NEAR-SURFACE GEOPHYSICAL SURVEYING METHODS FOR THE MANAGEMENT OF HYDROGEOLOGIC RESOURCES

Near-surface geophysical surveying methods can be utilized as an effective tool for locating, mapping, and preserving groundwater resources. These non-destructive methods, employed independently or at times in conjunction with one another, can add another dimension to one’s understanding of the subsurface for groundwater management applications and projects.

Electrical resistivity and induced polarization (IP) are two of the most effective geophysical surveying methods for groundwater investigations. Electrical resistivity methods send an electrical current into the ground and then map the resistance against that flow of current. IP methods measure the chargeability of the ground, which, as electrical resistivity, will differ with varying subsurface conditions and composition. The combination of resistivity and IP measurements is possible and can be done simultaneously, helping to refine an interpretation even further. Resistivity methods can also be an excellent technique to use for monitoring changes in ground conditions over time.

The transient electromagnetic method, or TEM, is an inductive method suitable for deep investigations (>500 m) where resistivity methods might be limited. A transmitter loop on the ground induces a transient current within the subsurface, and the receiver antenna(s) then measure the rate of change of the magnetic field associated with that current as it propagates through the earth. A high sensitivity to conductive materials makes TEM another method extremely useful in groundwater studies.

Depending on the aquifer type, near-surface seismic methods can be useful in the detection of the groundwater table, as in these situations, groundwater will affect the transmission velocity of seismic energy.

Near-surface geophysical surveying methods provide a non-destructive and cost-efficient way to help discover, delineate, and preserve groundwater resources. This session, suitable for participants with a wide range of backgrounds and experience levels, will provide a lecture on basic theory and examples of the aforementioned geophysical surveying methods as they relate to groundwater applications.