Revealing the dynamics of groundwater movement in the vadose zone is crucial to groundwater management and artificial recharge. The traditional hydrographic surveys are usually indirect, costly, and infrequent. In this study, the groundwater flow characterization of a pumping experiment in Jilin University campus was monitored through combining time-lapse electrical resistivity tomography (ERT) and self-potential (SP) data tomography. The ERT datum depicts the spatial distribution of resistivity, which is related to the dynamics of soil moisture content during the pumping process. We are able to correlate hydraulic heads and SP signal during a decline and recovery groundwater level period leading to interesting perspectives in understanding the dynamics of complex groundwater flow. The SP method provides a direct way to estimate the potential field distribution, which can be further used to invert soil permeability. A total of 24 hours of time-lapse geophysical surveys revealed a significant increase in resistivity but a decrease in permeability during water pumping and groundwater recharge, representing the process of groundwater decline and recovery. Results derived from time-lapse geophysical surveys matched well with in situ monitoring of the groundwater level. The study demonstrates that the combined ERT and SP data can provide a direct and reliable way to monitor groundwater flow or other time-lapse hydrogeological surveys.

Revealing the dynamics of groundwater movement in the vadose zone is crucial to groundwater management and artificial recharge. In this study, the groundwater flow characterization of the pumping process is monitored by the joint time-lapse electrical resistivity tomography (ERT) and self-potential (SP) data tomography. The ERT data invert the resistivity distribution, which relates to the variation of soil moisture content during the pumping process. Base on the groundwater motion feature, the SP data provide a direct way to invert the current density and estimate the permeability. A total of 24 hours of time-lapse surveys show a significant increase and decrease in resistivity and permeability during water pumping and groundwater recharge, which suggests groundwater decline and recovery process. These results have an excellent agreement with the groundwater level monitoring result. Combining ERT and SP data can provide a reliable way in groundwater or other hydrogeological surveys.