Gis-Based Assessment of Water Availability and Water Demand in Asa Catchment, Kwara State

TABLE OF CONTENTS

                                                                                                    Pages

Title page                                                                                               i

Certification                                                                                            ii

Dedication                                                                                              iii

Acknowledgement                                                                                   iv

Table of contents                                                                                    v

List of figures                                                                                          xiii

List of tables                                                                                           ix

Abstract                                                                                                  x

1.0     CHAPTER ONE: INTRODUCTION                                               1-6

1.1     Background to the Study                                                                1

1.2     Problem Statement                                                                        4

1.3     Aim and Objectives of the study                                                     5

1.4     Justification for the study                                                               5

1.5     Scope of Work                                                                               6         

2.0     CHAPTER TWO: LITERATURE REVIEW                                     7-24

2.1     Introduction                                                                                  7

2.2     Water Resources in Nigeria                                                            8

2.3     Water Management Practices and Policy in Nigeria                          10

2.4     Water Allocation Guidelines and Principles                                      10

2.5     Water Resources Management Models for River Basin Simulation     11

          2.5.1   MODSIM                                                                             12

          2.5.2   MIKE BASIN                                                                        13

2.5.3   RIBASIM                                                                             14

2.5.4   REALM                                                                                15

2.5.5   WEAP21                                                                              16

2.6     Description of the SWAT Modeling and SWAT Components              18

2.7     SWAT Strength and Limitation                                                       20

          2.7.1   Limitation of SWAT Model                                                    21

2.8     Previous Water Supply And Demand Studies                                   21

3.0     CHAPTER THREE: METHODOLOGY                                            25-36

3.1     Introduction                                                                                  25

3.2     Model Selection and Description                                                     25

3.3     Model Data Requirements and Collection                                        27

          3.3.1   Digital Elevation Model (DEM)                                              27

          3.3.2   Land Use and Land Cover (LULC)                                         29

          3.3.3   Soil Data                                                                             31

          3.3.4   Weather Data                                                                     32

3.4     SWAT Model Set-Up and Run                                                         33

          3.4.1   Model Setup                                                                        33

          3.4.2   Watershed Delineation                                                        34

3.5     Water Yield Potential and Estimation of Available Water Resources   35

3.6     Water demand estimation                                                              36

3.7     Population Forecasting                                                                   36

4.0     CHAPTER FOUR: RESULT AND DISCUSSION                           37-42

4.1     Prediction of Water Balance Component                                         37

4.2     Prediction of Water Yield Potentials in the Sub-basin of

Asa watershed                                                                              40

4.3     Estimation of Available Water Resources                                         41

4.4     Estimation of Water Demand of the River Basin                              41

4.5     Comparison of Water Supply and Demand                                      42

5.0     CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS    43-44

5.1     Conclusions                                                                                   43

5.2     Recommendations                                                                         44

          REFERENCES                                                                              45-51

ABSTRACT

This study arose from the growing water demand within the Asa River Basin due to population upsurge, the absence of existing water demand management strategies, the possibility of scarcity as a result of climate change, and the need for sustainable water resources management. The aim of the study was to assess water availability and water demand of Asa catchment using GIS-based hydrological model. The methodology involved the input of spatial and temporal data into Soil and Water Assessment Tool (SWAT) using Geographic Information System (GIS) as interface. After the model was configured, set up and run, the water balance components and water yield potential were predicted. The modelling results showed that evapotranspiration is the highest water balance component while the lowest is lateral soil flow. The spatial distribution of water yield potentials in the sub-basins of the study area showed that sub-basin 9 has the lowest water yield potential while sub-basin 84 has the highest. The total water yield potential of the study area is 1,296,676.5mm while the total area of the river catchment is 5,618.28km2. The available water resources in the catchment were estimated to be 7.2 billion m3. The projected total population of the domiciled local governments in the catchment for 2015 is 1,203,743 persons and the water demand for this population was estimated as 1.3 billion m3. Comparing the water demand with the available water resources shows that the available water resources outweigh the water demand, which implies that there was no scarcity. However, there may be future scarcity due to the increasing population and climate change.