Groundwater flow monitoring using time-lapse electrical resistivity and Self Potential data

Abstract Groundwater flow monitoring is crucial to groundwater management and pollution control . Traditional in-situ hydrological surveys monitor groundwater flow, pressure or temperature changes to infer the actual conditions of the underground, but there are characteristics of stratum destructiveness and difficult to obtain the regional variation characteristics of groundwater. Compared with geophysical methods , it has the advantages of non-destructive detection and regional quantitative interpretation, and indirect understanding of the physical properties of underground media and groundwater. In this paper, we combine the time-lapse electrical resistivity (ERT) and self-potential (SP) methods to monitor the groundwater flow. The ERT result establishes linkages between the resistivity and porewater content of the underground space, and captures the difference in resistivity through the change of underground water content. The SP method provides a direct way to predict groundwater flow according to its movement characteristics. Then, the joint resistivity and potential field are further used to estimate the soil's apparent-permeability. We carry out a real pumping experiment at a hydrological observation site to verify the proposed method. The time-lapse ERT and SP results reveal a significant increase in resistivity but a decrease in permeability during water pumping and groundwater recharge , representing the process of groundwater decline and recovery. The results also matched well with the groundwater level in-situ hydrological data. The study demonstrates that the joint ERT and SP data can provide a direct and reliable way to monitor groundwater flow or other time-lapse hydrogeological surveys in the vadose zone.