Groundwater resource assessment aims to obtain fundamental data and information needed to describe the hydraulic and chemical parameters in order to estimate the available groundwater resource which is suitable for drinking. This study was undertaken with the purpose of determining and estimating the groundwater occurrence, groundwater flow parameters, groundwater quality and storage in typical Karoo Main Basin aquifers such as in the Steynsrus study area in South Africa. The field investigations were designed to define and determine the sustainable yields and the properties of the aquifers and the exploitable volumes. The research places emphasis on the appropriate tools and their applications in order to understand the local aquifers so as to optimise the groundwater exploration for town water use and to determine the future water use.
The geophysical surveying methods, particularly the magnetic method, were utilised to investigate and determine borehole drilling targets, and to locate groundwater potential structures, which are often associated with high borehole yields. The quality of the magnetic data utilised for drilling by the external consultant was critically evaluated and was found to be ‘bad data’. Percussion drilling played an important role in providing geological subsurface information; in particular locations of fractures which are often associated with favourable groundwater flow were identified. Seventeen (17) boreholes were drilled in the whole project, seven (7) of the boreholes were sited by magnetometer survey and interpretation, and ten (10) of the drilled boreholes were sited by geological mapping and map interpretation. Twelve of the drilled boreholes were declared ‘unsuccessful’ due to yielding a blow yield below 1.00 L/s; therefore these boreholes were not considered for aquifer pump testing. Blow yields of five (5) of the newly drilled boreholes were between 1.5 and 24 L/s.
Based on these findings, the aquifers in the study were concluded to be a fractured system of alternating layers of sandstone and shale formations, characterised by the favourable groundwater flow characteristics at the dolerite fractures, and in some cases bedding plane fractures of sandstone formations. The study demonstrates the value in the methods and concepts applied in geohydrological studies to understand the local aquifer properties and in order to estimate the sustainable yields and the groundwater balance.
Table of Contents
- CHAPTER 1 INTRODUCTION
- 1.1 RESEARCH FRAMEWORK
- 1.2 WATER SUPPLY BACKGROUND
- 1.3 PROBLEM STATEMENT
- 1.4 METHODOLOGY
- 1.5 AIMS AND OBJECTIVES
- 1.6 STRUCTURE OF DISSERTATION
- CHAPTER 2 LITERATURE REVIEW
- 2.1 INTRODUCTION
- 2.2 OVERVIEW OF GROUNDWATER RESOURCE ASSESSMENT
- 2.3 GROUNDWATER RESOURCE ASSESSMENT CONCEPTS
- 2.3.1 Groundwater Occurrence
- 2.3.2 Groundwater Flow and Storage
- 2.3.2.1 Borehole sustainability and aquifer parameters
- 2.3.3 Groundwater Recharge
- 2.3.3.1 The Chloride Mass Balance Method (CMB)
- 2.3.3.2 Qualified guesses
- 2.3.4 Borehole Sustainable Yields
- 2.3.5 Groundwater Quality
- 2.3.5.1 Interpretation of chemical data
- 2.3.5.1.1 Piper and Durov diagrams
- 2.3.5.1.2 Schoeller diagram
- 2.3.5.1.3 Groundwater salinity
- 2.3.5.2 Statistical analysis
- 2.4 SUSTAINABLE DEVELOPMENT
- 2.5 GROUNDWATER ASSESSMENT CASE STUDIES
- 2.6 SUMMARY
- CHAPTER 3 SITE DESCRIPTION
- 3.1 OVERVIEW AND ECONOMIC DEVELOPMENT
- 3.2 PHYSIOGRAPHY AND DRAINAGE
- 3.3 RAINFALL AND CLIMATE
- 3.4 VEGETATION AND LAND USE
- 3.5 WATER RESOURCES
- 3.5.1 Surface Water
- 3.5.2 Local Groundwater
- 3.5.3 Groundwater Potential
- 3.5.4 Water Use in the Moqhaka Local Municipality
- 3.6 GEOLOGY AND GEOHYDROLOGY
- 3.6.1 General Geology
- 3.6.2 Geohydrology
- 3.7 SUMMARY
- CHAPTER 4 DESKTOP STUDY
- 4.1 INTRODUCTION
- 4.2 REMOTE SENSING AND MAP ANALYSIS
- 4.2.1 Borehole Siting
- 4.3 BOREHOLE INFORMATION
- 4.4 SUMMARY
- CHAPTER 5 GEOPHYSICAL INVESTIGATIONS
- 5.1 INTRODUCTION
- 5.2 MAGNETIC SURVEY
- 5.2.1 Results and Discussion
- 5.3 SUMMARY
- CHAPTER 6 DRILLING AND GEOLOGICAL CHARACTERISATION
- 6.1 INTRODUCTION
- 6.2 PERCUSSION DRILLING
- 6.2.1 Lithology
- 6.2.2 Unsuccessfully Drilled Boreholes
- 6.3 SUMMARY
- CHAPTER 7 PUMP TESTING AND AQUIFER PARAMETERS
- 7.1 INTRODUCTION
- 7.2 AQUIFER TESTING
- 7.2.1 Blow Yields
- 7.2.2 Step Discharge Test
- 7.2.3 Constant Discharge Test
- 7.2.3.1 Diagnostic plots
- 7.2.4 Recovery Test
- 7.2.5 Aquifer Parameters
- 7.2.5.1 Cooper-Jacob method
- 7.2.5.1.1 Validity of Assumptions of Cooper-Jacob method
- 7.2.5.1.2 Estimation of Transmissivity using Cooper-Jacob method
- 7.2.5.2 RPTSOLV program
- 7.3 SUMMARY
- CHAPTER 8 EXPLOITABLE GROUNDWATER RESOURCE
- 8.1 INTRODUCTION
- 8.2 RECHARGE ESTIMATION
- 8.2.1 Chloride Mass Balance Method
- 8.2.2 Qualified Guesses
- 8.3 GROUNDWATER RESOURCE SUSTAINABLE YIELD ESTIMATES
- 8.3.1 Borehole Recommended Yields
- 8.3.2 Water Balance
- 8.4 SUMMARY
- CHAPTER 9 HYDROCHEMISTRY
- 9.1 INTRODUCTION
- 9.2 STATISTICAL ANALYSIS
- 9.2.1 Univariate Statistics
- 9.2.2 Quality of Inorganic Chemistry Data
- 9.3 GROUNDWATER QUALITY
- 9.3.1 Irrigation suitability
- 9.4 HYDROGEOCHEMICAL CHARACTERISTICS
- 9.5 SUMMARY
- CHAPTER 10 CONCLUSIONS AND RECOMMENDATIONS
- 10.1 INTRODUCTION
- 10.1.1 Geophysics Survey
- 10.1.2 Geology and Geohydrology
- 10.1.3 Aquifer Parameters
- 10.1.4 Groundwater Quality
- 10.1.5 Groundwater Sustainable Use
- 10.1.6 Additional Findings
- 10.2 RECOMMENDATIONS
Objectives and Key Themes
This dissertation explores the groundwater resources of Steynsrus, a small town in the Free State Province of South Africa, to assess their suitability for supplementing the town's water supply. It investigates the geohydrological properties of the Karoo Main Basin aquifers in the study area, aiming to understand the factors controlling groundwater occurrence, flow, quality, and storage. The study employs various field and laboratory experiments to gather data and information about the aquifer, with a focus on optimizing groundwater exploration and determining sustainable water use for the town.
- Groundwater Occurrence and Exploration Methods
- Aquifer Properties and Parameters
- Groundwater Recharge and Sustainable Yield
- Groundwater Quality Assessment
- Water Balance and Sustainable Water Management
Chapter Summaries
- Chapter 1: Introduction: This chapter presents an overview of the research framework, the water supply background of Steynsrus, the problem statement, the methodology used in the study, and the specific aims and objectives of the dissertation.
- Chapter 2: Literature Review: This chapter reviews the relevant literature related to groundwater resource assessment, focusing on the concepts, methods, and challenges associated with understanding and utilizing groundwater resources in fractured rock aquifers. The review covers topics such as groundwater occurrence, flow, storage, recharge estimation, and sustainable development.
- Chapter 3: Site Description: This chapter provides a detailed description of the study area, covering aspects such as population, physiography, drainage, climate, vegetation and land use, water resources, geology, and geohydrology. It aims to establish a comprehensive understanding of the physical and geological setting of Steynsrus.
- Chapter 4: Desktop Study: This chapter details the desktop studies conducted for the project, including the analysis and interpretation of geological maps, aerial ortho photo maps, and airborne magnetic data contour maps. It also includes a summary of information gathered from a hydrocensus of existing boreholes in the area.
- Chapter 5: Geophysical Investigations: This chapter focuses on the geophysical surveys conducted in the study area. The chapter examines the use of the magnetic method for locating drilling targets and delineating subsurface structures. It critically evaluates the magnetic data obtained from the surveys, highlighting potential errors and inconsistencies.
- Chapter 6: Drilling and Geological Characterisation: This chapter describes the drilling process employed in the study area, including the percussion drilling method and geological logging of the boreholes. It analyzes the lithology encountered during drilling, focusing on the identification of water strikes, blow yields, and the geological structures associated with groundwater occurrence.
- Chapter 7: Pump Testing and Aquifer Parameters: This chapter delves into the aquifer pump testing conducted on the boreholes in the area. The chapter explains the use of step drawdown tests, constant discharge tests, and recovery tests for determining sustainable yields and estimating aquifer parameters. It uses diagnostic plots to characterize the flow regimes and analyze the hydraulic behavior of the aquifers.
- Chapter 8: Exploitable Groundwater Resource: This chapter focuses on the estimation of groundwater recharge and sustainable yields of the boreholes. It discusses the water balance of the study area, considering the estimated recharge, sustainable yields, and the projected water demands of the town. The chapter examines the potential for groundwater to meet the current and future water requirements of Steynsrus.
- Chapter 9: Hydrochemistry: This chapter presents an assessment of the groundwater quality in the study area. It analyzes the hydrochemical data from water samples collected during the study, evaluating the major and minor ions, and classifying the groundwater quality according to different standards. The chapter discusses the potential implications of the water quality for drinking and irrigation purposes.
Keywords
This research focuses on the assessment of groundwater resources in a fractured rock environment. The primary research focus includes the use of geophysical exploration methods, borehole drilling, aquifer pump testing, and groundwater quality analysis. The study emphasizes the determination of borehole sustainable yield, aquifer parameters, and the estimation of groundwater recharge and the water balance. These findings highlight the challenges and opportunities of sustainable groundwater management in the Karoo Main Basin of South Africa.
- Quote paper
- Lebogang Malefane (Author), 2016, Groundwater Resource Assessment for Town Water Supply in South Africa. The Case of Steynsrus in the Free State Province, Munich, GRIN Verlag, https://www.grin.com/document/910024
