| dc.description.abstract | Electrical resistivity surveying methods have been widely used to determine the thickness and resistivity of layered media for the purpose of assessing groundwater potential in fractured unconfined aquifers. In this study, we used Electrical Resistivity Tomography (ERT)
monitoring system at two study sites in the Pingtung Plain. One is the surface-borehole survey line at the Dashu, Kaohsiung City, Taiwan, and the other is the surface survey line at the Daliao, Kaohsiung City, Taiwan. We analyzed the change in the electrical properties of the gravel layer during the rainfall season at the Dashu site and analyzed the groundwater level change
by ERT method during the pumping event at the Daliao site which is the pumping station to understand the groundwater replenishment situation. The ERT results of Dashu site show that there is a significant change in the resistivity distribution of the ground resistance profile measured before and after rainfall. The resistivity can be calculated Relative Water Saturation (RWS) of the shallow formation fluid, and it reveal the permeability of the gravel layer and the hydrogeological characteristics of the sites. Affected by rainwater infiltration, the vertical infiltration of shallow aquifers is obvious, while the deep aquifers may be subject to vertical and horizontal infiltration to produce relative saturation changes. Due to the obvious vertical infiltration of shallow aquifers, depending on the depth and time , The hydraulic conductivity can be estimated as 1.73*10-4 m/ s . In August 2017, the ERT results of Daliao site show that it dropped about 10 meters with the water level of the pumping event, which is in line with theoretical estimates. During the ground resistance monitoring in 2019, with the pumping event, the relative saturation change of the area is calculated,
and its saturation change range is at a depth of 10 ~ 20 meters. Using the Kozeny-Carman-Bear equation of the resistivity of the Daliao area, the hydraulic conductivity can be estimated to be about 10−4~10−3m/s and the porosity is about 15% ~ 30%, as a reference for
hydrogeological parameters. Furthermore, we use the hydraulic conductivity coefficient theoretical trend line to analyze the data of WRA’s 34 wells in western Pingtung Plain. The results show that the sandstone and mudstones with small variables have smaller well-measured resistivity and a lower hydraulic conductivity. Affected by compaction, the porosity tends to decrease with increasing depth. On the west side of the Pingtung Plain, the particle sizes are relatively consistent, and the hydraulic conductivity is 10−4~10−3m/s . | en_US |