Source: Industrial Imaging Co., Inc. submitted to NRP
A NEW PASSIVE TECHNIQUE TO MONITOR, AND DISCOVER, AGRICULTURAL GROUNDWATER RESOURCES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
SMALL BUSINESS GRANT
Reporting Frequency
Annual
Accession No.
0199637
Grant No.
2004-33610-14349
Cumulative Award Amt.
(N/A)
Proposal No.
2004-00266
Multistate No.
(N/A)
Project Start Date
May 15, 2004
Project End Date
Dec 31, 2005
Grant Year
2004
Program Code
[8.4]- (N/A)
Recipient Organization
Industrial Imaging Co., Inc.
(N/A)
Salt Lake City,UT 84103
Performing Department
(N/A)
Non Technical Summary
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.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
11102102020100%
Knowledge Area
111 - Conservation and Efficient Use of Water;

Subject Of Investigation
0210 - Water resources;

Field Of Science
2020 - Engineering;
Goals / Objectives
The overall technical objective for Phase I is to demonstrate a low cost method to effectively monitor, and explore for, groundwater resources. Our proposed Telluric Magnetotelluric method can do this. The specific technical tasks we will complete during Phase I to meet this overall objective are: Task 1: We have already identified (or at least narrowed down to a few manufacturers) the hardware we want to use in our prototype basic TMT receivers. The important components we have identified are temperature controlled oscillators, low noise preamps and filters, GPS timing modules, 24 bit stereo A/Ds, microcontrollers, and data loggers. Task 2: Build and test the receivers. The 24 bit A/Ds do not really provide 24 bits in the frequency range in which are interested. The final low signal sensitivity, and linearity, will be important to assess. Task 3: Incorporate into a field worthy housing, connectors, etc. (sounds trivial but it is not). Task 4: Field test the system and compare the results with a full AMT system. We have access to a full AMT system for side-by-side comparison.
Project Methods
In the comparison of our proposed Telluric-Magnetotelluric (TMT) method with the conventional Audio Frequency Magnetotelluric (AMT) method it is important to focus on the major data acquisition problems encountered with using natural source fields. There are basically two technical problems in the successful development of our TMT method. These are the specific problems to be solved by this research. The problems are: * Digitizing the very low level natural source fields. * Timing synchronization between the TMT base site and the telluric sites. The hardware solutions to these problems must, of course, be incorporated in a low cost, low power, and reliable package. Our approach to doing this is to leverage technology developed for the consumer electronics market. Two such technologies developed for consumer electronics have recently become available and inexpensive. The first is the availability of low cost, audio frequency, two channel, 24 bit analog-to-digital converters. The second is the availability low cost, GPS, dedicated timing receivers.

Progress 05/15/04 to 12/31/05

Outputs
Termination Report: Contract/Agreement No. 2004-33610-14349 Start Date: 5/15/2004 Term Date: 12/31/2005 The focus of this work was to develop inexpensive, reliable, low power, receivers to measure naturally occurring electric and magnetic fields. The resulting electromagnetic (EM) data sets can then be related to the subsurface distribution of water resources. The name of this technique is the Telluric-Magnetotelluric (TMT) method. We have successfully met the goals of our project. Through the work of our project hydrologist, and assistance from Kennecott Copper Company, we have obtained and interpreted a TMT data set. We were able to compare our TMT interpretation of the groundwater regime to known hydrogeologic data supplied by Kennecott. The comparison was excellent. The real technical success of this project was in the construction of two prototype TMT receivers. Each receiver consumes less than 170mA of current. The approach put forth in our proposal worked as we had planned. Most geophysical equipment is of custom design and construction. This is an expensive and time consuming proposition. The hardware can also be unreliable and difficult to maintain. Our approach was to develop receivers using consumer electronics. The directly applicable markets are high fidelity audio equipment, GPS timing, and low cost laptop computing. The high fidelity audio electronics industry provides us with high speed, 24 bit, analog to digital (A/D) converters. Our receivers achieve about 20 bits resolution at 48kHz sample rate. This allows us to develop a very simple receiver, with high sensitivity, and large dynamic range. The audio industry also provides us with low noise, high input impedance, amplifiers. These preamps, in conjunction with high resolution A/D, allow us to sample low level naturally occurring EM signals. We also store our digitized waveforms in the industry standard wav file format. Total cost of preamp and digitizer board is about $200. The new cell phone requirements have created a large market for GPS timing receivers. These receivers generate a pulse per second timing signal. The rising edge is accurate to less than 50 nanoseconds (ns). We've designed our receivers to maintain a phase accuracy of about one degree at 10kHz. We require 300 ns time synchronization between our receivers. Although the GPS receivers are meeting their specification our receivers are not. Our first design is being replaced by a better timing implementation. The cost of a low power GPS timing receiver and antenna is about $80. The data streams are two 24 bit channels of either electric or magnetic fields, digitized at a rate of 48,000 samples per second per channel. Ten seconds of this data takes about 4mBytes of storage. Each receiver has a dedicated laptop computer to store these data sets. Each computer can store over 24 hours of continuous data. Each roving site only requires about ten seconds of occupation time. The base station only runs for a couple of hours at a time. The cost of one of these basic laptop computers is about $450.

Impacts
We have shown that the Telluric-Magnetotelluric (TMT) method, in conjunction with reliable, inexpensive, receivers is a practical noninvasive approach to monitor and discover ground water resources. In addition we have successfully demonstrated, by building two prototype receivers, that low cost, high quality, field worthy, TMT data acquisition hardware can be constructed using large-market consumer electronics components. The availability of this noninvasive groundwater monitoring technique can help relieve the strain imposed on water resources by drought and human impact. We have already attracted the attention of mining companies who are interested in assessing their influence on groundwater reserves.

Publications

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