5 What, after all, is Apollos? And what is Paul? Only servants, through whom you came to believe—as the Lord has assigned to each his task. 6 I planted the seed, Apollos watered it, but God has been making it grow. 7 So neither the one who plants nor the one who waters is anything, but only God, who makes things grow. 8 The one who plants and the one who waters have one purpose, and they will each be rewarded according to their own labour. 9 For we are co-workers in God’s service; you are God’s field, God’s building. 10 By the grace God has given me, I laid a foundation as a wise builder, and someone else is building on it. But each one should build with care. 11 For no one can lay any foundation other than the one already laid, which is Jesus Christ. 12 If anyone builds on this foundation using gold, silver, costly stones, wood, hay or straw, 13 their work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each person’s work. 14 If what has been built survives, the builder will receive a reward. 15 If it is burned up, the builder will suffer loss but yet will be saved—even though only as one escaping through the flames. 1 Corinthians 3:5-15, New International Version (NIV) Bible i DEDICATION This Thesis is dedicated to my wife Dinknesh and children ii DECLARATION BY CANDIDATE I hereby declare that the thesis submitted for the degree, Doctor Technologiae; Civil Engineering, at Tshwane University of Technology is my own original work and has not previously been submitted to any other institution of higher education. I further declare that all sources cited or quoted are indicated and acknowledged by means of a comprehensive list of references. iii ACKNOWLEDGEMENTS I thank Professor G.M. Ochieng for his decision to supervise my thesis. He risked himself to rescue me when I was in a bad situation. I am indebted to Professor G.M. Ochieng and Professor J. Snyman for organizing fund to settle all my debts in 2015 academic year and carefully commenting on the thesis report. I am grateful to M. Makaleng for his outstanding assistance towards completion of this thesis report. This report could not have been accomplished without the support and cooperation of him. R. J. van Vuuren contributed outstanding advice whenever I experienced problems. Professor B. van Wyk and Professor J.L. Munda played a great role towards the completion of this thesis report hence, I appreciate their remarkable decision. I thank iThemba Labs of National Research Fund (NRF) and Science Faculty Labs of Tshwane University of Technology for analyzing all the samples. I also acknowledge Institute of Agricultural Research, Department of Water Affairs and Department of Environmental Affairs for providing data to complete this thesis project. I also would like to thank members of community forum of Mafefe wetland and farmers who allowed us to install all hydrometric equipments and monitor during the last seven years. iv APPROVED BY STUDY PANNEL: PROFESSOR G.M. OCHIENG: SUPERVISOR __________________________________________ PROFESSOR J. SNYMAN: CO-SUPERVISOR __________________________________________ v ABSTRACT This study presents the findings of long-term monitoring of groundwater (GW) table levels, surface water (SW), environmental isotopes and water quality in the Mohlapitsi/Mafefe wetland and highlights the applicability of monitoring data to water resources issues. The specific objectives were to analyze and quantify the dynamics of water generation and retention within the wetland, trace flow dynamics using environmental isotopes and water chemistry as well as develop a workable water balance of the study site. Piezometers were installed along seven transects namely T1, T2, T3, T4, T5, T6 and T7. Long-term groundwater levels (GWL) were monitored in order to understand water table fluctuations. Water samples were collected from 2007 to 2013 for tritium, deuterium, oxygen-18 and water quality analyses, and analyzed in iThemba laboratory, Johannesburg. Water balance of the Middle Mohlapitsi Wetland was conducted and estimated using data from South African Weather Service (SAWS) and Department of Water Affairs (DWA) for the period 2006- 2012. Most of the piezometers closest to the river channel showed the lowest variations. For example, piezometer MRB101 (next to river channel) showed 1.42 m variation, while MRB102 (110 m from the channel) showed 3.21 m variation. In addition, MLB702 (102 m from the channel) in T7 showed least variation, which is 0.55 m, while MLB703 (154 m from the channel) showed 0.79 m variation. Hydraulic gradient is mainly towards the river, indicating GW moves from the wetland to the river. The relationships between rainfall, groundwater, and surface water showed that stream flow did not respond quickly to precipitation as vi expected. Statistical analysis showed that there is a significant moderate positive correlation (p = 0.0041) between rainfall and streamflow. The average Oxygen-18 composition between winter and summer seasons was significantly different (p = 0.0026), indicating winter season had higher O-18 values than summer (average 31.27 vs 20.43). The highest tritium value for tritium (3.2 TU) was measured during May 2008; indicating new rainfall water entered the spring storage and mixed with old water. The lowest tritium value measured for Valis bore hole was 0.3 TU, indicating this water is the oldest. Electrical conductivity (EC), alkalinity (Alk) and major ion analysis proved low mineralization CaMa-HCO3 type of water for samples from 2007 to 2010, while Na-HCO3 type water was analyzed for samples from 2011 to 2014. In both cases ion samples clustered together in the cation triangle, indicating the same origin of water. There was no significant difference (p = 0.4196) between average EC between summer and winter season. Water-budget equation was calculated for evapotranspiration (ET), the value of which was affected by errors of missing data, overestimated/underestimated quantities, and poor measurements. No water was imported to the study area, and no groundwater (GW) was exported to the surrounding catchments. In conclusion the results obtained in this thesis can be used as a tool in semi-arid wetlands conservation and management practices. This can be achieved by means of long-term monitoring research of wetland hydrological processes. It is recommended that in order to optimally manage a groundwater resource that is being utilised, it is highly important to update water balance calculations. vii Table of Contents Acknowledgements iv Abstract vi CHAPTER 1: BACKGROUND 1 1.0 Introduction 1 1.1 Wetlands definitions, identifications, loss and threats 6 1.1.1 Wetland definition 6 1.1.2 Wetland identifications 7 1.1.3 Global wetlands loss and their threats 8 1.2 South African wetlands 13 1.2.1 Issues in wetlands 13 1.3 Key questions 15 1.4 Background to the study 16 1.5 Problem statement 17 1.6 Aims and objectives of the study 17 1.7 Contribution of this thesis report 18 1.8 Structure of the thesis 22 CHAPTER 2: LITERATURE REVIEW 24 2.1 Introduction 24 2.2 Structure of the literature review 25 2.3 Wetland and ecological indicators 26 Acknowledgements2.3.1 Wetland vegetation ................................ ................................ ............................... ? 27 Abstract2.3.2 Hydric …………………………………………………………………….. soils ... i 27 CHAPTER2.3.3 Wetland 1:BACKGROUND hydrology .......................... 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Bookmark not defined. 29 2.4 Wetland processes 31 2.5 Ecological importance of wetlands 33 2.6 Values of wetlands viii 35 2.5 Ecological importance of wetlands 38 2.6 Values of wetlands 40 2.7 Threats to wetlands 41 2.7.1 Introduction 41 2.7.2 Wetland degradation due to agriculture 42 2.7.3 Impacts of irrigated agriculture on wetland ecosystem 46 2.7.4 Wetland degradation due to hydropower development 50 2.7.5 Natural impacts on wetlands 52 2.8 Groundwater and surface water interactions 53 2.8.1 Introduction 53 2.8.2 Interaction of groundwater and streams 55 2.8.3 GW-SW interactions in a catchment 61 2.8.4 GW-SW interactions in a wetland environment 67 2.8.5 GW-SW interactions in Karst terrain 83 2.8.6 GW-SW interactions in glacial and dune terrain 84 2.8.7 GW-SW interactions in coastal terrain 85 2.8.8 GW-SW interactions in River valley terrain 86 2.8.9 GW-SW interactions in mountainous terrain 87 2.9 Methods of investigation of GW-SW interactions 89 2.9.1 Wetlands water budget 89 2.9.2 Piezometers and wells 91 2.9.3 Seepage meters 92 2.9.4 Temperature 93 2.9.5 Hydrogeophysics 93 2.9.6 Hydrological models 94 ix Figures Figure 1.1 South African Wetlands………………………………………... ..10 Figure 1.2 South African Ramsar Sites…………………………………….. ..12 2.9.7 Isotopes and hydrochemistry 96 2.9.7.1 Stable isotopes 97 2.9.7.2 Radioactive isotopes 101 2.9.7.3 Hydrochemistry 104 2.10 Wetland management 105 2.11 Summary and conclusions 109 CHAPTER 3: STUDY CATCHMENT 120 3.1 Site descriptions 120 3.2 Climate of the study area 125 3.3 Population and unemployment 127 3.4 Geology 127 3.5 Soils 130 3.6 Hydrology of the wetland area 131 3.7 Sources of water feeding the wetland 135 3.8 Engineering structures 137 CHAPTER 4: METHODOLOGY 140 4.1 Instrumentation 140 4.2 Weather data 140 4.3 Piezometer installation and groundwater monitoring 143 4.3.1 Conceptual Modeling for flow generation within each Transect 148 4.4 Streamflow measurements 148 4.5 Water sampling for environmental isotopes, hydrochemistry and field parameters analysis 149 4.5.1 Water sampling for stable isotopes 149 4.5.2 Water sampling for tritium analysis 150 x Figures Figure 1.1 South African Wetlands………………………………………..