Many Aubois residents drive by it every day without knowing it.
Located near the southern ring road of the Troyes conurbation, the Courgerennes catchment field can supply 50 to 70% of the water needs of 90,000 inhabitants of the communes of Troyes, Sainte-Savine, Saint-André-Les-Vergers and La-Rivière-de-Corps, served by the Drinking Water Authority of the city of Troyes.
“A natural area of 80 hectares where there is no surface pollution”, underlines Marc Bret, president of the water policy council in Troyes at the Aube water union (SDDEA): “It allows us to produce between 3 and 4.5 million m3 per year depending on needs.
With the equipment being renovated, we could, if necessary, supply up to 120,000 people.
It's a treasure that we have in our hands, to be protected like the apple of our eye!
»
Also readGlobal warming: 25 questions/answers to understand everything
Its positioning is strategic, upstream and close to the population served, on a water table fed by the Seine, with water in quantity and quality.
“The water is pumped into the groundwater then pumped back by pumps at 1,000 m3/h into the semi-buried reservoir of Hauts-Clos,” explains Pierre Cannard, project manager at the SDDEA management team.
A historic work that the people of Aubois know well, below the water tower located next to the Troyes hospital center.
Underground, two tanks of 15,000 m3 each, made up of two distribution outlets.
The first is without pumping, because it is at a sufficient height to supply a large part of the Troy city in complete safety.
In the second outlet, water is pumped to supply the 6,000 m3 pillar tank, culminating at a height of 65 m.
Enough to provide additional pressure to supply the higher parts of the Troy city.
Also read: Are we ready to consume less water?
The work carried out on the Courgerennes catchment field is therefore all the more important.
Firstly, they consist of modernizing the accesses, buildings and electrical installations on the site, overhauling the pumps, but also adapting the wells to the future consequences of global warming on water withdrawals.
“We are already seeing it sometimes, warmer temperatures in summer, not necessarily less precipitation over the year, but rain which can be distributed differently,” notes Marc-Éric Joffroy, hydrogeologist at the Water Union.
A predictable evolution of groundwater recharge which requires anticipating very costly investments: “We have a major study underway with the Bureau of Geological and Mining Research (BRGM), to enable us to properly characterize all of this and to model the surface and groundwater of the department”.
Also readDrought: when rivers shrink, biodiversity and the economy are affected
Already, the idea is to gain flexibility and productivity on two of the three Courgerennes wells, which have the particularity of having radiant drains, small steel pipes which draw water up to 40 meters deep.
Divers are currently working to clean the drainage tools.
In addition, speed variators will be installed for greater pumping flexibility: “Today we are all or nothing, from 0 to 1,000 m3 per hour,” underlines Pierre Cannard.
The idea is to be able to have an intermediate flow, of 500 to 600 m3/h, because with climate change and the lowering of the level of the Seine, we also have a lowering of the water level in the wells ".
With the risk of having to stop the exploitation of Courgerennes and turn to other sources, in Essoyes or Jully-sur-Sarce.
The 2.2 million euro project, financed by the Troyes Territory Drinking Water Authority and the Seine Normandy Water Agency, will have no impact on the price of water, unchanged since 2017. “But the question is whether we take into account the increase in the price of electricity,” Marc Bret still wonders.