Potential Impact of Climate and Land Use Changes on the Water Resources of the upper Blue Nile Basin Michael Menker Girma Freie University of Berlin 6/19/2012 Department of Earth Sciences Institute for Geographical Sciences, Physical Geography Potential Impact of Climate and Land Use Changes on the Water Resources of the Upper Blue Nile Basin A Dissertation Submitted in fulfillment of the requirements for the degree of Dr. rer.nat to the Freie Universität Berlin by MICHAEL MENKER GIRMA Berlin, June 2012 Supervisor: Univ.-Prof. Dr. Brigitta Schütt Second examiner: Jun.-Prof. Dr. Wiebke Bebermeier Date of the viva voce/defense: June 19, 2012 Copyright © 2012, by Michael Menker Girma, All rights reserved i DEDICATION This is dedicated to WUBET ZEWDU ii ACKNOWLEDGEMENTS I would like to thank my advisor Prof. Brigitta Schütt for her constructive comments and suggestions on the draft of this dissertation and for providing professional support and space during the whole period of the research. This research was supported by the Deutscher Akademischer Austauschdienst (DAAD) through a study grant. The field work was sponsored by the International Water Management Institute (IWMI) as part of its research project, Rethinking Water Storage for Climate Change Adaptation. Dr. Seleshi Bekele, Dr. Matthew McCartney, and Dr. Fred Hatterman provided technical assistance during the implementation of this research project and deserve special thanks. I want to express my appreciation to Dr. Amare Haileslassie for his encouragement and cooperation in providing useful information for the research at the start of this research project. I want to acknowledge the assistance of the Ethiopian Meteorological Agency, the Ethiopian Ministry of Water Resources, the Ethiopian Electric Power Corporation and the Potsdam Institute for Climate Impact Research (PIK) in providing data for the research. I would like to express my appreciation to Pasquale Borelli, Maik Blättermann, Marlen Schlöffel, Zyliad and Steffen Schneider from Freie University of Berlin; Tobias Vater from PIK and Yordanos Abel from Berlin for their friendship and/or for their assistance while I was having personal difficulties in Germany. Solomon Bokasa from the Metahara sugar state and Tesfaye Dejene from the International Livestock Research Institute played significant role during the field work of this research project. Finally special thanks go to Dr. med. Holger Mellerowicz from the Emil von Behring Krankenhaus, Berlin, Dr. Axel Panzer from the DRK-Kliniken Westend, Berlin, my wife Elsabeth Demissie and my daughter Hermela Michael. This PhD work wouldn’t have been a reality without their kindness and unreserved assistance. Michael Menker Girma iii TABLE OF CONTENTS Pages ACKNOWLEDGEMENTS ........................................................................................................................... iii LIST OF TABLES ....................................................................................................................................... vii LIST OF FIGURES .................................................................................................................................... viii ACRONYMS AND ABBREVIATIONS ........................................................................................................... x ABSTRACT ............................................................................................................................................ xi ZUSAMMENFASSUNG ........................................................................................................................... xiii CHAPTER 1 INTRODUCTION ..................................................................................................................... 1 1.1 Hydrological impact of climate and land use change in the upper Blue Nile basin ....................... 1 1.2 Implications of climate change in the upper Blue Nile basin ......................................................... 2 CHAPTER 2 STATE OF THE ART ................................................................................................................. 5 2.1 Global circulation models and climate scenarios .......................................................................... 5 2.2 Climate change scenarios .............................................................................................................. 5 2.3 Observed regional trends in temperature and rainfall in the Nile Basin ....................................... 9 2.4 Climate change in the Nile basin .................................................................................................. 10 2.5 Land use change and the upper Blue Nile basin .......................................................................... 11 CHAPTER 3 METHODS and DATA USED ................................................................................................. 13 3.1 Overall design............................................................................................................................... 13 3.2 Data used ..................................................................................................................................... 14 3.2.1 Observed climate data .......................................................................................................... 14 3.2.2 Monthly reanalysis data ........................................................................................................ 15 3.2.3 Monthly global circulation model scenarios ......................................................................... 16 3.2.4 Downscaled regional data ..................................................................................................... 16 3.2.5 Land use soil and digital elevation model data ..................................................................... 16 3.2.6 Hydrologic data ..................................................................................................................... 17 3.3 Software used .............................................................................................................................. 18 3.4 Statistical analysis ........................................................................................................................ 18 CHAPTER 4 STUDY AREA ........................................................................................................................ 19 4.1 The upper Blue Nile basin ............................................................................................................ 19 4.2 Climate ......................................................................................................................................... 19 4.3 Relief ............................................................................................................................................ 21 4.4 Hydrology ..................................................................................................................................... 21 4.5 Soils .............................................................................................................................................. 24 4.6 Land use and land cover .............................................................................................................. 27 iv CHAPTER 5 CLIMATE DOWNSCALING .................................................................................................... 29 5.1 Statistical downscaling of rainfall ................................................................................................ 29 5.1.1 Selection of climate stations ................................................................................................. 29 5.1 2 Predictors for statistical downscaling ................................................................................... 30 5.1.3 Statistical downscaling .......................................................................................................... 31 5.1.4 Selection of domains ............................................................................................................. 32 5.1.5 Effect of combined predictors from different domains ........................................................ 34 5.1.6 Calibration and validation of statistical downscaling models ............................................... 34 5.1.7 Simulation of future climate scenarios ................................................................................. 39 5.2 Dynamical downscaling of temperature and rainfall ................................................................... 40 5.2.1 Regional model descriptions ................................................................................................. 40 5.2.2 Observed data ....................................................................................................................... 42 5.2.3 Bias correction ...................................................................................................................... 42 5.2.4 Changes in rainfall and temperature at basin level .............................................................. 43 5.2.5 Changes in rainfall and temperature at sub basin level ....................................................... 47 CHAPTERS 6 LAND USE CHANGE SCENARIOS IN THE UPPER BLUE NILE BASIN ..................................... 51 6.1 Description of land use and land cover based on field investigation .........................................