Analysis of groundwater level historical data to detect climate change impact in France

Abstract : The level of groundwater bodies depends for many of them on the infiltration of meteoric water and will therefore be necessarily impacted by climate change if it causes a change in the infiltration system (intensity, period). To assess and monitor the impact of this change, a dedicated groundwater monitoring network is necessary. As this impact is currently unclear, the implementation of such a network involves an analysis of existing groundwater level data series. The study was based on Mann-Kendall trend detection tests from groundwater level data and a comparison of trends between groundwater level data and climate data (precipitation, temperature, potential evapotranspiration). Trend detection tests were carried out on 377 piezometers of the french national groundwater quantitative monitoring network for which we had a data series of at least 25 years. In the end, 70 have a significant trend, 44 down and 26 up. Piezometers showing significant trend mostly concern aquifers with predominant annual hydrologic cycle. But most of aquifers in France have longer hydrologic cycles and statistical tests are not relevant because the data are autocorrelated and we do not have at our disposal long time series which are required for such tests. A sketch of spatial structuring trends has been identified, with rising levels for chalk aquifer in the Artois-Picardie basin and the center of the Seine-Normandy Basin and lower levels for chalk and Jurassic limestones aquifers in eastern Seine Normandy basin. Trends upward or downward may in some cases be influenced by groundwater pumping without that one can be demonstrated. The break tests show that the behavior change corresponds to the years in which water levels are significantly higher or lower than average or to the years that precede or follow these events. Finally, a tool for lumped hydrological modelling (Gardenia) was used to test the sensitivity of the groundwater level variations to potential evapotranspiration (PET). The results show that these variations have a relatively small impact on the groundwater levels, especially compared with model uncertainties. In conclusion, this study shows that we cannot demonstrate a significant impact of climate change on groundwater levels because of too short time series but it reinforces the need to set up a monitoring network dedicated to the impact of climate change on groundwater. In order to set up that network, about 40 aquifers were selected with following creteria : unconfined aquifer, recharge likely to be impacted by climate change, large piezometric fluctuations, aquifer weakly impacted by withdrawals, aquifer to preserve for the future. To select piezometers for each aquifer, the main criteria was a low anthropogenic impact
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Soumis le : jeudi 10 septembre 2015 - 11:45:19
Dernière modification le : vendredi 11 septembre 2015 - 01:09:14


  • HAL Id : hal-01196690, version 1



Jean-François Vernoux, Jean-Jacques Seguin. Analysis of groundwater level historical data to detect climate change impact in France. Our Common Future under Climate Change (CFCC) Conference : International scientific conference, Jul 2015, Paris, France. ⟨hal-01196690⟩



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