Drought in France: Data at the Heart of Hydrological Crisis Management

In two months, France went from 3 departments in crisis in early June to more than 70 by mid-August. This rapid deterioration reflects a particularly strained hydrological situation this summer.

This situation is due to a combination of exceptional heat and a significant precipitation deficit. Following a June that had already set temperature records, July 2026 became the hottest month ever recorded in France since measurements began in 1900. Precipitation during that month was also 67% below normal.

Drought is not limited to the condition of waterways. It affects the entire water cycle.

In July, 98% of mainland France had drier-than-normal soil, with 63% experiencing what is classified as an “exceptional” drought. Soil moisture levels reached levels comparable to those observed during the historic drought of 2022.

Groundwater levels are also under pressure: by the end of July, only 37% of monitoring sites had satisfactory levels, while 63% were below normal. Declining levels were observed at 94% of the monitored sites.

But it is perhaps among small waterways that the situation is most dramatic. 1,373 watercourses were affected by interrupted flow or drying up at the end of July, compared to 819 a month earlier. With 43% of watercourses experiencing interrupted flow or drying up, the ONDE network is recording its most critical situation since monitoring began in 2012.

The “crisis” level corresponds to the highest level of the water restriction system. It aims to reserve water for priority uses—including drinking water supply, health care, civil safety, and watering livestock—and to preserve the biological functions of waterways. Most non-priority uses are then prohibited or severely restricted.

However, it is important to note a key distinction: “71 departments in crisis” does not mean that water availability is equally strained across all of them. Restrictions are defined by alert zone and may apply differently to drinking water, surface water, and groundwater. The figure of 71 corresponds to the highest severity level observed in each department.

In the face of a rapidly changing situation, decision-support tools require reliable data. But to determine whether a situation is exceptional, deteriorating, or improving, it is not enough to have recent data: we must be able to compare it over time.

This requires long-term data series, produced using consistent and mutually comparable methods. It is this continuity that allows us to place current observations in a historical context, identify trends, detect breaks in the data, and better assess crisis situations.

This ability to compare data relies in particular on data standardization and interoperability. This is one of the roles of Sandre (National Administration Service for Water Data and Reference Frameworks), which establishes and makes available the water data reference framework for the french Water Information System (SIE). Sandre defines technical specifications and common standards to facilitate data exchange at the national level and ensure the interoperability of information systems.

In other words, the quality of today’s decisions also depends on the work done to ensure that data is comparable across the past, present, and future. Long historical time series thus constitute an essential resource for understanding changes in water resources and developing decision-support tools that are increasingly relevant.

To monitor and manage this situation, several data networks are being utilized: river flow rates, groundwater levels, field observations of small watercourses, and meteorological and hydrological forecasts. This information enables government agencies to adjust restriction levels based on changes in water availability.

This summer’s situation thus underscores how much water management relies on detailed, continuous, and comparable monitoring of water resources. In the face of heat waves and droughts that can intensify rapidly, a better understanding of water conditions is essential for anticipating events, adapting water use, and ensuring the long-term preservation of water resources.