Jean-Christophe Maréchal Hydrogeologist Karst Fractured

A fractured aquifer is not simply a porous medium with a few fractures.

At Maheshwaram, hydraulic tests at different scales were used to characterize the fractured-weathered layer. Slug tests, injection tests and pumping tests were interpreted using analytical approaches including double-porosity, anisotropic and fractional-flow models.

Key findings

Strong vertical anisotropy of hydraulic conductivity, with an average ratio close to 10.
Horizontal fractures play a major role in groundwater flow.
Fracture-network conductivity was estimated at approximately
2.1×10−52.1\times10^{-5} m/s.
Block conductivity was approximately
5.1×10−85.1\times10^{-8} m/s.
Thus, the fracture network is roughly 400 times more conductive than the blocks.
Effective porosity was estimated at 6.3×10−36.3\times10^{-3}.
Approximately 90% of storage was associated with the primary fracture network affecting the rock blocks, while the larger-scale secondary fracture network contributed about 10%.

Fractures control transmissivity, while smaller-scale fracture networks contribute substantially to groundwater storage.

Key publications

An Observatory of Groundwater in Crystalline Rock Aquifers Exposed to a changing Environment : Hyderabad, India

Jean-Christophe Marechal, Adrien Selles, Benoit Dewandel, Alexandre Boisson, Jerome Perrin, Shakeel Ahmed

Vadose Zone Journal, vol. 17, 2018 Nov

Determining the vertical evolution of hydrodynamic parameters in weathered and fractured south Indian crystalline-rock aquifers: insights from a study on an instrumented site

Alexandre Boisson, Nicolas Guihéneuf, Jérôme Perrin, Olivier Bour, Benoit Dewandel, Amélie Dausse, Mathieu Viossanges, Shakeel Ahmed, Jean-Christophe Maréchal

Hydrogeology Journal, vol. 23, 2015 Jun, pp. 757--773

Groundwater flows in weathered crystalline rocks: Impact of piezometric variations and depth-dependent fracture connectivity

Nicolas Guihéneuf, Alexandre Boisson, Olivier Bour, Benoit Dewandel, Jerome Perrin, A.mélie Dausse, Matthieu Viossanges, Shandra Chandra, Shakeel Ahmed, Jean-Christophe Maréchal

Journal of Hydrology, vol. 511, 2014, pp. 320-334