Equipped with boots and radars, two officials are increasing controls on the waterways of Ille-et-Vilaine, a department where the drought is “exceptional” at the beginning of August.
Their waders up to the hips will protect them no higher than the ankles: the graduation to two meters and fixed under a bridge shows the river Le Chevré, a depth of 98 mm, a level that has already been observed but “not before September”according to Fabien Simon, agent of the Regional Directorate of the Environment of Brittany (DREAL), eye riveted on a sensor of the small hydrometry station.
His colleague David Danet continues: “In July 2022 we carried out 132 measurements (in Brittany Editor’s Note), compared to 39 last year”a sign that the water situation in Brittany is critical.
To measure, to understand the control of the height and flow of a watercourse, this is the mission of these two hydrometers among the eight that count the DREAL.
“It all starts with us”explains Mr Danet, who thinks “well equipped to do the job”.
Their tools? A radar installed on the deck to measure the air draft, a pressure sensor for the draft, a rod equipped with a propeller at the expense of a new car for the current, floating planks equipped with Doppler and a water drone costing more than 100,000 euros .
With 200 colleagues in France, David and Fabien conduct studies sent to the French Biodiversity Office (OFB), which are then used to issue prefectural decrees restricting water use.
Seven months short
David Danet Refuses Any Panic And Warns It Will Be Necessary “years” before we can analyze the drought of 2022, but the prefecture of Ille-et-Vilaine is concerned.
Contacted by AFP, she assures that: “seven months of global precipitation deficit at regional level” observed since October 2021.
And the month of July was catastrophic: the rain gauges of Dinard and Rennes registered “an accumulation of precipitation of 3% compared to the average monthly precipitation”.
This rainwater usually drains into the dams that make up 75% of the drinking water production in Brittany and whose resources “for the delivery of public networks is the most worrying”again according to the prefecture.
Lost in the scaled-down Chevré, recognizes David Danet “small chance that it will stop”such as a dry river near Dol-de-Bretagne, the Guyoult, which already ran dry in 2003 or 2016.
Unfortunately, it is not enough that the water returns to allow the fauna and flora to follow: “Returning to a normal ecosystem after a drought takes months, even years”warns Fabien Simon.
Guyoult is in fact one of the seven countries of the department at the beginning of August. Without rain by the end of summer, “it is possible” that we only see drought observed “during the historic drought of 1976”, said Prefecture.
They are detected by automatic stations such as Chevré’s. There are 170 in Brittany, feeding a database of water levels every 6 minutes. A few hydrometers traverse this network to monitor the flow, inspect and maintain the installations.
With risks associated with traffic (they often work on the side of the road) and the water itself. Especially during floods, in which they train, Fabien Simon concludes: “We participate in whitewater courses, we are thrown into the water and have to get out ourselves”.
Provided you have water above your ankles.