Department of Earth Sciences Institute of Geographic Sciences Modeling the Effect of Climate and Land Use Change on the Water Resources in Northern Ethiopia: the Case of Suluh River Basin Dissertation to obtain the doctoral degree Submitted by Bizuneh Asfaw Abebe, M.Sc. Supervisors: Univ. Prof. Dr. Brigitta Schütt - Freie Universität Berlin Jun.-Prof. Dr. Wiebke Bebermeier - Freie Universität Berlin Date of the oral examination: 20.01.2014 This page is intentionally left blank. Acknowledgments I would like to thank my supervisor Prof. Dr. Brigitta Schütt for her support and invaluable advices throughout the research period. Her many fruitful suggestions and careful review of the draft have made the production of this thesis possible. It was a great pleasure for me to conduct this research under her supervision. I extend my deepest gratitude for my second supervisor Jun.-Prof. Dr. Wiebke Bebermeier for her invaluable comment and support to my effort. This research work is financially supported from Engineering Capacity Building Program (ECBP) under the framework of university reform. I would like to express my great gratitude to all of them for making the fund available. Thanks are also to Deutscher Akademischer Austauschdienst (DAAD) for the scholarship and the supports I obtained. I would like to thank particularly my contact person madam Ada-Samira Osinski. I am thankful to the hydrology section of Ministry of Water Resources, National Meteorological Services and Ethiopian Mapping Agency for the provision of stream flow, Meteorological data and topographical maps respectively. I gratefully acknowledge the use of facilities at Freie Universität Berlin, department of Earth Science and Mekelle University, Ethiopian Institute of Technology for allowing me to use the resources like vehicle and geotechnical laboratory facilities during my field work. I would like to thank Dr.-Ing. Joachim Lengricht for the encouragements and administrative support during my field work in Ethiopia. I deeply acknowledge staff and PhD-students in the Department of Physical Geography (Freie Universität Berlin) providing me an excellent working environment. I wish to express my sincere thanks to Dr. Jan Krause for the unrestricted support and encouragements and many useful contributions in the field work and facilitation of administrative works in Berlin. Special thanks to Steffen Schneider and Anette Stumptner. My acknowledgment also extends particularly to Nicole Lamm as she offered me unlimited support in editing and formatting my final thesis work. I thank to staff members of department of Civil Engineering Mekelle University for their support during my field and laboratory work. Special thanks to Dr. Haddush Goitom, Yonas Fitsum, Ahemd Umer, Zenebe Haile, Kenfe Mussie, Melaku Berhe and his family. My thanks also goes to Eskinder Gidey as he provided me unreserved support during image processing. I would like to thank my dearest friend Abraha Adugna for sharing all the fun and sorrow during my stay in Berlin. Thanks to Dr. Adem Hiko, we had unforgettable time in Berlin. I would like to appreciate Eshetu Adugna for his unreserved support regarding administrative issues in Addis Ababa. Last but by no means least I would like to convey a heartfelt gratitude to my family and friends for their unfailing support. Special thanks to Gebreanania Gebru and Letebrehan G/Medhin and all my sisters and brothers. My wife Azeb Gebreanania has been the key figure throughout my career, providing a bedrock of both stability and encouragement. Words are not enough to express what this has meant to me. Adiyam Bizuneh and Reena Bizuneh you are the gifts of my life and such an extra motivation and strength. Bizuneh Asfaw Abebe Berlin, January 2014 i Table of contents Acknowledgment ................................................................................................................................ i List of figures ...................................................................................................................................... v List of tables ...................................................................................................................................... ix List of abbreviations .......................................................................................................................... xi Abstract .......................................................................................................................................... xiii 1 Introduction ............................................................................................................................... 1 2 State of the art ........................................................................................................................... 3 2.1 Effect of climate and land use and land cover change on water resource .................................. 3 2.1.1 Global level ................................................................................................................................. 3 2.1.2 National level ............................................................................................................................. 4 2.1.3 Regional/local level .................................................................................................................... 6 2.2 Modelling of land use and land cover and climate change effect ............................................... 7 2.2.1 Overview of the hydrological model ......................................................................................... 7 2.2.2 Classification of hydrologic models ........................................................................................... 7 2.2.3 Application of HEC-HMS model ................................................................................................. 8 3 Methodology ............................................................................................................................ 11 3.1 Soil sampling and soil analysis ..................................................................................................... 11 3.2 Geomorphologic map .................................................................................................................. 12 3.3 Data preprocessing ...................................................................................................................... 13 3.3.1 Preprocessing mapping data ................................................................................................... 13 3.3.1.1 Base map of the study site ............................................................................................................................. 13 3.3.1.2 Watershed analysis ......................................................................................................................................... 13 3.3.1.3 Land use and land cover map ......................................................................................................................... 15 3.3.1.4 Data extraction and image processing ........................................................................................................... 16 3.3.1.5 Spatial maps overlay ....................................................................................................................................... 17 3.3.2 Preprocessing of meteorological data .................................................................................... 19 3.3.2.1 Rainfall ............................................................................................................................................................. 19 3.3.2.2 Evapotranspiration ......................................................................................................................................... 22 3.3.2.3 Downscaling of climate data .......................................................................................................................... 23 3.3.2.4 Statistical Downscaling of climate parameters .............................................................................................. 24 3.3.3 Preprocessing hydrological data ............................................................................................. 26 ii 3.4 Basics of hydrological models ...................................................................................................... 26 3.4.1 Runoff volume models ............................................................................................................ 27 3.4.1.1 Basic concept of deficit constant loss model ................................................................................................. 27 3.4.1.2 Basic formulation of Soil Moisture Accounting model .................................................................................. 27 3.4.2 Direct-runoff models ............................................................................................................... 29 3.4.3 Base flow models ..................................................................................................................... 29 3.4.4 Channel flow ............................................................................................................................ 29 3.4.5 Sensitivity analysis ................................................................................................................... 30 3.4.6 Calibration and validation parameters ..................................................................................