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This study deals with the impact of spatio-temporal heterogeneities on the assessment of lake ecological status according to the European water framework directive (WFD). A method, based on three-dimensional coupled hydrodynamic and ecological modeling, is presented to assess the variability of lake ecological status, and to locate the most representative sampling station of Lake Geneva (France/Switzerland). Five variables used in the lake ecological status evaluation were simulated by using the free software Delft3D. The numerical simulation results showed that the simulated ecological status based on chlorophyll a and total phosphorus concentrations measured at the regulatory monitoring station depend on the choice of the sampling date. Results also indicated a strong spatial heterogeneity in ecological status that varies from “poor” to “good” along an East-West gradient. Finally, the numerical simulation results showed that the most representative point of a mean theoretical ecological quality for Lake Geneva would be located in the center of the upper basin, close to the historical sampling station.

To better qualify the ability of nuclear power to contribute to the net-zero emissions transition, the nuclear power sector needs to understand its sensitivity to hydro-climatic and anthropogenic stresses at the local level. While current approaches based on statistical modelling can be used to assess climate change impacts on electricity networks at a global or national level, they are limited when extrapolated to regulatory thresholds at a local level. As part of a series of two papers aimed at assessing the impact of climate change on site-specific nuclear power outages, this paper presents a modelling chain for estimating hydro-climatic-policy scenarios for nuclear power generation. The second one will implement the modelling chain in context of climate change, based on downscaled IPCC scenarios, and applies the method to two contrasted French nuclear power plants. The modelling framework (power outages modelling bias of +7.0 %) appears as a strong basis for investigating the impact of climate change on nuclear power outages in terms of frequency and magnitude. Such work could inform on the evolving sensitivity of the nuclear fleet to support the energy grid, to potentially optimize its management, and to define water-energy nexus levers to better anticipate the effects of climate change. • Transferable methodology to evaluate the power outages for a nuclear power plant under a hydro-climatic policy scenario. • Improved understanding of nuclear plant sensitivity, considering local constraints. • Ability to assess cumulative sensitivity of current or planned nuclear fleet. [ABSTRACT FROM AUTHOR]