Identification of Groundwater potential in Deep Aquifer Using Electrical Resistivity Tomography in the Tibetan Tethys of Nepal Himalaya in Korala Naka (Nepal–China Border), Mustang District

Abstract

Reliable groundwater resources are essential for sustainable water supply in the high-altitude, arid environment of Upper Mustang, where surface water is limited and highly seasonal. To assess groundwater potential for this remote, high-altitude community, and two 720 m Electrical Resistivity Tomography (ERT) profiles were acquired parallel to each other using 60 stainless-steel electrodes spaced 12 m apart in a Wenner-array configuration. The inverted sections extend to a nominal depth of approximately 110 m, although the effective depth of investigation and resolution decrease toward the base of the models. After processing the apparent-resistivity data in RES2DINV, the inversions produced RMS errors of 8.2% and 9.4% for Profiles 1 and 2, respectively. Both profiles show a thin, relatively resistive surface zone (approximately 600–1400 Ωm) overlying broad low- to moderate-resistivity zones (approximately 30–350 Ωm) in the central to lower sections. In the context of the local Tethyan Himalayan geology, these lower-resistivity zones are interpreted as potentially water-bearing and may correspond to saturated fine-grained sediment, weathered material, or fractured sedimentary rock such as shale, mudstone, or sandstone/ Limestone. However, resistivity responses are non-unique, and clay-rich or poorly connected materials may produce similar signatures without constituting productive aquifers. Because no borehole, lithological log, water-level, or pumping-test data are available for calibration in the Nepalese Tethyan Himalaya, the study does not confirm aquifer productivity, recharge, hydraulic connectivity, or sustainable yield. The results should therefore be regarded as a preliminary geological and hydro-geophysical assessment that identifies priority targets for exploratory drilling and hydrogeological testing to support future water-supply planning for border infrastructure and nearby communities.