Towards a Time Monitoring of the Chalk Aquifer (Beauvais, North of France) Using the Magnetic Resonance Soundings

In the department of Oise (Picardie, France), the agricultural activities are essential and require a good management of water resources. It is therefore essential to improve the knowledge on the chalk aquifer. This is the reason for which the UniLaSalle Institute has a hydrogeological experimental site, composed of wells and piezometers allowing to characterize the chalk aquifer by adopting a multidisciplinary approach. This approach is based on hydrogeological measurements, near surface geophysics, logging, and Magnetic Resonance Soundings (MRS). The present paper, based on the MRS 2016–2017 campaign, deals with the time monitoring of the chalk aquifer, consisting in repeating each month and a half, four MRS. These are located north of the UniLaSalle hydrogeological experimental site, where the measurements conditions are suitable, unlike near the piezometers and wells. The results, consisting in curves of hydrogeological parameters (water content, relative permeability and transmissivity) versus depth up to 90m, improve the knowledge on the chalk aquifer properties and there time variations. However these results requires a calibration by pumping tests to estimate the value of the calibration coefficient Cp. The difficulty resides in the identification of a suitable site, both for MRS (low noise level, stable magnetic field) and for pumping tests.