Should I be afraid of a drought in the spring?

TO Cyril Duchen, meteorologist

Our winter 2021-2022 was not wet enough due to the drought which was wonderful for the Mediterranean. Does the last active rain in Languedoc-Roussillon give you a real respite before spring arrives? Should this month of March with low water in the north raise concerns about a dry spring? Here are some answers…

First of all, remember that there are 2 types of drought:

meteorological drought which corresponds to a long absence of precipitation in this place. This results in a surface drought called “agricultural drought” and corresponds to water scarcity in the surface layer of the soil. It is feared by gardeners and farmers.

hydrological drought which occurs when there is a significant shortage of water levels in hydrological reserves (lakes, rivers and groundwater). This occurs mainly after dry winters when groundwater recharge cannot be done properly. The prefectural regulations on water restrictions are made after observing this hydrological drought.

Winter 2021-2022 is too dry

Due to the predominance of anticyclonic conditions, the meteorological winter of 2021-2022 (December to February) was dry with an average rainfall deficit in France of 25%. After a slightly wetter than usual December (+12%), January and February were very dry, with a rainfall deficit of 45% in January and 40% in February, on average for France. The southeastern regions experienced a remarkable winter drought. Precipitation deficit was close to 60% throughout the meteorological winter (December, January, February) between Languedoc-Roussillon and the PACA region. In Corsica, it even reaches 75%. January and February were exceptionally dry: 1mm in Sète (34), 5mm in Montpellier (34), 6mm in Béziers (34), 11mm in Nîmes (30), 13mm in Alistro (2B) or even 19mm in orange (84).

Rainfall over the past few days has been positive in Languedoc-Roussillon, but too low in PACA and Corsica, where droughts remain. In other areas, the few rainy periods were not very active, but helped to avoid agricultural drought at a time when temperatures were not yet too high and when the vegetation was just beginning.

63% groundwater deficit as of March 1

At the end of winter, almost two-thirds of the groundwater level shows a deficit, while last year the situation was reversed. After a well-watered winter of 2020-2021. most groundwater levels showed excess levels by the arrival of spring. If this situation is not yet problematic, it may become so if there is less rainfall over the next few months and if there are early heatwave episodes.

Another alarming signal: on March 1, the level of more than half of the groundwater dropped. Usually at this time of the year most of the aquifers have not yet completed their recharge. However, starting in April, precipitation is mostly used for vegetation and little for groundwater filling.

Could the drought set in quickly in the spring?

Over the next few weeks, precipitation is expected to be sparse in the north and northeast, but more frequent in the southwest to the Mediterranean, with hydrological conditions expected to continue to improve. After that, our seasonal trend is for a return of more erratic and unsettled weather over the greater northern half in April and May. If this trend is confirmed, we will avoid the spring drought. In the southeast, a return of drier weather in April-May could create problems with rising temperatures and increased plant water requirements.

Therefore, it is necessary to closely monitor the weather situation in the southeastern part of the country (in particular in PACA and Corsica, given the significant rainfall deficit and the prospect of a dry spring. In addition, the Alpes-Maritimes cause increased vigilance). which encourages people and professionals to save water without water restrictions for now.

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