Operational Flood Forecasting System for Isere River Basin in Moutiers, France

1. Towards an operational flood forecasting system taking into account hydro-power plants operations Isere River basin in Moutiers (Northern Alps of France) Aurélien CLAUDE 1, Isabella Zin1, Charles Obled1, Alain Gautheron2, Christian Perret3 (1) Laboratoire d’étude des Transferts en Hydrologie et Environnement, Grenoble, France (2) DDT de l’Isère - Service de Prévision des Crues Alpes du Nord, Grenoble, France (3) EDF - Division Technique Générale, Grenoble, France ISERE DDT/SPC Grant – Grenoble INP/LTHE

2. Introduction Isere River catchment in Moutiers Flow regime modification Hydrological modelling Conclusions Introduction - issues SPCAN : Service de Prévision des Crues des Alpes du Nord / French Northern Alps Flood forecasting service (belonging to Direction Départementale des Territoires de l’Isère, France) • needs to implement an integrated flood forecasting system for the alpine Isere River basin in Grenoble, France (5720 km²) « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 2

3. Moutiers outlet Isere River Surface area = 5720 km² 2bis

4. October 2000 flood Reconstructed flows that would have observed in the naturals conditions (without hydropower system) Observed flows Introduction Isere River catchment in Moutiers Flow regime modification Hydrological modelling Conclusions Introduction - issues • SPCAN : Service de Prévision des Crues des Alpes du Nord / French Northern Alps Flood forecasting service (belonging to Direction Départementale des Territoires de l’Isère)  needs to implement an integrated flood forecasting system for the alpine Isere River basin in Grenoble, France (5720 km²) • A rain and snowmelt dominated regime...consequently :  have to taking into account snowmelt in the flood forecasting • The influence of this hydropower system on the river flows can be significant • So what modelling should we develop to take into account hydraulic devices in an operational context ? « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 2

5.  Storage Introduction Isere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Isere River catchment in Moutiers • Morph. characteristics • 909 km² • Elevation • - minimal : 468m • - median : 2200m • - maximal: 3840m • Glacial area : 4.5% • Hydro-electric devices • 2 accumulation reservoirs • 1 compensation reservoir • 49 water intakes • 9 hydropower plants • > 60 km of pipes, tunnels •  1import from the South • 1storage in Tignes Dam (230 Millions of m3 equivalentto30% of the observed annual water volume at the outlet) •  2exports to the North-East « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 3

6.  Storage Introduction Isere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Isere River catchment in Moutiers ..Available dataset (daily time step) • Obs. meteorological data • temperature of 8 stations • precipitation of 13 stations • (EDF and MeteoFrance) • Hydrological and hydraulic data • daily observed streamflow • turbinate flows • daily levels and volumes of reservoirs • level-discharge and level-volume relationships for each reservoir (EDF) « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 4

7. IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Analysis of the human-induced natural flow regime modification 1) Preliminary step : reconstruction of the natural flow 2) Mean intra-annual water balance Explanation of the difference between influenced and reconstructed natural discharges (Isere River basin in Moutiers ; 1992-2006) « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 5

8. IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Analysis of the human-induced natural flow regime modification 3) Flooding period water balance • Study of the water intakes behaviour • In flood period, the diverted discharges of all intakes depends only on the event meteorology (no special management, except for the intakes from the South); • Explanation of the difference between influenced and reconstructed natural discharges for several selected events(Isere River in Moutiers ; 1992-2006) « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 6

9. P, T, PET inverse square distance with observations Simulated flow (+ snow heights, etc..) IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Hydrological modelling 1) Description of the model : Routing System 2 (EPFL-LCH; Dubois,J., et al., 2007)  semi-distributed approach • operational in the Valais Swiss canton • Simulated processes - snow(+glaciers) : degree-day method • - infiltration : GR3 model(Michel, Edijatno, 1988; Consuegra & al., 1998) • -runoff : SWMM model(Metacalf, Eddy, 1971) • - channel routing : Muskingum-Cunge(Cunge J.A., 1969) • - hydraulic devices : water intakes, storage variation, etc.. • Model parameters (8) (for each sub-basin) - degree-day factors (3) - release coefficients of linear reservoir (2) - capacity and release coefficient of infiltration reservoir (2) - Strickler coefficient for the surface runoff sub-model (1) • Model inputs and outputs • Precipitation • Temperature • - PET : method (Oudin, 2004) with above estimated temperature « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 7

10. 2 1 3 IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Hydrological modelling 2) Method of taking into account the hydro-electric works • 3 different representations of the hydro-eletric devices tested(with various degrees of refinement) • 1st : no hydro-electric work(1 sub-basin) • 2nd : storage variationsof the Tignes reservoir (Tignes dam outputs forcing into the model) • 3rd : all hydro-electric works(12 sub-basins)(Tignes dam outputs forcing and a passive modelling of water intakes) 3) Calibration strategy • For each configuration : A then B • A) natural catchment modelling • CALIBRATION with the natural reconstructed flow; • B)adding hydraulic devices • VALIDATIONwith the observed flows and the previous calibration « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 8

11. Isere River daily flow at Moutiers; 2001-2002 1 2 3 IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Hydrological modelling 4) Calibration results (natural conditions)  model sensitivity to the splitting of the basin into several sub-basins « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 9

12. Isere River daily flow at Moutiers; 2001-2002 1 Isere River daily flow at Moutiers October 2000 flood IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Hydrological modelling 4) Taking into account the hydro- electric system No hydro-electric works  it is really necessary to represent the Tignes outputs and the exports to Roselend  satisfactory results by considering a passive management of water intakes Tignes reservoir destocking represented + Export to Roselend taken into account « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 10

13. IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Conclusions • Importance of the preliminary analysis of the human-induced natural flow modification • To understand the hydraulic operations imposed by the hydro-power system, firstly at the inter-annual scale and finally during individual floods. • Highlighted a possibility to represent the hydro-electric system with a passive management of the water intakes, and not to consider special operations. • Hydrological modelling test • Identification of the better model architecture to reproduce the observed meteorological variability according to the available data(simulation 2 with 3 sub-basins). • All hydro-electric works have to be represented in order to obtain a plausible estimation of floods peaks •  Development of a rather simple approach and of an appropriate calibration strategy to • model a complex network that involves imports, exports and storages •  good point for a decision support tool « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 11

14. IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Perspectives • Taking into account the basin elevation  Test with a better estimation of the precipitation : reanalyzed data (EDF archive, Gottardi, 2009; Safran archive, Durand et al., 1993) (works presented in the Nivologie-Glaciologie SHF conference, Mars 2010, Cemagref Grenoble)  Simulation with a sub-basin splitting into elevation bands (currently in progress) • Evolution towards the hourly time step Need to convert both meteorological (M2R of P.Martinez in progress) and hydraulic daily data • Extension to the entire Isere River basin in Grenoble  Application of the same method « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 12

15. Thank you for your attention.. • Acknowledgements • The “Laboratoire de Constructions Hydrauliques” at EPFL-Lausanne has kindly provided the RS2 simulation package; • MeteoFrance provided part of the available hydro-meteorological data used; • EDF provided hydro-meteorological data, discharges data, waterworks characteristics and for some periods logs of their operations. • This study is financed by a PhD grant from the “Service de Prévision des Crues” at DDT38; We greatly thank all of them.

16. IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Hydrological modelling 2) Method of taking into account the hydro-electric works / Model calibration « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 9

17. “During floods, the same type of operation is observed, according to the both intensify and conditions of the event”.

19. October 2000 flood Reconstructed flows that would have observed in the naturals conditions (without hydropower system) Observed flows Introduction Isere River catchment in Moutiers Flow regime modification Hydrological modelling Conclusions Introduction - issues Comparison between natural and influenced flows of Isere River in Moutiers from 08-01-2000 to 07-31-2001 « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 2ter

20. Introduction Isere River catchment in Moutiers Flow regime modification Hydrological modelling Conclusions Introduction - issues • SPCAN : Service de Prévision des Crues des Alpes du Nord / French Northern Alps Flood forecasting service (belonging to Direction Départementale des Territoires de l’Isère)  needs to implement an integrated flood forecasting system for the alpine Isere River basin in Grenoble, France (5720 km²) • A rain and snowmelt dominated regime...consequently :  have to taking into account snowmelt in the flood forecasting most parts of the basin are often harnessed for hydropower (e.g. Marnezy, 2008; Jordan,F.,2007). • The influence of this hydropower system on the river flows can be significant • So what model should we choice to take into account hydraulics devices in an operationnal context ? « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 2

21. Introduction Isere River catchment in Moutiers Flow regime modification Hydrological modelling Conclusions Introduction – objectives and method • Objectives  to understand the human-induced natural flow regime modification …in order…  to check that the model adequately reproduces the influenced flows at the • outlet of the basin, notably the flood peaks • Method  to implement a hydrological modelling able …. • to developp a Rainfall-Runoff approach • - to reproduce the hydro-electric system impact on the flows • - to represent the snow-glacial regime • - to run with a time step adapted to the flood forecasting applied to this basin « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 3

22. Summary Introduction II) Isere river snow catchment in Moutiers III) Analysis of the human-induced natural flow regime modification IV) Taking into account these observations in the hydrological modelling Conclusions and perspectives « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 2

23. Malgovert Exports Natural flow known Tignes Moutiers Natural flow ? Imports IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Analysis of the human-induced natural flow regime modification 1) Preliminary step : reconstruction of the natural flow • Interests  to understand the natural flow modification by comparison with the observed flow  to calibrate the model in the naturals conditions (without hydropower system) • Reconstruction method  outlet natural flow = upstream natural flow + observed flow (output - input) – imports + exports + storage variation « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 5

24. Isere River daily flow at Moutiers; 2001-2003 1 2 3 IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Hydrological modelling 4) Calibration results (natural conditions)  model sensibility to the basin separation into several sub-basins (evolution from 1 to 2)  control points = limiting factor for the simulation optimisation (from 2 to 3) « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 9

25. A study of the water intakes behaviour (several selected events) by estimating the ratio Qdiverted by intakes(m3/s) showed that their management is passive. • intakes capacity(m3/s) (no human intervention except for those in the South) IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Analysis of the human-induced natural flow regime modification 3) Flooding period water balance  « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 8

26. Daily precipitation Daily minimal temperature Daily maximal temperature

28. P, T, ETP Simulated flow (and snow heights, etc..) IntroductionIsere River catchment in MoutiersFlow regime modification Hydrological modelling Conclusions Hydrological modelling 1) Description of the model : Routing System 2 (Dubois,J., et al., 2007) • developped at the Ecole Polytechnique Fédérale de Lausanne (EPFL-LCH, Swiss) • operational in the Valais Swiss canton  semi-distributed approach • modelled processus - Snow(+glaciers) : degree-day method -Infiltration : GR3 model(Michel, Edijatno, 1988; Consuegra & al., 1998) • -Runoff : SWMM model(Metacalf, Eddy, 1971) • - Channel routing : Muskingum-Cunge(Cunge J.A., 1969) • - Hydraulics devices : water intakes, storage variation, etc.. • model parameters (8) per sub-basin - 3 degree-day factors (snow above a glacier or not and glacier melt) - 2 release coefficients of linear reservoir (snow and glacier) - (2)capacity and release coefficient of infiltration reservoir - 1 Strickler coefficient for the surface runoff sub-model  model inputs and outputs • Precipitation : reanalyzed data (EDF-Gottardi, 2009) • Temperature : inverse square distancewith observations • ETP : method (Oudin, 2004) with above estimated temperature « Towards an operational flood forecasting system taking into account hydro-power plants operations » BALWOIS Conference / Topic 3: Water related risks / May 26th 2010 8

29. Comparaisons de la saisonnalité des crues et moyennes des débits de pointes observées de l’Isère à Moutiers avant et après ouvrages

30. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives Partie glaciaire (4 paramètres) Exutoire Partie nivale (4 paramètres) III) Sensibilité du modèle II.1. Modélisation hydrologique : Routing System 2 • Exemple d’architecture de Routing System 2 : modélisation d’un sous-bassin nivo-glaciaire • En présence de glaciers : • distinction des dynamiques nivale et glaciaire Cf. résultats de première année : - Prise en main du modèle - Tests de sensibilité Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 20

31. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives -Barrage de Tignes -Point de contrôle Global sans ouvrages (D1) Semi-distribué 3 sous-bassins (D2) -Barrage de Tignes -Prises d’eau par agrégation(couleur) -Point de contrôle -Barrage de Tignes -Prises d’eau individuelles Semi-distribué 12 sous-bassins (D3) Semi-distribué 60 sous-bassins (D4) II) Modélisation des ouvrages II.1. Modélisation hydrologique : les 4 découpages testés Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 21

32. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives II) Modélisation des ouvrages II.2. Résultats des modélisations hydrologiques • Conditions de modélisation • Pas de temps : journalier • Données d’entrée : estimations réalisées avec les Stations Virtuelles de RS2 sans gradient de P. • Calage : sans ouvrages pour ne pas y introduire l’incertitude liée à la représentation des ouvrages ; (QNR;1999-2002) • Validation : sans (QNR) etavec ajout des ouvrages (Qobs);(1997-1998 et2003-2005) Précipitation, Température et Lame écoulée annuelles du bassin de l'Isère à Moutiers -Anomalie à la moyenne annuelle- • Construction de quatre architectures de modèle correspondant aux quatre découpages définis • Critères de performances du modèle : • - numériques : Nash, Biais en volume, débits classés, corrélation Qobs-Qcal • - visuels : reproduction des crues (critère qu’on a privilégié), étiages et dynamique des périodes de fonte Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 22

33. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives 1 Point de contrôle 1 sous-bassin (D1) 3 Points de contrôle 3 sous-bassins (D2) CALAGE : Comparaison des QNR et des débits simulés sans ouvrages Débits journaliers de l’Isère à Moutiers du 01/04/2000 au 31/12/2000 3 Points de contrôle Nash et Biais en volume pour les modèles D1, D2 et D3  Moyenne des années 1999-2003 12 sous-bassins (D3) II) Modélisation des ouvrages II.2. Résultats des modélisations hydrologiques A) Calage des modèles D1 à D3 sans ouvrages (1999-2003; D4 pas encore réalisé) Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 23

34. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives - Barrage de Tignes - Point de contrôle 3 sous-bassins (D2) - Barrage de Tignes - Prises d’eau par agrégation D2D3 Nash 0.37 0.69 Vol 1.22 0.89 12 sous-bassins (D3) Comparaison des débits observés et simulés avec les modèles D2 et D3 - Débits journaliers de l’Isère à Moutiers du 01/08/1998 au 31/07/1999 - II) Modélisation des ouvrages II.2. Résultats des modélisations hydrologiques B) Introduction des ouvrages : validation des simulations (1997-1998 2003-2005) • Modèle D2: forçage de la sortie de Tignes (Qj turbinés des Brévières) • Modèle D3 : - forçage de la sortie de Tignes (Qj turbinés des Brévières) • - prises d’eau par agrégation(loi linéaire Qdérivé = f[Qentrant]) Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 24

35. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives Volume annuels (1997-2005) des simulations de D2 et D3 Nash annuels (1997-2005) des simulations de D2 et D3 II) Modélisation des ouvrages II.3. Conclusions • Le modèle D2 (sorties de Tignes seulement) surestime les débits observés • La considération des prises d’eau dans le modèle hydrologique est indispensable • La qualité des simulations du modèle D3 est meilleure mais néanmoins insuffisante Il devient nécessaire de tester la sensibilité du modèle aux forçages météorologiques (type de précipitation) Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 25

36. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives IV) Conclusions • Analyse des données d’ouvrages • Reconstitution des débits naturels afin de comprendre : • Le fonctionnement global des ouvrages du bassin • Evaluer les différents transferts d’écoulement à l’échelle moyenne interannuelle • La modification du régime naturel des écoulements de crue : -Les imports de la Maurienne (surplus des dérivés vers Mont-Cénis) sont difficiles à prévoir ; négligeable - Stockage dans la retenue de Tignes dépendant à la fois de sa cote initiale et de l’événement; environ ¼ des A.T. (envisageable : stockage complet des ARR > 60 m3/s) - Export vers Roselend = Q équipé des prises (sauf arrêt centrale des Sauces?); environ 1/6ème des A.T. - Q>90 m3/s à Moutiers : Qréel = 0.6 * Qnaturel Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 42

37. Plan I Données d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives - Barrage de Tignes - Point de contrôle 3 sous-bassins (D2) - Barrage de Tignes - Prises d’eau par agrégation 12 sous-bassins (D3) IV) Conclusions • Modélisation des ouvrages • Test de 2 différentes représentations des ouvrages •  D2 et D3 ont montré que la considération des prises d’eau dans le modèle hydrologique est • indispensable pour représenter correctement tous les imports et exports du bassin •  D3 a montré que la méthode de représentation des prises d’eau était assez conforme • La qualité des simulations du modèle D3 est meilleure mais néanmoins insuffisante •  Nécessité de tester la sensibilité du modèle aux forçages météorologiques (type de précipitation) Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 43

38. Plan IDonnées d’ouvrages II Modélisation des Ouvrages III Sensibilité (précipitation, relief) IV Conclusion - Perspectives Sortie de TIGNES 29 m3/s 50 8 m3/s MOUTIERS 7 m3/s 19 m3/s I) Analyse des données d’ouvrages I.2. Analyse de la modification du régime naturel en période de crue • Rapport du débit réel et du QNR en crue (Δt journalier) Apport décennal au barrage de Tignes : 90 m3/s (estimé) Débit biennal de l’Isère à Moutiers : 160 m3/s (banque hydro) Aurélien CLAUDE Comité de suivi de thèse - 7 décembre2009 26