The main objective of this thesis is to quantify the impact and sustainability of small-scale "substitution" reservoirs in the context of global change, at the regional scale.
The methodology adopted is based on a distributed hydrological model, J2000, and a scenario-based approach to reconstruct databases on the characteristics and uses of current and future reservoirs.

Climate change increases the risk of water scarcity through higher probabilities of droughts and heatwaves, even in temperate climates. "Substitution" water reservoirs, which allow for storing water extracted in winter (from catchments, rivers, or groundwater) for use in summer, are considered by some stakeholders as an adaptation strategy for agriculture in response to climate change. However, there is currently no clear national regulation or policy on this issue, which complicates decision-making and fuels controversy. How can we ensure their sustainability in the context of global change? Sustainability, in this context, is understood in eco-hydrological terms: will the reservoirs be able to provide the required amount of water while preserving aquatic environments?

This thesis proposes to build and apply a methodology based on distributed hydrological modeling to quantify the impact and sustainability of these reservoirs in the context of global change, focusing on the Rhône and Loire River basins at the regional scale. Specifically, it will address scientific challenges related to: (i) the regional or even national scale, characterized by the heterogeneity of climate, soil types, dominant agricultural activities, irrigation practices, reservoirs, and their potential uses; and (ii) the limited data available on reservoirs.

The work will be based on the existing J2000 distributed hydrological model for these basins. Scenario-based work will be essential for constructing plausible scenarios for the existence and use of reservoirs, using data that is only partially available at the local scale. We hypothesize that (i) the use of spatially distributed hydrological modeling will allow for the integration of all the hydrological processes involved, including those related to water use (irrigation), the representation of variables beyond outlet flow (evapotranspiration, soil moisture, groundwater recharge, flow across the entire hydrographic network), and climate projections, to obtain a comprehensive view; (ii) the scenario-based methodology will allow us to make the best use of local data and knowledge, replicate it, and scale it up by building typologies, with a prospective rather than predictive goal. Rather than striving for completeness, the aim is to quantify possible trajectories that highlight vulnerabilities in the territories and encourage reflection.

Simulations will be conducted using these scenarios and climate change projections. These will be analyzed in terms of hydrological balance indicators, the ecological impact of water extractions, and the satisfaction of water demand. The goal is to provide quantitative elements to support public policies.

Funding

• 50% INRAE, AQUA Departement
• 50% OFB.

More information

• Blöschl, G., […], Vidal, J.-P., […] (2019) Twenty-three unsolved problems in hydrology (UPH) – a community perspective, Hydrological Sciences Journal, 64:10, 1141-1158, DOI: 10.1080/02626667.2019.1620507
• Bonneau, J., Branger, F., Castebrunet, H. and Lipeme-Kouyi, G. (2023): The impact of stormwater management strategies on the flow regime of a peri-urban catchment facing urbanisation and climate change: a distributed modelling study in Lyon, France, Urban Water Journal, DOI: 10.1080/1573062X.2023.2217809
• Branger, F., Bonneau, J., Pouchoulin, S., and Sauquet, E.: Cumulative impact of farm dams on catchment water balance and streamflow dynamics at the regional scale. A numerical experiment using a distributed hydrological model., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8106, https://doi.org/10.5194/egusphere-egu23-8106, 2023
• Morel, M., Pella, H., Branger, F., Sauquet, E., Grenouillet, G., Côte, J., Braud, I., & Lamouroux, N. (2023). Catchment-scale applications of hydraulic habitat models: Climate change effects on fish. Ecohydrology, 16(3), e2513. https://doi.org/10.1002/eco.2513
• Sauquet E., Arama Y., Blanc-Coutagne E., Bouscasse H., Branger F., Braud I., Brun J.-F., Chérel Y., Cipriani T., Datry T., Ducharne A., Hendrickx F., Hingray B., Krowicki F., Le Goff I., Le Lay M., Magand C., Malerbe F., Mathevet T., Mezghani A., Monteil C., Perrin C., Poulhe P., Rossi A., Samie R., Strosser P., Thirel G., Tilmant F., Vidal J.-P. (2016). Le partage de la ressource en eau sur la Durance en 2050 : vers une évolution du mode de gestion des grands ouvrages duranciens ? La Houille Blanche, 5: 1-6, http://dx.doi.org/10.1051/lhb/2016046