Decreasing trend of groundwater recharge with limited impact of intense precipitation: Evidence from long-term lysimeter data
Tendance à la baisse de la recharge des eaux souterraines avec un impact limité des précipitations intenses : données lysimétriques à long terme
Sobaga, Antoine ; Habets, Florence ; Beaudoin, Nicolas ; Léonard, Joël ; Decharme, Bertrand
Groundwater recharge is a key component of the hydrological cycle but it is a complex process difficult to observe. Direct observations are essential to improve our understanding of this process, and lysimeters are the only powerful tools to reach this goal. In this study, we analyze 45 years of drainage data from 10 lysimeters located in the north-east of France (Fagnières) in order to understand the mechanisms controlling groundwater recharge in this region. These observations enable to assess groundwater recharge behavior as a function of several factors: climate, land use and agricultural practices. In this study, we first parse the long-term evolution of the groundwater recharge as a function of all these factors, and secondly we conduct a specific analysis on the impact of intense precipitation events on lysimeters drainage. A decreasing trend of the groundwater recharge over the last 45 years (average of ?2.5 mm year?1) is found in relation to an increase in evapotranspiration which is in turn mainly driven by an increase in near surface air temperature and solar radiation, and a decrease of relative air humidity. Crop type and some agricultural practices (duration of rotation, catch crops) also impact the recharge rate. Finally, intense precipitation events represent 15% of annual precipitations and on average 15% of the recharge, while most of these events do not generate recharge because they occur mainly in summer. Only a few intense precipitation events in spring or summer time generate an important recharge event, and are associated with the most important accumulated precipitation.</p>
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