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  • The importance of the science-policy interface for water and climate

    1. The symposium titled “Water and climate - Interaction between scientists and politicians for action” was held in Paris in February 2015.
      Meetings N°30, Avril 2015
  • Observed trends in river flow rates in France

      1. Why do water shortages occur? Is this situation linked to excessive human usage or climate change? This document studies the fluctuations in water resources caused by climate factors in order to answer these questions.
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Water resources and climate change

Climate change will impact water resources in France. Groundwater levels, river discharges and the surface area of wetlands could all be affected..

There is no longer any doubt that human activities are causing climate change. "One of the clearest indications is the rise in sea levels, approximately 3 millimetres each year", notes Jean Jouzel, research director at the CEA institute and vice-president of the IPCC* scientific group, before adding that France will not be able to avoid the consequences. Depending on the climate scenario considered, the projections for France indicate that "the summer dry period will worsen around the Mediterranean and winters along the Atlantic coast will be increasingly temperate, with in exchange repeated disturbances and high precipitation". These projections, the product of combined climate and hydrological models, are subject to a certain degree of uncertainty, but the impact on water resources should be significant in France.

More severe water stress

Though the reduction in precipitation in France will be moderate on average, more severe local situations must be anticipated. In addition, due to the rise in temperature, "evaporation will increase at the end of winter and beginning of spring, resulting in greater water stress, i.e. longer and more intense periods of dry soil", notes Florence Habets, research director for hydrometeorology at the CNRS centre. Greater evaporation means that the soil will contribute less to river discharges, resulting in longer and more severe low-flow periods. "The heads of river basins risk going completely dry, which would have serious consequences for aquatic environments", warns Florence Habets. What is more, the projections signal a significant reduction of approximately 30% in mean discharges by 2050, though with spatial and seasonal variations. These impacts of climate change will also affect groundwater, with drops in piezometric levels that could reach crisis situations more frequently. This is an important factor given that groundwater is the main resource for drinking water.

Wetlands and coastal areas

Wetlands are often supplied with groundwater, consequently a drop in groundwater would result in a reduction in the surface area of wetlands. In coastal areas, wetlands often serve as buffer zones that protect nearby urban areas from flooding, notably in the overseas territories. The National ocean and littoral conservatory, whose objective is to acquire one-third of the French coastline to avoid its being built up or anthropogenised, must consequently take the effects of climate change into account in its strategy. "Since 2004, the Conservatory has launched studies and held symposia on the effects of the rise in sea levels. In 2012, an assessment of the socio-economic impacts on coasts was also carried out", notes Viviane Le Dissez, president of the Conservatory board and MP from the Côtes d’Armor department, "however, some information on water levels is still not available".

* IPCC: Intergovernmental panel on climate change.

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