Streaming Current Signals Associated with Pumping Test Experiments

Abstract

Self-Potential (SP) signals of the electrokinetic origin can be detected in the course of pumping test experiments. SP signals provide useful information about space heterogeneity of hydraulic properties of aquifers. SP signals are recorded with multi-voltmeters and a number of non-polarizing electrodes located around the pumping well to compliment information provided by drawdown measurements in pumping and observation wells. However, to the best of our knowledge, the streaming current (SC) has never been measured at pumping test experiments. We recorded the current in the course of a pumping test of shallow low-permeable aquifer using an ammeter connected to two electrodes grounded to the pumping interval of the well and to the ground surface. The recorded signal contains two components: (i) of electrochemical origin, produced by different physical-chemical properties at the interfaces of the two measuring electrodes; and (ii) of electrokinetic origin, produced by SC coupled with the groundwater flow. We decoupled the SC signal from the total signal. We found a correlation between SC and the flowrate, and we obtained the respective best fit. Based on the fit slope and the hydraulic conductivity value we calculated the SC coupling coefficient value, which is in reasonable agreement with published data.