This thesis focuses on the issue of river water temperature, particularly on characterizing the impact of groundwater contribution to thermal regimes.
The methodology relies on hydrological and thermal signatures, as well as a distributed hydrological model (J2000) and a physically-based thermal model (T-NET), both coupled.

Characterizing the thermal habitat of rivers, especially in the context of climate change, is a recent research area, with few available data and modeling tools. However, in recent years, local stakeholders have instrumented numerous rivers to assess the impact of river warming on ecological communities. The objective of this thesis is to characterize the thermal habitat of rivers at a regional scale, specifically the Saône River Basin, and to make use of this data by coupling a distributed hydrological model (J2000) and a physically-based thermal model (T-NET), both developed within the research unit. This objective can be broken down into several questions:

      - How to characterize thermal regimes to assess river sensitivity to low-flow discharges? More generally, how can hydrological and thermal signatures be used to improve model performance or characterize the vulnerability of ecosystems?
      - What is the sensitivity of water temperature to the influence of groundwater and groundwater-river exchanges in a lithologically contrasting watershed, and how can this be taken into account in modeling?

The methodology involves a set of hydrological and thermal signatures from the literature, calculated on 87 and 347 stations in the watershed, respectively, and analyzed together to reveal their complementarity in characterizing the influence of the dominant lithology of the watersheds on different aspects of hydrological and thermal regimes.

The J2000 and TNET models were then implemented and coupled on the Saône River Basin. While satisfactory calibration of the hydrology was achieved in terms of classic performance criteria, the thermal model still shows biases, and the diagnosis of these issues is still to be refined.

Funding

• 50% INRAE UR RIVERLY
• 50% Agence de l’Eau Rhône Méditerranée Corse.

References

• Hare, D.K., Helton, A.M., Johnson, Z.C., Lane, J.W., Briggs, M.A., 2021. Continental-scale analysis of shallow and deep groundwater contributions to streams. Nat Commun 12, 1450. https://doi.org/10.1038/s41467-021-21651-0
• Johnson, M.F., Wilby, R.L., Toone, J.A., 2013. Inferring air-water temperature relationships from river and catchment properties: AIR-WATER TEMPERATURE RELATIONSHIPS IN RIVERS. Hydrol. Process. n/a-n/a. https://doi.org/10.1002/hyp.9842
• Kessler, K., Rogers, K., Marsh, C., Hitt, N., 2023. Karst Terrain Promotes Thermal Resiliency in Headwater Streams. Proc. W. Va. Acad. Sci. 95. https://doi.org/10.55632/pwvas.v95i3.947
• Leach, J.A., Moore, R.D., 2019. Empirical Stream Thermal Sensitivities May Underestimate Stream Temperature Response to Climate Warming. Water Resour. Res. 55, 5453–5467.https://doi.org/10.1029/2018WR024236
• O’Driscoll, M.A., DeWalle, D.R., 2006. Stream–air temperature relations to classify stream–ground water interactions in a karst setting, central Pennsylvania, USA. Journal of Hydrology 329, 140–153. https://doi.org/10.1016/j.jhydrol.2006.02.010
• Poole, G.C., Berman, C.H., 2001. An Ecological Perspective on In-Stream Temperature: Natural Heat Dynamics and Mechanisms of Human-CausedThermal Degradation. Environmental Management 27, 787–802. https://doi.org/10.1007/s002670010188
• Rockstrom, J., 2013. Balancing Water for Humans and Nature, 0 ed. Routledge. https://doi.org/10.4324/9781849770521
• Seyedhashemi, H., 2022. Influence des retenues d’eau et du changement climatique sur la température des cours d’eau: modélisation à haute résolution et application au bassin de la Loire (PhD Thesis).
• Vörösmarty, C.J., McIntyre, P.B., Gessner, M.O., Dudgeon, D., Prusevich, A., Green, P., Glidden, S., Bunn, S.E., Sullivan, C.A., Liermann, C.R., Davies, P.M., 2010. Global threats to human water security and river biodiversity. Nature 467, 555–561. https://doi.org/10.1038/nature09440

For more information

Rouchy, L., Branger, F., Moatar, F. Hydrological and thermal signatures to characterize groundwater contribution to streams at a regional scale., in prep.