Quels futurs possibles pour les débits des affluents français du Rhin (Moselle, Sarre, Ill) ?

Abstract

Le projet MOSARH21 a réalisé une évaluation des effets du changement climatique anthropique sur les débits des affluents français du Rhin grâce à des projections climatiques récentes (expérience CMIP5). La démarche s'appuie sur deux modèles hydrologiques, GRSD et LARSIM, utilisés conjointement avec un ensemble de projections climatiques désagrégées. Les effets sont quantifiés à l'aide de divers indicateurs relatifs aux régimes des cours d'eau, aux crues et aux étiages. Les projections hydrologiques indiquent que les débits moyens interannuels seraient en légère augmentation, celle-ci pouvant même devenir importante pour le scénario radiatif RCP 8.5 (scénario le plus pessimiste en termes de réchauffement climatique). L'aléa de crue devrait s'intensifier dans un futur proche (2021–2050). En revanche, dans un futur lointain (2071–2100), l'évolution des indicateurs de crue est incertaine, les projections hydrologiques étant divergentes. Les débits d'étiages diminueraient dans un futur proche. Leur évolution pour la fin du siècle est plus incertaine, allant de la baisse drastique à une augmentation sensible selon le scénario choisi. Les résultats ont été comparés à ceux obtenus dans le cadre d'études d'impact antérieures réalisées dans la partie française du bassin du Rhin. Compte tenu des différences méthodologiques et des résultats obtenus, on peut conclure que la base de connaissances actualisée produite dans le cadre du projet MOSARH21 valide les tendances des études précédentes.

Discharge and Water Quality of the River Moselle from 1990 to 2020 as Related to Climatic Changes and De-Industrialization

“…A 150-year reconstruction of low flows for the Moselle River has been presented previously, confirming that the extreme low flows in the summers of 1976, 2003 and 2018 were unprecedented [33]. Nevertheless, the severity and frequency of floods will most likely intensify in the Moselle catchment in the near future (2021-2050), as has been modelled by Thirel et al [30]. In contrast to the Moselle, no relationship between precipitation sums and annual discharges of seven streams was found in the Baltimore region, but an increase in winter precipitation sums was confirmed [28].…”

“…A 150-year reconstruction of low flows for the Moselle River has been presented previously, confirming that the extreme low flows in the summers of 1976, 2003 and 2018 were unprecedented [33]. Nevertheless, the severity and frequency of floods will most likely intensify in the Moselle catchment in the near future (2021-2050), as has been modelled by Thirel et al [30].…”

“…In contrast to the Moselle, no relationship between precipitation sums and annual discharges of seven streams was found in the Baltimore region, but an increase in winter precipitation sums was confirmed [28]. Future changes in the seasonality, discharge regimes and flooding risks in the Rhine-Moselle catchment area can be studied using regional circulation and ecohydrological models under different climate change scenarios [29,30]. Still, it must be noted that such models will not be able to predict flooding events such as the Nancy flash flood 21/22 May 2012 [31] and, more recently, the catastrophic Ahr flooding of 14/15 July 2021.…”

“…Together with the increasing heat sum and thus a evapotranspiration from the land surface, the lower quantities of rainfall and dis may be perceived as an indicator of climatic change in the Moselle catchment area ever, such evaluations should be based on more than one measuring station and from climatic change, should consider changes in land cover and management [27 In contrast to the Moselle, no relationship between precipitation sums and annual discharges of seven streams was found in the Baltimore region, but an increase in winter precipitation sums was confirmed [28]. Future changes in the seasonality, discharge regimes and flooding risks in the Rhine-Moselle catchment area can be studied using regional circulation and ecohydrological models under different climate change scenarios [29,30]. Still, it must be noted that such models will not be able to predict flooding events such as the Nancy flash flood 21/22 May 2012 [31] and, more recently, the catastrophic Ahr flooding of 14/15 July 2021.…”

Combined Impacts of Climate Change and Water Withdrawals on the Water Balance at the Watershed Scale—The Case of the Allier Alluvial Hydrosystem (France)

“…Habets et al (2013) [56] agreed with a global decrease in streamflows and groundwater levels in the Seine and the Somme River basins. The results were more contrasted for Thirel et al (2019) [93] who forecasted a slight increase in the annual discharges of the Rhine River, which was even more important in RCP8.5, and a decrease in low flows by 2050. A more global study carried out at the French territory scale (Explore 2070 project, [94]) reported, in accordance with our results, a general decrease in river streamflows from 10% to 40%, with a stronger decrease in summer low flows.…”