The Explore 2070 study aimed to assess the possible impact on surface water, mainly in terms of stream flows, but also water temperature, of the intermediate climate change scenario of the Intergovernmental Panel on Climate Change (IPCC) by 2046-2065 in mainland France.

The assessment of possible changes in surface water by 2046-2065, compared to a reference state (∼1961-1990) indicate:

  • a possible increase in average air temperatures of the order of + 1.4 ° C to + 3 ° C according to simulations throughout the metropolis;
  • an uncertain evolution of precipitation, most models, however, agree on a downward trend in summer precipitation throughout the metropolis, on average in the range of -16% to -23%;
  • a significant overall reduction in average annual flows across the territory, of the order of 10% to 40% depending on the simulations, particularly pronounced in the Seine-Normandy and Adour-Garonne districts;
  • for a large majority of watercourses, a decrease in low flow rates (up to -70% on the Garonne) even more pronounced than the decrease on an annual scale;
  • more heterogeneous and overall less significant changes in floods.

Figure: Projected decreases in river flows in France by 2046-2065. © Explore 2070

The underground waters will also be negatively affected by climate change. The recharge of the tablecloths will be reduced on average by 20 to 30% (50% in the worst situations).

Figure: Variation of recharge between present time (1960-1990) and future time (2045-2065). Minimum, average and maximum deviations of the future time / present time recharge. © Explore 2070. BRGM, 2012.