True resistivities of saline aquifers and subsurface cavity filled with saline groundwater in the Northeastern Part of Thailand(Thai)

Abstract

     A serious problem for groundwater exploration, exploitation and management in the Northeastern region of Thailand is caused by near-surface salt-dome dissolution. The dissolution of the salt domes causes saline soil and saline groundwater in this region. Thus, the objective of this study was to apply 1D resistivity surveying for subsurface mapping of saline aquifers and subsurface cavities filled with saline groundwater. Results show that (1) an unconfined saline aquifer of sandy clay soil has true resistivities ranging from 0.25-3.10 Ohm-meters, an unconfined saline aquifer of clayey sand soil has true resistivities ranging from 1.30-7.80 Ohm-meters, an unconfined aquifer of weathered claystone has true resistivities ranging from 3.40-137.70 Ohm-meters, and an unconfined saline aquifer of weathered claystone has true resistivities ranging from 0.70-10.30 Ohmmeters. There is an overlapping zone of resistivity values between fresh-saline groundwater aquifers in various types of soil. Thus, the interpretation when having true resistivities located in the overlapping zone must be made with caution. (2) True resistivity value analyzed from the saline groundwater pumped from the saline weathered claystone aquifer is 0.03 Ohm-meters. Thus, when conducting 1D resistivity survey and its result shows true resistivities in near-surface layers of less than 0.25 Ohmmeters, it may indicate a subsurface cavity filled with saline groundwater.