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Estimation de la contribution des principaux aquifères du bassin versant de la Loire au fonctionnement hydrologique du fleuve à l'étiage

Abstract : The evolution of the Loire river low flows is a key issue for various uses such as water supply, irrigation or industrial needs. Power production is a major activity in the Loire basin with four nuclear power plants using the river water for the cooling system. To estimate the evolution of long term in-stream low flow distribution, it is necessary to have a good estimate of the contribution of a complex aquifer system to the river discharge. Three main overlaying aquifer units covering an area of 38000 km² are considered: Beauce Limestones (Oligocene), Chalks (Seno-Turonian) and Sands (Cenomanian). A distributed hydrogeological model (Eau-Dyssée) is implemented with the coupling of five modules: surface water budget, watershed routing, river routing, unsaturated zone transfer, and groundwater flow. The model is calibrated over a 10-yr period, validated over another 10-yr period, and then a test simulation is run over 35 years. A hybrid fitting methodology, based on an automated inverse method and a trial-error one, has been developed for the fitting of the Beauce aquifer unit. The other units are calibrated by trial and error. The fitted model simulates properly both discharges and piezometric heads over the whole domain, with a global RMSE between simulated and observed piezometric heads of 2.86 m, and all Nash efficiency at the Loire discharge gauging stations over 0.9. The fitted model has then been used to quantify the hydrosystem mass balance at different time scales. Mean aquifer contribution to Loire river discharge during low flow between 1975 and 2008 is estimated at 15 m3/s. First results of simulations under four different climate change projections indicate an averaged decrease of these contributions reaching 8 to 50% in 2100.
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Submitted on : Wednesday, March 7, 2012 - 10:29:40 AM
Last modification on : Monday, October 19, 2020 - 10:55:29 AM
Long-term archiving on: : Friday, June 8, 2012 - 2:22:00 AM

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  • HAL Id : pastel-00677056, version 1

Citation

Céline Monteil. Estimation de la contribution des principaux aquifères du bassin versant de la Loire au fonctionnement hydrologique du fleuve à l'étiage. Hydrologie. École Nationale Supérieure des Mines de Paris, 2011. Français. ⟨NNT : 2011ENMP0067⟩. ⟨pastel-00677056⟩

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