Tracking Fluid Flow In The Unsaturated Zone Using Cross-Borehole Resistivity And Ip

Contaminant plumes occurring in the unsaturated (vadose) zone often reach<br>ground-water aquifers, where they pose as a threat to human health. Current<br>hydrological methods of detection cannot adequately track the complex nature of<br>plume movement. A more useful and accurate method of tracking fluid flow is the<br>technique of resistivity and induced polarization (IP) tomography. Resistivity<br>tomography has been used in previous studies to reconstruct images of the vadose<br>zone. However, the use of IP data in a tomographical array to image the subsurface<br>is still under investigation. The study presented here attempts to explore the data<br>that can be obtained through IP measurements, which is complimentary to<br>information from resistivity image reconstruction.<br>Cross-borehole resistivity and II? experiments were carried out at the Avra<br>Valley Geophysical Test Site, west of Tucson, AZ, to follow water flow in the<br>unsaturated zone within a 30 m by 30 m sediment filled basin, The study involved<br>cross borehole resistivity and IP measurements using four, colinear wells, two<br>meters apart, to monitor the flow of 7600 gallons of tap water injected along a line<br>running the length of the basin.