Thesis defense of Jordan Labbe
Study of the vulnerability and reactivity of alluvial hydrosystems
to global change
Date and hour : October, 20, 2023 at 14:30 (Paris, GMT+2).
Abstract :
Alluvial hydrosystems are a favoured water resource for irrigation, industry and drinking water supply. These aquifer systems are shallow, permeable and therefore easy to exploit. It is these very characteristics that make them water resources under pressure in the face of global change. For example, in the catchment area of the River Allier (14,300 km²), rainfall, flow rates and alluvial groundwater levels are falling and abstractions by various uses are rising (Labbe et al., 2023). The river Allier is experiencing increasingly intense and recurrent low-water periods. The consequences of this reduction in flow over long periods on the Allier hydrosystem, and more particularly on the alluvial aquifer, are not known and are of concern to water resource managers. A rainfall-flow model in GARDENIA can be used to test different climatic scenarios. This shows that, by 2030-2070, river flows and groundwater levels will be falling. On a finer scale, numerical modelling using MODFLOW shows that while the Val d’Allier catchment field, used to supply drinking water to the town of Clermont-Ferrand, is still likely to meet water requirements, the drawdowns indicate a potential strain on the resource that will need to be taken into account in its future management. This phenomenon is amplified if the Allier continues to incise in its bed. At the alluvial scale, we use various methods (hydrodynamic, geophysical, descriptive and distributed temperature measurements) to demonstrate their heterogeneity, which has a direct impact on underground flows and therefore on the transport properties of the environment. Our integrated approach at different scales, using the Allier hydrosystem as an example, provides a better understanding of the complexity of the alluvial environment and offers food for thought in terms of its current and future management.
Location : Amphi Duffieux, Propédeutique building, UFR Sciences et Techniques, Besançon.
The presentation will be in French.
