Record Rainfall in Poitou-Charentes: Impact and Forecast

After the heat records recorded in September and early October, precipitation in turn reached excess levels compared to the averages of the last 50 years. On the surface, the water tables are recharging, certain rivers like the Charente are overflowing. But the decline is forecast for the end of the week.

“It started raining on October 17. And in less than a month, we recorded half of the annual rainfall in Saintes” notes meteorologist Emmanuel Moreau on November 14.

The flood of the Charente flooding the streets of Saintes since the Ciaran and Domingos storms is symptomatic of the regional meteorological situation.

Until mid-October, the anticyclonic regime and the dynamics of southerly flow had caused drought and heat records. The shift in winds to the West, normal for this season, took place while “the mass of precipitable water is more abundant than normal.“

>> Precipitation indicator 2023

“Humidity is higher in warm air masses“, specifies Emmanuel Moreau. “And the higher ocean temperature produces more evaporation. Both factors contribute to higher rainfall.“

In La Rochelle, we have recorded 341 mm of rain since mid-October: 211 mm in October (monthly average 84 mm) + 130 mm in November (monthly average 95 mm).

Since the start of the year, cumulative precipitation amounts to 778 mm, for an annual average of 754 mm.

The October monthly record for rain in 24 ha was broken on 27/10 with 39.7 mm.

In Cognacwe have recorded 285 mm of rain since mid-October: 155 mm in October (monthly average 6 mm) + 130 mm in November (monthly average 88 mm).

Since the start of the year, cumulative precipitation amounts to 848 mm for an annual average of 772 mm.

In Niortwe have recorded 345 mm of rain since mid-October: 193 mm in October (monthly average 88 mm) + 152 mm in November (monthly average 92 mm).

Since the start of the year, cumulative precipitation amounts to 968 mm for an annual average of 847 mm.

The annual 1,000 mm will probably be exceeded. The last time this happened was in 2000 (1084 mm) and this threshold of 1000 mm was exceeded 7 times between 1990 and 2000 (annual record 1376.9 mm in 1994).

HAS Poitiers, there has been 218 mm of rain since mid-October: 27 mm in October (monthly average 72 mm) + 91 mm in November (monthly average 75 mm).

Since the beginning of the year, cumulative precipitation amounts to 717 mm for an annual average of 695 mm.

(Source: Emmanuel Moreau – meteorologist)

Historically, this very marked rainy episode recalls the major floods of the winter of 1982-1983. “The difference is that this year, at the start of autumn, the soils are dry and absorb water, the consequences of flooding are therefore less significant than in 82-83”explains the meteorologist.

In deficit until the beginning of October after months of drought, underground water resources are recharged thanks to these rainy episodes. Located between 10 and 20 m deep, surface water tables are the first to collect water. They are now flush and can go so far as to overflow into fields in rural areas, or create pressure in drainage networks in urban areas.

>> Level of surface water tables

The recharging of deep aquifers will take longer. The recharge period lasts until the end of March, when vegetation resumes.

>> Level of deep water tables

This November 14, 10 to 15 mm of rain are expected in the departments of Poitou-Charentes, locally up to 20 mm in Charente. A new disturbance announced for this Thursday, November 16 should bring another 10 to 15 mm of precipitation, before a period of calm. “Then we will have much less disrupted weather, alternating clouds and clearings, without major precipitation” predicts Emmanuel Moreau.

A lull which should allow rivers still in flood orange alert (Charente and Sèvre-Niortaise) to begin to decline.