Climate: when drought forecasts worry at all levels

Both underground and at ground level, hydrogeologists have something to grind. And their analyzes of droughts, floods and groundwater levels are of interest far beyond the scientific sphere. Insurers, economists, planners of all kinds are now scrutinizing their findings, in addition to politicians. Not so easy.

Because, in this period of climate change, it is quite an art to move from the global to the very local, from the generalities to the specificities of this or that territory. To “ground realities”, according to the terms of the Water Plan and its 53 measures announced in mid-April. As for forecasting, it requires some algorithmic tact, especially when the scenarios must remain valid for several decades…

For the short time, it is also necessary to do with the probabilities. Thus, according to the bulletin of major trends from Météo France, at 50% we can expect a warmer quarter than normal in June, July and August next. For rain, drier, normal or wetter weather are all equally likely. The melody in the basement remains monotonous: 68% of the underground water tables showed below normal levels on May 1, and it is not going to get any better.

From Mediterranean red to Brittany blue

None shows a situation “making it possible to guarantee satisfactory levels until the fall”, according to the BRGM (the national geological service) and its review Geosciences, “for a sustainable Earth”. The important thing is to zoom in even more closely on its maps in seven colors, from the very red around the Mediterranean and in the Rhône-Saône corridor to the blue of Brittany. There are indeed 1,100 sub-basins in the country. And the devil hides in the details, not representable on this scale.

A heterogeneity that is not minor when it comes to drinking water – in 2022, 2,000 municipalities experienced tensions. If the dialogue bodies promised by the Water Plan for each sub-basin are put in place as planned, they too will have grain to grind…

Read alsoBasins, waste water… what the water plan provides for agriculture

Shrinkage-swelling of clay soils… and tripling of the amount of claims

When another concern grows at the same time, that of shrinkage-swelling of clay soils, followed by cracks in buildings. About ten million individual houses are concerned, according to the public establishment Cerema of assistance to communities and businesses for their ecological transition. The 200 scientists in its R&D branch, the Carnot Clim’adapt institute, have their work cut out for them.

In the fall of 2021, with its publication “Impact of climate change on insurance by 2050”, the French Insurance Federation raised a cry of alarm. Drought, enemy n°1, direct additional cost of seventeen billion euros, annual tripling of the amount of claims, ie 43 billion euros in thirty years. We wonder what parliamentarians will do.

On April 6, the bill “aimed at better compensating the damage to real estate caused by the shrinkage-swelling of clay” was adopted at first reading by the National Assembly. We do not know if the senators will be as sensitive to the realities on the ground.