Some rivers overflow in Vienne and Deux-Sèvres while the water tables are sometimes at their lowest

While many rivers overflow into Vienne or Deux-Sèvres, the level of groundwater remains too low. According to the Bureau of Geological and Mining Research, the deficits for the year 2022 explain this paradox.

According to the hydrogeological situation bulletin published by the BRGM (Office of Geological and Mining Research), “Groundwater recharge remains low. More than three-quarters of the water tables remain below the monthly normals.“And yet some rivers overflow in the region. This is the case of the Clain in the Vienne or the Sèvre Niortaise and the Thouet in the Deux-Sèvres.

The Poitou-Charentes region oscillates between the low and the very low on the map published by the BRGM. As this map of the groundwater situation at 1^is January.

A situation which can be explained by the very large water deficit recorded in 2022. The water tables had been so emptied that they are now struggling to regain an acceptable threshold. If we take the reading from the Prahecq piezometer in Sèvre-Niortaise, the level of the water table was -3.32 m on December 31, 2021, against -6.88 m on December 31, 2022. Clearly, the deeper the level, the less the aquifer is filled.

Same thing in Ruffec in the Charente basin. On 31/12/2021 the level was at -3.65 m a year later the level was at -8.58 m.

Winter rains will depend on the water levels available this summer and for the moment things are not looking the best, the rains of December were insufficient.

And on the surface, the rivers, for their part, begin to overflow. In Poitiers for example, the Clain was at 2.19 m this Monday morning at 8 a.m. and according to forecasts, it will be at 2.40 m at 7 p.m., knowing that the alert height is at 2.30 m. La Boivre is also coming out of its bed and residents of the two rivers are invited to register for the alert service. It’s a free service found at the city’s website.

In Deux-Sèvres, the floods are also underway and should last several days. “we have not reached the flood peak which was initially announced for this evening (Monday, editor’s note) in Niort. We expect 130 to 140 cubic meters per second and there are rain forecasts until Wednesday so it could still go up” explains Gilles Chourré, deputy director of the Interdepartmental Institute of the Sèvre Niortaise basin. “LThe first overflows took place this weekend on the downstream side of the basin, near the sea, this is what is called the effect of the plug closed by the sea. he continues.

In the commune of Chauray near Niort, the Sèvre has come out of its bed and the town hall is alerting the inhabitants.