I The Impact of Spatial Variability of Precipitation on the Predictive Uncertainty of Hydrological Models Von der Fakultät Bauingenieur- und Vermessungswesen der Universität Stuttgart zur Erlangung der Würde eines Doktor-Ingenieurs (Dr.-Ing.) genehmigte Abhandlung Vorgelegt von Tapash Das aus Khantura, India Hauptberichter: Prof. Dr. rer. nat. Dr.-Ing. András Bárdossy Mitberichter: Prof. Dr.-Ing. Gerd H. Schmitz Tag der mündlichen Prüfung: 20. November 2006 Institut für Wasserbau der Universität Stuttgart Stuttgart 2006 Heft 154 The Impact of Spatial Variability of Precipitation on the Predictive Uncertainty of Hydrological Models von Dr.-Ing. Tapash Das Eigenverlag des Instituts für Wasserbau der Universität Stuttgart D93 The Impact of Spatial Variability of Precipitation on the Predictive Uncertainty of Hydrological Models CIP-Titelaufnahme der Deutschen Bibliothek Das, Tapash: The Impact of Spatial Variability of Precipitation on the Predictive Uncertainty of Hydrological Models / von Tapash Das. Institut für Wasserbau, Universität Stuttgart. – Stuttgart: Inst. für Wasserbau, 2006 (Mitteilungen / Institut für Wasserbau, Universität Stuttgart: H. 154) Zugl.: Stuttgart, Univ., Diss., 2006 ISBN 3-933761-57-3 NE: Institut für Wasserbau <Stuttgart>: Mitteilungen Gegen Vervielfältigung und Übersetzung bestehen keine Einwände, es wird lediglich um Quellenangabe gebeten. Herausgegeben: 2006 vom Eigenverlag des Instituts für Wasserbau Druck: Sprint-Digital-Druck GmbH, Stuttgart Acknowledgment This work was done as a doctoral student within the International Doctoral Program “Environment Water” (ENWAT), Universität Stuttgart and was supported by a scholarship program (IPSWaT) initiated by the German Federal Ministry of Education and Research (BMBF) which is gratefully acknowledged and I feel honored for the same. First of all, I wish to express my deepest appreciation to Professor András Bárdossy, who accepted me as his doctoral student and provided me a precious opportunity to work on some of the most interesting problems in the area of Hydrology. In my endeavor for this work, I have been scrupulously trained by him, for which I am truly fortunate. Every discussion that I had with him has always been a pleasure, enlightening and educative, considering his wide knowledge and expertise in the subject. His enthusiasm and integral view on research has made a deep impression on me. This thesis would not have been what it is now but for his invaluable guidance, support, discussions and critical evaluation at each and every stage of my progress. I also express my sincere gratitude to Professor Gerd H. Schmitz for his willingness to co-supervise my work. The discussions that I had with him have been quite useful for successful completion of my work. I would like to take this opportunity to thank Professor Erwin Zehe for his continuous supports in many aspects of research, fruitful discussions and continuous encouragement. I would also like to thank Dr.-Ing. Yeshewatesfa Hundecha Hipra, Dr.- Ing. Greta Moretti and Dr. S. J. Birkinshaw for their helpful discussions. Of course, this endeavor would not have been possible without the help of other colleagues and friends like, Jens Götzinger, Pawan Kumar Thapa, Jürgen Brommundt, Wei Hu, Sachin Patil, Yi He, Eloise Byrne and Jeff Tuhtan, as well as all other colleagues in our group and in the Institute of Hydraulic Engineering who helped me directly or indirectly in the course of my journey to complete this work. I would like to extend my heartfelt thanks to my colleague Ferdinand Beck for taking the pain to write the German version of the summary of my work. I would also like to acknowledge Krista Uhrmann and Andrea Bange for their always being very helpful. I also express my sincere thanks to Dr.-Ing. Arne Färber for providing warm working atmosphere and continuous supports through out my stay. Finally, I am extremely grateful to my beloved parents, brothers, sisters and my wife who have always been a source of constant support and encouragement. I want to specially thank my brother, Palash and my wife, Mou for their moral support during hard days. I Table of contents List of Figures…………………………………………………………………………………...IV List of Tables…………………………………………………………………………………....XI Abstract………………………………………………………………………………………..XIV Kurzfassung……………………………………………………………………………….....XVII 1 Introduction............................................................................................................................1 1.1 Problems classification and motivation ...............................................................................1 1.1.1 Influences of rainfall variability.......................................................................................2 1.1.2 Complexity and challenges in distributed hydrological modeling ..................................4 1.2 Research questions and objectives.......................................................................................7 1.3 Structure of the dissertation .................................................................................................7 2 Study area and data description...........................................................................................8 2.1 Introduction..........................................................................................................................8 2.2 General description of the study area...................................................................................8 2.3 Physical structure of study area .........................................................................................10 2.3.1 Topography....................................................................................................................10 2.3.2 Geology..........................................................................................................................11 2.3.3 Soils................................................................................................................................12 2.3.4 Vegetation......................................................................................................................15 2.3.5 Land cover data..............................................................................................................15 2.4 Climate...............................................................................................................................16 2.4.1 Precipitation and temperature ........................................................................................19 2.5 Runoff ................................................................................................................................22 2.6 Evapotranspiration .............................................................................................................24 3 Model structure description................................................................................................27 3.1 Model selection for the study.............................................................................................27 3.2 The HBV model.................................................................................................................27 3.2.1 Snow accumulation and melt.........................................................................................28 3.2.2 Soil-moisture and effective precipitation.......................................................................29 3.2.3 Evapotranspiration .........................................................................................................30 3.2.4 The response function....................................................................................................31 3.2.5 River routing..................................................................................................................32 3.3 Development of different model structures .......................................................................32 3.3.1 Distributed model structure............................................................................................33 3.3.2 Semi-distributed model structure...................................................................................34 II 3.3.3 Semi-lumped model structure........................................................................................34 3.3.4 Fully-lumped model structure........................................................................................35 3.4 Automatic parameter estimation procedure for the HBV model .......................................35 3.4.1 Objective function..........................................................................................................38 3.4.2 Automatic optimization algorithm Simulated Annealing..............................................39 3.4.3 Automatic calibration for different model structures.....................................................41 3.5 Modeling time step............................................................................................................42 3.6 The SHETRAN model.......................................................................................................42 3.7 The SHETRAN model calibration.....................................................................................45 3.8 Goodness-of-fit criteria in simulations ..............................................................................46 3.8.1 Overall model simulations performance........................................................................46