Drought in Brittany: will the crisis last until November?

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Since August 12, all departments in Brittany have been in a situation of “drought crisis”, the highest level of the alert scale, which has led to a series of restrictions: a ban on watering gardens , fill the pool, clean private. vehicles, etc. Certain sectors have obtained exemptions, such as the vegetable garden (fruit and vegetables) which, in Finisterre, benefits from the authorization to irrigate field crops between 9.00 pm and 8.00 am, up to and including August 29. “All requests are studied but only strictly necessary exemptions are granted,” specifies the prefecture. “The prefectural decree lasts until November,” says Audrey Rousseau, from the communication department of Morbihan prefecture. “The DDTM (Departmental Directorate of Land and Sea) is following the situation closely. “The date is identical to Côtes-d’Armor, but it could be moved forward if we “find regular rains over the course of a month,” adds Éric Hennion, acting director of the DDTM in the department. Can the recent rains help? Precisely, during a few days, Brittany finally sees the return of rain. However, these few drops will not do because they will not play with the available water reserves. Summer accounts for only 2% of water inflows, compared to 48 % in winter, 40% in autumn and 10% in spring, according to data from the Ministry of Ecological Transition (see next). In Ille-et-Vilaine, the rainfall deficit was 20 % to 40% in the spring, depending on the sector, after an already hard winter with 20% less rain than normal. Morbihan has experienced a deficit of 40% since the beginning of 2022, even 60% in certain sectors! In the Côtes-d’Armor, “we have seen a slight rise in certain rivers in recent days. But they are starting to drop because the rains are low”, worries Éric Hennion. “Some rivers are even almost dry! »How to get out of the “drought crisis” state? To go back down from the crisis level (stage 4) to the “reinforced alert” (stage 3) of the drought alert level, “the flows of the reference rivers of the decree must all be returned below the thresholds of crisis” and “the exceptional exceptions to the reserved flows (consisting of the maintenance of a minimum flow in the rivers, ed.), granted to guarantee the supply of drinking water, must be repealed”, indicates the prefecture of Finisterre. Seven rivers refer to the department. For rivers, “several stations (read below) measure flows. Then we cross them with the meteorological data”, specifies Éric Hennion. Here are the flows measured by the stations in Brittany on the 17 ‘August. The red points correspond to a very low flow (close to 0 m3 per second), and the green to an average flow. (Screenshot Dreal Bretagne) In Finisterre, the situation is currently being reassessed every week. As soon as the situation approaches stage 3, it will be “every day.” Followed ment, the DDTM will propose a decree, “examined and validated by the Water Resources Management Committee (CGRE) then signed by the prefect”, the prefecture indicates. In a few days, in a week or in a month? No one will dare to give a date. 170 stations measure the water level in Brittany 170 measuring stations are used in Brittany to measure the height of rivers. “They are subject to exhaustive monitoring and frequent trips by the agents of the Regional Department of Environment, Planning and Housing (Dreal) to make assessments that guarantee the reliability of the data produced,” explains Dreal Bretagne, on its website. It is from this data that “the necessary measures are taken for optimal management of water resources” in times of drought crisis. But in recent days, obstacles have appeared in certain measurement areas, “such as stones installed to raise the water level and create a small swimming area”, warned the Dreal, on August 11. “The measured water level is no longer representative of the actual water level in that watercourse.” All data are accessible on the Hydrologie Bretagne website.
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