Anatomy of a South African Karst Hydrosystem: The Hydrology and Hydrogeology of the Cradle of Humankind World Heritage Site (Cave and Karst Systems of the World)

This book combines the results of the research activities in the assessment of water resources environment and an integrated water resource monitoring program to support preservation efforts of the aquatic environment of the Cradle of Humankind (COH), World Heritage Sites. A poor understanding of the surface and groundwater resources of the COH property has precipitated often alarmist reporting in the media regarding the negative impacts associated with various sources of poor quality water. The most notable of these is the acid mine drainage threat to karst ecosystems and fossil sites across the property. These circumstances have generated wide and considerable concern for the preservation of the UNESCO-inscribed fossil sites and integrity of the water resources of the property. Declaration Acknowledgements Historical Timeline of Key Events Relevant to this Dissertation Recent Timeline of Key Events Relevant to this Dissertation Extended Summary Introduction Surface Water Resources Sec6 Sec7 Groundwater Resources Sec9 Sec10 Conclusions Recommendations Contents Symbols, Acronyms and Abbreviations List of Figures List of Tables List of Plates List of Text Boxes Précis Synoptic Information on Sterkfontein Cave 1 Integrated Monitoring Approach 2 Introduction and Background 1 Legal and Physical Framework 2 Hydrophysical Framework 3 Aims and Objectives 4 Definition of the Study Area 3 Description of the Physical Environment 1 Morphology and Drainage 2 Climate and Rainfall 3 Vegetation and Soils 4 Geology and Geophysics 5 Mining Geology 6 Palaeontology, Archaeology and Ecology 4 Overview of Karst 1 General Overview of Global Karst 1.1 Age and Distribution 1.2 Karst and Acid Mine Drainage 2 Overview of South African Karst Water Resources 2.1 Water Supply Aspect 2.2 Geotechnical and Vulnerability Aspects 3 Speleogenesis of Karst Aquifers 3.1 Speleogenesis of South African Karst 3.1.1 Overview 3.1.2 Discussion 3.2 The Epikarst 3.2.1 General Discussion 3.2.2 Epikarst of the COH 5 Physical Hydrology 1 Surface Water Drainage 2 Skeerpoort River System 3 Bloubank Spruit System 3.1 Tweelopie Spruit 3.2 Blougat Spruit 3.3 Crocodile River 4 Regional Context and Synthesis 5 Surface Water Gains/Losses 5.1 Historical Information 5.2 Recent/Current Information 5.2.1 Tweelopie Spruit and Riet Spruit 5.2.2 Blougat Spruit 5.2.3 Bloubank Spruit 6 Surface Water Use 6.1 WARMS Data 6.2 Canals 6.3 Conclusion 6 Chemical Hydrology 1 Surface Water Chemistry 1.1 Skeerpoort River 1.2 Bloubank Spruit System 1.2.1 Locus of Mine Water Discharge (Decant) 1.2.2 Tweelopie Spruit 1.2.3 Riet Spruit 1.2.4 Blougat Spruit 1.2.5 Tweefontein Spruit 1.2.6 Bloubank Spruit 1.3 Crocodile River 1.4 Synthesis of Surface Water Chemistry 2 Salt Load Assessment 2.1 Catchment Scale 2.2 Subcatchment Scale 2.2.1 Tweelopie Spruit 2.2.2 Riet Spruit 2.2.3 Blougat Spruit 2.3 Regional Context and Synthesis 3 Pollution Indicators and Pollutants 3.1 Sulfate-to-Chloride Ratio 3.2 Nitrate-to-Phosphorus Ratio 3.3 Trace/Heavy Metals and Metalloids 3.3.1 Iron (Fe) and Manganese (Mn) 3.3.2 Mercury (Hg) 3.3.3 Aluminium (Al) 3.3.4 Arsenic (As) 3.3.5 Other Metals 3.4 Radionuclides 3.4.1 Uranium (238U and 234U) 3.4.2 Radon (222Rn) 3.4.3 Radium (226Ra and 228Ra) 3.5 Net Alkalinity and Net Acidity 4 Surface Water Fitness 4.1 Potable Use 4.2 Agricultural Use 4.2.1 Livestock Watering 4.2.2 Irrigation 4.3 Recreational Use 5 Mine Water Chemistry in the Receiving Drainages 5.1 Ad Hoc Observations 5.2 Opportunistic Observations 5.3 Visual Observations 5.4 Sediment Chemistry 5.4.1 Chemical Composition 5.4.2 Solubility and Remobilisation 5.5 Historical Observations 7 Physical Hydrogeology 1 Introduction 2 Basin (Compartment) Definition 2.1 Zwartkrans Basin 2.1.1 Vlakdrift Subcompartment 2.1.2 Sterkfontein Subcompartment 2.1.3 Zwartkrans Subcompartment 2.2 Krombank Basin 2.2.1 Kromdraai Subcompartment 2.2.2 Bloubank Subcompartment 2.3 Danielsrust Basin 2.4 Uitkomst Basin 2.5 Tweefontein Basin 2.6 Rietfontein Basin 2.7 Diepkloof Basin 2.8 Motsetse Basin 2.9 Rhenosterspruit Basin 2.10 Kalkheuvel Basin 2.11 Broederstroom Basin 2.12 Discussion of Basin Definition and Groundwater Recharge 3 Groundwater Level Behaviour 3.1 Zwartkrans Basin 3.2 Sterkfontein Cave System Water Level 3.2.1 General Discussion 3.2.2 Potentiometric Response Pattern 4 Springs 4.1 Zwartkrans Spring 4.2 Plover’s Lake Springs 4.3 Kromdraai Spring 4.4 Danielsrust Spring 4.5 Aquamine Spring 4.6 Tweefontein Spring 4.7 Nouklip Spring 4.8 Nash Spring 4.9 Uitkomst Spring 4.10 Cradle Spring 4.11 Anderson Spring 4.12 Barlow Spring 4.13 Lesedi Spring 4.14 Broederstroom Spring 4.15 Krugersdorp Game Reserve Springs 4.16 Spring Discharge Context and Significance 5 Water in the Mining Environment 6 Groundwater Drainage Pattern 7 Groundwater Fluxes 8 Conduit Flow Depth and Path 9 Groundwater Use 10 Closure of DWS Monitoring Stations 8 Chemical Hydrogeology 1 Regional Groundwater Chemistry 2 Subregional Groundwater Chemistry 2.1 Background 2.1.1 West Rand Group (Witwatersrand Supergroup) 2.1.2 Malmani Subgroup (Chuniespoort Group) 2.1.3 Pretoria Group (Transvaal Supergroup) 2.2 Temporal Groundwater Chemistry Assessment 2.3 Source-Specific Temporal Assessment 2.3.1 Mine Area (Locus of Decant) 2.3.2 Krugersdorp Game Reserve 2.3.3 Lower Riet Spruit 2.3.4 Sterkfontein Cave System 3 Groundwater Chemistry Assessment by GRU 3.1 Zwartkrans Basin 3.1.1 Vlakdrift Subcompartment 3.1.2 Sterkfontein Subcompartment 3.1.3 Zwartkrans Subcompartment 3.2 Krombank Basin 3.2.1 Kromdraai Subcompartment 3.2.2 Bloubank Subcompartment 3.3 Danielsrust Basin 3.4 Uitkomst Basin 3.5 Tweefontein Basin 3.6 Rietfontein Basin 3.7 Diepkloof Basin 3.8 Motsetse Basin 3.9 Rhenosterspruit Basin 3.10 Kalkheuvel Basin 3.11 Broederstroom Basin 4 Local Groundwater Chemistry Assessment 5 Isotope Chemistry 5.1 Previous Studies 5.2 Isotopic Information 5.2.1 Stable Isotopes 5.3 Radioactive Isotopes 6 Bacteriological Quality 7 Springwater Chemistry 7.1 Zwartkrans Spring 7.2 Danielsrust Spring 7.3 Plover’s Lake Springs 7.4 Kromdraai Spring 7.5 Tweefontein Spring 7.6 Aquamine Spring 7.7 Nouklip Spring 7.8 Nash Spring 7.9 Uitkomst Spring 7.10 Cradle Spring 7.11 Barlow Spring 7.12 Anderson Spring 7.13 Lesedi Spring 7.14 Broederstroom Spring 7.15 Krugersdorp Game Reserve Springs 8 Selected Impacts 8.1 Agriculture 8.2 Historical Mining 8.3 Human Settlement 8.4 Mine Water 9 Groundwater Fitness 9.1 Potable Use 9.2 Agricultural Use 9.2.1 Livestock Watering 9.2.2 Irrigation 9.3 Cave Ecosystems 10 Vertical Hydrochemical Variation 10.1 Introduction 10.2 Methodology and Approach 10.3 Results 10.3.1 #18 Winze 10.3.2 CPS Borehole 10.3.3 Borehole RG1 10.3.4 Borehole RG2 10.3.5 Borehole RG3 10.3.6 Borehole MGP1 10.3.7 Borehole MGP2 10.3.8 Borehole MGP3 10.3.9 Borehole MGP4 10.3.10 Borehole GP00305 10.3.11 Borehole GP00306 10.3.12 Borehole GP00307 10.3.13 Borehole GP00308 10.3.14 Boreholes A2N0583 and GP00304 10.3.15 Boreholes A2N0584 and GP00302 10.3.16 Boreholes A2N0586 and GP00300 10.3.17 Borehole GP00301 10.3.18 Borehole GP00309 10.3.19 Borehole GP00311 10.3.20 Borehole GP00312 10.3.21 Borehole GP00313 10.3.22 Borehole GP00314 10.4 Discussion 11 Bacterial Sulfate Reduction 12 Dissolution of Carbonate Strata 12.1 Natural Solutional Denudation 12.1.1 Formula Approach 12.1.2 Empirical Approach 12.1.3 Theoretical Approach 12.1.4 Application 12.1.5 Discussion 12.1.6 Conclusion 12.2 Interaction with Mine Water 12.2.1 Carbonate Dissolution 12.2.2 Dedolomitization 12.2.3 Dolomite Armoring 13 Hydrochemistry of Mine Water 13.1 Iron Chemistry 13.2 Net Alkalinity and Net Acidity 13.3 Local Studies 13.4 Conclusions 14 Carbon Flux in Springwater 14.1 Introduction 14.2 Approach 14.3 Results 14.4 Discussion 9 Conclusions 1 Surface Water Resources 1.1 Quantity 1.2 Quality 2 Groundwater Resources 2.1 Quantity 2.2 Quality 3 Mine Water Impact on Dolomite 4 Resource Water Quality Objectives 4.1 Quantity 4.2 Quality 5 Karst Solutional Denudation 6 Fossil Site Hydro-vulnerability 10 Recommendations Appendix_1 Glossary References Bibliography Index