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<p>Volcanic aquifers are a major groundwater source globally, particularly in Ethiopia, where basaltic regolith aquifers sustain domestic and agricultural water supply. However, their characterization is challenging due to strong lithological heterogeneity and litho-structural compartmentalization. This study investigates shallow basaltic aquifers in the drought-prone Kecha watershed of the Ethiopian volcanic highlands within the Upper Blue Nile Basin by integrating lithologic logs with resistivity responses across litho-structural settings. The integrated interpretation of lithologic logs and geoelectrical signatures reveals spatial variability in regolith thickness and groundwater prospect. Lithologic logs indicate thin topsoil/clay layers in the upper and central parts overlying weathered/fractured basaltic formations. These observations are consistent with geoelectrical signatures, which indicate that low-to-intermediate resistivities (2.25–25.60 Ω.m) correspond to saturated weathered/fractured basaltic units representing shallow basaltic regolith aquifers. Intermediate resistivities (25.60–38.44 Ω.m) indicate fractured basalt transitioning to less permeable basalt, while high resistivity zones (38.44–438.00 Ω.m) correspond to volcanic domes and massive basaltic units that impede groundwater movement. The spatial distribution of resistivity signatures aligns with the dominant structural lineaments across the watershed. Groundwater flow in the upper and lower watershed sections appears to be influenced primarily by NNW–SSE-trending lineaments, whereas NE–SW-trending lineaments are more prominent in controlling groundwater flow within the central watershed. NNW–SSE-oriented volcanic domes act as barriers that locally modify groundwater flow and create compartmentalized aquifer geometries. This study presents an integrated hydrogeophysical framework for delineating aquifer geometry and groundwater flow pathways in shallow basaltic regolith aquifers. The results demonstrate the value of integrated approaches in resolving litho-structural heterogeneity and enhancing understanding of groundwater flow paths, thereby supporting exploration and sustainable management of volcanic aquifers.</p>

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Litho-structural controls on shallow basaltic aquifers in the Ethiopian volcanic highlands: insights from integrating lithologic logs with resistivity responses

  • 期刊论文

  • 发表日期：

    2026年7月30日

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  • Getnet Taye Bawoke,
  • Atsushi Tsunekawa,
  • Nigussie Haregeweyn,
  • Mitsuru Tsubo,
  • Ayele Almaw Fenta,
  • Zena Tessema Terefe,
  • Ashebir Sewale Belay,
  • Alebachew Tareke Kehali

摘要

Volcanic aquifers are a major groundwater source globally, particularly in Ethiopia, where basaltic regolith aquifers sustain domestic and agricultural water supply. However, their characterization is challenging due to strong lithological heterogeneity and litho-structural compartmentalization. This study investigates shallow basaltic aquifers in the drought-prone Kecha watershed of the Ethiopian volcanic highlands within the Upper Blue Nile Basin by integrating lithologic logs with resistivity responses across litho-structural settings. The integrated interpretation of lithologic logs and geoelectrical signatures reveals spatial variability in regolith thickness and groundwater prospect. Lithologic logs indicate thin topsoil/clay layers in the upper and central parts overlying weathered/fractured basaltic formations. These observations are consistent with geoelectrical signatures, which indicate that low-to-intermediate resistivities (2.25–25.60 Ω.m) correspond to saturated weathered/fractured basaltic units representing shallow basaltic regolith aquifers. Intermediate resistivities (25.60–38.44 Ω.m) indicate fractured basalt transitioning to less permeable basalt, while high resistivity zones (38.44–438.00 Ω.m) correspond to volcanic domes and massive basaltic units that impede groundwater movement. The spatial distribution of resistivity signatures aligns with the dominant structural lineaments across the watershed. Groundwater flow in the upper and lower watershed sections appears to be influenced primarily by NNW–SSE-trending lineaments, whereas NE–SW-trending lineaments are more prominent in controlling groundwater flow within the central watershed. NNW–SSE-oriented volcanic domes act as barriers that locally modify groundwater flow and create compartmentalized aquifer geometries. This study presents an integrated hydrogeophysical framework for delineating aquifer geometry and groundwater flow pathways in shallow basaltic regolith aquifers. The results demonstrate the value of integrated approaches in resolving litho-structural heterogeneity and enhancing understanding of groundwater flow paths, thereby supporting exploration and sustainable management of volcanic aquifers.