Reference network for low-water monitoring (RRSE)

Together with Irstea, the AFB has defined a reference network for monitoring low water levels by selecting 250 hydrometric stations from Banque Hydro (including 14 overseas) which are not influenced by human activities.

This network has highlighted a clear downward trend in surface water resources over the past 40 years, with a worsening of low water levels particularly in the southern half of France.

While these trends are significant, they cannot be directly attributed to climate change. Indeed, the multi-decadal natural oscillations of the climate can potentially explain some of the observed evolutions.

The analysis of climatic oscillations highlights in particular the following elements:

• it is possible that part of the temporal trends detected in the severity of low water levels may be due to climatic oscillations;

• on the other hand, it seems that the trends observed in low-water seasonality (beginning, centre, end, duration) are not attributable to climatic oscillations but to climate change.