Cogs: "If we carry on like this, one day these aquifers will no longer be able to supply us with water".
Muriel Geeraert is a hydrogeology engineer at Géosciences Montpellier. In the Hérault and Pyrénées Orientales regions, she travels from borehole to borehole to collect the precious data that will enable the Transfer in Porous Media department to better preserve water resources. A mission she explains to us in the Rouages video series produced by the University of Montpellier. Get moving!
On this December morning, even the pink flamingos are trembling in the wind sweeping across the Etang du Prévost in Villeneuve-lès-Maguelone. We meet Muriel Geeraert on the thin lido separating the lagoon from the sea, a few hundred meters as the crow flies from the cathedral. With her thick coat, cap and gloves, the hydrology engineer has the broad smile of someone who will never be indifferent to the beauty of the site and the lights that bathe it. " It's very cold today, but it's great to be working here ", she declares, as she pulls out a chair and folding table from her van, where she can set down her equipment and, if the weather warms up, break a seed behind the container that stands there, the only bulwark against the wind.
60 meters deep
While the term drilling may conjure up images of a relatively imposing installation for the uninitiated, we were surprised by the bareness of the site until Muriel drew our attention to the thin PVC pipes emerging from the ground. " There are eight wells in all, but this one allows me to do all the data I collect in the field. It goes down to 60 meters and is fully cased to let the probe pass through and make very precise measurements ", she explains as she unfolds a winch some 2 meters high. To make sure we don't miss any explanations, we decide to equip her with microphones, for the face-to-face interview to follow.
A few minutes later, with the winch in place just above the well, the engineer pulls out a spindly metal cylinder from a black plastic box: " Here's the probe, I'm going to lower it down to the underground reservoir to bring up a small quantity of water. I'll take its PH and conductivity readings on the spot and send the rest of the samples to the laboratory for more detailed analysis." Muriel Geeraert quickly explains what's at stake in these manipulations, revealing the fragility of the ecosystem that surrounds us.
Salt water intrusion
"The problem here is the intrusion of salt water into coastal freshwater reservoirs. In summer in particular, we draw a lot of water for campsites and golf courses. The more we draw from aquifers, the more saltwater from the sea tends to enter them," notes Muriel Geeraert. If we carry on like this, one day these aquifers will no longer be able to supply us with water. We're having a big impact on nature," laments the engineer, originally trained in mechanics and industrial automation, who joined Geoscience in 2019 following the shutdown of the particle gas pedal she was working on. " It's true that I've come a long way and I'm learning a little more about the geosciences every day. It's such a vast field, I find it fascinating. "
As a member of Geosciences' "Transfers in Porous Media" (Tmp) department, Muriel Geeraert keeps a close eye on the human impact of the Villeneuve-lès-Maguelone site, but not only: " Every month, I take readings at Pégairolles-de-l'Escalette just above Lodève, also a very beautiful site, where we study the effect of landslides in greater detail. I also go to Le Barcarès and Canet-en-Roussillon, and the last site is in Majorca, but we don't go there much any more ". A lovely overview of the region for this Parisian by birth, who dreamed of coming to live in the South and appreciates more than anything the diversity of its activities, sites and climate.
Practical work
And when she's not in the field, Muriel Geeraert spends her days in the laboratory. " We have to maintain the equipment and recalibrate it. We also have to process all the data, some of which is added to databases open to the general public. Every year, she also takes part in hydrogeology practical work (TP), where students can discover field work directly on site. " I run this workshop with Emmanuelle Petelet, where we take out water samples and have the students carry out analyses. It's a really fun hands-on activity, and it's also a part of my job that I really enjoy! Except when a snake invites itself to the party...