from multi-temporal Sentinel-2 imagery, while GIS-based RUSLE-Sediment Delivery Ratio (SDR) modelling estimated soil erosion and sediment delivery. Topographic parameters were derived from a 12.5-m ALOS PALSAR DEM, and rainfall and soil data were obtained from ground observations. The results show substantial land degradation between 2016 and 2025. Basin-averaged estimated soil loss increased by 60.2%, from 53.0 to 84.9 t ha⁻¹ yr⁻¹, primarily due to cropland expansion and the conversion of approximately 150,546&#xa0;ha of natural and semi-natural vegetation to agricultural land. High-risk erosion zones (&gt; 30 t ha⁻¹ yr⁻¹) expanded to 71.5% of the watershed and contributed 95.0% of the total estimated soil loss. The most severe erosion hotspots were concentrated in the northern highlands and southeastern escarpment of the watershed, identifying priority areas for targeted conservation interventions. Priority I conservation areas (&gt; 50 t ha⁻¹ yr⁻¹) occupied 57.2% of the watershed and accounted for 88.3% of the total estimated soil loss. Using an empirical watershed-scale SDR of 6.3%, the estimated annual sediment yield increased from 3.73 to 5.98&#xa0;million tonnes. Although these estimates represent first-order basin-scale approximations rather than physically routed sediment fluxes, they indicate increasing sediment pressure on the reservoir. The proposed framework provides a practical and transferable approach for identifying erosion hotspots, prioritizing conservation interventions, and informing sustainable watershed management in data-limited mountainous environments.</p>

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Geospatial assessment of soil erosion, sediment delivery, and conservation priority areas in the Genale Dawa-3 hydropower Watershed, Ethiopia

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Brook Legese,
  • Mulualem Tarekegn,
  • Galma Godana,
  • Jidha Chamara,
  • Ashenafi Dechasa,
  • Negasi Haile Bihon ,
  • Ephrem Kabtimer

摘要

Soil erosion and reservoir sedimentation are major environmental challenges in Ethiopian highland watersheds, contributing to land degradation and increased sediment loads in downstream reservoirs. However, spatially explicit assessments that jointly evaluate soil erosion, sediment delivery, and conservation priority areas remain limited in data-scarce mountainous environments. This study applied an integrated geospatial framework to assess soil erosion, sediment delivery, and conservation priority areas in the Genale Dawa-3 Hydropower Watershed, southeastern Ethiopia. Google Earth Engine (GEE) was used to derive land-use/land-cover and vegetation information from multi-temporal Sentinel-2 imagery, while GIS-based RUSLE-Sediment Delivery Ratio (SDR) modelling estimated soil erosion and sediment delivery. Topographic parameters were derived from a 12.5-m ALOS PALSAR DEM, and rainfall and soil data were obtained from ground observations. The results show substantial land degradation between 2016 and 2025. Basin-averaged estimated soil loss increased by 60.2%, from 53.0 to 84.9 t ha⁻¹ yr⁻¹, primarily due to cropland expansion and the conversion of approximately 150,546 ha of natural and semi-natural vegetation to agricultural land. High-risk erosion zones (> 30 t ha⁻¹ yr⁻¹) expanded to 71.5% of the watershed and contributed 95.0% of the total estimated soil loss. The most severe erosion hotspots were concentrated in the northern highlands and southeastern escarpment of the watershed, identifying priority areas for targeted conservation interventions. Priority I conservation areas (> 50 t ha⁻¹ yr⁻¹) occupied 57.2% of the watershed and accounted for 88.3% of the total estimated soil loss. Using an empirical watershed-scale SDR of 6.3%, the estimated annual sediment yield increased from 3.73 to 5.98 million tonnes. Although these estimates represent first-order basin-scale approximations rather than physically routed sediment fluxes, they indicate increasing sediment pressure on the reservoir. The proposed framework provides a practical and transferable approach for identifying erosion hotspots, prioritizing conservation interventions, and informing sustainable watershed management in data-limited mountainous environments.