An adaptive hydrological model for multiple time-steps : diagnostics and improvements based on fluxes consistency Andrea Ficchi To cite this version: Andrea Ficchi. An adaptive hydrological model for multiple time-steps : diagnostics and improvements based on fluxes consistency. Hydrology. Université Pierre et Marie Curie - Paris VI, 2017. English. NNT : 2017PA066097. tel-01619102 HAL Id: tel-01619102 https://tel.archives-ouvertes.fr/tel-01619102 Submitted on 19 Oct 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THESE DE DOCTORAT DE L’UNIVERSITÉ PIERRE ET MARIE CURIE Ecole doctorale 398 Géosciences, ressources naturelles et environnement Présentée par M. Andrea Ficchí Pour obtenir le grade de DOCTEUR de l’UNIVERSITÉ PIERRE ET MARIE CURIE An adaptive hydrological model for multiple time-steps: Diagnostics and improvements based on fluxes consistency soutenue le 27 février 2017 devant le jury composé de : Mme Agnès Ducharne CNRS, Paris Présidente M. Marco Borga Université de Padoue (Italie) Rapporteur M. Nicolas Masséi Université de Rouen Rapporteur M. Lionel Berthet DREAL Centre-Val de Loire, Orléans Examinateur M. Hubert Savenije Université de Delft (Pays-Bas) Examinateur Mme Isabella Zin Obs. des Sciences de l’Univers, Grenoble Examinatrice M. Vazken Andréassian Irstea, Antony Directeur de thèse M. Charles Perrin Irstea, Antony Co-encadrant “L'acqua che tocchi de' fiumi è l'ultima di quella che andò e la prima di quella che viene. Cosí il tempo presente.” Leonardo da Vinci i Acknowledgments I want to express here my gratitude to the people who contributed to make my PhD journey pleasant and successful. First, I would like to warmly thank my two supervisors, Charles Perrin and Vazken Andréassian, for assigning me this interesting research project and for the careful guidance and expert advice during the three years spent at Irstea. Thank you for the inspiring discussions and suggestions, your teachings in hydrology and beyond, and for the trust and freedom conferred on my creativity. Your contagious enthusiasm and your positive attitude helped me to keep high motivation and optimism from the sources until the end (the sea?) of this adventure (apparently also the hydrological poems had an effect!). Also, I am grateful for your quick and effective reviewing of the thesis manuscript (fortunately, your reading flow rate was appropriate to the length of my chapters!). I would like to thank the members of my jury for the discussions at the PhD defence, and for the interest and the positive feedback on my work. I was honoured by the two rapporteurs, Marco Borga and Nicolas Massei, for agreeing to evaluate my dissertation, and I want to thank them for the constructive and relevant remarks on my work and on the manuscript. Thanks to Agnès Ducharne, serving as Chair of the committee, and to Hubert Savenije, Isabella Zin and Lionel Berthet for sharing relevant comments and appropriate suggestions to improve the manuscript. I would also like to thank the members of my PhD guidance committees, Nicolas Le Moine, Charles Obled, Federico Garavaglia, Pierre Javelle, Rémi Lamblin, and Flora Branger who participated to the two mid-term meetings on my research work. They shared their independent point of view and ideas on the possible directions to follow in this research and helped me to choose some good paths. Special thanks are owed to Nicolas for agreeing to represent my doctoral school (ED GRNE, UPMC) for these committees, and for the other inspiring discussions we had on other occasions. Many thanks also to Maria-Helena Ramos and Guillaume Thirel for participating in the discussions of the guidance committees, as permanent members of the team, and for the suggestions on other occasions. Thanks also to Bernard Cappelaere for his comments and exchanges by email for my mid-term committee. This PhD research work was financed by Irstea and SCHAPI (Service central d’hydrométéorologie et d’appui à la prévision des inondations). I owe thanks to the people at SCHAPI who believed in this project and agreed to support it, and particularly to Bruno Janet, Rémi Lamblin and Léa Garandeau, who significantly contributed to this. SCHAPI and Météo-France provided the hydro-climatic data used in this thesis and they need to be thanked for the essential steps of data collection and provision. I contacted also some French hydrological services of DREAL (regional environment agencies) and SPCs (flood forecasting services), to retrieve additional information on the streamflow data and I received many kind replies by managers and technicians. I owe my thanks to all of them. iii Working in the Catchment Hydrology team at Irstea (Antony) was an unforgettable experience and it is difficult to leave such a great team! The list of colleagues I had the chance to meet in these three years is long. I would like to mention all “les hydros”, but here I will do my best in remembering the names of all of those with whom I spent more time… Carine, Philippe, Louise, Laure, Alban, François, Florent, Pierre N., Olivier, Julie, Pierre B., Laurent, Carina, Angelica, Léonard, Cédric, Manon, Morgane, Jose, Helena, Guillaume, Charles, Vazken, David, Arnaud, Gaia, Julien, Damien, Sylvia, Audrey, Tito, Louise II, Cuan, and Jeff. My regards also go to all the nice people staying for a shorter time, as the stagiaires, for participating to the very nice ambiance, the sport activities, the socio-hydrological events at Chez Mamane, and the NASH celebrations for the new hydrological year. Special thanks to Alban and Julien for the nice scientific collaboration, to Olivier for sharing his multiple expertise in R, GIS, and statistics, and to the “anciens”, particularly François and Florent, for their good example and their support in the beginning. A friendly thought to all the PhD mates for the good moments, the coffee breaks, and the mutual support. I am already missing my “super colocs”, Philippe, Carine, Louise, and Manon (what a good company… sharing sweets and magic pears in the end!). Now I wish a successful continuation to the next PhD adventurers! I cannot forget all who shared many nice moments at Irstea playing Ultimate Frisbee and Football! In particular, thanks to the many people from my research unit HBAN. Thanks to the “MPG” players for the funny moments in real and simulated games. Thanks to the administrative and informatics team at Irstea, in particular to Roger, Sylvain, Nathalie, Laurence and Elizabeth, for their kind and expert support. Thanks to Dovy Tristani, François Baudin and Loïc Labrousse for the kind support, the opportunity of participating to the “stage de terrain”, and the training sessions of the Ecole Doctorale “Géosciences, Ressources Naturelles et Environnement”. Thanks also to David Dorchies, Pierre-Olivier Malaterre, Luciano Raso, and Francesca Pianosi for the inspiring collaboration during my MSc thesis which prompted me to embark on this journey. Thanks to my friends, “les cocos”, and my Parisian family of “Moulinois(es)” who made these years so lovely and rich of good times, music, cooking, and laughs. Heartfelt thanks to Anne, Diana, John, Thomas, Justine, Ulvika, and Ankur. Finally, last but not least, I would like to thank my family, especially my parents, and Massimo and Mari, for the continuous encouragement, love and great support over the years. Special thanks to my uncle Donato, for the support in the last days before the PhD defence. My highest thoughts go to my aunt, Maria, who passed away too soon, for her smile and positive approach to life that I will keep with me. Thank you all! Merci beaucoup! Grazie mille! iv Abstract This thesis aims at exploring the question of temporal scaling in lumped conceptual hydrological modelling. The main objectives of the thesis are to: (i) study the effects of varying the modelling time step on the performance, parameters and structure of hydrological models; (ii) develop a hydrological model operating at different time steps, from daily to sub- hourly, through a unified, robust and coherent modelling framework at different time scales. Our starting point is the chain of conceptual rainfall-runoff models called ‘GR’, developed at Irstea, and in particular the daily ‘GR4J’ lumped model. The GR4J model will be the baseline model to be effectively downscaled up to sub-hourly time steps following a top-down approach. An hourly adaptation of this model had already been proposed in previous research studies, but some questions on the optimality of the structure at sub-daily time steps were still open. This thesis builds on these previous studies on the hourly model and responds to the operational expectations of improving and adapting the model at multiple sub-daily and sub- hourly time steps, which is particularly interesting for flood forecasting applications. For our modelling tests, we built a database of 240 unregulated catchments in metropolitan France, at multiple time steps, from 6-minute to 1 day, using fine time step hydro-climatic datasets available: (i) 6-min rain gauges and higher spatial-density daily reanalysis data for precipitation; (ii) daily temperature data for potential evapotranspiration (making assumptions on sub-daily patterns); (iii) sub-hourly variable time step streamflow data. We investigated the impact of the inputs temporal distribution on model outputs and performance in a flood simulation perspective based on 2400 selected flood events. Then our model evaluation focused on the consistency of model internal fluxes at different time steps, in order to ensure obtaining a satisfactory model performance by a coherent model functioning at multiple time steps.