Constraining Groundwater Modeling with Magnetic Resonance Soundings
Article first published online: 7 DEC 2011
© 2011, The Author(s). Ground Water © 2011, National Ground Water Association
Volume 50, Issue 5, pages 775–784, September/October 2012
How to Cite
Boucher, M., Favreau, G., Nazoumou, Y., Cappelaere, B., Massuel, S. and Legchenko, A. (2012), Constraining Groundwater Modeling with Magnetic Resonance Soundings. Groundwater, 50: 775–784. doi: 10.1111/j.1745-6584.2011.00891.x
- Issue published online: 27 AUG 2012
- Article first published online: 7 DEC 2011
- Received April 2011, accepted October 2011.
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 km2 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% m3/m3) 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).