22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

: The resilience of the Alsatian aquifer, France to climate and anthropogenic change

24 Sep 2019, 12:15
15m
Multiuse room 1 ()

Multiuse room 1

Oral Topic 2 - Groundwater and climate change Parallel

Speaker

Ms Agnès Labarchède (LIVE (Institute of Imagery, City and Environment) - UMR 7362, Faculty of Geography and Regional Planning, University of Strasbourg, France)

Description

The vulnerability of the Alsatian aquifer to climate change and water abstraction has hardly been investigated whilst climate change impacts such as decreasing snowfall, droughts and heat waves are becoming stronger and water abstraction for irrigation is seasonally intensifying as a result. Despite being influenced by a European temperate climate, seasonal drying of springs and streams have been recently observed in the Middle Alsatian Plain and drought decrees in Alsace have intensified. The Alsatian aquifer, an alluvial aquifer located on the French side of the Upper Rhine, is one of the largest aquifers in Europe. It not only provides drinking water to approximately 1.5 million inhabitants but is also a highly important water supply for industry and irrigation. This study aims to improve our understanding of the interactions between groundwater levels of the Alsatian aquifer and river discharge during drought periods. Lying within the Upper Rhine Graben, this complex basin is flanked by the Vosges and Black Forest mountains to the West and East respectively. As such, the aquifer is influenced by both the River Rhine, its main tributaries and the Vosges mountains. At present, it is difficult to differentiate climate and anthropogenic signals in groundwater level lowering. In this study, spatial and temporal correlations of river discharge and groundwater levels are carried out based on meteorological and hydrological data available since 1955 from national and regional agencies, field studies and modelling. A high-resolution analysis at daily time steps is performed at representative sites in Alsace. In a first step, the focus is placed on extreme drought years such as 1976, 2003, 2015 and 2017. Climate change has decreased snow storage and snow water equivalent as well as increasing periods without precipitation and thereby increasing evapotranspiration over the last decades. Even though irrigation represents on average only 26% of groundwater abstraction in the Upper Rhine Department and 11% in the Lower Rhine Department over a territory that is 50% agricultural, water withdrawals are concentrated over a few months and their impacts are visible. First results show a strong link between summer water abstraction for irrigation and drying of streams implying that the impact of water abstraction could outweigh that of climate change during summer droughts. Because they can affect the sustainability of drinking water supply, biodiversity and economic activities, awareness on droughts impacts and water abstraction should be increased.

Primary author

Ms Agnès Labarchède (LIVE (Institute of Imagery, City and Environment) - UMR 7362, Faculty of Geography and Regional Planning, University of Strasbourg, France)

Co-authors

Prof. Carmen de Jong (LIVE (Institute of Imagery, City and Environment) - UMR 7362, Faculty of Geography and Regional Planning, University of Strasbourg, France) Dr Serge Dumont (LIVE (Institute of Imagery, City and Environment) - UMR 7362, Faculty of Geography and Regional Planning, University of Strasbourg, France)

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