STUDY OF THE MAGNETIC RESONANCE SOUNDING (MRS) TECHNIQUE IN GROUNDWATER INVESTIGATION

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National Seminar On "Adroitness in e-Content Development for Higher Education"

Ground water investigation carried out with traditional methods usually leads to good qualitative success, even if an evaluation of the quantity of water present into the ground is not possible due to the indirect relation between the physical parameter measured and the water. However, in the last decade, a new technique based on the Magnetic Resonance phenomenon has been developed in routine applications for direct detection of the presence of water from surface measurements through the excitation of the hydrogen protons of the water molecules. The advantage of magnetic resonance sounding (MRS) as compared to other classical geophysical methods is in its water selective approach and reduced ambiguity in determination of subsurface free water content and hydraulic properties of the media due to the nuclear magnetic resonance (NMR) principle applied. This technique is based on proton Magnetometry, where the hydrogen protons located in the sensor casing are activated to determine their precession frequency, hence the magnitude of the Earth magnetic field. The hydrogen protons of the underground water molecules are activated to characterize the water layer. The main applications of this technique concern the determination of water level and total quantity of water available in the depth. A loop laid on the surface of the ground is used for both transmitting the excitation pulse and measuring the response of the H proton. The linear relation between the measured signal and layer porosity allow interpreting the 1D sounding. A set of field data of various places points out both the advantages and the limitations of this technique.

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