STREAMFLOW VARIABILITY AND SEDIMENT YIELD IN NORTH-WEST UPPER TANA BASIN, KENYA IMELDA NGONYO NJOGU THESIS PRESENTED IN PARTIAL FULFILMENT OF THE REQUIRMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN INTEGRATED WATER RESOURCES MANAGEMENT IN THE SCHOOL OF ENVIRONMENT, WATER AND NATURAL RESOURCES, SOUTH EASTERN KENYA UNIVERSITY 2019 SOUTH EASTERN KENYA UNIVERSITY SCHOOL OF ENVIRONMENT, WATER AND NATURAL RESOURCES DEPARTMENT OF HYDROLOGY AND AQUATIC SCIENCES STREAM FLOW VARIABILITY AND SEDIMENT YIELD IN NORTH-WEST UPPER TANA BASIN, KENYA BY IMELDA NGONYO NJOGU THESIS PRESENTED IN PARTIAL FULFILMENT OF THE REQUIRMENTS FOR THE AWARD OF DEGREE OF MASTER OF SCIENCE IN INTEGRATED WATER RESOURCES MANAGEMENT IN THE SCHOOL OF ENVIRONMENT, WATER AND NATURAL RESOURCES, SOUTH EASTERN KENYA UNIVERSITY 2019 ii DECLARATION CANDIDATE This thesis is my original work and has not been submitted for examination in any other university ………………………………………… Njogu Imelda Ngonyo (W502/KTI/20677/2015) SUPERVISORS This thesis has been submitted with our approval as the university supervisors ........................................................................ Dr. Johnson U. Kitheka, PhD (University supervisor) ........................................................................ Dr. Hesbon Otieno, PhD (University supervisor) iii ACKNOWLEDGEMENTS I would like to express my gratitude and appreciation to all those who assisted in one way or the other in this study. I am highly indebted to my supervisors Dr. Johnson U. Kitheka-Dean, School of Water Resources Science and Technology and Dr. Hesbon Otieno-Dean, School of Engineering Technology who together have provided various suggestions that led to the successful completion of my research and preparation of this thesis. I would also like to appreciate the guidance provided to me by Dr. Moses Mwangi who is the Chairman, Department of Hydrology and Water Resources Management during this study. I am highly grateful to the Water Resources Authority (WRA), Embu Regional Office and in particular to Ms. Faith Wawira, the WRA Embu Database Manager for providing me with stream flow, sediment yield and TSSC data that was used in this study. I am also grateful to the Kenya Meteorological Department (KMD) in Nairobi for providing rainfall data used in this study. I would also like to acknowledge South Eastern Kenya University (SEKU) management for providing partial support that enabled me pursue the MSc degree programme in Integrated Water Resources Management (IWRM) at the School of Water Resources Science and Technology. iv DEDICATION This study is dedicated to God who has helped me all the way. I would also like to dedicate this work to my parents, Mr. Everton Njogu Njoroge and Mrs. Veronica Njoki Njogu and my brothers, Peter Ngugi and Ken Mwangi who tirelessly have been a pillar of strength and encouragement. v ABSTRACT The main objective of the study was to determine how river discharge and sediment yield in the basin is influenced by variations in rainfall and land use land cover change. The study was based on the analysis of hydrological and meteorological data archived by the Water Resources Authority (WRA) and the Kenya Meteorological Department (KMD), respectively. The river discharge, Total Suspended Sediment Concentration (TSSC) and sediment yield data was collected from established river gauging stations in the basin, namely Sagana (4AC03), Maragua (4BE01), Saba Saba (4BF01), Mathioya (4BD01), North Mathioya (4BD07), Irati (4BE03), Thiba (4DD01), Thika (4CC05) and Gikigie (4BE08),for the period 2010-2012. Rainfall data was for the period 1980- 2012, river discharge data was for the period 1980-2012 while sediment yield data was from the period 2010-2012.The study used Landsat 5 and 7 satellite data for Land Use Land Cover (LULC) change detection analysis and Geographical Information System (GIS). The statistical methods of data analyses applied in this study included regression analysis, correlation analysis, measures of central tendency, coefficient of determination (R2), and the analysis of variance (ANOVA). The study also applied Soil Water Assessment Tool (SWAT) Model to simulate the relationship between sediment yield, river discharge and rainfall in NWUT catchment. Nash Sutcliffe Efficiency (NSE) was used to test the efficiency of the SWAT model in predicting these parameters.This study found a positive relationship between river discharge and sediment yield in the NWUT catchment with (r) of 0.74 and (R2) of 0.55. The maximum Total Suspended Sediment Concentration (TSSC) was 1,433 mg/l at Saba Saba (4BF01) and the peak river discharge was 170.4 m3/s at Sagana (4AC03). Water yield and sediment yield from NWUT basin was 327,638,974 m3/month and 590,637.4 tons/month respectively. Sediment production rate from the basin was 59.55 tons/km2/month in the period O2010-2012. Land Use Land Cover Change (LULCC) detections analysis for the period 2000- 2014 found out there was increase on bare-land (from 6.5 to 9.7%), increase in build-up areas (from 0.2% to 0.8%), decrease in forest cover (from 32.3% to 21.7%), decrease in rangeland (from 17.0% to 12.7%), increase in plantation (from 12.7% to 15.0%), increase in silted water bodies (from 0.1% to 0.7%) and reduced waterbody (1.5% to 0.5%). SWAT modelling application in the simulation of river discharge and sediment yield was good with NSE above 95%. The study puts forward various recommendations for soil and water management in the basin. Some of the recommendations for land management include application of soil and water conservation measures, Payment for Ecosystem Services (PES), Integrated Water Resources Management (IWRM), Eco-Hydrology and reforestation to improve high ediemnt yield from the basin. vi Table of Contents DECLARATION................................................................................................................................... iii ACKNOWLEDGEMENTS .................................................................................................................. iv DEDICATION ........................................................................................................................................v ABSTRACT .......................................................................................................................................... vi LIST OF FIGURES .............................................................................................................................. xii LIST OF TABLES .............................................................................................................................. xiv LIST OF APPENDICES .......................................................................................................................xv LIST OF ACRONYMS AND ABBREVIATIONS ............................................................................ xvi CHAPTER ONE; INTRODUCTION .....................................................................................................1 1.1 Introduction ....................................................................................................................................... 1 1.2 Background of the Study ................................................................................................................... 1 1.3 Statement of the Problem .................................................................................................................. 2 1.4 Main objective ................................................................................................................................... 4 1.5 Specific objectives ............................................................................................................................. 4 1.6 Hypothesis ......................................................................................................................................... 4 1.7 Justification of the Study ................................................................................................................... 5 1.8 Scope of the study ............................................................................................................................. 6 CHAPTER TWO; LITERATURE REVIEW .........................................................................................7 2.1 Introduction ....................................................................................................................................... 7 2.2 Studies Done at Global Level ............................................................................................................ 7 2.2.1 Factors Influencing Sediment and Water Yield ............................................................................. 7 2.2.2 Relationship between Stream Flow and Sediment Yield ............................................................... 7 2.2.3 Spatial Temporal Variation in Sediment Yield .............................................................................. 8 2.2.4 Land Use Land Cover Changes and its Impacts on Stream Flow and Sediment Yield ................. 9 2.2.5 Modeling of Stream Flow and Sediment Yield .............................................................................. 9 2.3 Studies Done at Regional Level (Africa) ........................................................................................ 11 2.3.1 Factors Influencing Sediment and Water Yield ........................................................................... 11 2.3.2 Relationship between