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Resolution of MRS applied to the characterization of hard-rock aquifers

Legchenko, Anatoly and Descloitres, Marc and Bost, Adelphe and Ruiz, Laurent and Reddy, Mohan and Girard, Jean-Francois and Sekhar, Muddu and Kumar, Mohan MS and Braun, Jean-Jacques (2006) Resolution of MRS applied to the characterization of hard-rock aquifers. In: Ground Water, 44 (4). pp. 547-554.

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Official URL: http://www3.interscience.wiley.com/journal/1186269...

Abstract

The performance of the Magnetic Resonance Sounding (MRS) method applied to the investigation of heterogeneous hard-rock aquifers was studied. It was shown using both numerical modeling and field measurements that MRS could be applied to the investigation of the weathered part of hard-rock aquifers when the product of the free water content multiplied by the thickness of the aquifer is >0.2 (for example, 10-m-thick layer with a 2% water content). Using a currently available one-dimensional MRS system, the method allows the characterization of two-dimensional subsurface structures with acceptable accuracy when the size of the subsurface anomaly is equal to or greater than the MRS loop. However, the fractured part of hard-rock aquifers characterized by low effective porosity (<0.5%) cannot be resolved using currently available MRS equipment. It was found that shallow water in the weathered part of the aquifer may screen MRS signals from deeper water-saturated layers, thus further reducing the possibility of investigating deeper fractured aquifers. A field study using the NUMISplus MRS system developed by IRIS Instruments was carried out on an experimental watershed in southern India. A heterogeneous unconfined aquifer in a gneissic formation was successfully localized, and MRS results were confirmed by drilling shortly after the geophysical study. The top of the aquifer revealed by MRS was found to be in a good agreement with observed static water level measurements in boreholes.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Blackwell Publishing.
Department/Centre: Division of Mechanical Sciences > Civil Engineering
Date Deposited: 09 Apr 2009 04:57
Last Modified: 09 Apr 2009 04:57
URI: http://eprints.iisc.ernet.in/id/eprint/18464

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