1. Centre d’Ingénierie Hydraulique IEA GUIDELINES VOLUME 2 MODELING POST-IMPOUNDMENT EMISSIONS HYDRO 2015, Bordeaux, 26-28 October 2015 PowerPoint 2007 Pour appliquer ce modèle à une présentation existante : supprimez toutes les diapos de ce document, puis, onglet [Accueil], "Nouvelle diapositive", "Réutiliser les diapositives", dans le volet Office à droite, cliquez sur [Parcourir], "Rechercher le fichier", une fois le fichier sélectionné, clic droit sur une de ses miniatures, "Insérer toutes les diapositives". NB : ne pas cocher "Conserver la mise en forme source" en bas du volet d'insertion. © CERVOS Vincent Chanudet, Stéphane Descloux

2. | 2 CONTEXT DONE !

3. | 3 MODELING IMPLIES CHOICES ! http://scientiasalon.wordpress.com http://riverrestoration.wikispaces.com Images from:

4. | 4 MODELING IMPLIES CHOICES ! Complexity → time, money, required data but also precision, accuracy

5. | 5 MODELING IMPLIES CHOICES ! Auvergne-Tourisme 1D vertical is enough (?)… …3D is probably better (?) Water intake Dam O2O2 Adapted to the question to be answered!

6. | 6 WHY HYDRODYNAMIC IS SO IMPORTANT? First stage: get a proper hydrodynamic simulation (residence time, current velocity, thermal stratification…) - Processes governing WQ/GH are time dependent. Example: methane production - Produced or incoming chemical compounds are then transported in the reservoir Inlet Outlet t0t0 t1t1 Hydro 1 Hydro 2 Stratif. Res. time + + --

7. | 7 WHY HYDRODYNAMIC IS SO IMPORTANT? First stage: get a proper hydrodynamic simulation (residence time, current velocity, thermal stratification…) - Processes governing WQ/GH are time dependent. Example: methane production - Produced or incoming chemical compounds are then transported in the reservoir The hydrodynamics of the system (reservoir or river) should be thoroughly simulated and results should be carefully analyzed. => Potential hotspots or intense emission periods can be detected

8. | 8 FROM WQ TO GHG MODELS… WQ model, without GHGs, could be used as a first estimation tool to assess the potential GHG production and emissions. Example of O 2 and CH 4, Deshmukh et al. 2015 A process-based model simulating only GHG does not exist, but…

9. | 9 FROM WQ TO GHG MODELS… WQ model, without GHGs, could be used as a first estimation tool to assess the potential GHG production and emissions. If this approach is not enough then, GHGs, namely CO 2, CH 4 and N 2 O, should be considered as additional water quality parameters

10. | 10 FROM WQ TO GHG MODELS… WQ model, without GHGs, could be used as a first estimation tool to assess the potential GHG production and emissions. If this approach is not enough then, GHGs, namely CO 2, CH 4 and N 2 O, should be considered as additional water quality parameters GHG model should be able to simulate fluxes (and not only concentrations)

11. | 11 THE KEY POINT: THE DATA Data is required for the forcing inputs (meteorology, discharges, bathymetry, exploitation, chemical concentration in the rivers…), the initial conditions, the calibration and validation phases (temperature profile, chemical compound concentrations, fluxes…). Special care should be taken when collecting, validating and using data No good data = no reliable results

12. | 12 LAST BUT NOT LEAST: CALIBRATION AND VALIDATION This stage is crucial !!! The calibration should be done: on a sufficiently long period (at least one year) to be sure to cover seasonal variations, using statistical tools Chanudet et al., 2015

13. | 13 CONCLUSION Key messages : 1.The choice of the model (simplifications) should be made considering the question to be answered and knowing the advantages and drawbacks 2.The modeling assumptions and methodology should be transparently described 3.Data should be thoroughly analyzed and validated 4.The results should be always criticized keeping in mind the model content 5.The results and their uncertainties should be reported using the best scientific principles

14. | 14 THANK YOU ! “No one trusts a model except the man who wrote it; everyone trusts an observation, except the man who made it.” Harlow Shapley