Groundwater recharge dynamics and geohydrological

Groundwater recharge dynamics and geohydrological investigation in Kenton-On-Sea, Eastern Cape

Africa Khamusi Ramuima A thesis submitted in fulfillment of the requirements for the degree of Bachelor of Science (Honours)

Department of Geology Rhodes University, South Africa Supervisor: Dr. Afsoon Kazerouni

October 2018

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TABLE OF CONTENTS DECLARATION……………………………………………………………………………………...…...I I ACKNOWLEGDEMENT……………………………………………………………………………..IV ABSTRACT………………………………………………………………………………………..….......V ABBREVIATION……………………………………………………………………………………..…IX LIST OF FIGURES…………………………………………………………………………………........X LIST OF TABLES……………………………………………………………………………...……......XI Chapter 1: Introduction and Aim............................................................................................................ 16 1.2 Geology of Kenton-On-Sea .............................................................................................................. 17 1.3 Hydrogeology of Kenton-On-Sea ..................................................................................................... 20 1.4 Rationale ........................................................................................................................................... 20 1.5 Research Aims .................................................................................................................................. 21 1.6. Main Research Aims ........................................................................................................................ 21 1.6.1 Objectives .................................................................................................................................. 22 1.7 Thesis Structure ................................................................................................................................ 22 Chapter 2: Background Studies............................................................................................................... 23 2.1 Introduction ....................................................................................................................................... 23 2.2 Groundwater ..................................................................................................................................... 23 2.3 Types of recharge mechanisms ......................................................................................................... 33 2.4 Bushmans and Kariega Rivers .......................................................................................................... 34 2.5 Methods of predicting groundwater recharge ................................................................................... 34 2.6 Groundwater models ......................................................................................................................... 35 2.6.1 Water table fluctuation (WTF) and Chloride mass balance (CMB) method ............................. 36 2.7 Sustainability of water and groundwater reserves ............................................................................ 36 2.8 Relationship between sea water and fresh water in coastal regions.................................................. 37 2.9 NGA Boreholes positions in the studied area ................................................................................... 38 2.9.1 Drainage Directions ................................................................................................................... 40 2.10 Possible Risks and Mitigation ..................................................................................................... 41 2.11 Water Desalination and Reverse Osmosis ...................................................................................... 43 Chapter 3: Research and Methodology .................................................................................................. 45 3.1 Introduction ....................................................................................................................................... 45 3.2 Methods and analytical techniques ................................................................................................... 45 3.2.1. Sources of data ......................................................................................................................... 45 3.3. Field investigations ......................................................................................................................... 46

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3.3.1 Hydrogeological investigation .................................................................................................. 46 3.4. Geological methods ......................................................................................................................... 46 3.4.1 Rocks sampling and borehole identification .............................................................................. 46 3.4.2 Thin section preparation............................................................................................................. 50 3.4.2.1 Cutting of samples hand specimens ............................................................................... 51 3.4.2.2 Impregnation……………………………………………………………………….…50 3.4.2.3 Petrographic microscope analyses………………………………...……………..…...50 3.4.2.4 Petrographic thin section analysis……………………………………………............50 3.4.2.5 X-Ray Diffraction Method (XRD) Bulk rock samples……………………………….51 3.5. Hydrological and hydrogeochemical analysis .................................................................................. 53 3.5.1 Available hydrogeological databases ......................................................................................... 53 3.5.2 Water sample chemical analysis ................................................................................................ 56 3.5.3 Laboratory analyses ....................................................................................................................... 56 3.5.3.3 Water Samples from the Bushmans River .............................................................................. 60 3.5.3.4 Water samples from the Bushmans and Kariega River........................................................... 61 3.6. Software and diagram used ............................................................................................................... 62 3.6.1 Piper diagram analysis ................................................................................................................. 62 3.6.2 Durov plot…………………………………………………………………………...……….….63 3.6.3 Schoeller diagram analysis.......................................................................................................... 68 3.6.4 Stiff pattern ................................................................................................................................. 70 3.6.5 MicroFEM................................................................................................................................... 71 Chapter 4: Results ....................................................................................................................................... 76 4.1 Introduction ....................................................................................................................................... 76 4.2 Hydrogeochemical analysis .............................................................................................................. 76 4.3 Field petrography .............................................................................................................................. 89 4.4 Petrographic thin sections analysis ................................................................................................... 90 4.5 Bushmans and Kariega Rivers XRD analyses results ....................................................................... 95 4.6 Groundwater modelling .................................................................................................................... 98 4.7. Groundwater Modelling of Kenton-On-Sea area ............................................................................. 98 Chapter 5: Discussion ............................................................................................................................... 100 5.1 Introduction ..................................................................................................................................... 100 5.2 Hydrogeochemical analysis ............................................................................................................ 100 5.2.1 Piper and Durov diagrams........................................................................................................ 103

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5.2.2 Stiff and Schoeller diagrams .................................................................................................... 107 5.3 Field petrography, petrographic thin sections and XRD analysis ................................................... 108 5.4 Groundwater modelling using MicroFem ....................................................................................... 110 Chapter 6: Conclusions and Recommendations........................................................................................ 112 6.1 Introduction ..................................................................................................................................... 112 6.2 Hydrogeochemical analysis ............................................................................................................ 112 6.2.1 Piper and Durov diagrams....................................................................................................... 113 6.2.2 Stiff and Schoeller diagrams ................................................................................................... 113 6.3 Field Petrography, petrographic thin sections and XRD analysis................................................... 114 6.4 Groundwater modelling using MicroFem ....................................................................................... 114 6.5 Recommendation ............................................................................................................................ 114 References ................................................................................................................................................ 116 Appenidces…………………………...…………………………………………………………….……126

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Chapter 1 Introduction and Aim 1.1 Introduction Groundwater resources system responds to excitation from the external environment and it is not simple to comprehend, especially under complex hydrogeological conditions (Domenico, 1972). Origin of the groundwater resources are described as (I) dynamic groundwater resources which rely on the yearly recharge of precipitation into the system (II) static groundwater resources which rely on the inter-granular fissured porosity (III) Induced groundwater resources which rely on surface and groundwater interaction (Domenico, 1972).

Groundwater in semi-arid areas is considered rarest natural resources and is an important part of the entire water resources in many regions as it plays a vital role in the socio-economic expansion in many countries (Mutoti, 2015). He has also stated that an increase in population, a socioeconomic activity also increases within semi-arid basins that lead to the overuse of local and groundwater resources. Recharge estimation can be difficult to measure or model due to the complex estimation of the evapotranspiration that is impacted by different soil depth, plants, slope and altitude (Mutoti, 2015). However, the precise recharge approximation is required for groundwater management for population food production and water supply (Asano and Cotruvo, 2004). Therefore, approximating the accessible water in aquifers remains an essential role.

The extremely differentiated existence and significant variation in the availability and application of groundwater in South Africa, makes its management a difficult task. MicroFEM was performed out in the boreholes of the Quaternary Formation in Kenton-On-Sea as Quaternary formation are found at the entire stretch of the coastal belt of the studied area. This study highlights the necessity to implement an organized, economically viable and realistic framework for groundwater management based on groundwater modelling method. Through the course of the current study, a software namely MicroFEM for Windows was used to produce the groundwater models of Kenton-

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On-Sea in order to assess the groundwater system, its recent situation and estimate groundwater strain in the study area.

The use of groundwater cutting-edge modelling software technique remains a dependable and applicable tactic of groundwater modelling (Islam et al., 2015). MODFLOW does not offer the capabilities to simulate a particular complex physical feature to be modelled easily, thus MicroFEM modelling software was used. The research project pursues to create evidence on how applicable the groundwater modelling methods such as MicroFEM could be employed to further study the aquifers at a local scale (Kenton-On-Sea, in South Africa). Surface water studies are essential as it reveals the water playing a major role in recharging the aquifer (Islam et al., 2015). Through the interaction of surface water and a rock, the chemistry of the recharging water can be altered (Srinivasamoorthy et al., 2012). Therefore, the concept of examining the hydrogeology of the Kenton-On-Sea would be informative in terms of the types of rock it demonstrates together with their minerals. 1.2 Geology of Kenton-On-Sea The geological map (Fig. 1.2) of Grahamstown 1: 250 000 (3326) by the Council for Geoscience shows that the studied site is underlain by the Nanaga Formation of the Algoa Group (Kruger & Nel, 2015). Booth et al., (1999) discussed that the Alexandria Formation of the Algoa Group underlain the Nanaga Formation in a paraconformably manner which are both underlain by the Bokkeveld Group.

The Nanaga Formation consists of sandy limestones and semi-consolidated to well-consolidated calcareous sandstones (Kruger and Nel, 2015, Booth et al., 1999, Johnson and Le roux, 1994). Kruger and Nel (2015) stated that the Nanaga Formations is capped by a red soil or calcrete materials on the surface of around 3 m thickness. The relief of the formation controls the thickness which often increases to 150 m thick (Kruger & Nel, 2015). Smooth, rounded hills within ripplelike ridges structures form on this formation and they trend parallel to the current shoreline (Kruger and Nel, 2015).

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The Alexandria Formation that underlain the Nanaga Formation is made up of alternating calcareous sandstones, coquinite and a conglomerate is found on the bottom of the formation (Booth et al., 1999). Kruger and Nel (2015) pointed out that the Alexandria Formation is about 10 m thick and the clasts in this formation mainly comprised of the Cape Supergroup sandstones and Quartzite.

According to Kruger and Nel (2015), It is quite complex to differentiate separate formations of the group due to the extreme folding and the less exposure of the Bokkeveld Group. Thamme and Johnson (2006) noticed that the Bokkeveld Group consists of formations that are generally made up of mudstone or shale with minor sandstone. The Bokkeveld Group is found to have two Subgroups, which are the basal Ceres and the Traka (Kruger & Nel, 2015; Thamme and Johnson, 2006). According to Thamme and Johnson (2006), the basal Ceres Subgroup is overlain by the Traka Subgroup and it consists of numerous layers of different rock types. The rock types found on the Ceres Subgroup together with their thicknesses are the Gydo shale (600 m), Gamka sandstone (200 m), Voorstehoek shale (300 m), Hex River sandstone (60 m), Tra-Tra shale (350 m) and Boplaas sandstone (100 m) (Thamme and Johnson, 2006). On the other hand, the Traka Subgroup comprises of few rock types compared to the basal Ceres Subgroup which are the Karies shale (1300 m thick), Adolphspoort siltstone (600 m thick) and the uppermost Sandpoort shale (400m thick) (Reid et al., 2015). DWAF (2004) mentioned that the Bokkeveld Group is comprised mainly of black shales, siltstones and subordinate sandstones and they represent an ancient deltaic depositional environment. Shales from the Bokkeveld occur as low amplitude, southeast plunging anticline in the western part of Ndlambe (DWAF, 2004). DWAF (2004) has pointed out that only 10% of sandstone units is evident of the whole sedimentary package. Sandstones are mainly limited to the area west of the Kasouga River (DWAF, 2004).

Figure 1.1 shows some of the formations outlined by (Kruger and Nel 2015, Booth et al., 1999, & Johnson and Le Roux, 1994). However, according to Rossouw (2012), formations, namely Schelm Hoek (0.01 Ma) and Nahoon (1.8-0.01 Ma) also existed in Kenton-On-Sea. The Nahoon Formations (Fig. 1.1) is comprised of calcareous sandstone and palaeosols (Almond, 2010). Rossouw (2012) and Almond (2010) both pointed out that the Schelm Hoek Formation is also comprised of calcareous sand (aeolian) and shell middens. These formations are situated on the 18 | P a g e

shoreline and can be clearly observed in figure 1.2. Salnova Formation which was not outlined by Kruger and Nel (2015) also existed in figure 1.2 by Rossouw (2012) and by Le Roux (1988) also.

Figure 1.1: Schematic representation of the geology within Kenton-On-Sea (Modified from Rossouw, 2012).

Figure 1.2: Portion of 1:250 000 scale geological map 3326 Grahamstown, (Council for Geoscience, Pretoria, 1991) showing bedrock geology in the study area enclosed by black square. From oldest to youngest, strata consist of Palaeozoic Bokkeveld Group and cenozoic Algoa Group rocks (Modified from Rossouw, 2012). 19 | P a g e

1.3 Hydrogeology of Kenton-On-Sea The Algoa Group aquifer (the Alexandria and Nanaga Formation) is considered an intergranular aquifer (Kruger and Nel, 2015). Due to the presence of high porosity, water infiltrates rapidly through it prospective to become into contact with the underlying impermeable pre-Algoa Group rocks (Kruger & Nel, 2015). Water will then move towards the direction of the sea within the sandy material or the conglomerate and then appear at the coast as springs (Kruger & Nel, 2015). According to Kruger & Nel (2015), the analyses of boreholes showed that less than 60% of boreholes yield less than 0.5 L/s, meaning that 40% of boreholes yield more than 0.5 L/s (Kruger & Nel, 2015). The electrical conductivity of water proved that the groundwater was drinkable by measuring less than 300 mS/m (Kruger & Nel, 2015). But then the sodium (Na), calcium (Ca) and chloride (Cl) electrical conductivity often exceed the maximum allowable limits (Kruger & Nel, 2015).

Kruger and Nel (2015) estimated the sandstone:shale ratio in the Ceres Subgroup which is 30:70 and 5:95 in the Traka Subgroup for the Bokkeveld Group (Kruger & Nel, 2015). The sandstone:shale ratio is a very vital aspect and plays an important role in the amount of groundwater and quality (Kruger & Nel, 2015). Sandstone formations hold water of a good quality and quantity compared to the shale formations (Kruger & Nel, 2015). Yields of more than 5 L/s are common in the sandstone richer Ceres Subgroup but are not that much (Kruger & Nel, 2015). Yields of more than 5 L/s in the Traka Subgroup rarely occurs and normally less than 1 L/s (Kruger & Nel, 2015). The electrical conductivities in the Ceres Subgroup is more than 200 mS/m and 300 mS/m for Traka Subgroup. Sodium and chloride concentrations electrical conductivities surpass the permissible recommended limits in the Bokkeveld Group (Kruger & Nel, 2015). 1.4 Rationale Groundwater is one of the main sources of water in South Africa and has been widely used for irrigation, domestic and industrial purposes. Quantification of groundwater recharge is very vital for groundwater resource management as it can provide the critical information about the state of the groundwater availability. Quantification of groundwater is one of the complex tasks to carry out as groundwater fluctuates due to numerous factors which includes the amount of precipitation at a particular place is receiving annually. Therefore, not all the precipitation water infiltrates its 20 | P a g e

way to the water table but also it is very crucial to be determined. The estimation of a recharge provides the fundamental information of how much water an aquifer is receiving. Since groundwater is being utilized without the adequate knowledge of how is being damaged, numerous methods (WTF and CMB) have been developed to estimate groundwater recharge in order to quantify and the use of groundwater models (MicroFEM and MODFLOW). Estimation of groundwater recharge itself might not be a sufficient process but must be observed on the effectiveness of its value, skills to compute it and methods and application when it is necessary to evaluate, plan and use of groundwater resource. Partaking method for groundwater sustainable resource management is essential in countries such as South Africa, where optimal supervision of all water resources is therefore crucial.

The current study yet provides a better understanding of groundwater recharge using MicroFEM in Kenton-On-Sea and also focuses on how much groundwater is accessible throughout the study area. The Bushmans and Kariega Rivers are very important as surface water resources in the study area since they play an important role in its groundwater recharge. Analyzing chemistry of these two rivers will bring an insight into the recharge dynamics of the study area. Petrographical and XRD analysis are essential in comprehending the hydrogeology of the Kenton-On-Sea. Surface water geochemical studies by means of comparison diagrams to understand the type of water in the study area is also important. The study delivers a vision of utilizing groundwater models, surface water analysis to estimate the recharge which can further help with the sustainable use of groundwater. 1.5 Research Aims The aim of this thesis enlighten the overall purpose of the research study. The goal of this project has been outlined and various steps have been postulated to achieve the desired outcome. Adequate aims of this thesis is to produce new information or expand understanding of a Kenton-On-Sea hydrogeology. 1.6. Main Research Aims The main objective of the study is to evaluate the groundwater recharge dynamics and to carry out some fundamental geohydrological investigations at a local scale (Kenton-On-Sea in Eastern 21 | P a g e

Cape, South Africa). Enhancement of the knowledge and understanding of groundwater impacts in Kenton-On-Sea community by looking into the recharge flow, sustainability of resources, human lifestyles, projected through their livelihood water level fluctuations. Identifying the main significant factor that sustained the groundwater over the past years and to express ways in which the groundwater recharge could be measured. 1.6.1 Objectives ● To model the Kenton-On-Sea groundwater by utilizing MicroFem modeling software, ● To identify the hydrogeochemical factors affecting the groundwater through geochemical studies of the surface water of Bushmans and Kariega Rivers; and ● To recognize the hydrogeological impact of Kenton-On-Sea on the groundwater recharge system. 1.7 Thesis Structure This thesis is divided into six chapters. The first chapter outlines the structure of the research, defining the general information and explains the background aim within which the study was conducted. It also provides aims and objectives that steered the study. Chapter two focused on the literature review, where it includes background studies done in the study area and elsewhere. This chapter provided fruitful information about the study area. Chapter three focus on the research and methodology and describe how the data were obtained and how they have been used later. Chapter four provides results from one model (MicroFem) for estimating groundwater recharge. This chapter also describes the field petrographical investigations to be used for examining petrographic thin sections prepared from the sample collected from the study area as well as presenting hydrogeochemical analysis of the two studied rivers. Chapter five fully discuss the results and other vital parts of the thesis in detail. The last chapter six concludes the thesis findings and points out necessary improvements for future work.

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Chapter 2 Background Studies 2.1 Introduction The aim of this chapter is to outline the previous work on the estimation of groundwater recharge and presents a background on groundwater availability in the country in terms of management. Limited groundwater studies in the area were experienced, thus no fully detailed out evidence of that could be found through literature review can support this study. Further investigation showed that surface water studies can also give a fruitful information about its influence on the groundwater in the studied area by understanding the surface water which recharges to the KentonOn-Sea groundwater as a fundamental factor in understanding the groundwater chemistry variations. Groundwater recharge can be estimated using various methods depending on the availability of data acquired. The current chapter has discussed various methods that can estimate groundwater recharge. Since the area of the study is on the coastal side of the country, saline intrusion literature should be taken into account as it plays a big role in the quality of groundwater. The reviewed literature in this chapter has been presented following the certain aims of the research to deliver an organised review of the study area. 2.2 Groundwater According to Heath (1983), groundwater is a vital component of a hydrologic cycle (Fig. 2.1). A hydrologic cycle clarifies the likely origin of water and the way it gets transported to other sources of water such as rivers, lakes and springs (Perlman, 2016). As indicated by Heath (1983), groundwater or subsurface water is the water underneath the ground. Jones and Hunter (1997) mentioned that two different zones are capable of storing groundwater of which are known as saturated and unsaturated zones. In most areas, unsaturated (or vadose) zone is found immediately beneath the land surface (Nimmo, 2009; Heath, 1983). Nimmo (2009) stated that this zone is filled only with air and water. Eager (2003) and Heath (1983) stated that the unsaturated zone is always underlain by the zone of saturation. Heath (1983) hypothesized that the main water that is available to supply wells and springs is the groundwater in the saturated zone. The groundwater in the

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saturated zone is the main water to which the name groundwater is appropriately applied (Heath, 1983). Heather (1983) explained the recharge of a saturated zone as it happens when water is percolating the earth's land surface into the unsaturated zone. In groundwater, the unsaturated zone plays a fundamental role (Nimmo, 2009, and Holden & Fierer, 2005). (Heath, 1983) postulated that zone can be separated into three important components which are the higher part of the capillary fringe, intermediate zone and the soil zone. Heath (1983) stated that the zone that extends from the land surface to a certain depth of several meters is described as the soil zone and is the zone that plants rely on. Holden & Fierer (2005) mentioned that the soil zone has a high porosity and permeability than the underlying material. The intermediate zone was described by Heath (1983) as the zone that underlain the soil zone. This zone varies in thickness from place to place due to the thickness of the soil zone and the depth to the capillary fringe (Holden & Fierer, 2005, and Heath, 1983). The lowermost part of the unsaturated zone is the capillary fringe (Bleam, 2017, Holden & Fierer, 2005, and Heath, 1983). Heath (1983) describes this subzone as a boundary between the saturated zone and the unsaturated zone.

Figure 2.1: Block diagram showing a hydrological cycle and typical upland to lowland River Basin District (RBD) catchment, and the basic components of the hydrological system where groundwater flows through several aquifer types and it discharges to rivers, lakes, wetlands and the sea (Modified from Enger & Smith, 1998). 24 | P a g e

According to Raymond (1988), groundwater initially starts with a rainfall and snowmelt that leaches into the ground (Clark and Briar, 2001, and Raymond, 1988). Raymond (1988), explains that the quantity of water that seeps into the ground differs broadly from place to place. According to Danielson and Sutherland (1986), water seeps quickly in materials such as gravel or sand because of their porosity. Raymond (1988) suggested that about 20% of the rain and snowmelt may seep into the ground of a highly porous surface material. On the other hand, 5% of the rain will seep into the ground of less porous materials due to slow percolation rate (Raymond, 1988). (Cohen, 2009) postulated that the groundwater seepage is influenced strongly by the season of the year. During the warm months of year, evaporation through plants and in the ocean increases (Raymond, 1988). However, during cold months, evaporation decreases thus low rainfall (Cohen and Stanhill, 2015, and Cohen, 2009).

Kovalevsky et al., (2004) defined groundwater as an important source of water and have suggested that it brings the base flows for rivers. Kovalevsky et al., (2004) pointed out that groundwater movement is very slow, up to 100m/year which is a normal average lateral velocity and 1 m/year is a typical vertical velocity. The amount of water involved in groundwater flow is important when these velocities are multiplied by the cross-sectional areas through which the water moves (Kovalevsky et al., 2004). Hence, the important part of an aquifer system is to maintain the balance among the incoming water, outflows and amount of water stored (Kovalevsky et al., 2004).

Kovalevsky et al., (2004) described three types of aquifers namely confined, unconfined and leaky (semi-confined) aquifers (Fig. 2.2). De Conceicao (2018) described a confined aquifer as an aquifer filled with water and enclosed below and above by an impermeable layer, usually of clay/mudstone. An unconfined aquifer is enclosed below by an impenetrable layer, however, is not limited by a confining layer on top of it (Kovalevsky et al., 2004). The upper part of the unconfined aquifer is usually a water table that is subject to fluctuations (De Conceicao, 2018, and Kovalevsky et al., 2004). Kovalevsky et al., (2004) mentioned that an aquifer which is bounded above and below by aquitards, or one boundary is the aquiclude the other is the aquitard, is said to be a semi-confined aquifer. These aquitards allow water to flow freely up and down (Şen, 2015; Ge and Gorelick, 2015, and Flores, 2014).

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Figure 2.2: A) Confined aquifer. B) Unconfined aquifer. C & D) Semi-confined aquifers (After Kovalevsky et al., 2004).

2.2.1 Groundwater recharge in other countries Thomas et al., (2016) suggested that in order to manage groundwater effectively, one should fully comprehend the outflow and inflow of the groundwater system. Thomas et al., (2016) stated that difficulties that have been encountered for sustainable groundwater management were connected to the prediction of inflows and outflow. The inflows and outflows are then related to the water that seeps into the land surface and reaches the saturation zone (Thomas et al., 2016). Theis (1940) reported that the groundwater recharge water depends on the availability of water that is able to infiltrate the soil and makes its way to the water table. Thomas et al., (2016) mentioned that groundwater abstraction has forced hydrogeologists to practice artificial recharge and rainwater capture. Groundwater abstraction rate does not correlate with the volume of recharge into an aquifer system (Thomas et al., 2016). An outdated idea identified as safe yield has been changed 26 | P a g e

by the sustainable groundwater management which includes ecosystem services provided by the storage of groundwater including feeding streams through base flow and groundwater storage preservation (Thomas et al., 2016).

Another groundwater recharge situation has been presented by De Vries et al., (2000) focusing on the Kalahari cases. De Vries et al., (2000) stated that the semi-arid country of Botswana is located on the southward of the African highlands. The plateau is distinguished by a horizontal flat lying topography and an altitude of around 1 km above sea level (De Vreis et al., 2000). The Kalahari basin is made up of several meters of unconsolidated sandy materials deposited during Tertiary and Quaternary periods (De Vreis et al., 2000). De Vreis et al., (2000) stated that the underlying sedimentary rocks of the Kalahari are of the Palaeozoic to Mesozoic together with the basaltic rocks of the Karoo Supergroup. De Vreis et al., (2000) mentioned that from September to April, which is a summer period, rainfall is limited and its average ranges from 250 mm/year in the southwesterly side to 550 mm/year in the north-easterly side (Fig. 2.3). Okavango and Chobe Rivers deliver water from catchments in Angola and Zimbabwe, thus perennial water at the surface is only limited to the far north (De Vreis et al., 2000).

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Figure 2.3: Botswana’s physiographic structures and sites (Adapted from De Vreis et al., 2000).

Karoo rocks are usually the host rocks of the groundwater and the water tables range from 20 m beneath the land surface at the periphery of the Kalahari to higher than 100m in the middle section (De Vreis et al., 2000). De Vreis et al., (2000) reported that the groundwater recharge studies yielded an average value in the order of 5 mm/year for the peripheral of the Kalahari, declining to 1 mm/year or less for the middle part. Postulations done by De Vreis et al., (2000) shows that the decline in a groundwater recharge is likely to reflect the precipitation pattern since there is not an obvious change in the morphological conditions. De Vreis et al., (2000) mentioned that rainfall decreases from around 450 mm at the fringe of the Kalahari to below 350 mm in the centre. 28 | P a g e

2.2.2 Groundwater in Southern Africa A question such as “How much groundwater does South Africa have?” is a conundrum and is one of the most important questions that is being asked repeatedly (DWAF, 2010). The question itself is more tricky and difficult to answer due to unavoidable impacts of using groundwater in a sustainable way for water supply without harming the environment (Egoh et al., 2009). Numerous factors need to be taken into consideration when trying to supply groundwater without harming the environment (DWAF, 2010). Factors such as recharge, quality of groundwater, and aquifer properties (Egoh et al., 2009). An aquifer that supports only very low yielding bore holes may consists a lot of groundwater, but still be useless for water supply (DWAF, 2010).

The recent scientific studies estimated that groundwater in South Africa is in the same league, volumetrically, as our stored water resources (Talma and Vogel, 1992). South Africa has 10 343 million m3/a Utilisable Groundwater Exploitation Potential (UGEP) (Fig. 2.4) or 7 500 million m3/a under drought periods (DWAF, 2010). We normally use between 2000 and 4000 million m3/a of this groundwater (Table.1) (DWAF, 2010). An increase in supply of groundwater in South Africa is being considered (DWAF, 2010). In contrast, the assured yield of South Africa’s surface water resources is precisely 12 million m3/a, but over 80% of this is already issued (DWAF, 2010). Most large-volume water users rely on surface water but the majority of water supplies that are very important to livelihoods and well-being depend mainly on groundwater (DWAF, 2010).

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Figure 2.4: Utilisable underground water exploitation potential for South Africa (GRA 2) (Adapted from DWAF, 2010).

South Africa is a country prone to both dry and drought (Rosewarne et al., 2006). South Africa’s rainfall is very low and unpredictable with a recorded mean annual precipitation of 500mm compared to the world average which is about 860mm (Münch and Conrad, 2007). 21% of some parts of South Africa get less than 200mm/a (Rosewarne et al., 2006). Since the country has few water resources, is then ranked globally amongst other countries with limited water resources and are known as the most water-scarce countries (Rosewarne et al., 2006). According to Rosewarne et al., (2006), water resources distribution has controlled the settlements’ establishment, path of migrations and the way people live. It was measured that South Africa’s groundwater contributes 15% of the total volume consumed (DWAF, 2002). The percentage contradicted the fact that over 300 towns and the population of over 65% rely completely upon the groundwater for their supply of water. Groundwater has generally not been developed to its full potential because there is not enough hydrogeological

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information (Rosewarne et al., 2006). According to Rosewarne et al., (2006), over 12 million of people do not have sufficient supply of water to meet their primary necessity.

Aquifer systems that are underlying 80% of South Africa are low yielding, very shallow and weathered or fractured (Rosewarne et al., 2006). But then reasonable amount of groundwater can be drawn at quite high-rates in the northern and southern parts of the country from Quartzitic and dolomitic aquifer systems (Rosewarne et al., 2006). Hydrogeologists are failing to fully understand the exact amount of groundwater South Africa have, until recently, even the water resource engineers and planners are finding it as a big conundrum to solve (Rosewarne et al., 2006). The so-called ‘Harvest Potential’ (HP) map of South Africa was produced in 1998 using data from a national hydrogeologic mapping project that was done in 1995 (Rosewarne et al., 2006). Rosewarne et al., (2006) suggested that the map showed that 19 000 Mm³ of water can be abstracted from the ground on a yearly basis. Later on, the map was revisited in 2001 to take into consideration the permeable variability between different aquifer systems and the groundwater resources availability was down-scaled to 10 000 Mm³/a (Rosewarne et al., 2006).

Groundwater Phase 2 project was started by the Department of Water Affairs and Forestry (DWAF) in late 2003 in South Africa (Rosewarne et al., 2006). Rosewarne et al., (2006) pointed out that the project aim was to quantify the groundwater resources of South Africa on a national scale. The project completed in June 2005 consists of several companies that were involved including the SRK consulting leading the project collaborating together with the DWAF staff (Rosewarne et al., 2006). Ways of estimating aquifer storativity, recharge dynamics, baseflow and the groundwater reserve was developed (Lynch et al., 1997). Rosewarne et al., (2006) found out that the amounts derived for the important aspects of recharge, aquifer storativity and drawable groundwater were 30 520, 235 500 and 19 000 Mm³/a, respectively.

2.2.3 Factors influencing groundwater recharge in the study area

Due to the water from precipitation that does not fully infiltrate the subsurface, groundwater recharge is also impacted (Alley, 2009). Instead, most of the water is stored in the soil zone and 31 | P a g e

end up returning to the atmosphere through evaporation and evapotranspiration (Smith, 2017, and Mutoti, 2015). Factors such as weather patterns, surface soil properties, vegetation and local relief have been pointed out by Alley (2009) as one of the factors that influence groundwater recharge.

The image (Fig. 2.5) illustrates part of a familiar grand cycle in Kenton on Sea. Water that evaporated from the oceans normally precipitates and the water is collected in both the Kariega and Bushman’s rivers that eventually return it from its source (Ricketts, 2016).

Figure 2.5: Possible recharge mechanism in Kenton-On-Sea caused by the evaporation from the ocean and later resulted in a precipitation that triggers groundwater recharge (Modified after Villholth et al., 2008).

Ricketts (2016) mentioned that coastal aquifers are mainly the source of groundwater supply to the nearby communities. Both unconfined and confined aquifers extend beneath the sea floor and do not just end at the shoreline (Ricketts, 2016). There is a relationship of the land-derived fresh water, and seawater that enters the aquifer beyond the coast (Shimada et al., 2003, and Vengosh, 2003). Kacimov (2009) mentioned that pumping of the coastal aquifers without due diligence results in the seawater intrusion (Fig 2.7).

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2.3 Types of recharge mechanisms Recharge variability is vital to understanding the proneness of aquifers to contamination from surface-derived sources (Nolan et al., 2007). Alley (2009) proposed two types of recharge namely, diffuse and focus. Diffuse recharge happens over a large area as precipitation water infiltrates and percolates through the unsaturated zone to the saturated zone (Alley, 2009). On the other hand, while a focus recharge refers to water flowing percolating downward to an aquifer from a surfacewater body such as stream, lake and canal (Nolan et al., 2007). Diffuse recharge is commonly experienced in humid areas, while arid areas have deep water tables that characterize a focus type of recharge (Nolan et al., 2007).

Figure 2.6: Various groundwater recharge mechanisms categorized by Lerner (1997).

Lerner (1997) grouped recharge mechanisms as direct or diffuse, indirect and localized (Fig. 2.6). According to Gerhart (1986) direct recharge occurs through pathways such as near-surface bedrock fractures and sinkhole. Cuthbert et al., (2016) define indirect recharge as a subtype of a focused recharge by which the groundwater recharge happens due to the penetration from the

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streambeds such as transient streams. According to Alley (2009) localized recharge refers to the flow of water from surface water bodies to the subsurface groundwater system.

2.4 Bushmans and Kariega Rivers

According to Pearce (1973), the Bushman's River (Fig. 3.4) is an east to north-easterly flowing branch of the Tugela River, in the KwaZulu-Natal province of South Africa. It provides the Wagendrift dam and then flows past the Estcourt town to link the Tugela River near the Weenen town (Pearce, 1973). Its tributaries comprise the Little Bushmans River which links the Bushmans River at the Estcourt, Rensburgspruit, Mtontwanes River and the Mugwenya River (Pearce, 1973).

Kariega River (Fig. 3.4) is a river situated in the Eastern Cape Province in South Africa (Vorwerk et al., 2008). Vorwerk et al., (2008) mentioned that the river is an intermittent water course that gets to the ocean through an estuary. This river rises 24 km west of Grahamstown (Vorwerk et al., 2008). Similar to the Bushmans River, the Kariega River also show a winding in the channel which makes it a meandering type of river. 2.5 Methods of predicting groundwater recharge Groundwater recharge is an important factor in the water balance of any watershed Islam et al., (2015). Measuring groundwater recharge directly is nearly impossible, thus various methods, of different cost and complexity, have been utilized to predict the groundwater recharge (Healy, 2010). The bests recharge estimates are done by practicing hydrogeologists by using methods which are relatively easy and straightforward in their application and need only accessible hydrogeologic data (Islam et al., 2015). In the humid areas of the eastern United States Islam et al., (2015) reported that most streams’ water table is high and therefore recharge is predicted by groundwater level and stream flow records. Islam et al., (2015) suggested that base flow has also been used to estimate groundwater recharge, knowing that it is possibly less than the quantity recharging the groundwater-system. Healy & Cook (2002) mentioned that it is exceedingly helpful to apply numerous strategies for estimation and seek after some consistency in results despite the fact that consistency, by itself, ought not to be taken as a sign of accuracy. According to Scanlon 34 | P a g e

et al., (2002) methods that depend on the surface water and unsaturated zone data provide estimates of potential recharge, while technique that base on the groundwater data provides estimates of actual recharge. To increase the reliability of the results multiple methods must be used (Scanlon et al., 2002). Islam et al., (2015) stated that due to insufficient good-quality data it is quite difficult to estimates groundwater recharge using multiple methods. 2.6 Groundwater models Baalousha et al., (2013) postulated that groundwater modelling is a great apparatus for water assets administration, groundwater conservation and remediation. According to Sanford (2002), measurements done for groundwater recharge comprise a significant amount of uncertainty. Groundwater models have been used by hydrogeologists in the estimation of groundwater recharge due to the variety of methods used to make measurements of other parameters in the field (Sanford, 2002). Based on the geologic properties and recharge rate, groundwater models can be used to estimate the distribution of recharge in temporal and spatial scales (Baalousha et al., 2013).

In the studies associated with groundwater systems, groundwater flow and contaminant transport models are being used extensively (Wagner, 1992). The models for groundwater system are used to estimate recharge rate and direction of movement of groundwater through aquifers (unconfined/confined) in the subsurface (Islam et al., 2015). These calculations done by the models are known as simulations (Zhou and Li, 2011). According to Islam et al., (2015), there should be a thorough understanding of the hydrogeologic features of the site for the simulations of groundwater flow.

Wagner (1992) suggested that the precision and accuracy of models predictions rely on successful calibration and authentication of the model in determining groundwater flow movement and transport of pollutants. Islam et al., (2015) reported that two fundamental points have been outlined by Sanford (2002) which are: groundwater recharge is a very important part of groundwater models, one must evaluate how recharge is represented and how is measured by using groundwater models.

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2.6.1 Water table fluctuation (WTF) and Chloride mass balance (CMB) method Other important methods includes the water table method (WTF) and chloride mass balance (CMB). The basic assumptions in the WTF method is that, the increase in the groundwater level in unconfined aquifer is only because of recharge water received at the water table (Wang et al., 2014, Ahmadi et al., 2012, Crosbie et al., 2005, Lee et al., 2005, and Sophocleous, 1991). Obuobie et al., (2010) suggested that to determine the mean annual recharge using CMB, It is assumed that the chloride input source in groundwater system is from precipitation, in arid and semi-arid regions. According to Mutoti (2015), CMB method needs the annual precipitation information and chloride concentration in both precipitation and groundwater in where the precipitation has been received. If this information is obtained, thus groundwater recharge in the area of interest can be estimated (Mutoti, 2015). 2.7 Sustainability of water and groundwater reserves According to the South African Constitution, everybody has a right to a safe environment which is not detrimental to their health and wellbeing, to have an environment safe for the benefit of the future generations, to have access to appropriate food and quality drinking water (Parsons & Wentzel, 2006). Department of Water and Forestry main aim is to make sure adequate water of acceptable quality is accessible to all people, and to support economic and social growth (Parsons & Wentzel, 2006). According to Parsons & Wentzel (2006), water in South Africa should be managed and used sparingly because it is not a water-rich country. New law has been brought up for water management in South Africa and is based on three fundamental principles, namely sustainability, equity and efficiency (Parsons & Wentzel, 2006). According to the National Water Act (Act of 36 of 1998), before allocation of water for other uses, water has to be set aside for environmental and basic human necessities (Parsons & Wentzel, 2006). Classification of water resources would be a key mechanism to achieve this (Parsons & Wentzel, 2006).

The guiding principles of the NWA is sustainability and the Act takes account of water needs of present and future needs is taken account by the Act (Parsons & Wentzel, 2006). According to Parsons & Wentzel (2006), although the concept of sustainability is well acknowledged, but is problematic to quantify it. A definition of sustainability has been defined by DWAF (2014), which is something that should help generate economic growth, benefit all important parties equally and 36 | P a g e

must not be detrimental to the environment (Parsons & Wentzel, 2006). Sustainable water use is not defined in the NWA, in spite of being a guiding principle (Parsons & Wentzel, 2006). South Africa is one of a kind, as water must be made available to underprivileged citizens under the former political dispensation (Parsons & Wentzel, 2006).

When evaluating groundwater resources, both locally and internationally, the idea of a safe or sustained yield for aquifers has been extensively utilized (Parsons & Wentzel, 2006). A safe yield and sustainability are theoretically the same, and both are complex to quantify (Parsons & Wentzel, 2006). “Rate at which groundwater can be withdrawn without producing undesirable effect” is a definition of a safe yield by Bouwer (1978) reported by Parsons & Wentzel, (2006). Until recently, the idea of safe yield has been debated in the literature (Alley & Leake, 2004, Jacob & Holloway, 2004, and Bredehoeft, 1997), with much of the discussions that studies should be done more on local issues such as groundwater levels when considering sustainability rather than regional issues (Parsons & Wentzel, 2006).

Parsons & Wentzel (2006) suggested that understanding the part of groundwater in sustaining the environment is still new. As a result, the sustainable capacity of groundwater accessible for abstraction has to be measured in a broader context than recharge and rates of abstraction (Parsons & Wentzel, 2006). 2.8 Relationship between sea water and fresh water in coastal regions The case of saline intrusion in this study is very fundamental since the aquifer of a study area is subjected to the saline intrusion from the adjacent Indian Ocean. Thus the relationship between seawater and fresh water in coastal areas such as Kenton-On-Sea is essential to comprehend.

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Figure 2.7: The Ghyben-Herzberg principle displaying the position of the salt–fresh water interface based on the elevation of the water table above mean sea level. Zw and Zs relationship is approximately 1:40 (From Freeze and Cherry, 1979).

Saline intrusion is generally only addressed in coastal areas by Ghyben-Herzberg (Fig. 2.7) principle, but can also happen when two or more aquifers of different water qualities are mixed (Charlier & Arfib, 2016, and Mouton, 2004). These waters are usually a fresh water. Saline intrusion can be easily determined by tasting and/or electrical conductivity field measurement, thus the entrance of saline water into an aquifer is a fundamental indicator of when sustainable limits have been exceeded and the problem need to be fixed quickly (Ma et al., 2007). Parsons and Wentzel (2006) reported out some of the existing examples which include the Bushmans River Mouth (Reynders, 1984), Struisbaai (Weaver et al., 1999) and one of theirs which is Robben Island. Parsons and Wentzel (2006) suggested that in some cases, abstraction at too high a rate rather than exceeding the sustainable yield of the system results in the saline intrusion. Through good aquifer management, saline intrusion can be redressed since is usually a localized issue (Parsons & Wentzel, 2006). 2.9 NGA Boreholes positions in the studied area Extensive research was done by Kruger & Nel (2015) in the Kenton-On-Sea. Their work has brought a fundamental framework of this research project. During the desktop study ten boreholes were identified but only six out of 10 boreholes from the Nanaga Formation were identified during 38 | P a g e

study field trip (Fig. 2.8). Drainage directions, engineering geological report, groundwater investigations of neighbouring towns, possible risk of hydrocarbon spillage and mitigation of the Kenton-On-Sea have been briefly summarized below.

Figure 2.8: Position of the NGA Boreholes in Kenton-On-Sea (Modified from Kruger & Nel, 2015).

According to Kruger & Nel (2015), a Geological Environmental Services (GES) conducted a geological engineering investigation for the proposed service station at Kenton-on-Sea in 2005. A uniform soil profile was encountered on the Site when six test pits were exhumed to depths between 2 and 2.1 m bgl and the whole Site was covered by aeolian sand (Kruger & Nel, 2015). In some of the pits, calcrete nodules were encountered in some of the pits. However, there were no perched water tables encountered in any of the pits (Kruger & Nel, 2015)

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Neighbouring towns including Cannon rocks and Port Alfred have been numerously investigated hydrogeologically by Kruger & Nel (2015). Kruger & Nel (2015) mentioned that boreholes that were successful were established so they can supply these towns in the Algoa Group and the Bokkeveld Group aquifers too. Different abstractions rate were determined with Cannon Rocks town rates of up to 18 L/s (Kruger & Nel, 2015). 2.9.1 Drainage Directions According to Kruger & Nel, (2015), the surface drainage directions of Kenton-On-Sea were acquired by using the 5 m contour map of the Site (Fig. 2.9) and surrounding area. Kruger & Nel (2015) went on to mention that the slope of the Site at Kenton-On-Sea is gentle and the drainage direction of shallow groundwater and surface water of the Site is towards the north (Fig. 2.9), perhaps slightly north-northwest. Surface water and shallow groundwater will eventually flow in an east-northeastern direction to the Kariega River (Kruger & Nel, 2015).

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Figure 2.9: Generated contour map of the Site to determine the drainage directions of the area (Modified from Kruger & Nel, 2015).

2.10 Possible Risks and Mitigation The drainage direction of Kenton-On-Sea applies also to the direction of hydrocarbon flow towards the Bushmans and Kariega River, thus contaminating the both the surface and groundwater (Kruger & Nel, 2015). Hydrocarbon (fuel) is the key possible source of pollution in surface and groundwater (Kruger & Nel, 2015). Underground tanks at Kenton-On-Sea are used to store petrol and diesel (Kruger & Nel, 2015).

Following factors have been considered for risk measurements (Kruger & Nel, 2015): ➢ The possible pollution source (e.g. hydrocarbon); ➢ The existence of a path for the pollutant/contaminant to travel to a receptor (e.g. soil and groundwater); and 41 | P a g e

➢ The existence of a receptor (e.g. groundwater, a river and etc.)

A theoretical model was produced to exemplify the possible influence on the groundwater environment of a spillage or leak of Kenton-On-Sea (Kruger & Nel, 2015).

Figure 2.10: Conceptual Site Model-Water and Waste Management (From Kruger & Nel, 2015).

2.10.1 Hydrocarbon Spillage at Kenton-On-Sea During the refilling of the tanks, hydrocarbon could be split onto the surface or could spill from the pipe where it connects to the tanks (Kruger & Nel, 2015). (Kruger & Nel, 2015) postulated that it is unusual for the tanks themselves to leak, but it is also taken into consideration, or if during the installations of the tanks there were some damages done to the tanks. The Site (Fig. 2.10) is underlain by sandstone and sand which are materials with higher porosity and permeability compared to the mudstone and clay (Kruger & Nel, 2015). The hydraulic conductivity of sandstone can be as high as 8.6 cm/day and in sand can be up to 86.4 m/day according to the “Chapter III – Behaviour of Hydrocarbons in the Subsurface” by the United States Environmental Protection Agency (USEPA) (Kruger & Nel, 2015). The density and the dynamic viscosity of the liquid are of important factors of the flow of the hydrocarbons (Kruger & Nel, 2015).

Kruger and Nel (2015) found out that during the engineering geological investigations there were no perched water tables up to 2.1 m bgl were identified. The depth at which the water table currently not known (Kruger & Nel, 2015). Kruger & Nel, (2015) went on to state that the Site is currently placed at almost 47 m asl and the Kariega river is at approximately 5 m asl right to the 42 | P a g e

east of the Site. Assumptions of the water table to be equal to the baseflow level of the Kariega River were made, and seeing that the Alexandria and Nanaga Formations aquifer is considered unconfined in the area, it was inferred that the water level below this Site should be met at depths lower than 40 m bgl (Kruger & Nel, 2015). Recharge from rainfall will fluctuate the water level with the periods of higher rainfall increasing the water level and low water levels during the periods of lower rainfall (Kruger & Nel, 2015).

The NGA database indicates that the water levels could range from 0.7 to 22.3 m bgl (Kruger & Nel, 2015). These water levels were measured at elevations between approximately 5 and 36 m asl (Kruger & Nel, 2015). If a leak occurs relying on the amount of volume that is split as well as the time it takes to leak, then hydrocarbon could then descend into the unsaturated zone (Fig. 2.10) and may eventually reach the water table over time (Kruger & Nel, 2015). Afterwards, it will carry on towards the Kariega River, and end up towards the sea (Kruger & Nel, 2015). Kruger & Nel (2015), suggested that the periods of higher rainfall will influence the spilt hydrocarbon to infiltrate quicker. The water table will most likely increase (Kruger & Nel, 2015). Currently, in the area, there are unknown groundwater users (Kruger & Nel, 2015). River, groundwater (natural resource) and sea are the currently known potential receptors of these hydrocarbons (Kruger & Nel, 2015).

2.10.2 Mitigation of the possible Spillage at the site

Kruger and Nel (2015) proposed that to evade off-site contamination, stormwater runoff must be controlled. To detect possible leaks quicker in the USTs or possible pipeline failures, it is suggested that piezometers need to be installed within the tank excavations on the down-gradient side so that if any leakages occur, this should be reported and remediated immediately (Kruger & Nel, 2015). 2.11 Water Desalination and Reverse Osmosis According to Perlman (2016), the U.S Geological Survey have mentioned that the earth’s water found in seas and oceans goes as high as 96.5% and the remaining 1.7% of earth’s water is found in the ice caps. Greenlee et al., (2009) mentioned that almost 0.8% is freshwater and the outstanding percentage definitely made up of brackish water. den Hartog (1967) defined brackish water as the water with a higher concentration of salt than the freshwater but certainly not the sea 43 | P a g e

water. This partially salty water can be found in estuaries and also as underground water where aquifers bear salty water (den Hartog, 1967). Shortages of water have overwhelmed many people, thus people have been searching a way of water supply which includes the use of desalination processes (Greenlee et al., 2009). Khawaji et al., (2008) mentioned that a desalination process has been utilized generally for a considerable length of time, which is the removal of salt from a salt water to make it a fresh water.

A general term for extracting salt from water to yield freshwater by Khawaji et al., (2008) is known as desalination. Greenlee et al., (2009) has postulated that fresh water has known to have less than 1000mg/L of salts or total dissolved salts (TDS). If water has above 1000 mg/L, various water properties such as taste, colour and odour can be affected badly (Greenlee et al., 2009). Lee et al., (2011) stated that reverse osmosis (RO) is recently the most vital desalination technology and is growing significantly. According to Kronmiller (1994), reverse osmosis is being used worldwide as a desalination tool.

The Albany Coast Water Board (2006) mentioned that the bulk water (800 kL/day) is obtained from 7 wells in the sand dunes above the Diaz Cross aquifer located at Kwaaihoek. The water is then pumped to a lifting station that supplies the Ndlambe Municipal reservoirs at Kenton-On-Sea. Approximately 600 kl seawater is abstracted and then through the transported to the reverse osmosis desalination plant (Albany Coast Water Board, 2006). The desalinated water will then be will then be mixed with the Diaz Cross aquifer brackish water (Albany Coast Water Board, 2006).

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Chapter 3 Research and Methodology 3.1 Introduction This chapter defines the core of the research and methodology that was selected to fit in various fundamentals components of the current study, in so doing, making sure that the research aim is being addressed. This chapter outlines the technique and tools used for data accumulation and the methods used for data analysis. The chapter explains Kenton-On-Sea with attention to its hydrogeology, sampling, databases, drainage, possible risks and validation of NGA boreholes.

The design of the research brings the framework of the study and also explains features that brings the background study. This chapter displayed how the data required for the study was obtained based on the hypothetical theoretical framework. This chapter is vital as it a great influence on the reliability of the results achieved and to make the current research viable. Sampling sites and boreholes location of the study are shown. 3.2 Methods and analytical techniques 3.2.1. Sources of data Balakrishnan (2009) mentioned that in river basins, groundwater investigation comprises a wide variety of methods and techniques. Objectives, resources availability and terrain conditions where the research is taking place is the main key to driving a methodology of the research (Balakrishnan, 2009). During the field investigation information relating to the study area was gathered. The study area map which includes Google satellite map was studied focusing more on the specific areas relating to the research. The Department of Water and Sanitation (DWS) was contacted for other additional groundwater information about the study area and limited data was provided.

As repetitive hypothetical and investigational features of techniques used to categorize and find the mineralogical composition of various rocks such as calcareous sandstones, Quartzite, coquinite, shale and conglomerate. Examination of collected rocks and water samples acquired 45 | P a g e

from Kenton-On-Sea involves the use of various methods such as thin section preparation, petrographic microscopy and geochemical analysis. A link between the geochemistry of sampled water and the surrounding rocks is important to analyse so as to see if there was any contribution from the rocks. To model the hydrogeology of Kenton-On-Sea, MicroFEM 4.1 version was utilized.

3.3. Field investigations 3.3.1 Hydrogeological investigation Taking the whole area as a study section, a brief hydrogeological field investigation has been done in the Bushmans and Kariega River basins. A detailed investigation helps to better comprehend the hydrologic system. The aims of the hydrogeological investigation of Bushmans and Kariega River basins are to examine the main hydrogeologic sections and relate it with their distribution and recharge dynamics. Examining the groundwater through surface water studies in terms of hydrochemical components and their contamination to the groundwater of Kenton-On-Sea. Hydrogeological investigations in Kenton-On-Sea involved various methods which are geologic, geomorphological, and hydrogeological. 3.4. Geological methods 3.4.1 Rocks sampling and borehole identification A two days field trip to the study area took place in June 2018 to collect rock samples (Fig. 4.1), surface water samples (Fig. 3.1) and identify boreholes (Fig. 3.4). There were various purpose of rock sampling of which few of them was to understand the lithology of the study area and with the aid of field and lab analyses mineral constituents of the rock can be identified, rock samples delivered evidences about the time and environment in which they were formed and microscopic rock textures can be used to predict the deformation history the rock was exposed to.

A total of 7 rock samples were collected from different sampling sites (Fig. 3.3). Rocks were sampled mostly from the Nanaga (Fig. 3.1) and Alexandria Formations and from the undifferentiated formation of the Bokkeveld Group (Fig. 2.8). Transparent sample bags were used

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to put the sampled rocks from the different formations (Fig. 2.8). A minimum of 2-3 rocks were collected from each formations.

Figure 3.1: Nanaga Formation landscape of where the rock sample no: k068 was collected.

Figure 3.2: Schelm Formation landscape of where the rock sampling was performed and boreholes identification. Rock samples no: k067 and K069 were obtained from this formation.

Images (Fig. 3.3 A-F) show the borehole at which NGA obtained their information listed in Table 4. Only six boreholes were observed instead of seven in the Schelm Hoek Formation. These

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boreholes look dysfunctional and abandoned. According to Kruger and Nel (2015), three boreholes that were located on the Schelm Hoek Formation (Fig. 2.8) could not be identified.

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Figure 3.3: A. NGA boreholes situated on the Nanaga Formation in Kenton-On-Sea. The area has seven boreholes by Kruger and Nel (2015), however only six boreholes (A-F) were observed during the field trip.

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3.4.2 Thin section preparation Samples of interests were selected from the collection of rocks obtained during a two day field trip which were recorded in Table 3.1. Rock samples from different geological formations were collected and given sample numbers before thin section preparation process. Selected samples were then cut into a desirable small blocks using a rock cutter provided in the geology department. The blocks are then given to the chief technical officer to proceed with the normal thin sections preparation.

A polished thin section is much more valuable than a normal thin section (Moreland, 1968). A petrographic thin section may then be analysed using a polarizing petrographic microscope, electron microscope and electron microprobe (Moreland, 1968). A rock is cut from a desirable sample with a diamond saw and ground optically (Graham, 1963). The rock is then attached on a glass slide and ground smooth using gradually finer coarse grit until the sample gets to 30 μm thick (Graham, 1963). Kemet (2018) stated that Quartz is utilized as the measuring object to determine the thickness as it is one of the most abundant minerals.

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Table 3.1: Kenton-On-Sea rock samples specimen, showing their sampling locations and Formations.

Sample No.

Latitude

Longitude

Formations

K063

33°41’15’’S

26°39’39’’E

Bokkeveld Group (Undifferentiated Formations)

K065a

33°40’39’’S

26°40’38’’E

Alexandria

K065b

33°40’40’’S

26°40’40’’E

Alexandria

K067

33°41’34’’S

26°39’37’’E

Schelm Hoek

K068

33°40’41’’S

26°40’41’’E

Nanaga

K069

33°39’41’’S

26°40’50’’E

Schelm Hoek

The prepared thin section is placed perpendicular to the polarizing filters, thus optical minerals property in the thin section start to vary the colour and the intensity of the light as seen by the observer (Kemet, 2018). Kemet (2018) concluded that different minerals possess different optical properties, thus most rock-forming minerals can be simply recognized. 3.4.2.1 Cutting of samples hand specimens A rotary diamond in the Rhodes University, Geology Department was used in the process of making thin sections. A sample of rock is cut by a rotary diamond saw into a desirable block to make a petrographic thin section. During the process of cutting a rectangular block from a rock sample, a water is used as a lubricant to ease the friction and allow smooth surfaces. A rectangular block size is smaller in size compared to the size of a thin section slide of which it is going to be mounted on. A slurry made of grit and water are situated onto a lap into the centre of the plate when the level side of the sample is ground on it to make it exceptionally uniform and soft (Kemet, 51 | P a g e

2018). With a use of a medium grit, the sample is cleaned thoroughly and followed by a finer grit to allow an even and smooth rock surface.

3.4.2.2 Impregnation Due to softness and delicacy of some of the samples (sample no: K068), an impregnation of this sample was necessary. Fitzpatrick (1984), postulated that there are no difficulties when impregnating very porous soils, but double impregnation may be needed during impregnating soils that are tremendously dense. The use of a low viscosity resin and the process of carrying out the impregnation in a vacuum chamber produce the most adequate impregnations (Fitzpatrick, 1984). For a number of reasons, an impregnation is a compromise at the best of times because the best resin has not been produced (Fitzpatrick, 1984).

The closed chamber was used to store the sample overnight and evacuated to around 20 mm of Mercury (Hg), (Moreland, 1967). The sample was placed in a fume cupboard after being removed from the chamber, it was in a fume cupboard for a treatment for up to 3 weeks (Moreland, 1967). The sample is placed in an oven at a temperature of 40oC to ensure that there is an extraction of remaining acetone and styrene solvents (Moreland, 1967).

3.4.2.3 Petrographic microscope analyses The petrographic thin sections (1 mm thick, 75mm length and 25mm width) of sampled rocks were examined using a Leica transmitted light microscope in the Rhodes University geology department. Thin sections microphotographs were then obtained using an interconnected Nikon microscope fitted with a digital camera. These microphotographs allow graphical analysis of the existing minerals and explanation of the microscopic textures that are imperceptible to the naked eye.

3.4.2.4 Petrographic thin section analysis The texture (i.e. grain shapes, grain sizes, and sorting) and mineralogy (i.e. Quartz, Mica and etc.) of the thin section samples were identified using the following petrographic routine below:

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● Petrographic thin sections analyses of 7 selected rock samples using a light transmitted petrographic microscope were investigated to determine the following rock characteristics: mineralogy, grain sizes, grain shapes, grain orientation, sorting, textural maturity, roundness and porosity. ● Both cross- and plane-polarised light were used to study detrital grains such as Quartz, Feldspars and diagenetic constituents such as Quartz overgrowths.

3.4.2.5 X-Ray Diffraction Method (XRD) Bulk rock samples

X-Ray diffraction (XRD) analysis uses a diffractometer tracings. XRD pattern was recorded by utilization of a CU K radiation (1.5405 Å) that has Lynn's Eye detector fitted on it. The data was processed using a software program namely Crystal sleuth in which it helps with the identification of components in the samples. Only 5 selected samples namely (K063, K065a, K067, K068 and K069) from Kenton-On-Sea were prepared for the XRD analysis.

The rock samples were first crushed into a powder which was then uniformly smudged onto a Poly (methyl methacrylate) (PMMA) slide placed into the X-ray Diffractometer. X-Ray Diffractometer in the X-ray Diffraction (XRD) helps with the accurate identification of minerals in the sample. The device utilized was a Philips 34 PW XRD from the Department of Chemistry at Rhodes University. Copper K-α X-ray tubes which comprise x-ray wavelengths of 1.542 Å was utilised by the X-ray Diffractometer. After the X-ray diffractometer, the sample XRD scan is provided with different peaks of different minerals. A definitive objective is to recognize segments from powder diffraction test by a coordinate method of which parts below the peak are connected to the amount of each phase that is available within the example. 3.5. Hydrological and hydrogeochemical analysis 3.5.1 Available hydrogeological databases Prior to acquiring information from the SRK Consulting, NGA was queried and provided us with some of the borehole data in the area of Kenton-On-Sea. Some of these boreholes had missing data as seen on the data acquired from the SRK Consulting (table 3.2). The data for the Site and

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surrounding was enquired from the National Groundwater Archive (NGA) and was downloaded on 12 May 2015 by SRK Consulting team (Kruger & Nel, 2015). Kruger & Nel (2015) mentioned that NGA data is constantly updated. The NGA only comprises information of registered boreholes according to the requirements of the Department of Water and Sanitation (DWS), thus one can conclude that it may not be a fully completed database (Kruger & Nel). The DWS website states that the following users must register their water use: aquaculture, agriculture, irrigation, mining, industrial, recreation, power generation, urban and water supply service should enroll their water use (Kruger & Nel, 2015). This covers the use of surface and groundwater (Kruger & Nel, 2015). Kruger & Nel (2015) pointed out that borehole water use for domestic purposes was not included in the DWS website. However, boreholes occurrences that were not registered mainly because they are being used for domestic purposes can only be determinable by means a hydrocensus (Kruger & Nel, 2015).

NGA suggested that no boreholes are located in the vicinity of the site (Kruger and Nel, 2015). To have information on the aquifer, a radius of 2 km was enquired and only 14 boreholes were recognised of which only 10 had information (Kruger and Nel, 2015). These boreholes are listed in Table 3.2.

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Table 3.2: NGA Borehole Information. Borehole ID

Latitude

Longitude

Water level (

Discharge

Depth

m asl

m bgl)

Rate (L/s)

(m bgl)

(approximate)

3326DA00036*

-33.69342

26.65844

1.3-3.5

N/A

14.0

5

3326DA00169*

-33.69321

26.65819

0.7-3.33

2

6.5

5

3326DA00142*

-33.69043

26.65097

1.5-1.7

N/A

15.0

12

3326DA00053*

-33.6158

26.67736

9.1

0.7

89.0

36

3326DA00051

-33.6157

26.67736

N/A

N/A

141.7

36

3326DA00049

-33.6156

26.67736

N/A

N/A

86.9

36

3326DA00047*

-33.6155

26.67736

7.3

0.16

51.2

36

3326DA00048*

-33.6155

26.67737

22.3

1.29

96.6

36

*only used to create a model in this study.

The following interpretations are made from Table 3.2: Only 6 out of 10 boreholes water levels were obtainable and range between 0.7 and 22.3 m bgl (Kruger & Nel, 2015). The boreholes with water levels smaller than 5 m bgl are located at elevations between ~5 and 12 m asl (Kruger & Nel, 2015). The boreholes with deeper water levels between 7.3 and 22.3 m bgl are located at an elevation of approximately 36 m asl (Kruger & Nel, 2015). Borehole discharge rates were obtainable for 4 out of 10 boreholes and range between ~0.07 and 2 L/s. Borehole depths were available for all of the boreholes and ranges between 6.5.

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3.5.2 Water sample chemical analysis Sampling and analysis were two taken based on the detailed hydrogeological search, carry out the hydrogeochemical investigations. Samples were collected in new polyethylene bottles to avoid mixing of the sampled water from studied rivers. Prior to sampling, these bottles were cleaned with pure water and also rinsed thrice with the respective surface water under sampling. Exceptional considerations were utilized to evade the combination of water from studied rivers throughout sampling the water as of the prerequisite to be used as sample representativeness along with the geochemical content stability which is present. 3.5.3 Laboratory analyses

3.5.3.1 Sampled surface water analysis based on the Tap Water SA institution methodology Water collected from different sampling areas (Fig. 3.4) of Bushmans and Kariega River during the field excursion were subjected to physical and chemical investigation in the laboratory. Through following the standard operating procedures samples were brought to the laboratory for water analysis after pre-treatment by the Tap Water SA institution. In the laboratory the following primary ions were measured: Mg2+, Ca2+, HCO3-, Zn2+, Mn2+, Pb CO3-, Na+, Cl-, F-, Pb2+, SO42- and NO3-. Using a Flamephotometer, ions such as potassium and sodium were analysed (Systronics FPM digital model). Through the use of EDTA (0.01M) titrimetric method, estimation of calcium and magnesium were completed. Argentrometric titration was used to determine chloride using a silver nitrate standard as reagent. To get the bicarbonate and carbonate concentration, titration was completed against the standard hydrochloric acid (0.01N). Using a UV-visible spectrophotometer, iron and sulphate concentrations in the samples were completed. SPADNS reagent was used on the calorimetric method to determining the fluoride concentration. Table 3.3 show the methods used.

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Table 3.3: Techniques followed for determination of several physical and chemical parameters of surface water in Bushmans and Kariega River basins. SI. No:

Parameters

Methods employed

1

pH, TDS and conductivity

Electrolytic

2

Na+ and K+

Flame photometry

3

Ca2+, Mg+, HCO3-, CO32- and Cl-.

Titrimetry

4

SO42- , iron and fluoride

Spectrophotometry

During the lab analysis, it was very fundamental to test the unstable parameters such as temperature and pH.

The geochemical elements of the water samples were collected to be analysed from the Bushmans and Kariega Rivers. Jekatierynczuk-Rudczyk, 2008, stated that various factors linked to human activities have an undesirable impact on the river water quality. The primary factor described by Jekatierynczuk-Rudczyk (2008) included:

- Industrial and housing expansions (e.g. light construction, food businesses and other light industries), particularly in regions where there near-surface ground waters are drained by springs, - Presence of landfill sites, Seepage sewage systems in the catchment area, and - Contamination of the ground surface associated with the use of manures on plots situated in the catchment area.

Falah & Haghizadeh (2017), suggested that a general assessment of water can be completed through comparison of concentrations of physical and chemical substances that has dissolved in water. The quality of water can be impacted not only by processes that happens in the riverbed but also in the river basin, sediments and lithology of geological formations (Ligavha-Mbelengwa, 57 | P a g e

2017). The nature of the water that is depleted from also utilized regions relies upon the span of the catchment, flow rate in the riverbed, and morphometric parameters, particularly the length of a river, which regulate the water's potential to purify itself (Hermanowicz et al., 1999).

3.5.3.2 Reporting and analysis accuracy

The sampling of water for geochemical analyses was done in the Kariega and Bushmans river main current during June 2018. Laboratory analyses were conducted according to methods described by Hermanowicz et al., (1999). The author analysed: the colour of the water, hydrogen carbonate concentration, total hardness, calcium concentration (titrimetric method), magnesium concentration, and sodium and potassium concentrations. Metal concentrations analysed in the Kariega and Bushmans water samples are listed in appendix. Sampling Sites are shown in figure 3.4. The most common method that is used as a unit of measure to report the ionic concentration of groundwater was mg/L and µg/L. The precision and accuracy of the analysis have to be determined for water samples from the Kenton-On-Sea. Error in analysis can occur due to the chemical reagents employed for analysis, human error, and distilled water quality (Richards, 1954).

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Table 3.4 and 3.5 present the data obtained from the field using a Garmin GPSMAP 64. Table 3.4: GPS field data of the Bushman’s river in Kenton-On -Sea-acquired during the field trip. Bushmans River

Latitude

Longitude

Temperature

Sea level (m)

Elevation(m)

o

GPS Point no:

( C)

50

26°39'49.4"

33°41'14.9"

7

N/A

-56

51

26°39'48.5"

33°41'25.5"

7

N/A

-1

52

26°39'44.2"

33°41'22.5"

7

1

-2

54

26°39'41.1"

33°41' 21.2"

7

3

-1

57

26°39'31.9"

33°41' 33.3"

7

3

3

58

26°39'31.4"

33°41' 33.5"

7

8

N/A

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Table 3.5: GPS field data of the Kariega River in the Kenton-On –Sea acquired during the field trip. Kariega River

Latitude

Longitude

Temperature o

GPS Point no:

Sea level

( C)

(m)

Elevation(m)

59

26°40'40.7"

33°40'22.4"

7

N/A

-1

60

26°40'40"

33°40'17.7"

7

N/A

2

61

26°40'39.4"

33°40''15.7"

7

N/A

1

62

26°40'40.7"

33°40'40.7"

7

N/A

39

63

26°40'46.7"

33°40'45.6"

7

2

-3

3.5.3.3 Water Samples from the Bushmans River Surface water from the Bushmans River (Fig. 3.4) was sampled from 7 sites for acquiring geochemical data, each water sample being analysed for the parameters listed in Table a (Appendix). The Bushman River show a sinuous curve or winding in the channel which makes it a meandering type of a river.

Temperatures were recorded at the time of the sampling during the field trip using a digital thermometer (Model: DT-K 1118). The 250 ml water plastic bottles were first washed with river water before final sampling. Sample water were taken between 20-30 m distance apart from each other in order to identify if there is a consistency of the same hydrochemical analyses within the different river section as well as comparing the inconsistent chemical contents.

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Figure 3.4: A modified Google satellite map image showing the Bushmans and Kariega rivers in Kenton-On-Sea with sampling sites. Sampling sites from the Bushmans river are shown by red coloured numbers 1-7, whereas on the Kariega River are shown by black coloured numbers 1-4. 3.5.3.4 Water samples from the Bushmans and Kariega River Figure 3.5A-B and C-D show surface water sample locations taken from the Bushmans and Kariega River respectively from 4 different sections for analysing geochemical data and parameters listed in table 4.2. During water sampling rusty boats were observed in both rivers that can impact the chemical quality of the water. Due to the dysfunctional appearance of these boats, there is a high possibility of these boats to spill some foreign chemicals into the rivers. The temperatures of the rivers were recorded on site at the time of the sampling during the field trip using a digital thermometer (Model: DT-K 1118).

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Figure 3.5: Water sampling methods and tools. A) Water sampling of the Bushman’s river on the shoreline in Kenton-On-Sea. B) The Sampling of Bushman’s river where it connects with the ocean, thus a river mouth. C & D) Sampling 30 m apart of the Kariega River in Kenton-On-Sea.

3.6. Software and diagram used 3.6.1.Piper diagram analysis Piper (1944), suggested a viable realistic method to isolate pertinent analytical information to comprehend the source of the dissolved components in water. This strategy was conceived under the explanation that most natural waters comprise cations and anions in chemical equilibrium (Piper, 1944). Piper (1944) presumed that the most cations are two "alkaline earths" calcium (Ca2+) and magnesium (Mg) and one "Alkali" sodium (Na). The most widely recognized anions are one

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"weak acids" bicarbonate (HCO3-) and two "strong acids" sulfate (SO42-) and chloride (Cl-) (Piper, 1944). Less basic anion and cation-components are combined with the significant three anions and cations (Piper, 1944).

To make a graph with the significant water constituents, Piper (1944) proposed drawing two triangles relating with the cations and anions, separately, and one diamond that outline the two triangles (Fig 3.6) (Chadha, 1999, and Piper, 1944). The left triangle signifies the cations and one on the right the anions (Chadha, 1999, and Piper, 1944). The cation triangle base is the axis for calcium, the left side for magnesium and the right one for sodium combined with potassium (Chadha, 1999; Piper, 1944). With the anion one, the chloride is at the bottom, the left side for carbonate combined with the bicarbonate and the right one for sulfate only (Chadha, 1999, and Piper, 1944). As per the area of the example, the hydrochemical facies can easily be recognized (Chadha, 1999, and Piper, 1944).

Disadvantages Ravi, 2014, mentioned that even though the Piper diagram is one of the best graphical representation of hydrogeochemistry it has disadvantages. One identified disadvantage was that: ● Piper diagram requires renormalization of concentrations (Ravi, 2014). ● Since it cannot accommodate all waters, thus, it ignores other important major cations and ions (Ravi, 2014). Güler et al., (2002); and ●

O'Shea & Jankowski, 2006, and argued that trace (