Estimating the Specific Yield and Groundwater Level of an Unconfined Aquifer Using Time-Lapse Electrical Resistivity Imaging in the Pingtung Plain, Taiwan

This study aims to apply geophysical methods determine the Specific Yield (Sy) and Groundwater Level (GWL) in an unconfined aquifer of Pingtung Plain South Taiwan. Sy is important hydraulic parameter for assessing groundwater potential. Obtaining specific yield a large area impractical due limited coverage high cost pumping test, which limits potential evaluation regional groundwater. Therefore, we used time-lapse Electrical Resistivity Imaging (ERI) GWL. Seasonal variations were considered when measuring resistivity five different months 2019. We calculated GWL from inverted data using empirical formulas soil–water characteristic curve (SWCC). first Archie’s law calculate relative saturation change with depth each ERI profile, then Van Genuchten (VG) Brooks–Corey (BC) equations estimate Finally, compared obtained existing observation well verify findings our study. The results showed that VG BC are able predict GWL; however, result less consistent result. In area, dry season ranged 24.5 m 35.2 25.7 35.5 results. wet 26.5 38.9 26.4 38.2 spatial distribution shows gradient northeastern region, induced by significant proximal fan recharge. determined varies 0.15 0.21 0.14 0.20 results, indicating has resources. nondestructive imaging can be aid determination parameters.