The aim of this thesis is to quantify the impact of human activities on hydrology and their evolution over time in the Haut-Allier watershed. The methodology adopted relies on a distributed hydrological model, J2000, and a historical reconstruction approach, starting from the second half of the 19th century, by simulating the hydrology of three sub-periods: 1870-1900, 1940-1970, and 1990-2020.

A current challenge in hydrology is supporting territories and water resource managers in their strategies for adapting to climate change. To achieve this, it is necessary to understand the impacts of human activities on watershed hydrology. This thesis aims to reconstruct streamflow data since the late 19th century, taking into account major anthropogenic impacts (climate change, land use, water extraction for irrigation and drinking water, and storage infrastructure management), as well as their spatial and temporal evolution to better understand the hydrological evolution of an anthropized watershed.
The study area will be the Haut-Allier watershed near Vieille-Brioude (2300 km²), which has undergone significant reforestation since the 19th century. It is also a critical water resource (particularly through the Naussac dam), with significant usage concerns related to energy production (hydroelectricity and nuclear power) and irrigation downstream. The thesis will employ a spatially distributed hydrological modeling methodology, using the J2000 model, to quantify the impacts of human activities on river discharge within the watershed, as well as on various components of the hydrological balance.

The research questions are as follows:

• Can we reconstruct the hydrology of a watershed under both non-stationary climate conditions and non-stationary human activities through distributed hydrological modeling?
• How do different anthropogenic influences impact the hydrology of the watershed? Can we quantify their relative contributions to streamflow and other components of the hydrological balance ?
• What are the combined and/or cumulative effects of human activities on hydrology ?

Funding:

• 50% INRAE AQUA Department,
• 50 % ANR project BlueState

References

• Blösch et al. (2019). Twenty-three Unsolved Problems in Hydrology (UPH) – a community perspective. Hydrological Sciences Journal, 64(10), 1141–1158. https://doi.org/10.1080/02626667.2019.1620507
• Cinotti, B. (1996). Évolution des surfaces boisées en France: proposition de reconstitution depuis le début du XIXe siècle. Revue forestière française, 48(6), 547-562. https://dx.doi.org/10.4267/2042/26776
• Boyer, F. (2019) Le retour des forêts françaises, Confins; 39, https://doi.org/10.4000/confins.19070
• Flora Branger, Louise Mimeau, Louise Crochemore, Jeremie Bonneau, Baptiste Lévêque, et al.. Usages de l'eau et changement climatique sur le bassin du Rhône: quantification de l'impact sur la ressource de différentes stratégies d'adaptation. INRAE. 2024, 73 p. ⟨hal-05202062⟩