A Case Study of Ruiru and Ndarugu Basins, Kiambu County, Kenya
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SPATIO-TEMPORAL DYNAMICS OF LAND USE CHANGE ON RIVERS IN TROPICAL WATERSHEDS: A CASE STUDY OF RUIRU AND NDARUGU BASINS, KIAMBU COUNTY, KENYA. BY GEOFFREY MWANGI WAMBUGU A THESIS SUBMITTED IN PARTIAL FULFILLMENT FOR THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN ENVIRONMENTAL PLANNING AND MANAGEMENT IN THE DEPARTMENT OF GEOGRAPHY AND ENVIRONMENTAL STUDIES, UNIVERSITY OF NAIROBI MAY, 2018 DECLARATION ii DEDICATION To my Father, Simon Wambugu Mwangi, and my Mother, Sarah Wanjiku Mwangi, for their sacrifices and belief, even when everyone else was in doubt. iii ACKNOWLEDGEMENTS I sincerely thank the Department of Geography and Environmental Studies, University of Nairobi, for the support accorded to me during this study. Sincere gratitude also goes to the staff of Water Resources Management Authority, Kiambu Regional Office, for allowing me to access and use their long-term water quality monitoring data from the gauging stations of Ruiru and Ndarugu Rivers. I also thank the Ruiru-Juja Water and Sanitation Company for allowing me access to their plant and providing me with valuable input during proposal development for this study. This study was financed from two sources: first, from my employer, Karatina University (KarU) through the “Research Grant for Academic Staff Programme”; and second, from the National Commission for Science, Technology and Innovation (NACOSTI) Grant for PhD Studies. Much gratitude goes to the two institutions for providing the financial resources to facilitate the study. I gratefully acknowledge my supervisors, Dr. Isaiah Nyandega and Dr. Shadrack Kithiia for their unequaled support since the conception of the idea, throughout the proposal development, their support while I sought funding, and during the thesis write-up. My wife, Peris Wanjiku Mwangi, and my daughter, Claire Wanjiku Mwangi, endured long periods of my absence during data collection and gave me hope and strength during thesis write- up. The chairman of the Department of Geography and Environmental Studies, University of Nairobi, Dr. Samuel Owuor, has been very supportive to me. I would also like to thank the Kenyatta University Alumni Network for arranging access to Kenyatta University library. iv Dr. Chris George of Texas A & M University provided valuable technical advice with regard to the input files of the Soil and Water Assessment Tool (SWAT) model. My GIS advisor, Mr. John Musau was instrumental in introducing me to the workings of the SWAT model and debugging the errors encountered while running the model. I thank my research assistant, Mr. Ernest Ng’ang’a for enduring long days with me in the field. Special thanks to my family, who supported and encouraged me throughout the study. v TABLE OF CONTENTS DECLARATION.............................................................................................................. ii DEDICATION................................................................................................................. iii ACKNOWLEDGEMENTS ............................................................................................ iv LIST OF FIGURES ......................................................................................................... xi LIST OF PLATES .......................................................................................................... xv LIST OF TABLES ......................................................................................................... xvi ABBREVIATIONS AND ACRONYMS ..................................................................... xvii ABSTRACT .................................................................................................................... xix CHAPTER ONE: INTRODUCTION ............................................................................ 1 1.0 Introduction .................................................................................................................. 1 1.1 Study Background ........................................................................................................ 1 1.2 Statement of the Problem ............................................................................................. 6 1.3 Research Questions ...................................................................................................... 7 1.4 Objectives of the Study ................................................................................................ 7 1.4.1 Specific Objectives ................................................................................................... 7 1.5 Justification of the Study ............................................................................................. 8 1.6 Operational Definitions ............................................................................................... 10 CHAPTER TWO:LITERATURE REVIEW ............................................................... 11 2.0 Literature Review........................................................................................................ 11 2.1 Introduction ................................................................................................................. 11 2.2 Theoretical Literature .................................................................................................. 11 2.2.1 Land use change theories ......................................................................................... 11 vi 2.2.2 The River Continuum Concept ................................................................................ 12 2.3 Empirical Literature .................................................................................................... 21 2.3.1 Water as an Ecosystem Service ............................................................................... 21 2.3.2 Population Impacts on Watersheds .......................................................................... 23 2.3.3 Urbanization and Land use Change Dynamics ........................................................ 26 2.3.4 Hydroclimatic Conditions of Tropical East Africa .................................................. 29 2.3.5 Water Quality impacts on Ecological Integrity ....................................................... 37 2.3.6 Relationship between Land Use Patterns and Rivers’ Ecological Health ............... 42 2.3.7 Hydrologic modeling of Watersheds ....................................................................... 44 2.3.8 Comparison of GIS-based Hydrological Models ..................................................... 48 2.3.8 Application of the SWAT Model in Kenya ............................................................. 53 2.3.9 Practical Application of SWAT model in Kenya .................................................... 61 2.4 Conceptual Framework ............................................................................................... 62 2.5 Research Hypotheses .................................................................................................. 64 CHAPTER THREE: STUDY AREA ............................................................................ 65 3.0 Study Area ................................................................................................................. 65 3.1 Location ...................................................................................................................... 65 3.2 Geology and Soils ....................................................................................................... 66 3.3 Topography ................................................................................................................. 69 3.4 Climate and Hydrology ............................................................................................... 69 3.5 Flora and Fauna........................................................................................................... 71 3.5.1. Flora ........................................................................................................................ 71 3.5.2. Fauna ....................................................................................................................... 72 vii 3.6 Socio-economic Activities .......................................................................................... 73 3.6.1. Population ............................................................................................................... 73 3.6.2 Economic Activities ................................................................................................. 74 3.7 Land use and land Tenure ........................................................................................... 75 CHAPTER FOUR: RESEARCH METHODOLOGY ................................................ 79 4.0 research methodology ................................................................................................. 79 4.1 Study Design ............................................................................................................... 79 4.2 Data Types and Sources .............................................................................................. 82 4.3 Pilot Survey ................................................................................................................. 84 4.4 Assessing Spatio-temporal Land Use Dynamics ........................................................ 85 4.4.1 Classification Scheme .............................................................................................. 87 4.5 Water