Subsurface Characterization in Rugged Himalayan Terrain Using 2D ERT: Implication for Hydropower Development in Karnali, Nepal
DOI:
https://doi.org/10.64862/ajeg.2025.201.05Keywords:
2D Electrical resistivity tomography (ERT) , Wenner array, Peaking run-of-river, HydropowerAbstract
Hydropower development in the tectonically active and geologically complex Himalayan region requires advanced geophysical methods capable of resolving subsurface heterogeneity in rugged terrain. Two-dimensional Electrical Resistivity Tomography (2D ERT) is particularly effective in such environments due to its adaptability, resolution, and ability to delineate lithological and structural variations. In Nepal, ERT has become an essential tool for assessing overburden thickness, bedrock quality, aquifer characteristics, and potential instability zones critical for hydropower development. This study presents the application of 2D ERT at the proposed Peaking Run-of-River (PROR) hydropower project in the Mugu Karnali highlands of western Nepal. Sixteen high-resolution resistivity profiles were collected using the Wenner array with 5 m electrode spacing to image the subsurface. The results reveal distinct resistivity values from very low to very high (20 Ω·m - 4,500 Ω·m) corresponding to colluvium, weathered bedrock, and competent crystalline formations, including schist, quartzite, and granitic gneiss. Fractured and saturated bedrock zones were also identified, providing insights into site stability and foundation suitability. The resistivity models confirm that the project area possesses competent bedrock conditions appropriate for key hydropower structures. The successful application of ERT in this high relief, folded, and thrusted Himalayan setting underscores its reliability for geotechnical and hydropower feasibility studies. These findings demonstrate that integrating geophysical methods like ERT into project planning enhances the accuracy of subsurface evaluation and supports sustainable hydropower development in rural Nepal.
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