Long-term salinity changes in the Crocodile river catchment upstream of Hartebeespoort dam
Author: Albert van Eeden
Supervisor: Dr. Harold van Niekerk (Department of Water and Sanitation)
Submitted in partial fulfilment of the requirements for the degree of Master of Science in Water Resource Management
In the Faculty of Natural & Agricultural Sciences
University of Pretoria
Pretoria
27 November 2017
DECLARATION OF AUTHORSHIP
I, Albert van Eeden declare that the thesis/dissertation which I hereby submit for the degree Masters of Science in Water Resource Management at the University of Pretoria, is my own work and has not previously been submitted by me for a degree at this or any other tertiary institution.
SIGNATURE:
DATE: 27 November 2017
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ACKNOWLEDGEMENTS
First and foremost, I want to thank my Heavenly Father for His provision and giving me this opportunity to study further as well enabling me through His grace to do this research project, for without Him this research project wouldn’t have been possible at all. Secondly, I want to express my deepest gratitude and thanks to my supervisor Dr. Harold van Niekerk for his guidance, insight, patience and wisdom during the entirety of this research project from inception to completion. As well as his willingness to help and encouragement, it is something I will always be grateful for.
It is with great appreciation and recognition that the author would like to thank the following intuitions and individuals for their contributions in completing this thesis:
• The Department of Water and Sanitation for the use of their raw data; • And lastly, my whole family for their love, support, encouragement and prayers throughout the completion of this research project.
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TABLE OF CONTENTS
LIST OF ABBREVIATIONS ...... v LIST OF FIGURES ...... vi LIST OF GRAPHS ...... vi LIST OF TABLES ...... vii ABSTRACT ...... 1 CHAPTER 1: INTRODUCTION ...... 2 1.1 Project initiation, approach and objective ...... 2 CHAPTER 2: LITERATURE REVIEW ...... 4 2.1 General description of TDS (Total Dissolved Salts), EC (Electrical Conductivity) & ionic salts as essential background information regarding this research project ...... 4 2.2 Study area description ...... 6 2.3 Land use and water quality issues in the catchment ...... 8 CHAPTER 3: METHODOLOGY ...... 11 3.1 Site selection ...... 11 3.2 Data management ...... 12 3.3 Data interpretation ...... 13 CHAPTER 4: RESULTS ...... 15 4.1 A2H12, A2H44 & A2H45 five yearly average TDS Concentration, Loads and Volume: ...... 16 4.2 A2H12, A2H44 & A2H45 five yearly average SO₄ Concentration and Loads: ...... 19 4.3 A2H12, A2H44 & A2H45 five yearly average TAL Concentration and Loads: ...... 21 4.4 Monitoring station A2H12 on the Crocodile river: ...... 23 4.5 Monitoring station A2H44 on the Jukskei river: ...... 26 4.6 Monitoring station A2H45 on the Crocodile river: ...... 30 4.7 Monitoring station A2H23 on the Jukskei river: ...... 34 4.8 Monitoring station A2H40 on the Jukskei river: ...... 35 4.9 Monitoring station A2H42 on the Jukskei river: ...... 36 4.10 Monitoring station A2H47 on the Klein-Jukskei: ...... 37 4.11 Monitoring station A2H49 on the Bloubankspruit: ...... 38 4.12 Monitoring station A2H50 on the Crocodile river: ...... 40 CHAPTER 5: DISCUSSION AND CONCLUSION ...... 42 5.1 Discussion ...... 42 5.1.1 Five yearly average concentrations of TDS, SO₄ and TAL ...... 42 5.1.2 Five yearly average loads of TDS, SO₄ and TAL ...... 43 5.1.3 Five yearly average volume at monitoring stations A2H12, A2H44 and A2H45...... 44
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5.2 Conclusion ...... 45 REFERENCES ...... 47 APPENDIX A ...... 49 APPENDIX B ...... 65
LIST OF ABBREVIATIONS
AMD – Acid Mine Drainage
°C – Degrees Celsius
Ca – Calcium
CBD – Central Business District
CO₃ – Carbonate
DWAF – Department of Water Affairs and Forestry
DWS – Department of Water and Sanitation
EC – Electrical Conductivity
HCO₃ – Hydro carbonate
K – Potassium
MAP – Mean Annual Precipitation
Mg – Magnesium
Na – Sodium
NCMP – National Chemical Monitoring Programme
SO₄ – Sulphate
TAL – Total Alkalinity
TDS – Total Dissolved Salts
WMA – Water Management Area
WWTW – Waste Water Treatment Works
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LIST OF FIGURES
Figure 1: The study area’s rivers, urban centres and quaternary catchments ...... 6 Figure 2: Study area indicating location of monitoring stations ...... 12 Figure 3: Example of a Maucha diagram ...... 13 Figure 4: Maucha diagrams at monitoring station A2H12 on the Crocodile river ...... 15 Figure 5: Maucha diagrams at monitoring station A2H12 on the Crocodile river ...... 23 Figure 6: Maucha diagrams at monitoring station A2H44 on the Jukskei river...... 26 Figure 7: Maucha diagrams at monitoring station A2H45 on the Crocodile river ...... 30 Figure 8: Maucha diagrams at monitoring station A2H23 on the Jukskei river...... 34 Figure 9: Maucha diagrams at monitoring station A2H40 on the Jukskei river ...... 35 Figure 10: Maucha diagrams at monitoring station A2H42 on the Jukskei river...... 36 Figure 11: Maucha diagrams at monitoring station A2H47 on the Klein-Jukskei river ...... 37 Figure 12: Maucha diagrams at monitoring station A2H49 on the Bloubankspruit ...... 38 Figure 13: Maucha diagrams at monitoring station A2H50 on the Crocodile river ...... 40
LIST OF GRAPHS
Graph 1: Five yearly average TDS concentration at monitoring stations A2H12, A2H44 & A2H45 ..... 16 Graph 2: Five yearly average TDS loads at monitoring stations A2H12, A2H44 & A2H45 ...... 17 Graph 3: Five yearly average volume at monitoring stations A2H12, A2H44 & A2H45 ...... 18 Graph 4: Five yearly average SO₄ concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised ...... 19 Graph 5: Five yearly average SO₄ loads at monitoring stations A2H12, A2H44 & A2H45 tabularised. 20 Graph 6: Five yearly average TAL concentration at monitoring stations A2H12, A2H44 & A2H45 ..... 21 Graph 7: Five yearly average TAL loads at monitoring stations A2H12, A2H44 & A2H45 ...... 22 Graph 8: Five yearly average SO₄, TAL and TDS concentration at monitoring station A2H12 ...... 24 Graph 9: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H12 ...... 25 Graph 10: Five yearly average concentration of SO₄, TAL, TDS and Volume at monitoring station A2H12 ...... 26 Graph 11: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H44 ...... 27 Graph 12: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H44 ...... 28 Graph 13: Five yearly average concentration of SO₄, TAL, TDS and Volume at monitoring station A2H44 ...... 29 Graph 14: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H45 ...... 31 Graph 15: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H45 ...... 32 Graph 16: Five yearly average SO₄, TAL, TDS concentration and Volume at monitoring station A2H45 ...... 33 Graph 17: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H23 ...... 34 Graph 18: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H40 ...... 35 Graph 19: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H42 ...... 36 Graph 20: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H47 ...... 37 Graph 21: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H49 ...... 39 Graph 22: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H50 ...... 40
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LIST OF TABLES
Table 1: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H12...... 15 Table 2: Five yearly average TDS concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised ...... 16 Table 3: Five yearly average TDS loads at monitoring stations A2H12, A2H44 & A2H45 tabularised . 17 Table 4: Five yearly average volume at monitoring stations A2H12, A2H44 & A2H45 tabularised ..... 18 Table 5: Five yearly average SO₄ concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised ...... 19 Table 6: Five yearly average SO₄ loads at monitoring stations A2H12, A2H44 & A2H45 tabularised .. 20 Table 7: Five yearly average TAL concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised ...... 21 Table 8: Five yearly average TAL loads at monitoring stations A2H12, A2H44 & A2H45 tabularised .. 22 Table 9: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H12...... 23 Table 10: Five yearly average SO₄, TAL and TDS concentration at monitoring stations A2H12 tabularised ...... 24 Table 11: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H12 tabularised ...... 25 Table 12: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H44...... 27 Table 13: Five yearly average SO₄, TAL and TDS concentration at monitoring station A2H44 tabularised ...... 28 Table 14: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H44 tabularised ...... 29 Table 15: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H45...... 30 Table 16: Five yearly average SO₄, TAL and TDS concentration at monitoring station A2H45 tabularised ...... 31 Table 17: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H45 tabularised ...... 32
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ABSTRACT
This research study investigated the changes in the salinity composition and fluctuation of the Crocodile river and its catchment upstream of the Hartbeespoort dam covering the period of 1985 to 2015. By analysing the 35-year long-term data sets of nine monitoring stations in the study area’s catchment, various trends and patterns emerged. Maucha diagrams and various graphs were drawn by utilising the above-mentioned data sets. These Maucha diagrams and graphs indicated the changes that took place in the salt composition of the water sources in the catchment of the study area over the 35-year study period. The following three salts, TDS, SO₄ and TAL, showed the biggest margin of change while the other salts remained fairly stable over the study period. Thus, the study focussed on these three salts. The five-yearly average of the TDS, SO₄ and TAL concentration, loads as well as the volume of water coming down the catchment were calculated. By interpreting the results, it was clear which sub-catchments were responsible for the specific salinity changes identified, as well as the possible sources of those changes in the salinity composition and fluctuation. Both the Jukskei river and the Bloubankspruit had significant impacts on the salt composition, concentration and loads in the Crocodile river although the nature of their impacts differed. The main drivers of salinity changes in the Crocodile river catchment were found to be anthropogenic sources such as increased run-off resulting from urbanisation, the progressive expansion of hard surfaces, increase in economic and industrial activities with their corresponding pollution sources, population growth, water transfer from outside the study area’s catchment and an increase in the volume of water deposited study area’s catchment. The importance of continued monitoring and sampling programmes were emphasised during this research study.
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CHAPTER 1: INTRODUCTION
1.1 Project initiation, approach and objective
This research project came into being as a result of a research paper published by Van Niekerk et al. (2009) namely “Monitoring programme revision highlights long-term salinity changes in selected South African rivers and the value of comprehensive long-term data sets”. According to this research paper, long-term consistent data collection over many years at flow gauging stations (referred to in this research project as monitoring stations) were used to identify the long-term salinity changes occurring in South African rivers. This database of information is important in the sense that informed management decisions regarding South Africa’s aquatic ecosystems can be made and it can help with the assessment of our water resources. When salinity levels in water sources fluctuate or the salinity composition structure changes, it can negatively impact the agricultural, industrial and household sectors as well as the biodiversity component of the ecosystem.
All this forms part of the Department of Water Affairs National Chemical Monitoring Programme (NCMP) which has monitored South African rivers for more than 40 years and have data sets covering this period. According to this study, long-term data sets are imperative as a management and decision- making tool regarding the effective and sustainable management of water resources. The one major finding of the research paper, published by Van Niekerk et al. (2009), was that the TDS concentration at monitoring station A2H12 on the Crocodile river showed a decrease over a temporal scale (Van Niekerk et al., 2009). This research project namely “The long-term Salinity changes in the Crocodile river catchment upstream of Hartbeespoort dam” will use the above-mentioned research paper as a departure point and will built upon it, but will specifically examine in more detail the salinity changes in the Crocodile river’s catchment upstream of Hartebeespooort dam over the long-term (35-year period). The departure point will be at monitoring station A2H12 at the bottom of the catchment and then from this station onwards there will be systematically worked all the way up the Crocodile river and its tributaries to the other monitoring stations higher up the catchment.
In terms of the scope of the research project there will be focussed on the salinity characteristics and salinity composition of water quality such as the main salts and not on other factors influencing water quality. The reason for this is that there is a wealth of information available regarding various aspects of water quality in the Crocodile river and its catchment but research regarding changes in water salinity composition is not as widespread and well researched.
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This research project has the following objectives:
• To investigate the changes in the long-term salinity composition focussing on the main salts in the catchment of the Crocodile river upstream of Hartebeespoort dam over a period of 35- years stretching from 1980 to 2015. • To discuss potential drivers in the study area’s catchment that contributes and influences the changes in salinity composition over the period stretching from 1980 to 2015.
The research project was approached according to the following rationale:
• The starting point for this research project was the monitoring station on the Crocodile river nearest to the Hartbeespoort dam namely A2H12. The characteristics and composition of the main salts at this monitoring station was then compared with the other stations upstream or further up the catchment, including stations on the Jukskei river and tributaries of the Crocodile and Jukskei rivers. The monitoring stations that formed part of this research project is listed below (refer to Figure 2): o A2H12 on the Crocodile river o A2H44 on the Jukskei river o A2H45 on the Crocodile river o A2H42 on the Jukskei river o A2H40 on the Jukskei river o A2H23 on the Jukskei river o A2H47 on the Klein-Jukskei o A2H49 on the Bloubankspruit o A2H50 on the Crocodile river
By following this approach, the salinity changes could be documented in the different segments of the study areas catchment and the possible origin or causes of the salinity changes could be systematically determined. In the broader context, this research study is important since knowledge regarding water chemical composition, properties and interactions are important. It enables policy and decision- makers to better understand problems and challenges regarding water use and supply for a diverse range of sectors, for example fish breeding, hydropower, recreational activities, health and hygiene. Specialised knowledge also enables scientist and policy makers to asses water pollution, to recognise when there is sudden spike in the level of pollutants, to identify the sources of pollution and to make calculated, informed future predictions regarding the state of water resources (Nikanorov and Brazhnikova, 2009).
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CHAPTER 2: LITERATURE REVIEW
2.1 General description of TDS (Total Dissolved Salts), EC (Electrical Conductivity) & ionic salts as essential background information regarding this research project
Total dissolved salts (TDS) is used to measure the salinity of water. TDS can be measured in the following units, milligrams per litre (mg/l), grams per litre (g/l) and parts per million (ppm) (van Niekerk et al., 2014). The TDS is a measurement of the quantity of all the dissolved compounds present in water that has the capacity to conduct an electrical current. It is the ions in water that enables an electrical current to pass through it (DWAF, 1996). When the ion concentration in water rises so does the ability of the water to conduct electricity (van Niekerk et al., 2014). Some of these ions found in water are the following: Magnesium, Calcium, Potassium, Sodium, Nitrate, Sulphate, Chloride, Bicarbonate and Carbonate. The concentration of total dissolved salts is used to estimate the total dissolved solids in water.
TDS and electrical conductivity (EC) has a direct relationship with each other, by measuring the EC of water a reliable TDS measurement can be derived. It is much simpler to measure the EC than the total TDS in an aquatic medium. The concentration of TDS is used to determine the total dissolved solids in water. The natural sources of TDS in water is the minerals that originate from rocks (geology), soils and decomposing plant material that comes in contact with the water source. There are also anthropogenic sources of TDS in water, such as discharges and runoff of effluent from urban, industrial and agricultural sectors (DWAF, 1996).
The main anions that is present in water are the following: Chloride (Cl⁻), Sulphate (SO₄), Hydro carbonate (HCO₃), and Carbonate (CO₃) and the main cations are: Calcium (Ca²⁺), Sodium (Na⁺), Magnesium (Mg²⁺) and Potassium (K⁺) (Nikanorov and Brazhnikova, 2009).
Chloride ions (Cl⁻) possess the capacity to move around freely in conjunction with the high solubility of chloride salts such as magnesium, calcium and sodium. Chloride ions in water originate from the geology, minerals and saline deposits from where it leaches over time. It can also be found in rain water. An anthropogenic source of chloride ions is waste originating from the industrial and urban spheres (Nikanorov and Brazhnikova, 2009).
The presence of sulphate ions (SO₄) in water originates from different kinds of sedimentary rocks such as gypsum and anhydride. When organic matter that contains sulphur decomposes and oxidizes it adds to the amount of sulphur in aquatic systems. Anthropogenic activity further increases the sulphur content in water (Nikanorov and Brazhnikova, 2009). Anthropogenic activities such as mining leads to acidic water with a low pH and high levels of sulphates. Acid Mine Drainage (AMD) forms and takes
Page 4 place under the following circumstances. When sulphide minerals such as pyrite in the geological formations comes in to contact with water and oxygen it forms a solution of sulphuric acid and iron that leaches other metals from the geology. The high sulphate levels in water affected by Acid Mine Drainage stays at this elevated level even after the acidity of the water is neutralised. This negatively impacts water quality to such an extent that the water is not suitable for domestic and agricultural use. This water can’t even be used for certain industrial purposes. This water with the high sulphate levels will also lead to increased salinity levels of the water sources with which they come into contact with. There is Acid Mine Drainage that occurs in the Western Basin which impacts on the water sources of the study area (Council for Geoscience et al., 2010).
The presence of hydro carbonate and carbonate ions (HCO₃ - and CO₃) in water can be attributed to a range of carbonate rocks namely limestone, magnesites and dolomites which over time dissolves in water with the aid of carbon dioxide. Hydro carbonate ions are very prolific if the minerals in water occur in low quantities. When calcium ions are present, then it limits the amount of hydro carbonate ions in water. When the pH range of a body of water falls between 7 and 8.5 the dominant ion is hydro carbonate. When the pH of water falls to less than 5, the presence of hydro carbonate ions in water is negligible. If the pH of water rises above 8 then the occurrence of carbonate ions is by far the most prolific (Nikanorov and Brazhnikova, 2009). The buffering capacity of water is the ability of the water to resist changes in its pH as well as to neutralise pH. Alkalinity is a measure of the buffering capacity of water, thus alkalinity gives water the ability to resist changes in its pH. Alkalinity neutralises the acids in water thus keeping the pH stable (Ibanez et al., 2008).
Sodium ions (Na⁺) are very soluble and this gives it the capacity to move about with ease in a solution. As the amount of minerals rise in a water source, so the sodium levels increase as well. Sodium in water originates from various salts deposits trapped in the geology. When the weathering for example of limestone takes place, it releases sodium into the water sources (Nikanorov and Brazhnikova, 2009).
Potassium ions (K⁺) occurrence in the earth’s crust and its solubility capacity has a lot in common with sodium, although potassium doesn’t occur in such high concentrations in water as it doesn’t possess the mobility characteristics of sodium. Potassium plays a pivotal part in the biological processes of micro-organisms and plants that absorbs potassium (Nikanorov and Brazhnikova, 2009).
Calcium ions (Ca²⁺) originates from various sedimentary rocks such as limestone, dolomite and gypsum. Limestone and dolomitic rocks are dissolved when they come into contact with the carbonic acid that is present in water (Nikanorov and Brazhnikova, 2009).
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Magnesium ions (Mg²⁺) are present in surface water because of weathering and dissolution of dolomites and other rocks, it however is an ion that is rarely more numerous than the other ions in water. When the levels of mineralization in water becomes higher, then magnesium tends to dominate calcium concentrations (Nikanorov and Brazhnikova, 2009).
2.2 Study area description
Figure 1: The study area’s rivers, urban centres and quaternary catchments Source: (GIS, 2014)
The Crocodile West catchment is a heavily utilised and regulated catchment. It is like various other catchments and water resources in South Africa already under immense pressure and this pressure keeps mounting because of the tempo at which development takes place and the corresponding demand for water (DWA, 2013). According to a study done by Paul Keller of which the results was published in 1960 it states that the increase in the population density and the corresponding human activities has a detrimental effect upon the water quality and the health of the Crocodile-Jukskei river system and that if this trend in population growth continues that there will be compounding negative impacts upon this river system in the future (Keller, 1960). The Jukskei river drains an area of 800km² of the Witwatersrand ridge, which has since the discovery of gold morphed in to the region with the highest population density in Southern Africa as well as the region with the highest density of industries (Pitman, 1978). Ninety-seven percent (97%) of Gauteng’s population lives in urban areas. It
Page 6 has the highest population density of all the provinces in South Africa, with a population of 9,6 million people. Of the 9.6 million approximately 2.5 million people live in Northern Gauteng, which falls within the boundaries of the Crocodile West Marico Water Management Area. Northern Gauteng therefore constitutes the catchment of the upper Crocodile river (Venter, 2012) (Stone, 2009).
The Jukskei river’s catchment as well as the river’s headwaters are located within the City of Johannesburg. The Jukskei river flows through the informal settlement of Alexandria and eventually joins the Crocodile river (Burke and Bakoko, 2004) (Keller, 1960). The Crocodile river falls within drainage region A. It is one of the main tributaries of the Limpopo river which eventually spills its water in the Indian ocean on the Mozambican coast. The rivers that are considered the major tributaries of the Crocodile river are the Apies, Pienaars, Moretele, Jukskei, Hennops, Magalies and Elands river. All of these rivers make up the A20 tertiary catchment which is further divided in 39 quaternary catchments. The study area comprises of some of these quaternary catchments which together constitutes the upper portion of the Crocodile river’s catchment. This upper catchment is located south east of the Hartbeespoort dam in the Gauteng province. The Crocodile river and some of its tributaries originates in the Witwatersrand hills where it lies at an average of 2000m above sea level on the Highveld plateau and is located in the south of the catchment. From here the river flows through the landscape and passes through the Daspoort ridge until it reaches the Hartbeespoort dam at a 1200m above sea level near the Magaliesberg mountain range (DWAF, 2004). As can be seen in Figure 1, the main river of the study area is the Crocodile river with its smaller tributary being the Bloubankspruit and its larger tributary the Jukskei river. The Klein-Jukskei, Braamfonteinspruit and Sandspruit are tributaries of the Jukskei river.
The climate of the study area can be summarised as experiencing cold winters with daily temperatures during the day ranging from 1°C to 15°C. The summer months are warmer, with daily temperatures ranging from 10°C to 30°C. Frost can occur in the winter months. The study area falls within South Africa’s summer rainfall region with rain potentially occurring from October through to April, although December and January are the months when peak rainfall occurs. The study area’s average mean annual precipitation (MAP) is 800mm (DWAF, 2004), although extremes do occur in certain years with a recorded low of only 400mm and at the other end of the spectrum a high of 1600mm. The majority of the precipitation takes place in the form of thunderstorms with hail occasionally occurring (Pitman, 1978). There are dry and wet cycles that occur approximately every 7 to 10 years. The vegetation in the study area’s catchment is predominantly grassland and has undergone severe changes because of urban expansion and agricultural activities on smallholdings (DWAF, 2004). The majority of the study area’s catchment falls in the Grassland Biome of South Africa however a small portion located in close proximity of the Hartbeespoort dam falls in the Savanna Biome. The vegetation types represented in
Page 7 the study area’s catchment are Carletonville Dolomite Grassland, Egoli Granite Grassland, Soweto Highveld Grassland, Gold Reef Mountain Bushveld, Gauteng Shale Mountain Bushveld and Andesite Mountain Bushveld (Mucina and Rutherford, 2006).
2.3 Land use and water quality issues in the catchment
Water quality in the study area, is mostly affected by land use change and the high demand for water as well as the way this water is used (DWAF, 2004). The driving force behind the higher demand for water and the increasing pollution levels of our water resources are population growth and the need for economic development (Mukheibir and Sparks, 2003). Many of the urban areas in the study area’s catchment have waste water treatment works (WWTW) that are lacking in standard and capacity. These WWTW facilities cannot sufficiently process the high volumes of waste water that needs to be treated. The sewage infrastructure of Sandton and Alexandria also lacks capacity and have become over extended resulting in frequent sewage spills. Dumping and large-scale littering also take place on the banks of rivers and streams in the study area’s catchment. This together with the limited waste water treatment capacity leads to poor water quality in the rivers and streams of the catchment as well as the Hartbeespoort dam further downstream. Other contributing factors in the study area’s catchment are industries, compost making factories and old abandoned mines which are the source of Acid Mine Drainage (AMD). Some of these old gold mine dumps which are situated in the Krugersdorp (Mogale City) area decants and leaches into the water sources of the study area’s catchment which negatively affects the water quality. Fertilisers and pesticides, that are used in the agricultural sector, also has a negative impact on the water sources of the study area (DWAF, 2004).
Waste water from the upper Crocodile West water management area has inputs from the industrial, mining, agricultural and urban sectors. The pollution of the surface water in this area has a negative impact on the water quality of the Hartebeespoort dam in the sense that the dam is a source of potable water to many users, it also is used as a recreational playground by many people. The dam is also used by a large number of farmers for irrigation purposes (Roux et al., 2010). The standard of treatment at various waste water treatment works has also dropped because the finances to run these stations have become limited. The groundwater in the informal settlements and rural villages in the study area’s catchment becomes contaminated and polluted with nitrates and E. coli because of a lack of proper sanitation facilities and services in these informal settlements and villages. Where the density of latrines is high in these settlements it leads to high nitrate and salinity levels in the areas surrounding or adjacent to these settlements. Pollutants from the industrial and agricultural sectors has led to the excessive accumulation of nutrients in the water sources of the study area’s catchment. This in turn has led to eutrophication and algal blooms in the Hartebeespoort dam (DWAF, 2004). The
Page 8 pollution load that enters the Hartebeespoort dam can be largely attributed to the Crocodile river and the Jukskei river, with 95% of the total pollution load accredited to the Crocodile river, of which 60% originates from the Jukskei river and its catchment (Venter, 2012). The Braamfontein and Sandspruit both of which are tributaries of the Jukskei river receives sewage inputs (Keller, 1960).
Gold mines in the Witwatersrand area of the Gauteng Province have been operating for many years and the majority of these mines have closed down. This had the effect of a vast number of tailings dams being constructed across the Witwatersrand area. The tailings dams cover an area of 180km². The gold mines mined ore that contains elevated levels of sulphide minerals such as pyrite which in turn lead to Acid Mine Drainage developing in the tailings dams. In general, the seepage from these tailings dams have high concentrations of sulphates and toxic substances as well as low pH values. Pollution from these widespread tailings dams poses a massive threat to human and environmental health. This is especially relevant when considering that surface and groundwater sources can and have become contaminated in high density areas such as Johannesburg. The long-term management and the closure of the containment facilities of the gold mines such as the tailings dams have not been taken into consideration. Poor management of these facilities have led to Acid Mine Drainage contaminating the water sources underneath (such as dolomitic aquifers) and adjacent to these tailings dams (Rosner, 1999). The forecast is that the Bloubankspruit which is a tributary of the Crocodile river will receive water that is contaminated with Sulphate from the Western Basin through the Tweelopiesspruit as part of the Acid Mine Drainage (AMD) treatment process (DWA, 2013).
A crucial factor regarding the fluctuation in the chemical composition of river water is the seasonal change in the flow of the river. Anthropogenic activities such as the release of sewage (quality and quantity) in to a river system also further contributes to the change in chemical composition of water sources (Siwek et al., 2008). The volumes from waste water works to the Crocodile river has increased to such an extent that the runoff is almost double that of the natural mean annual runoff. The same scenario occurs in the Jukskei river and its catchment where the flow of water in the Jukskei’s catchment is perennial in nature mainly because of discharge originating from the city’s waste water treatment works (Burke and Bakoko, 2004). An increase in the salinity of a water resource is a clear indication that the water resource is subject to pollution inputs (Roux et al., 2010).
The city of Johannesburg is the economic hub of the Gauteng province and plays a key role in the economic landscape of Southern Africa (Todes, 2012). The above mentioned is the reason why a substantial portion of the unemployed have migrated from the rural areas and neighbouring countries such as Zimbabwe and Mozambique (in many instances illegal immigrants) to informal settlements around Johannesburg and Tshwane (Pretoria) (DWAF, 2004) (Todes, 2012). Which in turn creates a
Page 9 greater demand for housing and the services that go with it such as water and sanitation. The older township of Alexandria continues to offer a suitable housing option for migrant workers, while newer informal settlements such as Diepsloot has emerged to cope with the growing low income and unemployed population of Johannesburg (Todes, 2012). This influx of people adds even more pressure to the already stressed water infrastructure and also increases the pollution load that ends up in the study catchment’s water sources (DWAF, 2004).
The water resources in the city of Johannesburg is under immense pressure including the Jukskei river and its catchment mainly because of the high population density. The main contributing factors of water pollution and poor water quality in the city of Johannesburg are:
• Leakages in the sewer system • Inefficient storm water drainage systems • Mining activities • Litter from various sources • Sanitation infrastructure that is not up to standard • High silt loads from erosion (Burke and Bakoko, 2004)
Pelindaba and Valindaba which can be classified as two heavy industries extract water directly from the Crocodile river upstream of the Hartebeespoort dam. The catchment of the Crocodile river is one of the most developed catchments in the whole of South Africa with a high level of anthropogenic influences. It contains the largest urban areas in South Africa namely the Midrand area as well as the northern, north eastern and north-western areas of the city of Johannesburg. Large parts of this catchment are covered by Northern Johannesburg and Pretoria which comprises rapidly expanding urban and industrial land uses. There is a high volume of effluent discharge from urban and industrial sources, with the majority ending up in the river after treatment. These large volumes that are discharged into the river system compromises the water quality of these systems significantly (DWA, 2013).
There are three power stations located in the catchment of the Crocodile river namely: Kelvin, Pretoria-West and Rooiwal (DWA, 2013). Johannesburg’s central business district (CBD) has undergone decentralisation since the 1970’s, with office and rental space being filled in economic centres further north such as Sandton, Rosebank and Midrand. Newer residential development densities are much higher than the densities of the older suburban areas. Existing suburban areas have also undergone redevelopment in the sense that suburban houses with large properties have been changed into offices, retail space and higher density residential units. Urban sprawl is still a problem in a city such as Johannesburg, with hectares of land falling under the “poorly planned and managed”
Page 10 banner. Many of these areas as well as areas that have previously housed only low residential densities have wastewater and electricity infrastructure that cannot cope with the current population density. Informal settlements and public “RDP” housing has over the years grown vastly and become part of the urban landscape of Johannesburg. This is also the form of housing that the low income urban dwellers can afford or have access to (Todes, 2012).
CHAPTER 3: METHODOLOGY
3.1 Site selection
The data sets that were used in this research project was sourced from the Department of Water and Sanitation (DWS). These data sets originated from sampling that took place at various monitoring stations along the Crocodile river and its tributaries. The following nine monitoring stations fall within the boundaries of the study area and are named below as well as the river or tributary on which they are situated (refer to Figure 2):
• A2H12 on the Crocodile river • A2H44 on the Jukskei river • A2H45 on the Crocodile river • A2H42 on the Jukskei river • A2H23 on the Jukskei river • A2H40 on the Jukskei river • A2H47 on the Klein-Jukskei • A2H49 on the Bloubankspruit • A2H50 on the Crocodile river
Monitoring station A2H12 is the monitoring station that is situated the furthest down the study area’s catchment. It is the last monitoring station before the Crocodile river flows in to the Hartebeespoort dam. This makes it the most significant monitoring station in the sense that it is representative of the water quality of the other eight monitoring stations which in turn represents the whole catchment. Thus, monitoring station A2H12 is used as the departure point to determine where specific influences on the water quality originates from. Monitoring stations A2H44 on the Jukskei river and A2H45 on the Crocodile is also very significant in the sense that each represent water quality from two distinct sub-catchments before they converge and flow together to monitoring station A2H12. Thus, by investigating their water quality parameters, the origin of the changes in specific salts can be determined. Many of the factors that influence salinity changes at monitoring station A2H12 can be
Page 11 traced to its origin higher up the catchment at the eight other monitoring stations, thus explaining the change in salinity composition seen at monitoring station A2H12.
Figure 2: Study area indicating location of monitoring stations Source: (Google, 2017)
3.2 Data management
The data sets that were sourced from the Department of Water Affairs and Sanitation (DWS) wasn’t immediately usable. The data sets firstly had to be converted to the correct format so that it could be clearly interpreted. Secondly all the data that didn’t fall within the time period of the research study had to be deleted as it only complicated the data sheets and was irrelevant to the study objectives. Thirdly there was various other information in the data sheets that didn’t have a direct correlation with the focus of the study and with great care this data had to be deleted so that the data sheets were free from data that didn’t fall within the scope of the research study. Thus after “cleaning” the data the uncluttered workable data sheets were ready to be used to draw graphs and make interpretations from. Great care was taken to package the data correctly because your results and conclusions are only as good as the quality of your data.
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3.3 Data interpretation
The data sets covered a period of thirty-five years namely from 1980 to 2015, except for two monitoring stations namely A2H40 and A2H42 on the Jukskei river, which only covered the period 1980 to 1997 as a result of data only being available at these specific monitoring stations for the first seventeen years of the 35-year study period. The data sets at each of these nine monitoring stations where then divided into five-year intervals. For each monitoring station per five-year period the following was calculated:
• Maucha diagrams (Silberbauer and King, 1991). The major cations are plotted on the right- hand side of the Maucha diagram while the major anions are plotted on the left-hand side. It was clear from the Maucha diagrams that the salt composition at the monitoring stations underwent significant changes over the 35-year study period especially concerning TDS (Total Dissolved Salts), SO₄ (Sulphate) and TAL (Total Alkalinity), which is why these three salts were chosen for further investigation and study.
Maucha diagram example
Circle K Na Ca Mg SO4 Cl TAL
Figure 3: Example of a Maucha diagram
• Five yearly average Magnesium (Mg), Calcium (Ca), Sodium (Na), Potassium (K), Chloride (Cl), TDS (Total Dissolved Salts), SO₄ (Sulphate) and TAL (Total Alkalinity). Graphs were drawn for each of these elements. • Five yearly average TDS, SO₄ and TAL Loads. Graphs were drawn for each of these. (this was only done for monitoring stations A2H12 on the Crocodile river, A2H44 on the Jukskei river and A2H45 on the Crocodile river. The rationale behind why it was only done for these three stations is that A2H44 represents all the influences from the one major sub-catchment whereas A2Hh45 represents the influences from the other major sub-catchment. A2H12
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represents the influences from both these sub-catchments and thus the whole catchment). The loads were determined in the following way: By using the monthly TDS, SO₄ and TAL concentrations from the raw data sheets at each of the three monitoring stations namely A2H12, A2H44 and A2H45 the five yearly average concentration was calculated for each of these three salts at all three of the monitoring stations. The same was done for the volumes, thus the five yearly average volume was calculated from the raw data sheets for each of the three monitoring stations. The five yearly average concentration and the five yearly average volume where then multiplied with each other to determine the five yearly average loads. • Five yearly average TDS, SO₄ and TAL Concentration and Volume. Graphs were drawn for each of these. (this was only done for monitoring stations A2H12 on the Crocodile river, A2H44 on the Jukskei river and A2H45 on the Crocodile river. The reason why this was only done for these three stations is that A2H44 represents all the influences from the one major sub-catchment whereas A2H45 represents the influences from the other major sub- catchment. A2H12 represents the influences from both these sub-catchments and thus the whole study area’s catchment).
By comparing the Maucha diagrams and the various graphs with each other over the 35-year study period, various changes in the salinity composition could be observed at each monitoring station and the possible reasons for these changes could be identified.
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CHAPTER 4: RESULTS
The Maucha diagram from monitoring station A2H12 which lies at the bottom of the study area’s catchment is used as the departure point for this research study to determine potential changes in the salt composition. Figure 4 and Table 1 below clearly indicated a change from a SO₄ dominated system to TAL dominated system with very little change in the contribution of the other salts. This results section therefore aims to reflect the long-term changes in the concentration and loads of SO₄, TAL and TDS as well as the changes that occurred in the volume of water coming down the catchment at all the monitoring stations over the entire 35-year study period. Firstly, the results and findings from monitoring station A2H12, A2H44 and A2H45 are discussed in unison. Where after the results from all nine monitoring stations are discussed individually.
K Na Ca Mg SO₄ Cl TAL
Figure 4: Maucha diagrams at monitoring station A2H12 on the Crocodile river
Table 1: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H12
% Contribution of % Contribution of % Contribution of % Contribution of Date Ca towards TDS Cl towards TDS K towards TDS Mg towards TDS 1980-85 18,27 12,56 1,73 14,08 1986-90 19,09 13,44 2,06 11,46 1991-95 18,04 14,5 2,34 11,46 1996-2000 19,09 13,16 1,82 12,99 2001-2005 18,06 14,33 2,25 11,99 2006-2010 19,4 14,85 2,03 11,58 2011-2015 18,03 13,28 1,93 12,39 % Contribution of % Contribution of % Contribution of Date Na towards TDS SO₄ towards TDS TAL towards TDS 1980-85 19,65 19,7 13,93
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1986-90 19,67 16,44 17,42 1991-95 20,25 14,44 18.87 1996-2000 17,611 12,16 23,09 2001-2005 19,18 10,57 23,56 2006-2010 19,54 9,57 22,91 2011-2015 19,68 11,61 23,01
4.1 A2H12, A2H44 & A2H45 five yearly average TDS Concentration, Loads and Volume:
A2H12, A2H44, A2H45 Five yearly Avg TDS Concentration
A2H12 Five yearly Avg TDS Concentration (mg/l) A2H44 Five yearly Avg TDS Concentration (mg/l) A2H45 Five yearly Avg TDS Concentration (mg/l) 700 600 500 400
MG/L 300 200 100 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 1: Five yearly average TDS concentration at monitoring stations A2H12, A2H44 & A2H45
Table 2: Five yearly average TDS concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised
A2H12 Five yearly Avg A2H44 Five yearly Avg A2H45 Five yearly Avg Date TDS Concentration (mg/l) TDS Concentration (mg/l) TDS Concentration (mg/l) 1980-85 515,94 578,84 390,45 1986-90 473,64 497,57 422,46 1991-95 430,35 422,64 449,60 1996-2000 431,57 414,99 400,07 2001-2005 400,29 363,33 391,41 2006-2010 405,26 373,26 386,37 2011-2015 412,33 369,66 481,90
Graph 1 and Table 2 indicates the five yearly average TDS concentration at monitoring stations A2H12, A2H44 and A2H45. At monitoring station A2H12 there was a decrease in the 1986-1995 period in relation to the opening of the study period in 1908-1985. There was a slight increase in the 1996-2000 period, then a decrease occurring again in the 2001-2005 period. However, the last ten years of the study period showed an increase from 2006-2015. Monitoring station A2H44 showed a decrease from
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1980 all the way to 2005. However, the period of 2006-2010 showed a slight increase. The last five years of the study period namely 2011-2015 there was a slight dip that could be observed. Monitoring station A2H45 showed an increase in the five yearly average TDS concentration for the period 1980- 1995. Then there was a decrease that occurred in the 1996-2010 period. The last five years (2011- 2015) of the study period however showed a significant increase in the five yearly average TDS concentration reaching its maximum for the study period at this monitoring station namely 481,90 mg/l.
A2H12, A2H44, A2H45 Five yearly Avg TDS Loads
A2H12 Five yearly Avg TDS Loads (ton/year) A2H44 Five yearly Avg TDS Loads (ton/year) A2H45 Five yearly Avg TDS Loads (ton/year) 250000
200000
150000
100000 TON/YEAR
50000
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 2: Five yearly average TDS loads at monitoring stations A2H12, A2H44 & A2H45
Table 3: Five yearly average TDS loads at monitoring stations A2H12, A2H44 & A2H45 tabularised A2H12 Five yearly Avg A2H44 Five yearly Avg A2H45 Five yearly Avg Date TDS Loads (ton/year) TDS Loads (ton/year) TDS Loads (ton/year) 1980-85 89110,93 59264,45 11635,39 1986-90 78843,81 53619,47 9691,77 1991-95 76371,28 47696,21 7654,04 1996-2000 170554,95 88188,24 26972,06 2001-2005 91001,14 42317,43 12959,67 2006-2010 192673,85 94272,91 24600,75 2011-2015 227169,95 99264,31 35842,22
Graph 2 and Table 3 indicates the five yearly average TDS loads at monitoring stations A2H12, A2H44 and A2H45. At all three these monitoring stations there were a decrease in the five yearly average TDS loads from 1980 to 1995. Then there was a significant increase in the 1996-2000 period at all three monitoring stations. The 2001-2005 period experienced a drop at all three monitoring stations in the five yearly average TDS loads. However, the last ten years of the study period showed major increases at monitoring stations A2H12, A2H44 and A2H45. At all three monitoring stations in the last 5 years
Page 17 of the study period the maximum five yearly average TDS loads were reached for the whole 35-year study period.
A2H12, A2H44, A2H45 Five yearly Avg Volume
A2H12 Five yearly Avg Volume (m³/s) A2H44 Five yearly Avg Volume (m³/s) A2H45 Five yearly Avg Volume (m³/s) 600
500
400
300 M³/S 200
100
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 3: Five yearly average volume at monitoring stations A2H12, A2H44 & A2H45
Table 4: Five yearly average volume at monitoring stations A2H12, A2H44 & A2H45 tabularised A2H12 Five yearly Avg A2H44 Five yearly Avg A2H45 Five yearly Avg Date Volume (m³/s) Volume (m³/s) Volume (m³/s) 1980-85 172,71 102,38 29,79 1986-90 166,46 107,76 22,94 1991-95 177,46 112,85 17,02 1996-2000 395,18 212,50 67,41 2001-2005 227,33 116,46 32,53 2006-2010 475,42 252,56 63,67 2011-2015 550,93 268,52 74,37
The five-yearly average volume of monitoring station A2H12, A2H44 and A2H45 can be seen from Graph 3 and Table 4. The five-yearly average volume of monitoring station A2H12 indicated a decrease in the 1986-1990 period in relation to the 1980-85 period, after which it increased for the next ten years namely the 1991-2000 period, then there was a drop in the 2001-2005 period. The last ten years of the study (2006-2015) showed substantial increases in the five yearly average volume. Monitoring station A2H44 indicated that the five yearly average volume increased from 1980 to 2000. There was a decrease observed in the 2001-2005 period but after this period increases in the last ten years was evident. Monitoring station A2H45’s five yearly average volume has decreased from 1980 to 1995. In the 1996-2000 period, an increase could be observed. After this there was a drop that occurred in the 2001-2005 period. The last ten years of the study period indicated an increase in the five yearly average volume. The five-yearly average volume of A2H12 was the highest of the three monitoring
Page 18 stations. This can be explained by the fact that A2H12 is located where the Crocodile and Jukskei rivers has already converged and thus the volumes of both rivers contributes at monitoring station A2H12. The last ten-year period of the study increases could be observed in the five yearly average volume at all three monitoring stations with the last five years of the 35-year study period indicating a maximum reached for all three monitoring stations.
4.2 A2H12, A2H44 & A2H45 five yearly average SO₄ Concentration and Loads:
A2H12, A2H44, A2H45 Five yearly Avg SO₄ Concentration
A2H12 Five yearly Avg SO₄ Concentration (mg/l) A2H44 Five yearly Avg SO₄ Concentration (mg/l) A2H45 Five yearly Avg SO₄ Concentration (mg/l) 180 160 140 120 100
MG/L 80 60 40 20 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 4: Five yearly average SO₄ concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised
Table 5: Five yearly average SO₄ concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised A2H12 Five yearly Avg A2H44 Five yearly Avg A2H45 Five yearly Avg Date SO₄ Concentration (mg/l) SO₄ Concentration (mg/l) SO₄ Concentration (mg/l) 1980-85 129,93 168,11 80,19 1986-90 105,40 128,13 88,29 1991-95 75,12 82,07 86,70 1996-2000 68,56 75,34 62,62 2001-2005 53,89 49,95 61,39 2006-2010 50,76 51,97 59,79 2011-2015 45,91 48,67 151,17
Concerning Graph 4 and Table 5 above, the five-yearly average SO₄ concentration at monitoring stations A2H12 decreased over the entire 35-year time span of the research study whereas the five- yearly average SO₄ concentration at monitoring station A2H44 decreased from 1980 to 2005, with a slight increase occurring in the 2006-2010 period but a drop could be seen in the last 5 years of the study period. The five-yearly average SO₄ concentration of monitoring station A2H45 increased in the 1986-1990 period in relation to the start of the study period in 1980-1985. A decrease was observed
Page 19 all the way up until the 2006-2010 period, however the last five-year period namely the 2011-2015 period showed a significant increase in the five-yearly average SO₄ concentration reaching the maximum for the whole study period.
A2H12, A2H44, A2H45 Five yearly Avg SO₄ Loads
A2H12 Five yearly Avg SO₄ Loads (ton/year) A2H44 Five yearly Avg SO₄ Loads (ton/year) A2H45 Five yearly Avg SO₄ Loads (ton/year) 30000
25000
20000
15000
TON/YEAR 10000
5000
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 5: Five yearly average SO₄ loads at monitoring stations A2H12, A2H44 & A2H45 tabularised
Table 6: Five yearly average SO₄ loads at monitoring stations A2H12, A2H44 & A2H45 tabularised
A2H12 Five yearly Avg A2H44 Five yearly Avg A2H45 Five yearly Avg Date SO₄ Loads (ton/year) SO₄ Loads (ton/year) SO₄ Loads (ton/year) 1980-85 22441,09 17211,42 2389,48 1986-90 17538,95 13807,22 2025,51 1991-95 13331,77 9261,34 1475,96 1996-2000 27092,70 16010,81 4221,87 2001-2005 12251,35 5817,87 1997,24 2006-2010 24132,61 13126,17 3806,71 2011-2015 25294,33 13069,96 11243,05
According to Graph 5 and Table 6 the five-yearly average SO₄ loads at monitoring station A2H12, A2H44 and A2H45 decreased in the period 1980 to 1995 but showed an increase in the 1996-2000 period. Directly after this period there was a drop observed in the 2001-2005 period, but since then an increase was noted all the way to the end of the study period in 2015 except for monitoring station A2H44 which showed a slight decrease in the five-yearly average SO₄ loads during the last five years of the research study (2011-2015).
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4.3 A2H12, A2H44 & A2H45 five yearly average TAL Concentration and Loads:
A2H12, A2H44, A2H45 Five yearly Avg TAL Concentration
A2H12 Five yearly Avg TAL Concentration (mg/l) A2H44 Five yearly Avg TAL Concentration (mg/l) A2H45 Five yearly Avg TAL Concentration (mg/l) 180 160 140 120 100
MG/L 80 60 40 20 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 6: Five yearly average TAL concentration at monitoring stations A2H12, A2H44 & A2H45
Table 7: Five yearly average TAL concentration at monitoring stations A2H12, A2H44 & A2H45 tabularised
A2H12 five yearly avg TAL A2H44 five yearly avg TAL A2H45 five yearly avg TAL Date Concentration (mg/l) Concentration (mg/l) Concentration (mg/l) 1980-85 98,14 68,21 136,94 1986-90 99,62 72,77 141,97 1991-95 114,91 92,54 158,90 1996-2000 136,01 104,91 151,86 2001-2005 127,93 107,37 142,73 2006-2010 126,03 109,70 138,83 2011-2015 130,13 112,45 128,39
Graph 6 and Table 7 indicates the five yearly average TAL concentration at monitoring stations A2H12, A2H44 and A2H45. In the first twenty years of the study period increases in the five yearly average TAL concentration at monitoring station A2H12 could be noted, however the next ten-year period namely 2001 to 2010 decreases were observed. The 2011-2015 period showed a recovery with an increase that could be noted. Monitoring station A2H44 showed a continuous upwards trend in the five yearly average TAL concentration throughout the duration of the 35-year study period. Monitoring station A2H45 indicated an increase in the five yearly average TAL concentration for the period 1980 to 1995. Since the 1996-2000 period however there was a clear downward trend occurring to the end of the study period in 2015.
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A2H12, A2H44, A2H45 Five yearly Avg TAL Loads
A2H12 Five yearly Avg TAL Loads (ton/year) A2H44 Five yearly Avg TAL Loads (ton/year) A2H45 Five yearly Avg TAL Loads (ton/year) 80000 70000 60000 50000 40000
TON/YEAR 30000 20000 10000 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 7: Five yearly average TAL loads at monitoring stations A2H12, A2H44 & A2H45
Table 8: Five yearly average TAL loads at monitoring stations A2H12, A2H44 & A2H45 tabularised
A2H12 five yearly avg TAL A2H44 five yearly avg TAL A2H45 five yearly avg TAL Date Loads (ton/year) Loads (ton/year) Loads (ton/year) 1980-85 16951,50 6984,09 4080,79 1986-90 16584,01 7842,08 3257,07 1991-95 20392,29 10443,47 2705,14 1996-2000 53752,76 22295,08 10238,09 2001-2005 29085,22 12505,89 4643,92 2006-2010 59919,55 27706,96 8927,48 2011-2015 71694,24 30198,13 9549,83
Graph 7 and Table 8 indicates the five yearly average TAL loads at monitoring stations A2H12, A2H44 and A2H45. At monitoring station A2H12 there was a very slight drop from the 1980-1985 period to the 1986-1990 period. The following ten-year period (1991-2000) there was an increase, with a drop in the 2001-2005 period. The last ten years of the study indicated an increase in the five yearly average TAL loads with the two highest five yearly average TAL loads being recorded for the whole study period at monitoring station A2H12. Monitoring station A2H44 showed an increase for the period 1980 to 2000. A drop occurred in the 2001-2005 period, however the following ten-year period until the end of the study period showed an increase. At monitoring station A2H45 a downward trend could be identified in the period 1980 to 1995. The 1996-2000 period showed a spike with drop again in the following five-year period. The last ten years namely 2006 to 2015 showed an increase in the five yearly average TAL loads.
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4.4 Monitoring station A2H12 on the Crocodile river: This is the only monitoring station in the research study that is located on the Crocodile river where the Jukskei river and the Crocodile river have already converged, the other stations are either located on just the Jukskei, Crocodile, Bloubankspruit or Klein Jukskei.
K Na Ca Mg SO₄ Cl TAL
Figure 5: Maucha diagrams at monitoring station A2H12 on the Crocodile river
Table 9: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H12
% Contribution of % Contribution of % Contribution of % Contribution of Date Ca towards TDS Cl towards TDS K towards TDS Mg towards TDS 1980-85 18,27 12,56 1,73 14,08 1986-90 19,09 13,44 2,06 11,46 1991-95 18,04 14,5 2,34 11,46 1996-2000 19,09 13,16 1,82 12,99 2001-2005 18,06 14,33 2,25 11,99 2006-2010 19,4 14,85 2,03 11,58 2011-2015 18,03 13,28 1,93 12,39 % Contribution of % Contribution of % Contribution of Date Na towards TDS SO₄ towards TDS TAL towards TDS 1980-85 19,65 19,7 13,93 1986-90 19,67 16,44 17,42 1991-95 20,25 14,44 18.87 1996-2000 17,611 12,16 23,09 2001-2005 19,18 10,57 23,56 2006-2010 19,54 9,57 22,91 2011-2015 19,68 11,61 23,01
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As observed from Figure 5 and Table 9 the percentage contribution of TAL towards TDS has increased from 1980 to 2005. With a slight drop occurring in the 2005-2010 period. An increase occurred in the last five-year period. The percentage contribution of SO₄ towards TDS on the other hand showed a decreasing trend from 1980 to 2010 with a slight increase only occurring in the 2011-2015 period. All the other elements remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H12 Five yearly Avg TDS, SO₄, TAL concentration
Five yearly avg TDS concentration (mg/L) Five yearly avg SO₄ concentration (mg/L) Five yearly avg TAL concentration (mg/L) 600
500
400
300 MG/L 200
100
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 8: Five yearly average SO₄, TAL and TDS concentration at monitoring station A2H12
Table 10: Five yearly average SO₄, TAL and TDS concentration at monitoring stations A2H12 tabularised Five yearly Avg SO₄ Five yearly Avg TAL Five yearly Avg TDS Date Concentration (mg/l) Concentration (mg/l) Concentration (mg/l) 1980-85 129,93 98,14 515,94 1986-90 105,36 99,62 473,64 1991-95 75,12 114,91 430,35 1996-2000 68,55 136,01 431,57 2001-2005 53,89 127,93 400,29 2006-2010 50,75 126,03 405,26 2011-2015 45,91 130,13 412,33
As seen from Graph 8 and Table 10 it is clear that the five yearly average TDS concentration has decreased from 1980 to 1995 with a very slight increase in the 1996-2000 period. After this period, there was a slight drop in the 2001-2005 period. Since the 2006-2010 period there was a slight upward trend until the end of 2015. The five-yearly average SO₄ concentration decreased over the entire 35- year study period. The five yearly average TAL concentration has risen from 1980 to the year 2000 where it reached its maximum for the 35-year study period. The next ten years of the study period
Page 24 showed slight decreases with the last five-year period showing an increase the five yearly average TAL concentration.
A2H12 five yearly Avg SO₄ TAL TDS Loads
Five yearly Avg SO₄ Loads (ton/year) Five yearly Avg TAL Loads (ton/year) Five yearly Avg TDS Loads (ton/year) 250000
200000
150000
100000 TON/YEAR
50000
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 9: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H12
Table 11: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H12 tabularised
Five yearly Avg SO₄ Loads Five yearly Avg TAL Loads Five yearly Avg TDS Loads Date (ton/year) (ton/year) (ton/year) 1980-85 22441,09 16951,50 89110,93 1986-90 17538,95 16584,01 78843,81 1991-95 13331,77 20392,29 76371,28 1996-2000 27092,70 53752,76 170554,95 2001-2005 12251,35 29085,22 91001,14 2006-2010 24132,61 59919,55 192673,85 2011-2015 25294,33 71694,24 227169,95
When considering Graph 9 and Table 11 the five-yearly average SO₄ loads decreased from 1980 to 1995. There was a spike in the period 1996-2000, after this a slight dip but the upward trend continued from 2001 up until the end of the study period in 2015. The five yearly average TAL loads increased from 1980 up until the year 2000 with a slight drop after the year 2000 but then from there onwards the upward trend continues up until the end of the study period reaching its maximum in the 2011- 2015 period. The five yearly average TDS loads dropped slightly from 1980 to 1995, then there was a spike in the period from 1996 to 2000, after this period there was a drop but it picked up drastically towards the end of the study period in 2015 claiming the highest five yearly average TDS load of the entire study at monitoring station A2H12.
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A2H12 Avg SO₄ TAL TDS Concentration and Volume
Five yearly Avg SO₄ Concentration (mg/l) Five yearly Avg TAL Concentration (mg/l) Five yearly Avg TDS Concentration (mg/l) Five yearly Avg Volume (m³/s) 600
500
400 ³/S
300
200 MG/L & M & MG/L
100
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 10: Five yearly average concentration of SO₄, TAL, TDS and Volume at monitoring station A2H12
As is evident from Graph 10 the five yearly average volume increased, with only a drop in the 2001- 2005 period, since then the five yearly average volume climbed reaching its maximum level in the 2011-2015 period. The five-yearly average SO₄ concentration decreased steadily from 1980 until it reached a minimum at the end of the study period in 2015. The five yearly average TAL concentration climbed until the 1996-2000 period from there it only slightly dropped but started to increase again from 2006 to 2015. The five yearly average TDS concentration went down until the 2001 to 2005 period when it started picking up again towards the end of 2015 although very slightly.
4.5 Monitoring station A2H44 on the Jukskei river:
K Na Ca Mg SO₄ Cl TAL
Figure 6: Maucha diagrams at monitoring station A2H44 on the Jukskei river
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Table 12: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H44 % Contribution of % Contribution of % Contribution of % Contribution of Date Ca towards TDS Cl towards TDS K towards TDS Mg towards TDS 1980-85 16,67 14,21 2,27 10,12 1986-90 19,18 14,03 2,5 9,03 1991-95 18,59 15,57 2,83 8,29 1996-2000 19,49 14,19 2,4 10,07 2001-2005 18,06 15,14 2,68 9,9 2006-2010 18,89 15,32 2,39 10,53 2011-2015 17,89 13,98 2,39 10,72 % Contribution of % Contribution of % Contribution of Date Na towards TDS SO₄ towards TDS TAL towards TDS 1980-85 25,13 22,58 8,91 1986-90 23 20,76 11,42 1991-95 22,94 15,05 16,62 1996-2000 20,36 14,35 19,05 2001-2005 21,29 11 21,84 2006-2010 20,12 10,74 21,91 2011-2015 21,1 10,51 23,3
It is clear from Figure 6 and Table 12 how the percentage contribution of SO₄ towards TDS has receded from 1980 throughout the whole study period up until the end of the study period in 2015 whereas the percentage contribution of TAL towards TDS is the exact opposite, showing an increase over this exact same period. All the other elements remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H44 five yearly Avg TDS SO₄ TAL concentration
Five early avg TDS concentration (mg/L) Five yearly avg SO₄ concentration (mg/L) Five yearly Avg TAL concentration (mg/L) 700 600 500 400
MG/L 300 200 100 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015 Graph 11: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H44
Page 27
Table 13: Five yearly average SO₄, TAL and TDS concentration at monitoring station A2H44 tabularised
Five yearly Avg SO₄ Five yearly Avg TAL Five yearly Avg TDS Date Concentration (mg/l) Concentration (mg/l) Concentration (mg/l) 1980-85 168,10 68,21 578,84 1986-90 128,12 72,77 497,57 1991-95 82,06 92,54 422,64 1996-2000 75,34 104,91 414,99 2001-2005 49,95 107,37 363,33 2006-2010 51,97 109,70 373,26 2011-2015 48,67 112,45 369,66
As observed from Graph 11 and Table 13, the five yearly average TDS concentration has decreased since 1980 reaching its lowest level in the 2001-2005 period, from where it has increased slightly in the 2006-2010 period but then it dropped again ever so slightly in the 2011-2015 period. The five- yearly average SO₄ concentration has steadily decreased and shows a downward trend since the 1980- 85 period all the way through to the 2001-2005 period. The 2006-2010 period showed a slight increase but the last five years of the study period indicated a drop again. The five yearly average TAL concentration showed an increasing upward trend for the whole 35-year study period.
A2H44 five yearly Avg SO₄ TAL TDS Loads
Five yearly Avg SO₄ Loads (ton/year) Five yearly Avg TAL Loads (ton/year) Five yearly Avg TDS Loads (ton/year) 120000
100000
80000
60000
TON/YEAR 40000
20000
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 12: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H44
Page 28
Table 14: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H44 tabularised Five yearly Avg SO₄ Loads Five yearly Avg TAL Loads Five yearly Avg TDS Loads Date (ton/year) (ton/year) (ton/year) 1980-85 17211,42 6984,09 59264,45 1986-90 13807,22 7842,08 53619,47 1991-95 9261,34 10443,47 47696,21 1996-2000 16010,81 22295,08 88188,24 2001-2005 5817,87 12505,89 42317,43 2006-2010 13126,17 27706,96 94272,91 2011-2015 13069,96 30198,13 99264,31
As is clearly evident in Graph 12 and Table 14 that the five-yearly average SO₄ loads have showed a decrease since the 1980-85 period up until 1991-1995 period. The 1996-2000 period indicated an upwards spike. After this period there was a drop in the 2001-2005 period. However, the last ten years of the study period (2006-2015) an upwards trend could be observed. The five yearly average TAL loads show a general increasing trend up until the 1996-2000 period, after this period there was a drop in the 2001-2005 period but since the 2006-2010 period increases are visible up until the end of the study period in 2015. The five-yearly average TDS loads have decreased since 1980-85 to the 1991- 1995 period with an upwards spike occurring in the 1996-2000 period, after this period there is a drop visible in the 2001-2005 period and then the last ten years a major upwards trend could be observed.
A2H44 five yearly Avg SO₄ TAL TDS Concentration and Volume
Five yearly Avg SO₄ Concentration (mg/l) Five yearly Avg TAL Concentration (mg/l) Five yearly Avg TDS Concentration (mg/l) Five yearly Avg Volume (m³/s) 700 600
500 ³/S 400 300
MG/L & M & MG/L 200 100 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 13: Five yearly average concentration of SO₄, TAL, TDS and Volume at monitoring station A2H44
As seen from Graph 13 the five yearly average volume shows an upwards curve with only a dip in the 2001-2005 period after that the upwards trend continues quite significantly all the way up to the end of the study period in 2015. The five-yearly average SO₄ concentration shows a clear general downward trend throughout the whole 35-year study period. The five yearly average TAL on the other
Page 29 hand showed the exact opposite with an increase over the whole 35-year study period. The five yearly average TDS declined reaching a low in the 2001-2005 period, since then there is a slight upwards trend visible up until the end of the study period in 2015.
4.6 Monitoring station A2H45 on the Crocodile river:
K Na Ca Mg SO₄ Cl TAL
Figure 7: Maucha diagrams at monitoring station A2H45 on the Crocodile river
Table 15: Percentage contribution of different salts in the Maucha diagram towards the TDS at monitoring station A2H45 % Contribution of % Contribution of % Contribution of % Contribution of Date Ca towards TDS Cl towards TDS K towards TDS Mg towards TDS 1980-85 22,16 7,62 0,51 22,35 1986-90 21,17 9,09 0,68 20,13 1991-95 20,69 9,2 0,88 19,47 1996-2000 20,11 9,18 0,85 19,16 2001-2005 19,98 10,42 0,99 18,29 2006-2010 19,57 10,96 1,1 16,98 2011-2015 22,29 7,82 0,96 16,55 % Contribution of % Contribution of % Contribution of Date Na towards TDS SO₄ towards TDS TAL towards TDS 1980-85 7,19 14,75 25,32 1986-90 9,31 15,57 23,94 1991-95 10,01 14,18 25,47 1996-2000 10,9 11,98 27,75 2001-2005 11,74 11,84 26,63 2006-2010 13,29 11,84 26,16 2011-2015 11,45 22,56 18,29
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Concerning Figure 7 and Table 15, the trend at this monitoring station is that the percentage contribution of TAL towards the TDS at this monitoring station has slightly decreased in the 1986-90 period with an increase visible in the next ten years namely from 1991-2000. From 2001 to 2015 which is at the end of the study period a decrease could be observed. The percentage contribution of SO₄ towards the TDS has increased in the first ten years of the study period namely the 1980-1990 period. From there on a decrease took place up until the 2006-2010 period. The last five-year period showed a significant increase in the percentage contribution of SO₄ towards TDS. All the other salts remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H45 five yearly Avg TDS SO₄ TAL concentration
Five yearly Avg TDS (mg/l) Five yearly Avg SO₄ (mg/l) Five yearly Avg TAL (mg/l)
500 450 400 350 300 250 MG/L 200 150 100 50 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 14: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H45
Table 16: Five yearly average SO₄, TAL and TDS concentration at monitoring station A2H45 tabularised
Five yearly Avg SO₄ Five yearly Avg TAL Five yearly Avg TDS Date Concentration (mg/l) Concentration (mg/l) Concentration (mg/l) 1980-85 80,18 136,94 390,45 1986-90 88,29 141,97 422,46 1991-95 86,70 158,90 449,60 1996-2000 62,62 151,86 400,07 2001-2005 61,38 142,73 391,41 2006-2010 59,78 138,83 386,37 2011-2015 151,16 128,39 481,90
As observed in Graph 14 and Table 16 the five yearly average TDS concentration has risen from 1980 up until 1995, since then it has decreased up until the 2006-2010 period. After this period, there was a significant increase in the last five-year period of the study namely the 2011-2015 period. The five- yearly average SO₄ concentration showed the same trend as the five yearly average TDS concentration with a significant increase in the last five-year period. The five yearly average TAL concentration has
Page 31 risen in the first fifteen years up until 1995 but since then it has steadily declined to its lowest point in the 2011-2015 period.
A2H45 five yearly Avg SO₄ TAL TDS Loads
Five yearly Avg SO₄ Loads (ton/year) Five yearly Avg TAL Loads (ton/year) Five yearly Avg TDS Loads (ton/year) 40000 35000 30000 25000 20000
TON/YEAR 15000 10000 5000 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 15: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H45
Table 17: Five yearly average SO₄, TAL and TDS loads at monitoring station A2H45 tabularised
Five yearly Avg SO₄ Loads Five yearly Avg TAL Loads Five yearly Avg TDS Loads Date (ton/year) (ton/year) (ton/year) 1980-85 2389,48 4080,79 11635,39 1986-90 2025,51 3257,07 9691,77 1991-95 1475,96 2705,14 7654,04 1996-2000 4221,87 10238,09 26972,06 2001-2005 1997,24 4643,92 12959,67 2006-2010 3806,71 8927,48 24600,75 2011-2015 11243,05 9549,83 35842,22
As seen in Graph 15 and Table 17 the five-yearly average SO₄ loads has declined in the first fifteen years, then in the 1996-2000 period there was a sharp increase but then a drop occurred in the 2001- 2005 period. Since this period there was significant increases in the last ten years until it reached its maximum in the 2011-2015 period at the culmination of the study. The five yearly average TAL loads showed a decreasing trend in the first fifteen years until the 1991-1995 period. In the 1996-2000 period, there was a spike that occurred. After this period there was a drop, but from that point onward there was a fifteen-year increase until the five yearly average TAL loads reached its maximum in the 2011-2015 period. The five yearly average TDS loads has declined in the first fifteen years of the study period, then in the 1996-2000 period there was a sharp increase but then a drop occurred in the 2001- 2005 period, but since this period there was significant increases until the five yearly average TDS loads reached its maximum in 2015, the highest level of the whole 35-year study period.
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A2H45 five yearly Avg SO₄ TAL TDS Concentration and Volume
Five yearly Avg SO₄ Concentration (mg/l) Five yearly Avg TAL Concentration (mg/l) Five yearly Avg TDS Concentration (mg/l) Five yearly Avg Volume (m³/s) 600
500
400 ³/S
300
200 MG/L & M & MG/L
100
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 16: Five yearly average SO₄, TAL, TDS concentration and Volume at monitoring station A2H45
As is evident from Graph 16 the five yearly average volume decreased the first fifteen-year period with a marked increase in the 1996-2000 period, after which a drop occurred but since then the volume has steadily climbed for the last fifteen years of the study period. The five-yearly average SO₄ concentration has increased steadily the first fifteen years of the study period. The following fifteen years showed a decline, however the last five-year period of 2011-2015 showed a major increase resulting in the maximum SO₄ concentration level of the entire 35-year study period. The five yearly average TAL concentration showed an increase in the first fifteen years of the study period up until 1995. The following twenty-year period of the study showed a steady although minor decline up until the end of 2015. The five yearly average TDS concentration has increased steadily the first fifteen years of the study period. The following fifteen years showed a decline, however the last five-year period of 2011-2015 showed a major increase resulting in the maximum five yearly average TDS concentration level of the entire 35-year study period.
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4.7 Monitoring station A2H23 on the Jukskei river:
K Na Ca Mg SO₄ Cl TAL
Figure 8: Maucha diagrams at monitoring station A2H23 on the Jukskei river
Concerning Figure 8, it is clear that the percentage contribution of SO₄ towards TDS has receded from 1980 throughout the study period up to the year 2015, whereas the percentage contribution of TAL towards TDS is the exact opposite, it increased from 1980 reaching a maximum level in 2015. All the other salts remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H23 five yearly Avg TDS SO₄ TAL concentration
Five yearly Avg TDS concentration (mg/l) Five yearly Avg SO₄ concentration (mg/l) Five yearly Avg TAL concentration (mg/l) 700 600 500 400
MG/L 300 200 100 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 17: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H23
As observed from Graph 17 the five yearly average TDS concentration at this monitoring station has declined by a fair margin until reaching its minimum in the 2001-2005 period from where it has recovered to such an extent that slight increases are visible at the end of the study period in 2015. The five-yearly average SO₄ concentration has decreased over the whole 35-year study period. The five
Page 34 yearly average TAL concentration on the other hand showed steady increases over the entire 35-year period reaching its maximum at the end of the study period in 2015.
4.8 Monitoring station A2H40 on the Jukskei river:
K Na Ca Mg SO₄ Cl TAL
Figure 9: Maucha diagrams at monitoring station A2H40 on the Jukskei river
As is evident from Figure 9 the percentage contribution of SO₄ towards TDS has decreased over the period stretching from 1980 to 1997 although it is still quite high, whereas the percentage contribution of TAL towards TDS has increased as well as the percentage contribution of Mg towards TDS although lastly named to a lesser extent. The percentage contribution of Ca towards TDS could also be observed as steadily increasing over this period. All the other salts remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H40 five yearly Avg TDS SO₄ TAL concentration
Five yearly Avg TDS concentration(mg/l) Five yearly Avg SO₄ concentration (mg/l) Five yearly Avg TAL concentration (mg/l) 1000
800
600
MG/L 400
200
0 1980-85 1986-90 1991-95 1996-97
Graph 18: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H40
It can be clearly seen from Graph 18 that the five yearly average TDS concentration has decreased over the first fifteen years of the study period reaching its lowest point in the 1991-1995 period but has slightly recovered in the period 1996-1997 period. The five yearly average SO₄ concentration has decreased over this entire period in relation to the five yearly average TAL concentration that has showed an increase over the same period.
Page 35
4.9 Monitoring station A2H42 on the Jukskei river:
K Na Ca Mg SO₄ Cl TAL
Figure 10: Maucha diagrams at monitoring station A2H42 on the Jukskei river
According to Figure 10, the percentage contribution of SO₄ toward TDS has decreased over the period stretching from 1980 to 1997 whereas the percentage contribution of TAL towards TDS has increased as well as the percentage contribution of Mg and Ca towards TDS. All the other salts remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H42 five yearly Avg TDS SO₄ TAL concentration
Five yearly Avg TDS concentration (mg/l) Five yearly Avg SO₄ concentration (mg/l) Five yearly Avg TAL concentration (mg/l) 800 700 600 500
400 MG/L 300 200 100 0 1980-85 1986-90 1991-95 1996-97
Graph 19: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H42
According to Graph 19 the five yearly average TDS concentration has decreased since the 1980-85 period reaching its lowest point in the 1991-1995 period but has slightly picked up in the 1996-1997 period. The five-yearly average SO₄ concentration has decreased over the entire 1980-1997 period while the five yearly average TAL concentration has showed an increase over the same period.
Page 36
4.10 Monitoring station A2H47 on the Klein-Jukskei:
K Na Ca Mg SO₄ Cl TAL
Figure 11: Maucha diagrams at monitoring station A2H47 on the Klein-Jukskei river
Concerning Figure 11, the percentage contribution of SO₄ towards TDS showed a slight decrease from the 1980-85 period to the 1986-90 period and then remained relatively stable while the percentage contribution of TAL towards TDS has remained high throughout the whole 35-year study period. All the other salts remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H47 five yearly Avg TDS SO₄ TAL concentration
Five yearly Avg TDS concentration (mg/L) Five yearly Avg SO₄ concentration (mg/L) Five yearly Avg TAL concentration (mg/L) 300
250
200
150 MG/L 100
50
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 20: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H47
When observing Graph 20 it is clear that the five yearly average TDS concentration has fluctuated over the entire 35-year study period, but the general trend shows an increase over the whole 35-year study period with the last ten-year period indicating some of the highest five yearly average TDS concentrations, with the 2006-2010 period indicating the maximum five yearly average TDS
Page 37 concentration for the whole 35-year study period. The five-yearly average SO₄ concentration has fluctuated slightly over the 35-year study period with no clear trend being visible over this time period. The five yearly average TAL concentration remained stable the first ten years, with the following ten- year period (1991-2000) showing an increase. Following this period there was a slight drop in the 2001-2005 period, with 2001-2010 reaching the maximum five yearly average TAL concentration of the whole 35-year study period. There was just a slight drop in the final five-year period.
4.11 Monitoring station A2H49 on the Bloubankspruit:
K Na Ca Mg SO₄ Cl TAL
Figure 12: Maucha diagrams at monitoring station A2H49 on the Bloubankspruit
According to Figure 12 the percentage contribution of SO₄ and TAL towards the TDS has remained relatively stable for thirty years but in the last five-year period from 2011-2015 drastic changes took place. The percentage contribution of SO₄ towards TDS had a major increase in the last five-year period whereas the percentage contribution of TAL towards TDS showed a major decrease over this same period. All the other salts remained fairly stable over the study period and showed only minor percentage increases and decreases.
Page 38
A2H49 five yearly Avg TDS SO₄ TAL concentration
Five yearly Avg TDS concentration (mg/L) Five yearly Avg SO₄ concentration (mg/L) Five yearly Avg TAL concentration (mg/L) 700 600 500 400
MG/L 300 200 100 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 21: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H49
When observing Graph 21, it is clear that the five yearly average TDS concentration has increased the first fifteen years of the study period after this period there was a very slight decrease in the following ten-year period with the last ten years showing an upward trend especially the last five years which recorded the highest five yearly average TDS concentration for the whole 35-year study period. This 2011-2015 period was also remarkably higher than the previous thirty years. The five-yearly average SO₄ concentration increased in the first ten-year period, after which there was a slight fifteen-year decline. The last ten-year period of the study there was a steep upward trend. The last five years recorded the highest five yearly average SO₄ concentration for the whole 35-year study period. It was also remarkably higher compared to the previous thirty years. The five yearly average TAL concentration showed a steady upwards curve for the first twenty years of the study from 1980 to 2000, reaching a maximum in 1996-2000 period. The last fifteen years of the study showed a gradual decline with the five yearly average TAL concentration reaching its lowest level in 2011-2015 period.
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4.12 Monitoring station A2H50 on the Crocodile river:
K Na Ca Mg SO₄ Cl TAL
Figure 13: Maucha diagrams at monitoring station A2H50 on the Crocodile river
Concerning Figure 13, the percentage contribution of SO₄ towards TDS has decreased from 1980 until the end of 2000 where it has remained relatively stable up until 2015. The percentage contribution of TAL towards TDS has increased from 1980 until 2000, since then it remained relatively stable at this elevated level. All the other salts remained fairly stable over the study period and showed only minor percentage increases and decreases.
A2H50 five yearly Avg TDS SO₄ TAL concentration
Five yearly Avg TDS concentration (mg/L) Five yearly Avg SO₄ concentration (mg/L) Five yearly Avg TAL concentration (mg/L) 350 300 250 200
MG/L 150 100 50 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Graph 22: Five yearly average TDS, SO₄ and TAL concentration at monitoring station A2H50
According to Graph 22 the five yearly average TDS concentration was highest in the 1980-1985 period of the research study after which it reached its minimum level in the 1996-2000 period but since this period it started climbing and showed a clear upwards curve to the end of the 35-year study period in 2015. The five-yearly average SO₄ concentration has decreased for the first twenty-five years of the
Page 40 study after it only ever so slightly started to increase in the last ten years of the study period. The five yearly average TAL concentration shows an upward trend over the 35-year study period with the highest levels recorded in the last ten years of the study period namely 2006-2015.
Page 41
CHAPTER 5: DISCUSSION AND CONCLUSION
5.1 Discussion
5.1.1 Five yearly average concentrations of TDS, SO₄ and TAL
The three main salts that had the greatest influence on the salinity composition, loads and concentrations of the Crocodile river and its tributaries in the study area where SO₄, TAL and TDS.
Monitoring station A2H12: This monitoring station which lies on the Crocodile river at the bottom of the study area’s catchment indicated a general decreasing trend for the five yearly average TDS concentration as seen in Graph 1 and Table 2. According to the Maucha diagrams for monitoring station A2H12 (refer to Figure 4 and Table 1 or Figure 5 and Table 9) it is clear that the percentage contribution of sulphate (SO₄) towards TDS was high at the beginning of the study period in 1980 and decreased as the study period progressed. The opposite is true for total alkalinity (TAL), its percentage contribution towards the TDS increased as the study period progressed. The salinity composition of the Crocodile river has changed from a SO₄-dominated system to a TAL-dominated system.
Monitoring station A2H44: This monitoring station which lies on the Jukskei river, upstream from monitoring station A2H12, confirmed a general decreasing trend for the five yearly average TDS concentration as seen in Graph 1 and Table 2. The Maucha diagrams (refer to Figure 6 and Table 12) clearly shows that the percentage contribution of SO₄ towards TDS decreased as the study period wore on whereas the percentage contribution of TAL increased as the study period progressed. This influence can be seen further downstream at monitoring station A2H12 which shows the same results. Monitoring station A2H40 which is one of the monitoring stations farthest up the study area’s catchment, as well as monitoring station A2H42 and A2H23 showed an increase in the five yearly average TAL concentrations as can be seen from the Maucha diagrams and the graphs at these monitoring stations (refer to Figure 9, Graph 18, Figure 10, Graph 19, Figure 8 and Graph 17). Thus, the increase in the five yearly average TAL concentration at A2H44 originates from higher up the study area’s catchment as confirmed by the increase in the five yearly average TAL concentration at monitoring stations A2H23, A2H42 and A2H40. The increase in the five yearly average TAL concentrations at these three monitoring stations and the increase in the five yearly average TAL loads (refer to Graph 12 and Table 13) at monitoring station A2H44 can be ascribed to the increased run-off factor from a progressively urbanised catchment where hard surfaces proliferate as well as an increase in pollutants that end up in the water sources of the study area’s catchment.
Page 42
Monitoring station A2H45: This monitoring station which lies on the Crocodile river, upstream from monitoring station A2H12 showed a decreasing trend for the five yearly average TDS concentration for the last twenty-year period of the research study except for the last five years which showed a significant increase (refer to Graph 1 and Table 2). The Maucha diagrams shows that the percentage contribution of SO₄ towards TDS decreased for the majority of the study period but had a massive increase in the last five years of the study period namely 2011-2015, whereas the percentage contribution of TAL towards TDS gradually declined for the last twenty-five years of the study period (refer to Figure 7 and Table 15). This is the opposite trend that could be observed at monitoring station A2H44 on the Jukskei river. Higher up the western part of the study area’s catchment is monitoring station A2H49 located on the Bloubankspruit. From the Maucha diagrams for monitoring station A2H49 it is clear that the percentage contribution of SO₄ towards TDS has increased reaching a maximum for the 35-year study period in the last five years namely 2011-2015 (refer to Figure 12). This explains the results seen lower down the study area’s catchment at monitoring station A2H45 located on the Crocodile river, where the five-yearly average SO₄ loads (refer to Graph 5 and Table 6) have increased as well towards the end of the study, reaching its maximum for the study period in the last five years namely the 2010-2015 period. The high five-yearly average SO₄ concentration at A2H49 and the corresponding high five yearly average SO₄ concentration at A2H45 is in all likelihood caused by the Acid Mine Drainage (AMD) decanting into the Tweelopiesspruit and ending up in the Bloubankspruit. This part of the study area’s catchment near the Bloubankspruit falls within the Krugersdorp area where there is a high concentration of old abandoned gold mines with an AMD problem. The water contaminated by AMD has very high levels of SO₄.
5.1.2 Five yearly average loads of TDS, SO₄ and TAL
The five yearly average TDS, SO₄ and TAL loads have all showed an increase in the last ten-year period of the research study at all three monitoring stations namely A2H12, A2H44 and A2H45 (refer to Graph 2, Table 3, Graph 5, Table 6, Graph 7 and Table 8). There was an increase in the five yearly average TDS, SO₄ and TAL loads ending up in the study area’s water sources. This shows a very strong correlation with the increase in the five yearly average volume that also showed an increase in the last ten years of the study period. The main contributing factor that has caused an increase in the five yearly average TDS, SO₄ and TAL loads in the study area’s catchment is the increased volumes of water being deposited in the study area’s water sources over the 35-year study period. The increase in the volume can be indirectly ascribed to population growth in the study area’s catchment, which in turn necessitates water being transferred from the Vaal dam, which is situated outside the study areas catchment. This transfer of water coupled with an increase in industries, businesses, informal
Page 43 settlements, hard surfaces and overloaded waste water treatment works contributes increased volumes year-round to the study area’s water sources. Another factor why the five yearly average loads have increased can be explained by the land use change in the study area’s catchment and increasing urbanisation in the study catchment area. Thus, the sources of the TDS, SO₄ and TAL loads in the study area’s catchment has drastically increased over the 35-year study period.
5.1.3 Five yearly average volume at monitoring stations A2H12, A2H44 and A2H45
There is a clear pattern of increase in the five-yearly average volumes at all three monitoring stations namely A2H12, A2H44 and A2H45 in the last ten years of the study (refer to Graph 3 and Table 3). The five yearly average volume plays a crucial role influencing the results of the five yearly average loads and the five yearly average concentrations. The five yearly average TDS, SO₄ and TAL loads increased not just because the sources increased in the study area’s catchment but the volume of water increased as well which transports more TDS, SO₄ and TAL loads into the water sources of the study area’s catchment than would otherwise be the case if the volumes were less. The volumes influence the concentrations of TDS, SO₄ and TAL in the sense that these concentrations are diluted by the increased volumes of water being deposited in the water sources of the study area’s catchment. The last ten years of the study period showed the highest five yearly average volumes of the whole 35- year study period across all three monitoring stations.
The increase in the five yearly average volumes at all three monitoring stations is three-fold. Firstly, as the study area’s catchment develops and the population increases the demand for water also increases. Rand water has to respond to that demand by transferring water from other sources located outside the study area’s catchment such as the Vaal dam. This has a significant impact on base flows during dry periods or in the winter months in the sense that the base flows are increased by this anthropogenic intervention. Secondly the increase in the five yearly average volume of the study area’s water sources is related to the increase of hard surfaces in the study area’s catchment. Urbanisation converts vast tracks of natural or agricultural land from a natural state or near natural state to a build-up state. This increases the amount of land under hard surfaces such as concrete, cement and tiles. Thus, when it rains or any other source of runoff the water can’t ingress and be absorbed by the soil as is the case in a natural piece of veld covered with grass and other vegetation. Thirdly it can be ascribed to an increase in anthropogenic sources that proliferated as the 35-year study period wore on for example leakages from various pipes that aren’t addressed.
The rationale behind the general decreasing trend in some of the concentrations was that the volumes in the study catchment’s water sources increased which subsequently diluted the concentrations of the salts in the study catchment’s rivers and tributaries. The volumes increased because of
Page 44 anthropogenic factors such as huge amounts of untreated and treated waste water from overstressed waste water treatment facilities, proliferation of hardened surfaces (for example roads, pavements, roofs), urbanisation, lack of infrastructure maintenance, transfer of water by Rand Water from the Vaal dam to urban areas in the study area’s catchment and population growth. All of this changed the run off patterns of the study area’s catchment in the sense that the run off takes place faster as there is less soil and vegetation that can slow and absorb the run off.
5.2 Conclusion
It was clear from this research study that the composition, loads and concentration of TDS, SO₄ and TAL in the study area’s catchment underwent changes over the 35-year study period. The changes in the salt composition of the study area’s water sources is in all likelihood linked to the following:
• The runoff from an increasingly modified, urbanised and hard-surfaced catchment. • Additional sources of water from outside the study area’s catchment which has a different salt composition than the water occurring in the catchment. • As well as a proliferation of anthropogenic impacts upon the catchment’s water sources as the 35-year study period wore on.
Significant changes in the concentration of TDS, TAL and SO₄ were observed over the 35-year study period, whereas the volumes of water and the loads of TDS, TAL and SO₄ in the study catchment’s water sources increased. This clearly indicates that even though some of the salt concentrations at monitoring stations A2H12, A2H44 and A2H45 showed a decreasing trend it doesn’t mean that the amount of salts ending up in the study catchment’s water sources have decreased but in reality, has increased as is evident from the increased loads observed. It is imperative when water quality is researched and monitored that there isn’t only focussed on the various salt concentrations as this gives a skewed representation of what is occurring in a given water source, but by also taking the salt loads into account a much more balanced picture is construed. A slight increase in the last five-yearly average SO₄ concentration at monitoring station A2H12 is in all likelihood the result of Acid Mine Drainage that decants and leaches sulphate rich water into the catchment’s water sources which is reflected at monitoring station A2H49 on the Bloubankspruit which is located upstream from monitoring station A2H12.
Rand water transfers water from the Vaal dam to the major urban areas in Gauteng. This additional source of water led to changes in the volumes, loads and concentrations of the study area’s water sources. The base flow in the water sources of the study catchment such as the Crocodile and Jukskei rivers is much higher than it would have been in drier periods or during the winter months because of
Page 45 this additional source of water. Both the Jukskei river and the Bloubankspruit had significant impacts on the salt composition, concentration and loads in the Crocodile river although the nature of their impacts differed. Mining, urbanisation, population growth and an increase in hard surfaces as a result of urbanisation also impacted upon the study area’s water sources and led to changes in the volumes, loads and concentrations of TAL, TDS and SO₄.
The increase that is observed in the five-yearly average TDS, TAL and SO₄ loads at monitoring stations A2H12, A2h44 and A2H45 is in all likelihood two-fold. Firstly, the elevated volumes increase the loads of TDS, TAL and SO₄ that is deposited in the Crocodile river and its tributaries. Secondly, the proliferation of anthropogenic sources in the study area’s catchment changes the run off characteristics of the study area’s catchment as well as providing additional sources of TDS, TAL and SO₄. The increasingly urbanised character of the study area’s catchment with its hardened surfaces provides weatherable material such as concrete which increases the TAL loads ending up in the water sources of the study area’s catchment. Urbanisation and development also disturbs the soils which elevates the weathering rates. The urban landscape is also rich in hydro carbons and industrial effluent such as oil and fuel which further impacts the water quality of the catchment’s water sources.
It is clear from the results in this study that Crocodile river’s catchment as described in this research study is heavily impacted by anthropogenic sources as well as the resulting pollution of the catchment’s water sources. These anthropogenic influences and their pollution loads modified the salinity composition and TDS, SO₄ and TAL loads of the Crocodile river and its various tributaries. It is difficult to see how this is going to change in the near future as the population of the study catchment is just going to increase further and in many instances unplanned and unregulated development of the study catchment is not going to slow down. Humans are responsible for the state of the Crocodile river’s water quality and therefore are also responsible to find solutions. There is not sufficient management and responsibility taken in regards to the study catchment’s water sources. This occurs at a micro scale, for example an industry discharging untreated effluent into a stream in the study area’s catchment. It also occurs at a macro scale where the catchment management authority as well as the municipality of the urban centres in the study area’s catchment don’t take the responsibility for the management of study catchment’s water sources seriously. Monitoring the water quality of the Crocodile river, especially the salt composition, concentration and loads is a useful tool that can be used by scientist and policy makers to better manage the Crocodile river’s catchment for the benefit of man and nature if it is correctly and diligently implemented.
Page 46
REFERENCES
BURKE, J. & BAKOKO, T. Optimisation of Surface Water Quality Monitoring within the City of Johannesburg. Water Institute of Southern Africa (WISA) Biennial Conference, 2-6 May 2004 Cape Town, South Africa. 702-709.
COUNCIL FOR GEOSCIENCE, DEPARTMENT OF WATER AFFAIRS, DEPARTMENT OF MINERAL RESOURCES, COUNCIL FOR SCIENTIFIC AND INDUSTRIAL RESEARCH, MINTEK & COMMISSION, W. R. 2010. Mine Water Management in the Witwatersrand Gold Fields with special emphasis on Acid Mine Drainage.
DWA 2013. Classification of significant water resources in the Crocodile (West) and Marico Water Management Area (WMA) and Mokolo and Matlabas catchments: Limpopo WMA. Pretoria: Department of Water Affairs.
DWAF 1996. South African Water Quality Guidelines. Volume 7: Aquatic Ecosystems. Pretoria: Department of Water Affairs and Forestry
DWAF 2004. Crocodile River (West) Catchment: Internal Strategic Perspective. Pretoria: Department of Water Affairs and Forestry.
GIS 2014. Arcview GIS. 10.2 ed.: ESRI.
GOOGLE 2017. Google Earth Pro.
IBANEZ, J. G., HERNANDEZ-ESPARZA, M., DORIA-SERRANO, C., FREGOSO-INFANTE, A. & SINGH, M. M. 2008. Alkalinity and Buffering Capacity of Water. Environmental Chemistry: Microscale Laboratory Experiments. New York, NY: Springer New York.
KELLER, P. 1960. Bacteriological aspects of pollution in the Jukskei — Crocodile river system in the Transvaal, South Africa. Hydrobiologia : The International Journal of Aquatic Sciences, 14, 205-254.
MUCINA, L. & RUTHERFORD, M. C. 2006. The vegetation of South Africa, Lesotho and Swaziland, Pretoria :, South African National Biodiversity Institute.
MUKHEIBIR, P. & SPARKS, D. 2003. Water resource management and climate change in South Africa: visions, driving factors and sustainable development indicators. Report for Phase I of the Sustainable Development and Climate Change project. Energy and Development Research Centre (EDRC), University of Cape Town.
NIKANOROV, A. M. & BRAZHNIKOVA, L. V. 2009. Water Chemical Composition of Rivers, Lakes and Wetlands. Types and Properties of Water, Encyclopaedia of life support system (EOLSS).
PITMAN, W. V. 1978. Flow generation by catchment models of differing complexity — A comparison of performance. Journal of Hydrology, 38, 59-70.
ROSNER, T. 1999. The environmental impact of seepage from gold mine tailings dams near Johannesburg, South Africa. Doctorate, University of Pretoria.
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ROUX, S., OELOFSE, S. & DE LANGE, W. The rising costs of both sewage treatment and the production of potable water associated with increasing levels of pollution in a portion of the Crocodile-West Marico water management area (A Case Study). WISA 2010 Biennial Conference ICC Durban, South Africa, 2010. 18.
SILBERBAUER, M. J. & KING, J. M. 1991. GEOGRAPHICAL TRENDS IN THE WATER CHEMISTRY OF WETLANDS IN THE SOUTH-WESTERN CAPE PROVINCE, SOUTH AFRICA. Southern African Journal of Aquatic Sciences, 17, 82-88.
SIWEK, J. P., ZELZANY, M. & CHELMICKI, W. 2008. Annual Changes in the Chemical Composition of Stream Water in Small Catchments with Different Land-use (Carpathian Foothills, Poland). Soil & Water Res, 3, 129-137.
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TODES, A. 2012. Urban growth and strategic spatial planning in Johannesburg, South Africa. Cities, 29, 158-165.
VAN NIEKERK, H., SILBERBAUER, M. & HOHLS, B. 2009. Monitoring programme revision highlights long-term salinity changes in selected South African rivers and the value of comprehensive long-term data sets. Environmental monitoring and assessment, 154, 401-411.
VAN NIEKERK, H., SILBERBAUER, M. J. & MALULEKE, M. 2014. Geographical differences in the relationship between total dissolved solids and electrical conductivity in South African rivers. Water SA, 40, 133-138.
VENTER, P. 2012. Overview of the programme : Hartbeespoort Dam remediation. Civil Engineering, 20, 15-18, 21-23.
Page 48
APPENDIX A
Monitoring station A2H12 on the Crocodile river:
A2H12 five yearly avg Cl concentration (mg/L) 62
60
58
56
MG/L 54
52
50
48 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H12 five yearly avg K concentration (mg/L) 12
10
8
6 MG/L
4
2
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 49
A2H12 five yearly avg Mg concentration (mg/L) 25
20
15 MG/L 10
5
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H12 five yearly avg Na concentration (mg/L) 70
60
50
40
MG/L 30
20
10
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H12 five yearly avg Ca concentration (mg/L) 60
50
40
30 MG/L
20
10
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 50
Monitoring station A2H23 on the Jukskei river:
A2H23 five yearly avg Cl concentration (mg/L) 90 80 70 60 50
MG/L 40 30 20 10 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H23 five yearly avg Ca concentration (mg/L) 70
60
50
40
MG/L 30
20
10
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H23 five yearly avg K concentration (mg/L) 14
12
10
8
MG/L 6
4
2
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
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A2H23 five yearly avg Mg concentration (mg/L) 25
20
15 MG/L 10
5
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H23 five yearly avg Na concentration (mg/L) 90 80 70 60 50
MG/L 40 30 20 10 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Monitoring station A2H40 on the Jukskei river:
A2H40 five yearly avg Ca concentration (mg/L) 82
80
78
76
74 MG/L 72
70
68
66 1980-85 1986-90 1991-95 1996-97
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A2H40 five yearly avg Cl concentration (mg/L) 120
100
80
60 MG/L
40
20
0 1980-85 1986-90 1991-95 1996-97
A2H40 five yearly avg K concentration (mg/L) 20 18 16 14 12
10 MG/L 8 6 4 2 0 1980-85 1986-90 1991-95 1996-97
A2H40 five yearly avg Mg concentration (mg/L) 35
30
25
20
MG/L 15
10
5
0 1980-85 1986-90 1991-95 1996-97
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A2H40 five yearly avg Na concentration (mg/L) 160
140
120
100
80 MG/L 60
40
20
0 1980-85 1986-90 1991-95 1996-97
Monitoring station A2H42 on the Jukskei river:
A2H42 five yearly avg Ca concentration (mg/L) 67 66 65 64 63
MG/L 62 61 60 59 58 1980-85 1986-90 1991-95 1996-97
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A2H42 five yearly avg Cl concentration (mg/L) 100 90 80 70 60
50 MG/L 40 30 20 10 0 1980-85 1986-90 1991-95 1996-97
A2H42 five yearly avg K concentration (mg/L) 16
14
12
10
8 MG/L 6
4
2
0 1980-85 1986-90 1991-95 1996-97
A2H42 five yearly avg Mg concentration (mg/L) 30
25
20
15 MG/L
10
5
0 1980-85 1986-90 1991-95 1996-97
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A2H42 five yearly avg Na concentration (mg/L) 120
100
80
60 MG/L
40
20
0 1980-85 1986-90 1991-95 1996-97
Monitoring station A2H44 on the Jukskei river:
A2H44 five yearly avg Ca concentration (mg/L) 60
50
40
30 MG/L
20
10
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H44 five yearly avg Cl concentration (mg/L) 90 80 70 60 50
MG/L 40 30 20 10 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
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A2H44 five yearly avg K concentration (mg/L) 16
14
12
10
8 MG/L 6
4
2
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H44 five yearly avg Mg concentration (mg/L) 20 18 16 14 12
10 MG/L 8 6 4 2 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H44 five yearly avg Na concentration (mg/L) 100 90 80 70 60
50 MG/L 40 30 20 10 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
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Monitoring station A2H45 on the Crocodile river:
A2H45 five yearly avg Ca concentration (mg/L) 70
60
50
40
MG/L 30
20
10
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H45 five yearly avg Cl concentration (mg/L) 45 40 35 30 25
MG/L 20 15 10 5 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H45 five yearly avg K concentration (mg/L) 6
5
4
3 MG/L
2
1
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 58
A2H45 five yearly avg Mg concentration (mg/L) 35
30
25
20
MG/L 15
10
5
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H45 five yearly avg Na concentration (mg/L) 40
35
30
25
20 MG/L 15
10
5
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Monitoring station A2H47 on the Klein-Jukskei:
A2H47 five yearly avg Ca concentration (mg/L) 36 35 34 33 32
MG/L 31 30 29 28 27 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 59
A2H47 five yearly avg Cl concentration (mg/L) 35
30
25
20
MG/L 15
10
5
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H47 five yearly avg K concentration (mg/L) 4,5 4 3,5 3 2,5
MG/L 2 1,5 1 0,5 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H47 five yearly avg Mg concentration (mg/L) 18 16 14 12 10
MG/L 8 6 4 2 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 60
A2H47 five yearly avg Na concentration (mg/L) 25
20
15 MG/L 10
5
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Monitoring station A2H49 on the Bloubankspruit:
A2H49 five yearly avg Ca concentration (mg/L) 100 90 80 70 60
50 MG/L 40 30 20 10 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H49 five yearly avg Cl concentration (mg/L) 45 40 35 30 25
MG/L 20 15 10 5 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 61
A2H49 five yearly avg K concentration (mg/L) 4,5 4 3,5 3 2,5
MG/L 2 1,5 1 0,5 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H49 five yearly avg Mg concentration (mg/L) 45 40 35 30 25
MG/L 20 15 10 5 0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H49 five yearly avg Na concentration (mg/L) 40
35
30
25
20 MG/L 15
10
5
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 62
Monitoring station A2H50 on the Crocodile river:
A2H50 five yearly avg Ca concentration (mg/L) 28 27,5 27 26,5 26
25,5 MG/L 25 24,5 24 23,5 23 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H50 five yearly avg Cl concentration (mg/L) 60
50
40
30 MG/L
20
10
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2H50 five yearly avg K concentration (mg/L) 12
10
8
6 MG/L
4
2
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 63
A2H50 five yearly avg Mg concentration (mg/L) 14
12
10
8
MG/L 6
4
2
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
A2h50 five yearly avg Na concentration (mg/L) 60
50
40
30 MG/L
20
10
0 1980-85 1986-90 1991-95 1996-2000 2001-2005 2006-2010 2011-2015
Page 64
APPENDIX B
Monitoring station A2H12:
Page 65
Page 66
Monitoring station A2H44:
Page 67
Page 68
Monitoring station A2H45:
Page 69
Page 70