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Évolution des températures de l'épilimnion et de l'hypolimnion des plans d'eau DCE nationaux

Abstract : Water temperature is one of the most important physical variables for freshwater ecosystem organisms. Its vertical distribution in water bodies also gives rise to physicochemical gradients, affecting other equally important variables such as dissolved oxygen concentration. Furthermore, water temperature and dissolved oxygen concentration are 2 of the 6 physicochemical parameters supporting the biological parameters in the European Water Framework Directive and must be taken into account in the assessment of the state of water bodies. The 2016-2018 number CK Onema action, aims at the determination of the threshold values and the reference conditions for water temperature and dissolved oxygen. The determination of threshold values and reference conditions for water temperature must take into account the interannual and intra-annual variability of natural origin and, where appropriate, the mandatory technical constraints derived from the management of water bodies. This analysis should be based on available data and knowledge of the physical functioning of lake ecosystems. To optimize the use of available data (generally rare and at discrete times for WFD water bodies) and the exploitation of existing knowledge in physical limnology, the proposed solution is the use of hydrodynamic models physically based, especially GLM: General Lake Model. Hydrodynamic models are tools that simulate the thermal and hydrodynamic behaviour of a water body using meteorological, hydrological, hydromorphological and water transparency data. But models are approximations of reality and therefore limited. Their limitations derive either from the input data (bias, measurement errors, measurement frequency, etc.) or from the model itself (model implementation, undetected bugs, parametrization of physical phenomena, etc.). And the uncertainty due to these limitations must be taken into account when interpreting their predictions. This report presents the application of the model GLM to the simulation of the hydrodynamic behaviour of the overall set of WFD water bodies. First, the configuration options are presented, as well as the models used to estimate the inflow temperature and hypsometric curve. Then, preliminary results, without calibration of the model, are presented. The effect of the use of estimated hypsometric data instead of measured bathymetries is also analysed.
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https://hal.inrae.fr/hal-02607210
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Submitted on : Saturday, May 16, 2020 - 1:48:42 PM
Last modification on : Friday, July 10, 2020 - 10:14:07 AM

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  • HAL Id : hal-02607210, version 1
  • IRSTEA : PUB00056949

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J. Prats, P.A. Danis. Évolution des températures de l'épilimnion et de l'hypolimnion des plans d'eau DCE nationaux. [Rapport de recherche] irstea. 2017, pp.34. ⟨hal-02607210⟩

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