Monitoring of groundwater flow with electrical resistivity at Haslemoen, Hedmark county
The purpose of this study was to investigate the possibility of using surface resistivity measurements to monitor the movement of an injected saltwater pulse. The experiment was conducted in the unconfined groundwater aquifer at Haslemoen. In the study area, the grounwater flows mainly towards the south with a velocity of approximately 0.2 m/day. The depth to groundwater level is approximately 2.5 m. The experiment took place from May 1 to May 4, 1991. Saltwater was injected in the aquifer. The gradient and velocity of flow were artifically increased by continuous pumping from a well located 3 m northwest of the injection well. The "charged potential" (CP) configuration was used to monitor saltwater movement. The metal casing in the injection well served as the near electrode, and electrical potential differnce was measured between electrodes placed in a radial array around the injection well. Investigation of the change in potential as a function of time resulted in identification of the direction of groundwater movements. The effect of the pumping is seen clearly. The data also indicates that the direction of natural flow is locally towards the southeast. There appears to be a correlation between change in potential and velocity of groundwater flow. This study confirms that surface resistivity measurements can be used to monitor groundwater flow. An advantage with using surface resistivity measurements over convential tracer methods, is in the cost, as only one well for injection of the tracer is required.