Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 251 - 300 of 795 results
Title Presenter Name Presenter Surname Area Conference year Keywords

Abstract

We present findings from a current project in the Hout Catchment, Limpopo Province in South Africa, In grounding the discussion, we propose a citizen science framework that builds on ideas of the living lab, trust and research integrity. The idea of research integrity is not only about ethics but also about methods and we propose participatory methods that are inclusive, just and fair. We achieve trust and practices of research integrity, applying participatory action research methods which not only address the hydrological void in data by identifying water features in the catchment but also have intrinsic value, enhancing well being and brokering trust. The frame presents the idea of water literacy – where the material aspects of CS (dip-meters, rain gauges etc.) intersect with the more intangible goods that have to do with human well-being. In our application we redress the bias where the focus lies more on the natural science aspect rather than the humanities with its attention to human well-being and the recognition of difference and diversity. Considering CS within the frame of feminist philosophy, it is personally transformative with the element of ‘surprise’ that the end point is undetermined – and it focusses on diversity and difference across segments and within segments in the catchment. Participatory parity has intrinsic value (equity and a more just social context) but also extrinsic value (better data and plotting of map features for remote rural areas otherwise difficult to access). CS is a powerful emancipatory tool that is able to generate virtuous cycles of inclusion and equality. We propose a CS frame that captures the ideas of trust, the living lab, SDGs and the emancipatory notion of citizen science, narrowing the divide between the natural and social sciences and acknowledging research integrity and the opportunity for what we call ‘authentic’ learning.

Also Refer Article published in the BWJVol131 https://bwa.co.za/the-borehole-water-journal/2021/12/28/south-african-groundwater-project-shows-the-power-of-citizen-science

Abstract

The Council for Geoscience has a corporate responsibility in rural development projects as part of the South African government initiative in food and water security. Geophysical surveys were carried out at Elizabeth Conradie School in Kimberley, Northern Cape Province South Africa aimed on siting production boreholes to supply the school with water. Traditional geophysical techniques including magnetic, electromagnetic and resistivity were used to locate groundwater bearing structures. The magnetic method was used to locate intrusive magnetic bodies (i.e. Dolerites), while electromagnetic and resistivity were used to map conductivity and resistivity distribution associated with the subsurface geology.

The magnetic method delineated possible groundwater bearing structures which may be related to dolerite dykes and sills. The electromagnetic method appears to have identified shallow fresh dolerite sill. The resistivity method was good in identifying areas of low resistivity which might be related to fractures and/or faults. The high resistivity values might be related to dolerite dykes or sill.

The results of the study showed that geophysical methods are useful non-intrusive tools for mapping groundwater resource. The 1:250 000 scale geological reconnaissance map used to constrain the geophysical interpretation is at a bigger scale when compared to the geophysical interpretation resolution. Considering this and also the ambiguity and none uniqueness in geophysical interpretation, results need to be consolidated by a local scale hydrogeological mapping and drilling results.

Abstract

In response to the serious 2015-2018 “Day Zero” drought, the City of Cape Town implemented large-scale augmentation of the Western Cape Water Supply System from deep groundwater resources within the Table Mountain Group (TMG) fractured aquifers. Several planned TMG wellfields target the Steenbras-Brandvlei Mega-fault Zone (SBMZ), the northern segment of which hosts the Brandvlei hot spring (BHS) – the hottest (~70°C) and strongest (~4 million m3/yr) in the Western Cape. Considering its possible “neohydrotectonic” origin, the BHS may mark the site of a major palaeo-earthquake, suggesting that SBMZ structures are prone to failure in the current crustal stress regime. Despite the “stable” intraplate tectonic setting, the SW Cape has experienced historic large (magnitude >6) earthquakes. Therefore, a better hydrogeological and seismotectonic understanding of the regional “mega-fault” structures is needed.

The South African TrigNet array of continuously recording Global Navigational Satellite System (GNSS) stations can be used to measure surface deformation related to confined aquifer depressurisation and vertical compression during groundwater abstraction. Time-series data from 12 TrigNet stations were used to establish a monitoring baseline for the SW Cape. Observed vertical motions range from slow subsidence to variable slow uplift with superimposed cyclical uplift/depression patterns of seasonal and multi-year variability. Baseline deformation/strain rates were calculated using 27 station pair lengths, ranging between compressive (-0.47 nanostrains/yr) and extensive limits (+0.58 ns/yr), indicating a rigid intraplate setting.

Anomalous high strain rates (> 10 ns/yr), associated with three stations, are probably due to station mount/foundation issues, rather than neo-seismic activity. Regional results show that seismo-geodetic monitoring is an important tool for understanding fractured aquifer compressibility and hydroseismicity, the latter of which may potentially be induced by large-scale TMG groundwater abstraction and/or natural earthquakes in the Western Cape. A local seismo-geodetic monitoring system is therefore being established at Steenbras Wellfield for further observations and analysis.

Abstract

McGibbon, D; Riemann, K

The Cape Flats Aquifer Management Scheme (CFAMS) includes both abstraction of groundwater and managed aquifer recharge (MAR) as part of the City of Cape Towns (CoCT) New Water Programme to diversify their bulk water supply and build resilience against future droughts. Since the project was initiated in early 2018, over 250 boreholes have been drilled for exploration, monitoring, abstraction, and MAR. Rotary mud drilling was used for most of the drilling due to its suitability in unconsolidated geological material, typical of the CFA. As effective as rotary mud drilling is for large scale development, it lacks in accuracy for detailed geological interpretation used for borehole siting and design (gravel pack and screen aperture size and screen position). This is due to the mixing of material and the circulation of the drilling mud washing away fine sediment which can skew grain size analysis results and obscure the vertical position and thickness of thin confining clay or organic rich lenses. The clay and organic rich layers can cause surface flooding during injection as they act as confining layers which effects borehole design and more importantly siting of MAR boreholes. To overcome this, two additional drilling techniques were explored, sonic and air core. Air core was disregarded early on due to the air creating a cavity in the underlying unconsolidated sediments. Sonic drilling, however, was successful in retrieving a continuous undisturbed core log through high resonant energy that liquefies the sediments, which are then brought to surface in a core barrel. The undisturbed continuous nature of the log allows for accurate grain size analysis and detailed vertical geological logging which can be used for facies analysis to interpret the paleoenvironment and predict the lateral extent of clay or organic rich layers that influence borehole siting, design, and the hydrochemistry.

Abstract

This study investigates and elaborates the development and testing of a multilevel sampling device. The primary purpose of this device is to achieve multilevel sampling in a well simultaneously, producing samples that are representative of the in situ groundwater. The device has been designed to have four different depths from which extraction of groundwater samples can be performed. Testing of the device involves a two-part process. A laboratory based testing and field based testing. The laboratory testing was done in a simulated well where three water tests were performed; normal tap water, salt water and hot boiling water. The field based testing was done on existing boreholes in the Rietvlei Wetland Reserve in the Western Cape. In the two processes involved, hydrochemical parameters were used to test for the efficiency of the device in terms of its working performance and to furthermore analyse the water chemistry which enables us to determine the water quality.

Abstract

Fourie, F

Communities reacted differently to the drought. In some cases, you would notice a proactive approach and good management of the wellfields. In other cases, communities have been under a misconception that they received good rainfall for a recharge which did not reflect in monitoring data, and lastly, you get the communities that are mismanaging the groundwater. Various lessons were learned from the change in the climate and environment. But a lot can be done to minimise the impact of these changes on the water supply to communities. This paper addresses the changes that we can apply to deal with the changing environment around us to provide a sustainable water supply. The changes can include relooking at operating rules to ensure better management on the aquifer and borehole level. Recharge determined during pump test must be considered periods low to no recharge. Methods to enhance the recharge to the aquifer will ensure recharge occur during low rainfall events By implementing these rules, groundwater can be sustainably managed for future use.

Abstract

Globally, cumulative plastic production since 1950 is estimated to have reached 2500 Mt of plastic. It is estimated up 60% of this plastic is either resting in landfills or the natural environment, including groundwater settings. Microplastics are small pieces of plastic ranging between 1μm – 5mm in size and have been found in every ecosystem and environment on the planet. Much of the available literature on microplastics is focused on marine environments with few in comparison focused on freshwater environments, and even fewer on groundwater settings.

The aim of this study is therefore to investigate the attenuation process responsible for influencing microplastic transport in saturated sands. This research will adapt colloid transport theory and experiments to better understand the movement of microplastics through sandy media. Saturated aquifer conditions will be set up and simulated using modified Darcy column experiments adapted from Freeze & Cherry (1979). Modified microplastics will be injected into the columns as tracers and the effluent concentrations measured by Fourier-transform infrared spectroscopy (FTIR). Breakthrough curves will then be plotted using the effluent concentrations to determine the attachment efficiency (α). It is expected the attachment efficiency will vary by microplastic type and size range. The Ionic strength of the solution flowing through the column and the surface charges of both microplastics and sandy surfaces are likely to influence the degree of attenuation observed. The relationship between different types of microplastics and collector surfaces from a charge perspective and their influence on the degree of attenuation will be evaluated.

Given the lack of literature, its ubiquitous presence and postulated effects on human health, this research is significant. Through this research, the transport and attenuation of microplastics through sandy aquifers can be better understood, and in the process inform future research and water resource management.

Abstract

The South African government is considering shale gas extraction in the Karoo basin, South Africa. To protect groundwater resources, there is an urgent need to do a groundwater baseline in possible gas extraction areas. Various groundwater samples have therefore been taken at a borehole and 2 soekor wells in the Northern Cape, from 2016 to 2021. The groundwater samples were analysed for dissolved gasses, specifically focussing on methane. As laboratories became more efficient ethane was also included in later analyses. From the analyses we found that drought might influence the dissolved gas concentrations in the groundwater via pressure influences on the groundwater flow and the dissolved gas flow towards the shallow aquifers. Artesian conditions at this site are helping with the flow of dissolved gasses from deep to shallow aquifers via preferential pathways. The possibility of shallow-deep groundwater interconnections and the migration of deep methane to shallow aquifers make it important to establish a groundwater baseline in the Karoo. By focusing on boreholes and wells that are emitting methane, a better understanding of groundwater flow and interaction with geological layers can be determined. If other gasses like propane and butane can be analysed in addition to methane, more information can be gathered to determine the origins of the methane and whether it is thermogenic or biogenic.

Abstract

The proximity of aquifer systems to sources of contamination exposes them to severe environmental threats. Pollutants that leak from petrol stations, industrial areas and landfills eventually seep through the vadose zone to reach shallow groundwater, leading to groundwater contamination. One of these pollutants is Methyl Tertiary-Butyl Ether (MTBE), which is a polar organic compound that is volatile at room temperature. As a result of its high solubility compared to other gasoline additives, MTBE can cause serious environmental issues. The aims of this study were to characterize the extent of MTBE in groundwater and characterize natural attenuation in a Saudi Arabian MTBE and methanol manufacturing company.

The aims were achieved by analyzing monthly MTBE concentrations (to observe the seasonal changes of MTBE) and annual MTBE concentrations (to observe long-term changes) in 5 out of 18. Groundwater samples were collected, and in each year the MTBE, Total organic carbon (TOC) and Electrical conductivity (EC) concentrations were recorded. Because of inconsistency in the data, the results for the monthly data were from 2007 to 2010, and from 2007 to 2012 for the annual data. The results indicated a positive relationship between MTBE and TOC, and as a result TOC can be used to monitor and indicate the presence of MTBE. There was plume growth in 2 of the 5 wells (well 4 and well 14) with well 4 recording the highest MTBE concentration in all years. The reason for the high concentration might be because of spillages during truck loading. The other 3 wells showed signs of natural attenuation. Results from seasonal data suggested that temperature influences MTBE concentrations and therefore the rate of natural attenuation. There are many methods to remediate MTBE and each of them is site specific, but bioremediation was recommended for this site due to its cost-effectiveness.

Abstract

Kürstein, J;  Thorn, P; Vermaak, N; Kotzé, YL; Pedersen, PG; Linneberg, MS; Fourie, F; Magingi, A

Water supply relies entirely on groundwater in Denmark. A national groundwater mapping programme was established in 2000 to protect this valuable resource. It builds on a thorough and holistic understanding of the hydrogeological settings, obtained through an extensive data collection, culminating with an identification of threats and aquifer vulnerablility. As part of the programme, new approaches, methods, and instruments have been developed, such as airborne geophysical survey by Sky-TEM that allows the mapping of large areas in a fine resolution. Another key element in the mapping is the development of three-dimensional hydrogeological and numerical models. These are used to understand the groundwater flow paths and delineate wellhead capture zones as well as infiltration areas, which, depending on the assessed vulnerability, may be subject to protective measures.

The Danish mapping approach have been tested at selected South African sites through the Strategic Sector Cooperation (SSC) between Denmark and South Africa. The approach was applied in a study supporting Umgeni Water to identify groundwater resources to supply numerous villages near the town of Ladysmith. The study illustrated a high potential for adapting relevant parts of the Danish approach to South Africa, but also revealed some challenges, e.g. related to the fractured geology, where groundwater recharge can be concentrated along dykes, a process very different from what is generally observed in Denmark.

The SSC has initialised the project “South African Groundwater Mapping and Assessment Approach (SAGMAA)” to share knowledge gain through the national groundwater mapping programme in Denmark with South Africa and explore the possibility of adapting elements from the Danish approach to South African conditions in a broader context. The objective of the project is to provide recommendations to South African guidelines, and the paper will present results from the comparison of approaches in the two countries and preliminary recommendations to guidelines.

Abstract

The Smuts House in Centurion is under threat of subsidence due to sinkholes. These sinkholes are linked to the Malmani Dolomite Formation, a Proterozoic carbonate sequence within the Chuniespoort Group of the Transvaal Supergroup, and is subject to sinkhole development (Clay, 1981). In addition to Smuts House, the areas are populated by thousands of people meaning risk of financial damage and, in some cases, loss of property and lives (Trollip, 2006).

The Jan Smuts House Museum is located in a natural park of indigenous trees and shrubs. The area is generally flat-lying; however, various ridges bisect the site in a north-south trend. A koppie (Cornwall Hill) is situated in the north. Outcrops of dolomite and chert characterise most of the study area. The two major streams in the area are that of the Sesmylspruit and Olifantspruit.

This study was undertaken to examine the relationship between subsidence of the Smuts House Museum, subsurface features (geological and anthropogenic) and the local geology. Magnetic and resistivity, active seismic and ground-penetrating radar (GPR) geophysical data were collected, along with x-ray fluorescence (XRF) geochemical data and hydrogeological data.

Abstract

Enslin,S; Webb, SJ

The Vredefort Dome 120 km southwest of Johannesburg is a meteorite impact crater that formed at approximately 2 Ga. The region hosts farmland, and the town of Parys is situated in the northwestern part of the dome. The dome is the location of the annual Wits University/AfricaArray Geophysical Field School. The aim of the field school is to teach geoscience students several geophysical techniques while conducting scientific research in the area.

A geophysical survey during the 2019 field school over an open field just outside of Parys revealed a buried fracture that hosts ground water. A 150 m long magnetic profile over the fractures shows a magnetic low (approximately 500 nT) that correlates with a low resistivity region on the inverted electrical resistivity data (dipole-dipole method). Euler deconvolution depth estimates and magnetic modelling estimate an overburden thickness of around 10 m and a similar fracture thickness. The magnetic low of the fracture is due to weathering and removal of any magnetic material in the granites in the region.

Two existing boreholes that lie 618m due south and at a 10 m lower elevation have water levels of around 6.4 m. Both boreholes lie near a riverbed and vegetation, and appear to lie along an extension to the fracture. This fractures detected using geophysical methods seems to form part of a larger fracture system within the Vredefort Dome, that is linked to the formation of the dome. These fractures provide a vital source of water for the local farming community.

Abstract

Wiegmans, FE

The increasing water demand for the Northern Cape Province resulted in the detailed assessment of the exploitation potential of three groundwater development target areas namely SD1, SD2 and SD4, largely underlain by karst aquifers. Since 2014 the implementation of the wellfields was delayed pending authorisation. The potential impact on the groundwater resources was raised by several stakeholders as part of the process, resulting in the re-assessment of the SD1 and SD2 wellfields. The model update considered crucial data retrieved from several groundwater level loggers from April 2014 to December 2019. As a precursor to the model update the Cumulative Rainfall Departure (CRD) curves for the relevant rainfall stations for the study areas was updated. While for most sites a good relationship between rainfall and groundwater fluctuations was observed. A poor response of groundwater levels in comparison to the observed CRD curve suggests abstractions more than the recharge of the aquifer. Metered groundwater use is for most parts not available but was estimated based on the hydrocensus data. Once the models demonstrated to reproduce past behaviour, they were used to forecast the future behaviour. More importantly was to assess whether the 2014 proposed abstraction rates still held true after the re-calibration of the model. Several simulations were carried out iteratively to identify the optimal pumping rates and the temporal variability of the withdrawal period considering the impact on the groundwater resource. Based on the results the 2014 proposed production rates were reduced from 751,608 m3/month to 597,432 m3/month representing a 2019 mitigated (optimised) proposed abstraction scenario. The case study is an excellent example of adaptive groundwater management informed by crucial datasets and scenario modelling.

Abstract

Water is regarded as a source of life and access to potable water supply delivery remains the building block to improving and maintaining the community member’s health and productive life. The demand for water supply has been increasing due to population growth and climate change phenomena. Hence, there is need to assess the current state of potable water supply system in selected rural areas of Vhembe District Municipality (VDM), South Africa. About 14 villages in VDM were visited to assess the state of water supply. Interview were held with three municipal officials who deals with water supply systems and 14 focus group discussions were held in each village with the communities and their leaders. 448 head of households, 14 councillors completed the questionnaires on potable water supply situation in their area. The results indicated that the main sources of water supply are boreholes followed by tap water from dams. In areas where the two sources are not available, the rivers, fountain and the water tankers were also the main sources. In terms of water usage, the boreholes recorded the highest responses of 45% from households, followed by the tap water from dams at 35%, 4% from rivers, 5% from fountain and 10% from water tankers. In addition, about 53.6% of participants collect water once a week from the main source (boreholes and tap water from dams). Rural communities of Vhembe District Municipality were not satisfied with the quantity, distance and reliability of boreholes. Therefore, this article recommended that the municipality, communities, councillors and traditional leaders should work together in addressing the pressing water issues. Part of which include provision of more sources of water to complement growing population. In addition, village water committees need to be established to assist in water provision management.

Abstract

Lourens, PJ

West of the world-renowned conservation site, Kruger National Park, lies the larger extent of the Greater Kruger National Park within the Limpopo province. Boreholes have been drilled here in the last few decades to century for the provision of water supply to game lodges, large resorts, watering holes for game viewing and also historically for agriculture and livestock. The area contains both primary and secondary aquifers classified as having yields between 0.5 and 5.0 l/s, based on the geological setting which consist of gneiss intruded by dolerite dyke swarms. A geohydrological assessment of the area revealed that groundwater quality within the project area is characterised as having an EC of 100 - 450 mS/m, which seems to link to borehole proximity to surface water systems. The Makhutswi Gneiss and Doleritic Dyke swarms are the major controlling geology of the area, with higher yielding boreholes located in close proximity to dykes and major structural lineaments (faulted / weathered zones) of the Gneiss. A major concern identified through geohydrological assessment and hydrocensus observations is that boreholes frequently dry up after a few years and require either deeper drilling / redrilling or drilling a new borehole and that the very aggressive calcium hardness in the water frequently damages equipment and leads to overall higher maintenance costs. This project investigates the feasibility of increasing recharge to the aquifer with seasonal flooding / rainfall events by constructing artificially enhanced recharge locations overlaying several doleritic dykes. This is expected to decrease the salinity and hardness of the groundwater, which will reduce operational costs. Water security will also be increased through enhanced long-term sustainability of the groundwater by balancing some of the current annual abstraction.

Abstract

The West Coast in the Western Cape of South Africa is a water-scarce area. With pressure from population and industrial growth, recurring droughts and climate change, there is increasing urgency in the West Coast to protect groundwater resources. Saldanha Bay is dependent on groundwater as part of its bulk water supply system. Where the natural groundwater recharge is no longer sufficient to meet the growing groundwater needs, practices such as Managed Aquifer Recharge (MAR) can be used to ensure the sustainability of these groundwater resources.

This study aims to identify areas within the Saldanha Bay Local Municipality suitable for Managed Aquifer Recharge to maximize the water available during periods of limited surface water supply. As such, the MAR study site identification requires a comprehensive geohydrological assessment of the Saldanha Bay aquifer. This includes an understanding of the quality and quantity of the source water available for recharge, the aquifer structure and hydraulic properties, the space available to store water, and the compatibility of the recharged water with the groundwater.

MAR research methods included Time Domain Electromagnetic (TDEM) airborne geophysical surveys, infiltration tests, pumping tests and hydrochemical analysis. TDEM surveys provided clarity on the various aquifer geological properties. Infiltration and pumping tests shed light on the horizontal and vertical hydraulic properties of the aquifer. PhreeqC modelling outputs helped predict the outcome of the mixing between groundwater and potential MAR water resources.

Geological features were delineated through TDEM surveys and inferred five suitable MAR sites where clay layers were missing. Infiltration and pumping tests showed that Langebaan Road is better suited to borehole injection, whereas Hopefield has the benefit of infiltration MAR techniques as an additional option. PhreeqC outputs exhibit that both pipeline and Berg River water show promising results as potential source water resources for MAR as compared to other resources.

Abstract

The year 2020 will forever be synonymous with the Covid-19 pandemic and the immeasurable impact it has had on all our lives. During this time, there was one avenue that reigned supreme: technology. Whether it was Zoom calls or Netflix, online consultations or video conferencing at work, technology took charge. In light of this, GCS (Pty) Ltd started exploring ways that technology could assist with the most common problem identified in the Water and Environmental sectors, which is the management of large volumes of geodata. Thus, the invention of eSymon.

Monitoring of the environment usually generates a significant amount of data. If this data is not systematically stored, problems often arise with:

• Limited access to historical data due to poor storage;

• Different formats of stored data (if they are kept in digital form at all);

• Continuity and integrity of the data; and

• Security of the data.

Therefore, years of historical data cannot be used or trusted. The solution was to develop eSymon, which is an acronym for Electronic Data Management System for Monitoring. eSymon is primarily designed to:

• Systematically import, store, view and manipulate large volumes of monitoring data;

• Provide remote and instantaneous access to site-specific information;

• Allow data visualization using an interactive GIS interface; and

• Create various outputs such as time series graphs, geochemical diagrams and contour maps.

The main idea of the software is to have all historical data for a site on one platform and have it be accessible and functional at the touch of a button. This results in several key benefits, including saving time, providing accurate and up to date information, not having to wait for technical reports to assess trends and compliance, providing several means of data visualization and, most importantly, ensuring data security.

Abstract

This study is based on the presence and concentration of antiretroviral drugs in water bodies around the Western Cape Province in South Africa, these areas include wastewater treatment plants, water treatment plants, stormwater, and landfill boreholes. South Africa has the highest rate of HIV and AIDS in the entire world, statistics from 2018 show that 7.7 million South Africans are infected with HIV/AIDS and 68% of them are on antiretroviral treatment (UNAIDS). South Africa has the largest antiretroviral treatment program (ART) in the world, due to the lack of proper water and sanitation these drugs are deposited in the environment poorly and reach water bodies, therefore, contaminating them. This study involves the collection of samples from areas such as Mitchell’s Plain, Khayelitsha, Athlone, Cape Flats, and Atlantis around the western cape, these samples are analyzed to determine the presence of 5 antiretroviral drugs used in South Africa which are Efavirens, Lopinavir, Nevirapine, Ritonavir, and Tenofovir. Water samples are prepared for analysis by filtering 2.5ml water through a 1µm glass fiber filter, the sample is then placed into sample vials and analyzed on HPLC-QTOF/MS. Mass Hunter software is used to identify the specific ARVs in the water samples analyzed, by searching for the compounds via their chemical formulas. With a match made if their chemical formula, retention time and mass to charge ratio of the compounds correspond. Concentrations range between 0.0855ng/ml Nevapine to 4.3289ng/ml Lopinavir, this analysis has determined that all the mentioned antiretroviral drugs are indeed present in different water bodies around the identified areas within the Western Cape in varying concentrations.

Abstract

Saldanha Bay Local Municipality appointed Skytem to conduct an airborne geophysical 3D aquifer mapping survey. As part of improving the sustainable management of the groundwater resources and exploring the options of Managed Aquifer Recharge, a better understanding of the aquifers is required. The Skytem technology unlocked a rich understanding of the subsurface geology and the groundwater contained in it.

Before the main survey commenced, a trial survey was conducted to investigate the quality of the data that may be expected from the main survey. The trial survey was conducted over the existing water supply wellfield where there were existing groundwater data including borehole lithology from drilling and ground geophysics. Consequently, the main survey commenced and consisted of the following:
1) Magnetic survey providing information regarding bedrock composition and where it changes due to faults or deposition,
2) Time Domain Electromagnetic survey providing conductivity/resistivity of the subsurface,
3) Detailed elevation along flight paths, and
4) 50Hz signal to understand where interferences can be due to power lines.

The survey interpretation showed the following important aquifer characteristics that will be useful for future management of the aquifer system:
1) Bedrock elevation and paleo topography, 2) Areas with different bedrock composition, 3) Geological faults in the bedrock, 4) Bedrock below the surface, 5) Areas with thick dry sand, 6) Clay layer extent and area without clay, 7) Areas with different water quality, and 8) Areas with very high concentrations of salt.

The survey output and interpretations are regarded as very useful for the update of the conceptual models for the area. Data can now be used to update the numerical models and improve the management of the wellfields.

Abstract

Monitoring groundwater storage is conducted in the study. World Health Organisation estimates, about 55 million people affected by drought yearly. However, Surface water holds 0.3 percent of the freshwater, and groundwater holds 30.1 percent of the freshwater. Hence, monitoring groundwater storage is vital. Though the GRACE (Gravity Recovery And Climate Experiment) satellite provides global-scale groundwater data, but does not provide any information about changes in groundwater flow systems and has uncertainties, due to large noise produced. A correlation has to be established between gravity changes and groundwater storage variations through a program that simulates the flow of groundwater. The relationship between developed numerical models and data derived from superconducting gravity is imperative. This study is conducted in South African Geodynamic Observatory Sutherland (SAGOS) area at Sutherland, South Africa. The study aims to develop a numerical geohydrological model to monitor subsurface variations in water distribution through superconducting gravimeters (SG) records. The interpretation of the SG measurements to directly compare to one another at a higher resolution is considered in the study, through the correlation of the developed model and installed superconducting gravimetric residual data. A numerical groundwater flow model is developed using model muse on MODFLOW. Assigned boundary conditions, fractured rocks were activated by the model. Hydraulic conductivities were simulated for any layer, including storage coefficient. Hence, hydraulic conductivity is an important aspect of the study. In conclusion, gravity is an excellent tool for measuring groundwater recharge within the immediate vicinity of the SAGOS. This implies that gravity can aid in monitoring groundwater recharge and discharge in semi-arid areas. The application of the hydrological model at various scales comparing the Superconducting Gravimeter and GRACE satellite data is paramount to improve modelling groundwater dynamics. The consideration of developing numerical hydrological to monitor groundwater storage will add much value to missing information.

Abstract

During 2017-2018, the City of Cape Town, South Africa faced an unprecedented drought crisis with the six main water storages supplying Cape Town falling to a combined capacity of just under 20%. With the threat of severe water shortages looming, various additional water sources were examined to supplement the municipal water supply network. These were focussed on groundwater, desalination and treated effluent. However, private citizens and businesses also made plans to avoid shortages, resulting in numerous uncontrolled water sources competing with the municipal supply network. Throughout the crisis, groundwater was considered the most important alternative urban water supply source but also the most vulnerable to contamination through accidental and uncontrolled return flows from the municipal network, private residences and agricultural industries. This project aims to constrain the water supply network in the Stellenbosch municipality and monitor the augmentation of groundwater into the network using stable isotopes. Long term monitoring points have been established at 35 tap water sites, 20 private wells as well as at the supply reservoirs that feed the municipal network. Preliminary data show’s distinct isotopic signals associated with each supply reservoir as well as in the local groundwater. The data also shows significant return flow into the alluvial aquifer system during warmer months when private stakeholder’s water consumption is at its highest. Groundwater is expected to supplement this urban supply network in the latter part of 2021 and will likely disrupt the current distribution of stable isotopes in the network, providing further insight into the potential return flow into the local groundwater system.

Abstract

Mabenge B; Famah FIB

Groundwater resources are under increased pressure from population growth, climate change and human activities, leading to widespread groundwater depletion and pollution. It is important, as groundwater professionals to communicate to the younger generation and the broader community, about this vital resource. The Groundwater Kids Educational Program was initiated in November 2020, to educate and share groundwater knowledge amongst primary and high school learners. The program consists of a series of 1 – 2 hour groundwater educational workshops held at schools throughout Gauteng Province. Each workshop comprises a short educational video clip on a selected groundwater topic, followed by an activity that involves the topic of the day, and distribution of groundwater awareness material. Lessons are prepared based on the age group and the level of comprehension of the learners. Learners get the opportunity to engage in activities designed to make learning about groundwater more exciting. These workshops provide a knowledge base for our children participate in efforts to save this resource in generations to come.

Abstract

Managed aquifer recharge (MAR), the purposeful recharge of water to aquifers for subsequent recovery, is used globally to replenish over-exploited groundwater resources and to prevent saltwater intrusion. Due to increased water shortage worldwide, there is a growing interest in using unconventional water resources for MAR such as reclaimed water or surface water impaired by wastewater discharges. This, however, raises major concerns related to pollution of our drinking water resources. MARSA is a new Danish-South African research project aiming at developing MAR technologies allowing a broader span of water resources to be used for MAR, including storm water, river water, saline water, and even treated wastewater. It is hypothesised that improved removal of organic pollutants, nitrogen species, antibiotic resistance, and pathogens can be achieved by establishment of reactive barriers or creation of different redox environments through injection of oxidizing agents to anaerobic aquifers during recharge. In MARSA we will carry out feasibility studies, as flow-through columns, first in Denmark and later in South Africa, to investigate the capacity of South African aquifer sediments to remove organic pollutants, nitrogen species, antibiotic resistance genes, and pathogens. Then, based on these studies, MAR options will be further investigated at field conditions in South Africa using real source water from MAR sites. For this presentation we will give an overview of the MARSA-project and show results from previous feasibility studies investigating the potential of reactive barriers to remove organic micropollutants and ammonium. These studies have shown that establishment of reactive barriers will cause oxygen depletion, but also more efficient ammonium and organic micro-pollutant removal. MARSA is funded by the DANIDA fellowship centre, Ministry of Foreign Affairs of Denmark. Project no. 20-M03GEUS.

Abstract

It has become increasingly apparent that understanding fractured rock mechanics as well as the interactions and exchanges between groundwater and surface water systems are crucial considering the increase in demand of each in recent years. Especially in a time where long term sustainability is of great importance for many water management agencies, groundwater professionals and the average water users. Previous callow experience has shown that there is a misunderstanding in the correct interpretation and analyses of pumping test data. The fracture characterisation (FC) method software provides a most useful tool in the overall understanding of a fractured rock aquifer, quantification of the aquifer’s hydraulic (flow regime and flow boundary conditions) and physical properties, only if the time-drawdown relationships are correctly interpreted and when the theoretical application principles are applied. Interpretation is not simply a copy and paste of the aquifer test data into the software to get a quick answer (especially when project time constraints are considered), however, recent experiences with numerous field examples, required intricate understanding of the geological environment, intended use and abstraction schedules coupled with the academic applications on which the software was based for correct interpretation.

Through the application of correct interpretation principles, a plethora of flow information becomes available, of which examples will be provided in the presentation itself. By achieving this, flow can be conceptualised for inputs into a conservative scale three-dimensional numerical flow model and calibrated based on measurable data in a fraction of the time of a conventional regional model. Although higher confidence levels are achieved with these practical solutions, monitoring programmes are still required to provide better insight of the aquifer responses to long-term abstraction and recovery.

Abstract

The impact of the future closure of the KROPZ phosphate mine in the West Coast on the various potential receptors including the underlying Elandsfontein Aquifer System (EAS), Langebaan Lagoon (RAMSAR-site) and wetlands were assessed. This abstract/paper describes the geochemical characterization and management options related to the waste streams from the mining activity, to assess the post closure contribution to groundwater flow from the mine towards potential receptors. The PHREEQC geochemical modelling code was used to predict potential mine water impacts. The input water quality parameters used in the model included: background groundwater quality, pit water and processed water generated from phosphate separation process at the mine. Various scenarios were simulated combining the different process water streams with the tailings and soft stockpile material at the mine. The geochemical predictions showed some management options that should be prevented, while also providing guidance to promising options where most of the chemical parameters does not exceed the WUL stage 1 thresholds. There is however, an increase in sulphate concentrations that need attending to before the mine goes into production phase. Currently there seems to be no immediate concern on the Lagoon relating to the prediction of mine water impacts post mine closure. Some of the management scenarios do however show low levels of potential impacts on SANParks property 100 years post closure. These predictions do however correlate to areas where limited calibration data is available. At the time of this abstract the sites for new boreholes have been selected and the initial boreholes are being drilled to confirm aquifer properties in areas with limited data.

Abstract

The study area is located in a Swiss alpine valley at the border between Switzerland and France and is situated in Valais. It is delimited by the hydrologic catchment of the river “La Vièze de Morgins”. The catchment area is situated in the Municipality of Troistorrents and of Monthey. Its population is approximately 4500 inhabitants. From the geological point of view, the valley “Val de Morgins” is mostly comprised of sedimentary rocks, amongst others breccia, schist, flysch, limestone, and quaternary sediments. The valley is affected by several natural hazards, such as landslides, rockfalls, and avalanches. Hydrogeologically, the valley contains few main springs that are outlets of porous and fissured aquifers. For this study, an inventory and monitoring of springs and rivers has been carried out since 2018 until April 2021. Particularly, more than 110 springs and rivers have been registered and observed during this time. The data includes GPS coordinates, photos, measurements of physical-chemical parameters and flowrates. Complementary to measurements, specific geological and topographical maps, and site information have been gathered. The analysis and interpretation of this huge set of hydrogeological data will be concluded with a new and innovative approach using different data science libraries that are implemented for the Python programming language. In this case study, groundwater sampling training is used to increase the understanding of the water quality. Four years of field measurements enable a better understanding of the parameter variability in relation to seasonality. Furthermore, new data analysis can aid the integrated resource management for the municipal water supply. The sampling and monitoring are key aspects to ensure water security, in terms of quality and volume. Additionally, it can also unlock prospective groundwater resources for municipal water supply. Case study data will also be compared with South African and other Swiss dataset of similar aquifer type.

Abstract

Israel, S; Kanyerere, T

Globally, surface waters are severely unsustainably exploited and under pressure in semi-arid coastal regions, which results in increasing demand for groundwater resources. Currently, Cape Town and its neighbouring towns along the West Coast of South Africa are facing water shortage related problems. Managed Aquifer Recharge (MAR) is a nature based solution to improve groundwater security in drought prone regions such as the West Coast. The objective of this study was to design a groundwater monitoring network using a hybrid hydrochemical, geophysical and numerical modelling approach to assess and mitigate the potential impacts of MAR for the West Coast Aquifer System (WCAS). An Analytical Hierarchy Process method was used to perform a Multi-criteria analysis employed in GIS (ArcMap 10.3).

The factors of importance for optimized groundwater monitoring network design were based on available data and consultations with hydrogeologists and environmental scientist at stakeholder workshops. The factors which were considered included: elevation (m), geology, density of existing boreholes (wells/km2), electrical conductivity (mS/m), water rise (m), water level decline (m), transmissivity (m/day), saturation indices and lithological thickness (m). Factors were weighted based on their level of importance for the design of the groundwater monitoring network using Analytical Hierarchy Process (AHP). Priorities were calculated from pairwise comparisons using the AHP with Eigen vector method. The Consistency Ratio (CR) calculated was 5.2% which deems the weighting coefficients statistically acceptable. The results show that high priority monitoring areas occurs in the areas where there are fresh groundwater, high borehole density, elevated topography, higher recharge rates and decline in water levels are found. The monitoring network will include boreholes from the low priority areas to ensure that hydrogeological conditions are monitored and impacts are not worsened. Geophysical, numerical and chemical modelling aspects of the methodological approach will be incorporated into the initial groundwater monitoring network design.

 

Abstract

With increasing population growth and a subsequently increased demand for food production, the agricultural sector has had to grow and develop continuously despite drought-stricken water resources in recent years. The expansion in this sector requires increasingly efficient water use management and increases in water supplies, which are often met through groundwater utilization. In the past several years the use of groundwater in the Western Cape has increased exponentially and thus has forced the sharing of resources. The question pertains to how an invisible water resource that is difficult to measure and quantify, can be shared. Issues of varying complexities can arise when submitting a water use licence application (WULA), such as historical water use debates, interactions between groundwater and surface water, seasonal stresses on resources, etc. In one case study in De Doorns, a WULA became side-tracked soon after initiation by a neighbour’s complaint that his production borehole was severely affected by the drilling of the applicant’s boreholes. In the second case study in the Hexriver Valley, a WULA was complicated by a gentleman’s agreement stating that no one in the valley is allowed to abstract groundwater from deeper than 6 m. This gentleman’s agreement stems from past disagreements regarding such practices. The final case study was not a WULA but arose out of concerns for dropping weir levels connected to a new borehole. The borehole was equipped with new casing to case off the alluvium; it was suspected to be the cause of the disturbance. The scientific method was used to evaluate the borehole’s impact on the weir. Case studies such as these will become more prevalent as the demand on water resources will increase. Hydrogeologists needs to more informed of the complexities that can and will arise in the future as a result of shared water resources.

Abstract

Estimating pumping rates for the purpose of equipping boreholes with suitable pumps that will not over abstract either the boreholes or the aquifer(s) that are intersected is often assessed through test pumping of the boreholes prior to pump selection. While the South African National Standard has guidelines on the methodologies and durations of these tests (SANS 10299-4:2003), many production boreholes in the agricultural and industrial sectors are still equipped based upon so called Farmer Tests or Pump Inlet Tests (PIT), often of a short (6-24 hour) duration. These tests are also frequently and incorrectly confused with a Constant Head Test (CHT), both of which are different in methodology to SANS 10299-4:2003 testing, which relies to a high degree on data collected during a Constant Discharge/Rate Test (CDT or CRT) and recovery thereafter. The study will assess differences in test pumping methodology, data collection, analysis methodology and final recommendations made between Farmer Tests and SANS 10299-4:2003 methodology tests for 20 boreholes in which both tests were performed. The selected sites cover a variety of geological and hydrogeological settings in the Western Cape. Test comparisons include boreholes drilled into the Malmesbury Group, Table Mountain Group and Quaternary alluvial deposits, with tested yields ranging from 0.5 – 25 L/s.

Abstract

Ewart Smith, J; Snaddon, K; de Beer, J; Murray, K; Harillal, Z; Frenzel, P; Lasher-Scheepers, C

Various analysis techniques are available for assessing the groundwater dependence of ecosystems. Hydrogeological monitoring within the Kogelberg and greater Table Mountain Group (TMG) aquifer has provided various datasets from multiple scientific disciplines (hydrological, hydrogeological, geochemical, climatic, ecological and botanical). Using a variety of analysis techniques, and using the Kogelberg as a case study, this paper assesses the groundwater dependence of several ecological sites (wetlands and streams). The starting point is a sound geological and hydrogeological conceptualisation of the site. The approach involves conceptualisation and analysis within each scientific discipline, but also requires bridging between areas of specialisation and analysis of a variety of datasets. This paper presents the data and analyses undertaken and the relevant results as they pertain to several sites within the Kogelberg.

Abstract

Stringent drinking water standards for constituents like chromium, arsenic, and nitrates, combined with continually higher demand for groundwater resources have led to the need for more efficient and accurate well characterization. Many boreholes are screened across multiple aquifers to maximize groundwater production, and since these aquifers can have different water qualities, the water produced at the wellhead is a blend of the various water qualities. Furthermore, the water entering a well may not be distributed equally across the screened intervals, but instead be highly variable based on the transmissivity of the aquifers, the depth of the pump intake, the pumping rate, and whether any perforations are sealed off due to physical, chemical, or biological plugging. By identifying zones of high and low flows and differing water qualities, well profiling is a proven technology that helps optimize operational groundwater production from water supply boreholes or remediation systems. This frequently results in increased efficiencies and reduced treatment costs. By accurately defining groundwater quantity and quality, dynamic profiling provides the data needed to optimize well designs. Conventional exploration methods frequently rely on selecting well screen intervals based on performing and analyzing drill stem tests for one zone at a time. Using dynamic flow and water quality profiling, the transmissivity and water quality can be determined for multiple production zones in a matter of one to two days. It also allows the location and size of the test intervals to be adjusted in the field, based on real-time measurements.

In this paper we discuss dynamic well profiling techniques with project case examples of characterization different types groundwater boreholes for a variety of applications and industries resulting in significant cost saving and sustainable water abstraction.

Abstract

As populations, agricultural and industrial demands grow with time, increasing attention is placed on developing groundwater resources in a sustainable manner. At the small, local scale, this tends to involve exploration (scientific and otherwise) and test pumping (also subject to more and less scientific methods). While there can be some subjectivity in the analysis of scientific test pumping data (the selection of representative periods of drawdown stability, the inclusion of potential boundary conditions and the estimation of available drawdown), published methodologies such as the FC method (2001) and the Q20 (1959) and R20 (2006) concepts attempt to calculate sustainable abstraction rates based on these tests. At a larger catchment or aquifer scale, water balance estimates of inflows, storage and outflows are also used to estimate the effects of groundwater abstraction within such a “water budget”. This can be done conceptually, but is often also through a numerical model. A drawback of such methods is the difficulty in estimating representative annual inflow volumes, such as groundwater recharge. One such methodology is the Aquifer Firm Yield Model (2012) which assesses sustainable groundwater supplies based on threshold recharge inflows, baseflow and evapotranspiration outflows, and a 5 m aquifer saturated fluctuation limit. While this was intended for use at a preliminary stage of investigations, before sufficient hydrogeological data would be available for a numerical model, it nonetheless provides an estimate of the available groundwater for abstraction based on a water budget concept rather than test pumping data analysis. A comparison of the results of these two approaches is provided for several newly developed municipal production boreholes in the Karoo to compare where the assumptions inherent to each approach may be highlighted by noticeable differences in results.

Abstract

Maphumulo B; Mahed G

Disastrous droughts sweeping across South Africa has led to the population turning towards groundwater as their primary source of water. This groundwater movement has increased the need for proper groundwater management in terms of both quality and quantity. Groundwater sampling is a crucial, and yet often overlooked, component of water quality assessment and management. This thesis evaluated the various groundwater sampling methods used within fractured rock aquifers in the Beaufort West region. Each sampling method was evaluated in terms of their precision and accuracy according to their hydrochemical results. Historical hydrochemical data from past reports was utilised to determine how various groundwater sampling techniques influence results. This helped gained a better understanding of the requirements required to correctly and accurately sample different water sources such as boreholes and windmills. These requirements include the importance of purging in order to remove stagnant water from windmills. By understanding these sampling techniques, it is possible to create a groundwater sampling protocol which should be followed when sampling fractured rock aquifer in order to ensure best possible results.

Abstract

Approximately 982 km3 /annum of the world’s groundwater reserve is abstracted, providing almost half of all drinking water worldwide. Globally, 70% is used for agricultural purposes while 38% for irrigation.

Most water resources of South Africa are threatened by contamination caused by industrial, agricultural, and commercial activities, and many parts of the country face ongoing drought with an urgent need to find alternative freshwater sources, such as groundwater. Groundwater constitutes approximately 15% of the total volume consumed, hence it is an important resource that supplements insufficient surface water supplies across South Africa.

Very little attention has been afforded to understanding the anthropogenically altered vadose zone as a potential source or buffer to groundwater contamination. This is evident from few research studies that has applied multiple isotopic tracers to characterise this zone. Most subsurface systems in South Africa are characterised by fractures, whereby flow and transport are concentrated along preferential flow paths.

This study aims to evaluate the performance of different tracer classes (environmental and artificial) with one another, and create a better understanding of the hydraulic properties, mean residence time and transport mechanisms of these tracers. The influence of unsaturated zone thickness on recharge mechanisms will also be evaluated.

Site visits will be conducted for the proposed study areas, and the neighbouring sources of contamination will be assessed. The matric potential and unsaturated hydraulic conductivities will be measured using various techniques. Water samples will be collected and analysed for the various tracers from the vadose zone using gravity lysimeters including suction cups. Several tracers will also be injected into boreholes where samples will be collected to calculate tracer residence times (BTC’s) and further constrain the hydraulic properties of the vadose zone. All samples will be analysed, interpreted, and simulated using the numerical finite-element modelling code SPRING, developed by delta h. The software derives quantitative results for groundwater flow and transport problems in the saturated and unsaturated zones of an aquifer.

The research is expected to provide more insight into the selection and use of environmental and artificial tracers as markers for detecting, understanding the transport processes and pathways of contaminants in typical altered South African subsurface environments. The impact derived improved characterisation of the pathways, transport, and migration processes of contaminants, leading to groundwater protection strategies and appropriate conceptual and numerical models. The output from this study will determine the vertical and horizontal flux for both saturated and unsaturated conditions.

Abstract

Modie LT; Stephens M

Stable isotopes and hydrochemical analysis were undertaken to investigate groundwater-surface water (GW-SW) interactions and their possible implications on the quality and quantity of water in the karstified dolomite-dominated Notwane River Catchment (NRC) in semi-arid South East (SE) Botswana. Stable isotopes (δ18O & δ2H) and other hydrochemical parameters were analyzed from water samples (groundwater, river water and rain) collected in the upstream, middle stream and downstream of the Ramotswa Wellfields to investigate the potential GW-SW relationship in the study area. In addition field observation were also undertaken to support results obtained through stable isotopes and hydrochemical methods. Similarity in isotopic signatures taken during the dry and wet seasons respectively for groundwater (δ18O -1.4‰, δ2H -10.8‰; δ18O 1.4-‰, δ2H -10.9‰) and surface water(δ18O -2.04‰, δ2H -6.2 ‰; δ18O -2.56‰, δ2H -7.1‰) suggests groundwater recharge through the streambed at a site further downstream in the study area. In upstream study sites the average groundwater isotopic signature values of (δ2H -24.1,δ18O -4.1) suggests a more direct link to the Meteoric Water Line(MWL) indicating possibility of a rapid infiltration and quick watershed response to heavier rainfall events(δ2H -51.7, δ18O -8.6) rather than recharge through the riverbed. A further assessment on the GW-SW hydrochemistry was provided using Hierarchical Cluster Analysis (HCA) to investigate the influence of groundwater on stream water. The median EC values from the clusters are in an increasing order Cluster A-B2-B1 indicating cluster A(all river samples) as the most dilute samples with the shortest resident time relative to the groundwater clusters(B2 and B1). These results therefore rules out groundwater discharge through the streambed into the river as not a dominant process for GW-SW interaction in the study area. The study has concluded that GW-SW interactions in the NRC part under study vary from connected to no connection from one site to another.

Abstract

Sternophysingids are a group of stygobitic amphipods that inhabit groundwater networks characterised by large fractures, cracks and voids, as well as smaller pores, fissures, cavernous openings and interstitial spaces. Two species occurring in Gauteng, South Africa, Sternophysinx filaris and Sternophysinx calceola, were studied using morphological descriptions and molecular analyses to elucidate the distribution, evolutionary history, phylogeny and population structure. The population structure and distribution of stygobitic amphipods is a reflection of the physical structure of groundwater networks, and their evolutionary history can be used to understand the formation of groundwater bodies. S.filaris is a small and common inhabitant of aquifers in the northern regions of the country, while S. calceola occurs in many of the same locations but is much larger and rarer. No morphological differences were observed between individuals of different populations of S. filaris or S. calceola and detailed illustrations have been provided for each. This finding is not believed to be indicative of a high degree of connectivity within the subterranean groundwater network, lending to high rates of gene flow, instead, these morphological similarities are a symptom of cryptic speciation. Sternophysingids are likely to arise from an very ancient and widespread ancestor inhabiting much of Gondwanaland prior to its breakup. Using the COI gene, S. calceola collected from the type locality in Matlapitse Cave was successfully PCR-amplified and sequenced. Phylogenies were constructed using a limited variety of crangonyctoid sequences and the sternophysingids were confirmed to belong to the Crangonyctoidea superfamily, being most closely allied with the Western Australian paramelitids. The relationship between these groups is still distant and ancient; it is expected that the South African paramelitids would be more closely related, as well as other African, Madagascan and Indian crangonyctoids.

Abstract

Governing groundwater in a way that does not deplete the source of water, nor cause any form of degradation is a global challenge. In South Africa, scholarship shows an extensive history of groundwater governance doctrines. Yet, the country’s groundwater remained a poorly governed resource. A recent regulatory regime change culminated in the National Water Act 36 of 1998 (NWA), which was specifically promulgated to ‘provide for fundamental reform of the law relating to water resources’. While the NWA provided an ideal opportunity for the judicious governance of South Africa’s groundwater, groundwater governance remain problematic. The regulatory focus is still very much on surface water. In fact, up to date, no regulations have been made to specifically protect vulnerable aquifers, or aquifers on which communities depend as a source of water supply, or aquifers that supports large scale agriculture. This paper sets out to achieve three objectives: to assess South Africa’s existing regulatory approach to the protection of groundwater; to identify gaps in the regulatory framework; and to explore regulatory opportunities to strengthen groundwater governance. The discussion follows a focussed approach, and hinges on the case of the dolomitic aquifer of Delmas. The Delmas case study is expected to show why policy makers and planners need to be more concerned about groundwater. It will also introduce, explain and propose an established international or foreign legal measure that may be incorporated to strengthen the regulatory status of the Delmas aquifer. The paper concludes with recommendations for strengthening South Africa’s groundwater regulation.

Abstract

When conducting water quality monitoring, questions arise on which water quality guidelines to use and where to apply them. For example, the use of South African Water Quality Guidelines (SAWQG) for Domestic usage compared to the use of the South African National Standards (SANS) for Potable Water Quality when monitoring drinking water quality. The World Heath Organization (WHO) published a set of water quality guidelines for drinking water which can also be used instead of SANS. Using various water quality guidelines to assess water quality can give different outcomes on the state of water quality of a particular site. For example, SANS water quality guidelines are less strict when compared to the SAWQG target values, however, SAWQG are comprised of different sets of standards for different usages. SAWQG distinguish between drinking water, livestock and irrigation, aquatic systems and industrial usage while SANS are only used for potable or bottled water. The International Finance Corporation (IFC) that is part of the World Bank Group published the Environmental, Health, and Safety (EHS) Guidelines for Environmental Wastewater and Ambient Water Quality, guidelines set specifically for wastewater and ambient water quality. Utilizing this poster, I will explain when to use which guidelines with different types of water samples. I will also discuss the stringent water use license limits applied at some sites compared to the national standards of South Africa.

Abstract

The National Water Act, 1998 (Act 36 of 1998) requires water resources management be driven at a local level, in keeping with the local nature of water systems. Polokwane Local Municipality (PLM) as the Water Services Authority, is responsible for supplying adequate domestic water to 16 Rural Water Schemes and Groundwater Schemes. The Department of Water and Sanitation (DWS) Masterplan highlighted that the DWS, Catchment Management Agencies and Water Boards need to develop wellfields and management plans to ensure sustainable use of aquifers. The Aquifer Management Plan (AMP) for the Polokwane Urban Complex (PUC) within the Olifants-Sand Water Supply Scheme was developed with an overall aim of achieving integrated and adaptive management of the aquifer. This is to assist in confronting climate change challenges and water security at local level. The AMP forms part of the Integrated Water Resource Management and should be seen in the context of other related guidelines and activities, such as catchment management, water conservation and demand management, waste water management, and water resource planning and management. Extensive consultation with PLM and various other stakeholders as part of the Aquifer Management Plan was meant to foster a groundwater management relationship between the Department, PLM and other stakeholders to create an enabling environment for implementation of the Aquifer Management Plan. A set of goals, targets and actions were developed for the Aquifer Management Plan These goals and targets serve as steps that allow for ‘zooming’ into the more specific actions. During consultations with the PLM, relevant Professional Service Providers, the DWS Limpopo Provincial Office and numerous other stakeholders, 75 actions within the 10 goals were identified. Ultimately, an Aquifer Management Plan had to identify actions that can improve groundwater resource management within the Polokwane Urban Complex and develop a supportive cross-institutional relationship in which to pursue them.

Abstract

More often these days we hear concerns from water users regarding “how much water is the newly drilled borehole of a neighbor extracting from “their” river water”. These are serious question with serious repercussions for sustainable use and economic development. No one wants to lose what they have invested in. On the other hand, from a groundwater perspective, this is very one sided.

Numerical modelling solutions are often proposed to clients as a more accurate method of determining the groundwater surface water interaction, with the addition of volumes removed from the modelling domain, to present to decision makers the changes in volumes of discharge into streams or volumes of infiltration of stream water into the aquifer. However, this is an expensive and time-consuming exercise, and will most likely incur additional costs to accumulate sufficient meaningful data sets for input into these detailed models. A robust combination of analytical and numerical solutions is proposed, while keeping aquifer assumptions conservative, where a lack of regional data exist. This is useful in quantifying this interaction and associated volumes better without the full time and cost associated with calibrated regional flow and transport models. Analytical calculations assist in the quantification of the aquifer’s hydraulic and physical properties and is used to conceptualize flow better and determine the inputs for a conservative well field scale numerical model, in which the change in flow between groundwater and surface water system are also evaluated. The well field scale model is calibrated in a fraction of the time as a conventional flow model (less than 20%), while volumes derived is defendable and based on measurable data. This combination is viewed to be a critical step in providing time effective solutions

Abstract

Because the quality of groundwater is influenced by the host rock through which it moves, it differs on a site-specific basis, and is often naturally brackish or even potentially harmful to people. In spite of this, many practitioners incorrectly use the SANS 241 Drinking Water Standard as “compliance requirement” to compare groundwater quality against. This standard only applies to water that has been purified to be suitable for potable purposes at a water treatment works in terms of regulations made under the Water Services Act 108 of 1997. The only circumstance in which it could be used to compare the quality of natural groundwaters against, is where such groundwater is (to be) used, for potable purposes (with or without treatment), and then only to provide guidance on the level of treatment required to facilitate suitability for such domestic use, and not to determine possible ‘unacceptable’ levels of contamination. Therefore, the comparison of groundwater quality results against the SANS 241 Drinking Water Standard is not only a scientifically flawed practice, it has no basis in law. It is furthermore a scientifically flawed practice to refer to groundwater quality as ‘good’, ‘bad’, or ‘poor’, as it reflects a judgemental anthropocentric perspective that has no place in modern discussions on judicious environmental management and monitoring.

 This then raises the question, what are, or should the limit values be against which groundwater quality results should be compared to determine if it has been negatively affected by anthropogenic activity to such an extent that a scientifically substantiated claim can be made that the groundwater has been ‘polluted’, an allegation with criminal liability implications?

This paper aims to answer this question in the context of South African Framework law and policy, and propose a methodology to determine appropriate site-specific limit values for groundwater quality.

Abstract

Siloam, a village in the Northern province of South Africa (SA) has groundwater reportedly characterised by concentration of fluoride greater than the permissible limit of 1.5 mg/L by the World Health Organization (WHO). In response to reported high incidences (80%) of dental fluorosis in Siloam, sources of fluoride in the groundwater of Siloam village was investigated. Earlier hypothesis suggest that the source of fluoride could be fluorite. Physicochemical parameters were determined using a combined multimeter; while total fluoride (TF) was determined using Ion Chromatograph and Fluoride Ion Selective Electrode. Mineralogy of the rocks and soil in the village was determined using X-ray Fluorescence and X-ray diffraction, respectively. Results revealed that groundwater fluoride concentration ranged from 3.92 to 4.95 mg/L, which are far above the WHO permissible limit and South African National standard. Na-Cl water type was found to be dominant in the water samples which could be due to the heavy weathering of plagioclase present in the parent rocks. TF content of the rocks and soils of the village ranged from 10 to 2000 mg/L. Leachates were obtained by soaking the pulverised rocks and soil in de-ionized water over a period of 24 hours. TF in leachates ranged from 0.27 to 14.88 mg/L and 0.05 to 10.40 mg/L at induced, and non-induced temperature, respectively. Although, previous research hypothesize fluorite to be the possible source of fluoride in the village, this research shows that the main contributors of fluoride to groundwater in Siloam were smectite clays and the muscovite present in the sandstone, Investigation also revealed that the geothermal temperature of groundwater in the area is also a major factor enhancing the release of fluoride from the clay material into the groundwater.

Abstract

Groundwater flow system responses have been understood using derivative analysis. The argument is that the use of derivative analysis derived from pumping test data improves the understanding of aquifer types and curve matching in a hydrogeologic setting. The different aquifer systems encountered in Western Cape Government Business Continuity Programme (WCBCP) of South Africa was used as case study where the analysis of the time versus draw-down derivative plots were applied to validate the aquifer characteristics to explaining the groundwater flow systems. Key findings showed that analysis from the time versus draw-down derivative plots can be used to infer conditions within the wellbore, groundwater flow to boreholes and boundary conditions within the aquifer to provide insights. In addition, results confirmed that the archetypal time vs draw-down responses enabled characterizing the aquifer types and such analysis showed unique responses to the pumping. Lastly, long term operation of boreholes for water supply were ascertained when the analysis was interpreted. The analysis was enhanced when the geological information that was collected during drilling operations, were added to the conceptual understanding of groundwater flow studied aquifer system. However, due to costs implications of conducting long-term aquifer hydraulic pumping tests, deviations from the conventional draw-down responses are expected. In this study, it is suggested that due to complexities associated with heterogeneous flow in aquifer types, it is essential to combine derivative analysis with pumping methods to improve interpretation and assessing long term operation of boreholes for water supply

Abstract

The hydrological cycle consists of several components, with two of the major processes being that of surface water flows and groundwater flows. It has been proven before that these two components interact with each other and are often critical to the survival of the associated users and ecosystems, especially in non-perennial river systems. Non-perennial river systems have a limited number of studies, especially on its link to groundwater and the management of the system. Surface water and groundwater individually contribute to the quality, quantity and distribution of water available and the effect on down gradient users. Understanding these processes would help greatly in managing the non-perennial river/groundwater catchment systems along with its respective ecosystem. The aim is, therefore, to provide an understanding of the groundwater and surface water interactions in the research catchments of Agulhas, Touws and Tankwa-Karoo, and to understand the influence of management decisions related to groundwater use. To achieve this aim, conceptual models will be formulated for the different sites using borehole, geophysics, hydraulic and geochemical data collected in the research catchments. Prediction of the effects of groundwater use on the river systems, and river modifications on groundwater levels, will be done using numerical models to simulate the flow processes and the interactions. With the often strong reliability on groundwater in semi-arid and arid regions to support ecosystems and surface water pools, it is expected that the results will indicate a decrease in river flows (and existence of pools) with an increase in shallow aquifer groundwater abstraction. However, the regional flow of groundwater and surrounding faults and springs may have an influence large enough to counter the expected result.

Abstract

The quality of groundwater is, in part, controlled by the character of the rock in which it is stored and the water - rock contact time. Rainfall (or recharge) is also a contributing factor as the mineralisation of groundwater increases from east to west across South Africa. It is well established that groundwater is more mineralised than surface water, and with most of South Africa's domestic supplies being sourced from dams, municipal water supplies are generally of low salinity. The exception to this is where water supplies are sourced from groundwater - such as in the Karoo and along the West Coast. The assessment of water potability is based on both the South African National Standard 241 and the Department of Water and Sanitation guidelines, with the former being a legal requirement. Previously, SANS 241 had two classes of water with the lower class only being allowed for a limited period. In 2015, Class II water was done away with and only a single class of water is now specified. While this may have been done to conform to World Health Organisation standards, it disregarded the realities of a resource-strapped South Africa where in large parts the municipal water supplies simply cannot meet the SANS241 standard. This paper examines the implications of the SANS 241 standard on efforts to establish emergency groundwater supplies during the drought impacting the Western Cape Province.

Abstract

The mitigation of groundwater impacts related to gold mining tailings disposal within the Orkney-Klerksdorp region was assessed and presented as a case study. The most pressing concern for the facility owners is the potential for pollution of water resources in the vicinity of the mines, especially after mine closure. The key focus of this paper is to describe how methods were applied to characterise the aquifer and keeping the source-pathway-receptor principles in mind. Characterisation also involves lessons learn by comparing pre-tailings deposition and post-tailings deposition aquifer bahviour. Ultimately the process followed in this paper has led to the development of a logical approach to estimate groundwater liability costs in a typical tailings environment. The link between hydrogeology, geotechnical engineering and civil engineering was identified as a critical foundation for the development of a successful groundwater management strategy

Abstract

The purpose of this study was to determine the optimal sampling methods for the analysis of radioactive material in fractured rock aquifers. To achieve this a number of data sets were used which span a 40 year period in and around Beaufort West. Well purging requires the pumping out of stagnant water. This step is crucial as the idle well water may not be representative of the entire aquifer. This step was found to be critical in the studies analysed and had a direct impact on the results. It is necessary to pump out the entire well volume and recommended to pump out at least two well volumes before sampling commences. Samples may also be taken prior to well-purging as a means of checking the effects of purging. Another important aspect for sampling is that of multi-level sampling, particularly in the case of boreholes which feature multiple fracture or aquifer interception points. Prior to sampling, sampling containers should be well washed and cleaned using HCl and rinsed with deionised water. This is done to remove any contaminants which may hinder laboratory analysis. It was found that the multilevel sampling method yielded the best results. Furthermore, the samples stemming from windmills also had good results. The evolution of sampling as a science has improved over the past 40 years, but a fundamental understanding of sampling as a science needs to be incorporated

Abstract

Groundwater monitoring, especially from the end users' point of view, is often considered an add-on, or even unnecessary overhead cost to developing a borehole. Simply measuring groundwater level over time can however tell a story on seasonal rainfall fluctuations as well as the response of an aquifer to the removal of an abstracted volume of water. In this case an artesian borehole of high yield and exceptional quality was drilled in an area of minimal groundwater use because of known poor quality and low yields. The borehole was drilled in two stages with the deeper drilling resulting in significantly higher yields and the artesian flow. Sediment free water, deep artesian water strikes and a lack of flow around the casing led to the conclusion that capping at surface would control the visible artesian flow of 4 L/s. A slight drop in pressure indicated that subsurface leakage may however be occurring. Neighbouring boreholes with automated water level monitoring provided data showing a correlation of drop in water level to the second deeper drilling event. The artesian borehole was yield tested and this too was visible in the water level monitoring data. Hereafter it became apparent that each activity performed at the artesian borehole had an impact on the monitoring boreholes, and that a subsurface leak was causing local depressurization of a semi-confined to confined aquifer. An initial attempt to save the artesian borehole was unsuccessful, resulting in the necessary blocking and abandonment of a high yielding, superior quality borehole. If monitoring data was not available the local drop in water level would never have been noticed with disastrous effect and no evidence for the cause. Simple water level monitoring has averted this and kept neighbourly relations and ground water levels intact

Abstract

The expectation that during yield tests, a borehole will react within the expected framework of the existing numerical models, is often not met within real-world scenarios. This is mainly due to the observation that the Theis solution for confined aquifers, Neuman solution for unconfined aquifer and Barker Generalised Radial Flow Model for hydraulic tests in fractured rocks all include idealised assumptions regarding the physical aspects of a hypothetical. In order to interpret the data from a yield test these methods, along with the Flow Characteristic method for sustainable yield estimates, are commonly used. However, as these assumptions are not always met, the analysis is usually focused on time periods within the test that approximate these solutions. In some cases, the extent to which these assumptions are not met can produce drawdown data that is not well described by the usual analytical models used to analyse this data. This study addresses some of the shortcomings experienced during testing in non-ideal aquifers, as well as briefly describing some tests where small budgets, short deadlines, a lack of information and/or unforeseen circumstances resulted in similar challenges to analyses. This study does not present new solutions to drawdown data analyses, but rather discusses how the mentioned solutions were used during testing to accommodate for the shortcomings experienced.

Abstract

Due to the recent drought in the Western Cape province of South Africa, surface water can no longer meet our current demand of water and as a result groundwater usage has increased. High iron concentration in groundwater is a problem which results in iron encrustation and iron clogging. This results in decreased borehole yields, decreased water quality and expensive treatments to remove iron encrustation or the drilling of entirely new boreholes. From both international and local literature there are two common factors which stand out which is that high concentration of iron in groundwater is a global issue, the second common factor is that the occurrence and influencing factors of high iron concentrations are site specific. Boreholes drilled for drought relief in health facilities across the Western Cape have reported increased concentrations of iron. Understanding of the geology, hydrogeology and hydrogeochemical conditions that cause the increased iron concentrations in groundwater at these specific locations is required. The objectives of this research project are to: 1) Assess spatial and temporal variations in iron and manganese concentrations; 2) Establish site specific processes that control the concentration of iron in groundwater; and 3) model the geochemical processes that impact iron levels in groundwater. These objectives will be achieved through historical groundwater quality data analysis, geochemical modeling, field work where samples will be collected and laboratory analysis of the samples collected. The information provided from this research project will allow for the effective management decisions to be made in terms of iron removal from groundwater and early preventative measures that can be made to ensure iron clogging and encrustation does not occur. The study is currently ongoing and there are currently no results available at this point however, at the time of the conference there will be information ready to share.