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Constraining groundwater modeling with magnetic resonance soundings.

Authors :
Boucher M
Favreau G
Nazoumou Y
Cappelaere B
Massuel S
Legchenko A
Source :
Ground water [Ground Water] 2012 Sep-Oct; Vol. 50 (5), pp. 775-84. Date of Electronic Publication: 2011 Dec 07.
Publication Year :
2012

Abstract

Magnetic resonance sounding (MRS) is a noninvasive geophysical method that allows estimating the free water content and transmissivity of aquifers. In this article, the ability of MRS to improve the reliability of a numerical groundwater model is assessed. Thirty-five sites were investigated by MRS over a ∼5000 km(2) domain of the sedimentary Continental Terminal aquifer in SW Niger. Time domain electromagnetic soundings were jointly carried out to estimate the aquifer thickness. A groundwater model was previously built for this section of the aquifer and forced by the outputs from a distributed surface hydrology model, to simulate the observed long-term (1992 to 2003) rise in the water table. Uncertainty analysis had shown that independent estimates of the free water content and transmissivity values of the aquifer would facilitate cross-evaluation of the surface-water and groundwater models. MRS results indicate ranges for permeability (K = 1 × 10(-5) to 3 × 10(-4) m/s) and for free water content (w = 5% to 23% m(3) /m(3) ) narrowed by two orders of magnitude (K) and by ∼50% (w), respectively, compared to the ranges of permeability and specific yield values previously considered. These shorter parameter ranges result in a reduction in the model's equifinality (whereby multiple combinations of model's parameters are able to represent the same observed piezometric levels), allowing a better constrained estimate to be derived for net aquifer recharge (∼22 mm/year).<br /> (© 2011, The Author(s). Ground Water © 2011, National Ground Water Association.)

Details

Language :
English
ISSN :
1745-6584
Volume :
50
Issue :
5
Database :
MEDLINE
Journal :
Ground water
Publication Type :
Academic Journal
Accession number :
22150349
Full Text :
https://doi.org/10.1111/j.1745-6584.2011.00891.x