Why was a well packed with technology installed in the middle of a Beauce field in the small village of Villamblain?

Nearly thirteen months of construction and four years of “conceptualization” for the well (four meters in diameter), plunging twenty meters below the surface of the Beauce and this farm in the small village of Villamblainnear Patay.

An installation “unique in the world”, we recalled this Tuesday, during the inauguration of the O-ZNS research platform, born of close collaboration between the CNRS, the University of Orléans and the BRGM.

Water quality

It will be our eye on the water table of Beauce, our observatory”then explained in the morning in the sun the deputy director of the Institute of Earth Sciences of Orleans (ISTO) and project manager, Mohamed Azaroual.

Water tables are at extremely low levels in the Loiret

Mohamed Azaroual is the deputy director of the Institut des sciences de la terre d’Orléans (ISTO) and the project manager.

The well “will allow us to monitor the quality of the groundwater (chemical composition) and its evolution in relation to agricultural practices.“We will inevitably find in it” what the farmers spread in the fields, herbicides, pesticides, fertilizers. This will allow us to understand how the soil fixes, degrades or allows inputs to pass to the water table”.

And this, by studying the behavior of the zone not saturated with water, which is found between zero and twenty meters below the surface, the size of the well, equipped with sensors at all depths and starting in all directions.

After 2003, the summer of 2022 was the hottest ever recorded in the Loiret

How long does the water take to go down

The well (built by the Bouygues company) is located in the unsaturated water zone, that is to say, between the surface of the field and the water table. Photo: David Criff

Our observatory, completes Mohamed Azaroual, “will also make it possible to monitor the groundwater for micropollutants, emerging pollutants and endocrine disruptors“, also from agriculture. All thanks to mini-boreholes, “horizontal and oblique” from the well, “to take samples of water and rocks and then analyze their chemical compositions”.

The sensors found around the entire circumference of the cavity “offer highly resolved and spatialized data, allowing us to know how long it takes for water, rain or irrigation, to reach the groundwater”.

We could go down there on Tuesday, well, not all the way down. Photo: David Criff

Note that the purpose of the installation is not to establish the level of the water table (“which we know from elsewhere”), but to measure how long it takes for the water to sink. If 30 mm falls, “we can determine, with precision, what quantity arrives in the water table, is retained before by the roots or has evaporated into the atmosphere.”

A forty-year lease

With regard to “global changes”, understanding human activity and climate change, “this will allow us to fully understand how it works” and the impacts that major surface upheavals have on the groundwater table.

Mohamed Azaroual adds “that by compiling a whole lot of information (on pollutants, infiltration, etc.), we will be able to predict the future evolution of the Beauce aquifer”. The data entered in software, “memory effect”, will thus make it possible to determine its state on the horizon of the next hundred years, “through different scenarios, including that of the IPCC (Intergovernmental Panel on Climate Change).”

The scientific teams at work around the technology well see far, which explains why the plot under which it dives is now leased to its owner for the next forty years. Time to see coming…

The plaque.

David Criff

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