A New Passive Technique to Monitor, and Discover, Agricultural Groundwater Resources

World-wide agricultural water resources are strained by drought, over pumping, contamination, and competition for use. We are proposing an inexpensive method to explore for new water resources and continuously monitor the level, and perhaps contamination, of existing heavily used aquifers. What we are proposing is an electromagnetic method of geophysical exploration that can be used to map the electrical conductivity of an aquifer over large areas. Our technique, known as the telluric-magnetotelluric (TMT) method, is related to the magnetotelluric (MT) method. Geophysicists have been using MT for mineral and oil exploration for more than forty years. It is unique among electrical methods because MT uses natural electromagnetic fields as the source field excitation. These natural fields provide excellent depth of exploration. The depth of exploration for the high frequency portion of the spectrum (known as the AMT range) can easily be greater than one kilometer. The direct application of AMT to groundwater exploration is too expensive to be practical. Our TMT method increases data acquisition, speed while decreasing hardware cost, by an order of magnitude. Our field sensors can be built for a few hundred dollars. A full AMT system costs tens, to hundreds, of thousands of dollars The purpose of this project is to build and test prototype telluric-magnetotelluric sensors. The test results will be compared to results obtained with conventional audio frequency magnetotelluric equipment.