Application of high-density electrical resistivity tomography and audio magnetotellurics for groundwater exploration in the karst area in southwestern China
Huize County of Yunnan Province is situated in the karst area in southwestern China,where karst groundwater is its primary water source.To conquer local difficulties in drinking water,this study constructed a conceptual model of groundwater occurrence by fully investigating the hydrogeological conditions of the Huize area.Moreover,this study evaluated the applicability and optimal combi-nation of geophysical methods based on the measurement results of petrophysical properties.According to the actual local needs,this study deployed a comprehensive profile combining high-density electrical resistivity tomography(HDERT)and audio magnetotellurics(AMT)in Tuogu Village,Huize County.The groundwater enrichment site was delineated relying on resistivity anomalies,effectively guiding the layout of boreholes.The boreholes achieved the maximum single-borehole water yield of 20.76 m3/d,thus effectively alle-viating the local drinking water problem.The HDERT-AMT combined exploration method proves to be optimal for prospecting for groundwater in carbonate rock areas.HDERT can accurately characterize weathered layer thicknesses,bedrock boundaries,fissure evo-lutionary degrees,and water-bearing properties of strata,constraining groundwater recharge channels,thus counteracting AMT's defects for identification of near-surface stratigraphic structures.AMT can accurately reflect the spatial structures of fracture zones and the mac-rostructures of strata,limiting the boundary conditions(aquicludes)of water-bearing structures,thus making up for the defects of in-sufficient detection depths of HDERT in high-resistivity stratigraphic regions.HDERT and AMT,which are complementary to each oth-er in terms of accuracy and depth,can be applied to identify and constrain the spatial occurrence conditions of groundwater migration,storage,and enrichment.
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