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    -Claire Grisez \ Ecology ministry
    "The national plan for adaptation to climate change voted in 2011 recommends acquiring effective tools to monitor water resources...."

    -Jean-François Vernoux \ BRGM
    "By increasing temperatures and reducing precipitation, climate change may reduce groundwater recharging. The creation of a piezometric network to monitor groundwater levels is indispensable to assess the phenomenon and its consequences..."

Monitoring the effects of climate change on groundwater

To evaluate the impact of climate change on groundwater, Onema participated in developing a piezometric network and a standardised indicator on groundwater status.

Among the other consequences of climate change, a reduction in precipitation combined with a rise in temperatures could increase evaporation and evapotranspiration of plants and result in reduced infiltration of rainwater. In that infiltration plays a major role in groundwater recharge, the impact of climate change on groundwater resources is a major issue. To assess and monitor the consequences, Onema ordered a three-year study (2010- 2012) from BRGM in view of setting up a piezometric reference network (a piezometer in a device to monitor groundwater levels).

Effective rainfall is the essential parameter

The BRGM researchers first identified 237 groundwater bodies requiring priority monitoring due to their sensitivity to climate change. They did so by cross-checking the existing database on groundwater bodies with estimates on changes in effective rainfall, i.e. the difference between total precipitation and evaporation, for the period 2041 to 2065. The data on effective rainfall were provided by Explore 2070, a project run by the Ecology ministry. Of the 237 water bodies, they then selected 105 existing piezometer stations (one per water body) as the basis for the future network. Another 130 water bodies still require additional work to correctly position a piezometer station.

A standardised indicator in the future

To make the monitoring network complete, the researchers have proposed a standardised indicator for groundwater levels. Though many aspects still require work, the indicator will make it possible to consistently characterise the piezometric level of unconfined groundwater on the regional or national level, to monitor the evolution of levels over time and to quantify the impact of climate change.

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