Magnetic resonance sounding for the estimate of hydrogeologic characteristics of chalk aquifers (North of France)
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ORIGINAL PAPER
Magnetic resonance sounding for the estimate of hydrogeologic characteristics of chalk aquifers (North of France) Lahcen Zouhri 1 & Pascale Lutz 1 Received: 1 April 2019 / Accepted: 10 September 2020 # Saudi Society for Geosciences 2020
Abstract The hydrogeological characteristics are required for investigating the modelling processes. The transmissivity and hydraulic conductivity values which are obtained from the inverse methods and pumping tests are not representative in the northern part of France where the major aquifer is composed of the chalk deposits. In addition, these methods are costly and time-consuming. In the north of the Paris Basin and by using the magnetic resonance sounding (MRS), the chalk aquifer reveals the vertical distribution of the porosity, the hydraulic conductivity, and the transmissivity. The decay constants of the MRS signal which have been identified from the MRS analysis are considered parameters which control the permeability and the transmissivity values. Five MRS surveys were realized and performed by the electrical resistivity tomography (ERT) aiming to characterize the lithology variation and the thickness of the hydrogeological units. This comparison shows the power of MRS methods of the chalk aquifer in the characterization of the hydrogeological system in the north of France. The water content which is deduced from the MRS highlights a heterogeneous distribution in the aquifer and the water content can reach 35%. Results which are deduced from the pumping test and the MRS are consistent. Indeed, the transmissivity values vary generally between 10−3 and 10−2 m2/s. This comparison shows the utility of the multidisciplinary approaches in the characterization of the chalk system in the north of France. Keywords Chalk aquifer . Hydrogeological characteristics . RMP . France
Introduction The understanding of the groundwater flow in the deep and shallow chalk aquifer is very complex. The hydrodynamic, hydrodispersive parameters and the geometrical properties of the saturated/vadose zone constitute the principal parameters which control the contaminant migration and the groundwater flow in the chalk environment deposits. The distribution of the hydraulic conductivity, the transmissivity, and the storage coefficient highlights important fluctuations according to depth and time scales (Painter 2003; Scott et al. 2007) and the structural control in the lithologic variations (Zouhri et al. 2004). Responsible Editor: Narasimman Sundararajan * Lahcen Zouhri [email protected] 1
AGHYLE, Institut Polytechnique UniLaSalle Beauvais, SFR Condorcet FR CNRS 3417, 19 rue Pierre Waguet, BP 30313, F-60026 Beauvais Cedex, France
Groundwater modelling shows in several works that transmissivity values and storativity coefficient are obtained from the calibration model, especially in the steady and transient state by using data coming from the measured groundwater levels (Bracq and Delay 1997; Zouhri et al. 2004) or by the optimization processes within the inverse methods (S
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