Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 501 - 550 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort descending	Keywords
Groundwater development for Municipal water supply in response to drought of 2015 to 2019.	Dale	Barrow	Western Cape	2019	Drought, TMG
Abstract The geographic positioning of the Western Cape results in a Mediterranean climate - receiving majority of its rainfall during the winter months. A demand on the water supply throughout the year is typically met by storing water from winter rainfall in large dams. The Western Cape experienced a significant drought between 2015 and 2019. As a result, the supply dams have not been filled to capacity and drastic water restrictions had to be implemented. In the search for alternative water sources, groundwater exploration became a priority. Groundwater development projects were implemented rapidly in attempt to alleviate the implications caused by severe water restrictions and ultimately prevent running out of water. As a local groundwater institution, GEOSS got involved in several fast-tracked groundwater development projects for Department of local government, local municipalities, as well as other industrial and agricultural corporations. For obtaining the required water volumes, alternative measures were implemented. Previously under developed aquifers were targeted. In certain instances, in order to target the Table Mountain Group Aquifer (TMG), horizontal exploration drilling was conducted. The results of exploration and drilling yielded valuable learnings in terms of relevant hydrostratigraphy within the study areas. Additionally, there were learnings in terms of managing projects of this nature. In fast-tracked projects, careful management of the contractors, data collation (and storage) and public perception is critical to the success of the project. In this paper on water supply development for Municipalities, the various components of groundwater development are detailed along with relevant learnings from the recent emergency drought response measures.
Investigation The Effect Of Excess Pumping On The Groundwater Salinity In Semi-Arid Aquifers Using Predicted Future Scenarios	Mohammed	Seyam		2019	Hydrological Modeling, Groundwater Quality, Salinity, Prediction scenario
Abstract The groundwater quality in semi-arid aquifers can be deteriorated very rabidly due to many factors. The most important factor affecting the quality of groundwater quality in Gaza Strip aquifer is the excess pumping that resulting from the high population density in the area. The goal of this study to investigate the future potential deterioration in groundwater salinity using scenario analysis modeling by artificial neural networks (ANN). The ANN model is utilized to predict the groundwater salinity based on three future scenarios of pumping quantities and rates from the Gaza strip aquifer. The results shows that in case the pumping rate remains as the present conditions, chloride concentration will increase rapidly in most areas of the Gaza Strip and the availability of fresh water will decrease in disquieting rates by year 2030. Results proved that groundwater salinity will be improved solely if the pumping rate is reduced by half and it also will be improved considerably if the pumping rate is completely stopped. Based on the results of this study, an urgent calling for developing other drinking water resources to secure the water demand is the most effective solution to decrease the groundwater salinity.
The Relationship Between Groundwater Governance And Management At Local Municipal Level.	Fanus	Fourie	National	2019	Governance, Management
Abstract The terms 'Management' and 'Governance' are used interchangeably when referring to groundwater such as policy, protection, operations, financial systems and infrastructure. Governance and management are not separate scales of action, but different processes. Both processes can take place together at local, regional, national or global scales. (Seward 2015). The influences from the different levels of government are also linked. Governance and management can in most case not be split into two blocks and handled separately. The degree of governance vs management differs per level of government from institution to institution. The line between governance and management is thus very flexible between the different areas/location or aquifers where groundwater is being used and protected. Some functions, responsibilities and roles are very difficult to place under governance or management alone and can fall under both. The term 'Implementation Governance' was created to describe the overlap of functions, and this also links closely to the term 'Local Level Governance' that focuses on governance at the local municipal level. The paper describes the relationship between governance and management functions at different government levels and illustrates it through five scenarios/examples of the different government organisations at the municipal level.
Groundwater Assessment using Borehole Magnetic Resonance	Benjamin	Birt		2019	magnetic resonance
Abstract Hydraulic behaviour of an aquifer is defined in terms of the volumes of water present, both producible and not (specific yield and specific retention), and the productivity of the water (hydraulic conductivity). These parameters are typically evaluated using pumping tests, which provide zonal average properties, or more rarely on core samples, which provide discrete point measurements. Both methods can be costly and time-consuming, potentially limiting the amount of characterisation that can be conducted on a given project, and a significant measurement scale difference exists between the two. Borehole magnetic resonance has been applied in the oil and gas industry for the evaluation of bound and free fluid volumes, analogous to specific retention and specific yield, and permeability, analogous to hydraulic conductivity, for over twenty years. These quantities are evaluated continuously, allowing for cost-effective characterisation, and at a measurement scale that is intermediate between that of core and pumping tests, providing a convenient framework for the integration of all measurements. The role of borehole magnetic resonance measurements in hydrogeological characterisation is illustrated as part of a larger hydrogeological study of aquifer modeling. Borehole magnetic resonance has been used for aquifer and aquitard identification, and to provide continuous estimates of hydraulic properties. These results have been compared and reconciled with pumping test and core data, considering the scale differences between measurements. Finally, an integrated hydrogeological description of the target rock units has been developed.
Observation and monitoring of field parameters for springs and rivers of a Swiss alpine valley in relation to seasonality.	Cedric	Meier	Switzerland, France	2021	Monitoring, data management, data science libraries, Water security, Groundwater Sampling, training, municipal water supply
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.
An investigation of the natural groundwater recharge and discharge of the Saldanha Bay Aquifer Systems, South Africa	Aqeela	Parker	Saldanah Bay	2021	Bulk water supply, recharge, Discharge
Abstract Saldanha Bay is partially dependent on groundwater as part of their bulk water supply, as surface water resources in the area are extremely limited and fully allocated. Due to this, there is lots of pressure on the groundwater resources by industrial development and residential growth. Despite studies being conducted on these aquifer systems since 1976, they are still poorly understood especially with regards to their recharge and discharge processes. This study aimed at providing better insight and understanding on the natural groundwater recharge and discharge processes in order to assist in the better management of groundwater resources in Saldanha Bay. Recharge investigations included a Time Domain Electromagnetic airborne geophysical survey, the assessment of groundwater levels, infiltration tests, hydrochemical analyses as well as stable and radioactive isotope analyses. These methods allowed for the delineation of the geological layers and extent, determination different water quality spatially across the aquifer, determination of flow paths through the saturated and unsaturated zones, identification of inter-aquifer flow as well as different recharge processes in the area. The results of this study showed that is highly likely that the Saldanha Bay Aquifers are mainly recharged via deep flow paths from the Aurora Mountain Range and Moorreesburg region. Investigations also showed that it is unlikely that the Aquifer Systems are recharged by local rainfall due to thick unsaturated sands and low annual rainfall, except for runoff at the foot of granite hills through focused recharge processes. The Berg River, Langebaan Lagoon and the Atlantic Ocean were identified as being the main discharge zones for the area. It is recommended that further hydrogeological investigations are conducted in the Moorreesburg region in order to get a fuller picture of the regional groundwater recharge processes and flow to Saldanha Bay.
Aquifer structure and extent based on Airborne Geophysical investigation: A case study based in Saldanha Bay Local Municipality, West Coast.	Angelo	Johnson	Saldanah Bay	2021	Poster, Skytem, 3D mapping survey, MAR, interpretation, aquifer management
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.
Using geophysics to detect water-hosting fractures in the Vredefort Dome: A training opportunity	Elvis	Tamilo	Gauteng	2021	Poster, Geophysics
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.
Test pumping Well field analysis of a heterogeneous fractured rock aquifer.	Reuben	Lazarus	Cape Town	2021	Shales, wellfield testing, cluster connectivity
Abstract A Case study done in the heterogeneous Tygerberg shales underlying the northern section of the Cape flats aquifer. A well field consisting of five boreholes within a 1.6 Ha area was test pumped to determine aquifer parameters and sustainable yields for the well field. The wellfield located in a highly heterogeneous geological setting, proved to be an interesting scenario for wellfield analysis and determination of sustainable borehole yields. A variety of analytical methods were used to analyse the test pumping data including the Advance FC analysis and the Cooper Jacob Wellfield analysis, both producing different results. Through the test pumping data analysis, the wellfield could be divided into sub wellfield clusters based on drawdown interconnectivity during testing. Sub wellfield clusters were confirmed using groundwater chemistry, providing higher confidence in limiting uncertainty in long term cluster connectivity.
The Role of GRACE data in mapping groundwater drought in the Southern African Development Community: Updating the groundwater drought risk map	Zaheed	Gaffoor	SADC	2021	Drought, GRACE, SADC, Groundwater storage, mapping
Abstract Pietersen, KC; Musekiwa, C; Chevallier, L Groundwater plays an integral role in the fresh water supply for both rural and urban populations of the Southern African Development Community (SADC). However, the sustainable use of groundwater is negatively impacted by persistent and recurring droughts in the region. Understanding the characteristics of drought and the risk to groundwater, will contribute towards better planning and management of water supply in the region. In this study, a novel approach is demonstrated, that uses data from the Gravity Recovery and Climate Experiment (GRACE) to map and characterise the risk to groundwater storage from drought, across the SADC region. In addition, this study also demonstrates and evaluates the inclusion of this new feature, groundwater storage sensitivity, as an additional input into a revised Groundwater Drought Risk Mapping and Management System (GRiMMS), in-order to update the SADC groundwater drought risk map developed in 2013. Specifically, the GRACE Groundwater Drought Index is calculated and used to characterise the total length, average intensity and trend, in groundwater storage drought conditions. These three factors are then combined into a new layer, groundwater storage sensitivity, and validated through comparison with groundwater level data. The groundwater storage sensitivity, which represents the risk to groundwater drought associated with groundwater storage deviations, is then included at the modular level in the GRiMMS algorithm. The inclusion of the GRACE derived groundwater storage sensitivity further highlights regions of known hydrological drought, emphasising the impact groundwater storage plays in mitigating drought risk. In conclusion, GRACE provides a unique tool that can be used to map the impact of drought across the SADC region.
Assessment of the state of potable water supply system in selected communities ofVhemb District Municipality, Souh Africa	Tuwani	Malima	South Africa	2021	community supply, local municipality, main source, Groundwater Quality, distance to source, reliability
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.
Update of regional groundwater flow models for the Vaal Gamagara SD1 and SD2 wellfields	Martin	Holland	Northern Cape	2021	Demand, exploitation potential, Simulations, CRD, Production rates, Prediction scenario, adaptive management
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.
FrackSA: A tool to aid in the enforcement of groundwater regulations during unconventional oil and gas extraction	Charissa	Worthmann	South Africa	2021	Poster, Unconventional gas, hydraulic fracturing, Regulations, enforcement, civic informatics, mobile application, groundwater protection
Abstract South Africa is currently considering unconventional oil and gas (UOG) extraction as an additional energy resource to improve the country’s energy security. In a water-scarce country such as South Africa, which has experienced more frequent and more intense climate extremes due to climate change, the water-related impacts of UOG extraction is a concern. The South African government is however determined to proceed with UOG development as soon as regulations to protect natural resources have been drafted. The country’s intricate governance system can however not enforce such regulations effectively, as it experiences repeated inter-departmental miscommunication, fails to collaborate with stakeholders effectively, and lacks human and financial resources for enforcement. A lack of transparency in fracking operations and between stakeholders is another challenge for enforcing UOG extraction regulations. Poor regulatory enforcement presents an obstacle for the protection of groundwater resources if fracking were to commence. This study, therefore, focuses on addressing the enforcement challenges of UOG regulations aimed at protecting groundwater resources. It proposes the use of civic informatics on a technology platform, specifically via a mobile application (FrackSA), to assist with on-the-ground enforcement of these regulations. While many UOG mobile applications are used internationally, they mostly focus only on UOG related aspects (news, information, pricing, geological information, and fracking well information). FrackSA uses civic informatics to address both groundwater monitoring and management as well as UOG extraction operations in a single platform, to enable regulators to protect groundwater resources more effectively during UOG extraction, while simultaneously enhancing transparency in the UOG industry.
Using geophysics to detect water-hosting fractures in the Vredefort Dome: A training opportunity	Stephanie	Enslin	Vredefort Dome, Gauteng	2021	Field School, fractures, geophysical methods
Abstract Tamilo, T; Webb, S.J. 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.
Groundwater Kids Program	Izelda	Mbatha	Gauteng	2021	Awareness, Schools, Science Education
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.
Managed aquifer recharge in South Africa (MARSA)	Jens	Aamand	South Africa, Denmark	2021	Pollutants, Reclaimed water, Anaerobic aquifer, Anaerobic degradation, Nitrate, Nitrospine, Nitrification, Compost, Contaminant, Infiltration, Pathogens
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.
Practical Solutions for Academic Based Applications – Understanding the importance of correct aquifer test data interpretations	Jorette	Van Rooyen		2021	Gw-Sw interaction, test-pumping, FC, Monitoring
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.
Hydrogeological modeling of a coastal wetland: The development of a steady-state numerical groundwater flow model for Rietvlei Wetland, Cape Town	Nathasha R	Gariremo	Cape Town	2021	Poster, coastal wetland, wetland management, groundwater budget, numerical model, wetland hydrodynamics
Abstract The Rietvlei Wetland, located in the Western Cape of South Africa is well recognised for harbouring numerous bird species, and is ranked the 6th most important coastal wetland in the South-western Cape. Researchers perceive that the wetland could be threatened by the growing drought hazards, and increased water demand in Cape Town. The extent of the effects is however unquantified and unknown. This therefore calls for extensive research and novel approaches to understand and quantify wetland hydrodynamics, to shape wetland management frameworks. Conducting thorough field work to understand wetland processes, and the use of numerical models for future prediction of black swan events are well recommended. Thus, the study aims to develop a conceptual hydrogeological model for Rietvlei Wetland, and to develop a numerical model to quantify the wetland’s groundwater budget. To achieve this, historical data was gathered, and field work which included groundwater monitoring, collection of sediment profiles and water quality analysis was undertaken. Preliminary results show that the wetland is underlain by an unconsolidated aquifer, largely overlain by different types of sand, mixed with clay and silt, and precipitation is the main source of groundwater into the wetland. A distinct relationship is seen between elevation, soil type and soil structure, such that during the peak rainy season, groundwater tends to be above the ground surface in the low-lying salt pans, dominated by clayey layers on their surfaces. These surfaces tend to crack during the dry season, facilitating preferential flow pathways at onset of rain. This information, and other historical data will be used to develop a numerical model using MODFLOW-NWT and ModelMuse. The numerical model is perceived to be the basis of groundwater modeling using open-source software for Rietvlei Wetland, and may be used for predicting the impacts of drought and increased groundwater abstraction on the wetland’s hydrodynamics.
Geochemical investigations to improve the prediction of mine water impacts: A case study in the Elandsfontein Aquifer System, West Coast.	Angelo	Johnson	West Coast	2021	Phosphate mine, waste sreams, mine water impacts, PHREEQC, geochemical
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.
Investigating groundwater and surface water interactions using stable isotopes and hydrochemistry in the Notwane River Catchment, South East Botswana.	Piet	Kenabatho	Botswana	2021	Gw-Sw interaction, Isotopes, Hydrochemistry, HCA
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.
Sustainable rehabilitation of production boreholes: Application of ph-neutral iron(III)dissolvers by closed-circuit injection	Päivi	Puronpää-Schäfer	Finland, Germany, others	2021	Rehabilitation, maintenance, closed-cicuit injection
Abstract Clogging of existing boreholes due to natural well ageing is the most common cause of decreasing yield worldwide, also in South Africa. Maintenance plans based on systematic monitoring are required including inspection, service and rehabilitation to lengthen production times and to slow down ageing processes. Therefore a prerequisite of economical well operation is to apply the most efficient measures to secure their production capacity at the lowest possible cost. Rehabilitations by mechanical, hydraulic or impulse methods do often not lead to acceptable yield increases. Acids of all kinds have been applied to remove iron(III) and manganese(III,IV) clogging, although pH values of < 1.0 are required before any significant dissolution takes place. This treatment does not only affect substances in adjacent geology but also well construction materials and technical equipment. Alternatives for acidization were researched and developed at the Technical University of Aachen (RWTH) in 1990’s by Prof. Dr. Treskatis and Dr. Houben. Since then iron(III) and manganese(III,IV) are removed by pH-neutral reductants with 50 times greater dissolving capacity than hydrochloric acid at pH 1.0 in identical molar concentration. The closed-circuit injection technique was proved to be the only method to transfer chemical agents as far as the borehole wall in a study by Dresdner Groundwater Center on behalf of German Gas and Water Association in 2003. Low pressure circulation based on large volume flow is accomplished by means of state-of-the-art gravel washers. The application of pH-neutral dissolvers by closed-circuit injection has proved its effectiveness not only in Germany, but also in Switzerland, Austria, Netherlands, Spain, UK, UAE and Peru. Our case study documents its successful introduction in Finland 2020. Until then stand-by acidization had been the only means of battling well ageing. Research funds enabled rehabilitations in different parts of the country resulting in unexpected high yield increases.
Groundwater monitoring of South Africa through numerical model	Akhona	Maqhubela	Sutherland	2021	Monitoring, numerical modelling, GRACE, SG measurements, MODFLOW, SAGOS
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.
Stable Isotope Techniques for the Evaluation of Water Sources for Domestic Supply in Stellenbosch, South Africa	Jared	Van Rooyen	Stellenbosch	2021	Poster, stable water isotopes, Monitoring, Monitoring, urban water supply
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.
Combined use of Environmental and Artificial Tracers to Characterise the Vadose Zone.	Yazeed	Van Wyk		2021	Poster, vadose zone, isotopic tracers, recharge mechanisms, Protection, aquifer protection
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.
Fracking regulations to protect groundwater resources during unconventional oil and gas extraction: Getting it right.	Surina	Esterhuyse	National	2021	Fracking, Regulations, enforcement
Abstract The South African government is actively pursuing unconventional oil and gas (UOG) extraction to augment energy supplies in South Africa, but it risks damaging water quality. The Department of Water Resources and Sanitation recently released regulations to protect water resources during UOG extraction for public comment. Regulations are one of the main tools that can be used to minimise UOG extraction impacts on water resources and enhance an environmentally sustainable economy. This tool must however be used correctly. Many states in the US and Canada have extensive regulations to protect water resources during UOG extraction but they are often ineffective, either because they were poorly drafted or because they are not properly enforced. Since South Africa is a water-scarce, groundwater-dependent country, we asked South African groundwater experts what regulations are needed and how to enforce them. Focusing on the interface between science and public policy, we critically analyse and recommend the most appropriate fracking regulations to protect groundwater resources. Additionally, we consider the enforcement mechanisms required to ensure the proper regulation of fracking. The results from this study can assist the government in ensuring that regulations that they are currently drafting and finalising, are appropriate to protect groundwater resources, and that they would be able to enforce them effectively.
Geophysical Borehole Siting at Elizabeth Conradie School in Kimberley, Northern Cape Province, South Africa	Matome	Sekiba	Kimberley, Northern Cape	2021	geophysical methods, mapping , Drilling
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.
Sustainable Groundwater Development Perspectives: Differences in sustaining individual abstraction rates based on test pumping data analysis with recharge based firm yield estimations for an aquifer or localised area.	Kes	Murray	Karoo	2021	development, water balance, groundwater budget
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.
Optimizing borehole performance through dynamic flow and chemistry profiling	Steve	Kalule		2021	Drinking water standards, Groundwater Quality, supply boreholes, remediation system, optimised well design, well profiling
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.
Diamonds on the soles of their feet: groundwater monitoring in the Hout Catchment, Limpopo	Jacqueline	Goldin	Limpopo	2021	Citizen Science, framework, participatory methods, Rainfall, Groundwater Sampling, Data collection
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
Assessing groundwater dependence of wetlands and streams within the Table Mountain Group Aquifer: A Case Study from the Kogelberg	Dale	Barrow	Western Cape	2021	Ecosystems, datasets, conceptualisation, Monitoring
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.
AI_GEO software platform for regional groundwater potential mapping	Emannuel	Sakala	Free State	2021	Mapping methodologies, AI, algorithms, Drought, exploitation potential
Abstract Delineation of groundwater resources of a given area is importance for management of groundwater resources. This is often done manually by combining various geo-scientific datasets in Geographic Information System (GIS) environment, which is time consuming and is prone to subjective bias and also suffers from other human induced uncertainties and difficult to cope with increasing volumes of data. The explosive growth of data leading to ‘rich data, but poor knowledge’ dilemma yet we have challenges to be solved. Artificial Intelligence (AI) has been successfully used in fields such as robotics, process automation in engineering, industry, medical and domestic households. Artificial Intelligence tool have the able to bridge this gap by augmenting the human capabilities in understand science far better than before. Incorporating AI into groundwater potential mapping greatly improves computation speed, reduces the subjectivity nature of manual mapping and lessens human induced uncertainties. The software platform includes artificial intelligence algorithms such as artificial neural networks, support vector machines, random forest, index-overlay and fuzzy logic. The software platform is semi-automatic to allow the user to control some of the processes yet automating the other processes. The possible inputs to the AI for training includes; aquifer types, topographic slope, lineament and drainage density, land-use / land-cover (LULC), distance to lineaments, distance to streams and soil clay content. Yield values of selected boreholes are used as training outputs. The software was tested using data gathered for the area surrounding Maluti-a-Phong in the Free State Province of South Africa. The area was chosen because of recent drought which has hit the country and local municipalities are searching for groundwater resources for building wellfields to supply local communities with fresh water. The groundwater potential map of the area was validated using borehole yield values of boreholes which were not used for modelling. Good correlation values as high as 0.85 was obtained between model values and borehole yield. The final groundwater potential map was divided into four zones; very good, good, poor and very poor. Based on this study, it is concluded that the high groundwater potential zones can be target areas for further hydrogeological studies. The usage of the software proved to be efficient in minimising the time, labour and money needed to map large areas. The results of which can be used by local authorities and water policy makers as a preliminary reference to narrowed down zones to which local scale groundwater exploration can be done. AI should be viewed as augmented intelligence as it aid the decision-making process rather than replacing it. Data-driven approaches should also be knowledge-guided for efficient results.
Test Pumping: Comparing the Farmer Test, Constant Head Test and SANS 10299-4:2003 methodologies with regards to estimating groundwater abstraction. Data, analyses and recommendations.	Kes	Murray	Western Cape	2021	test-pumping, Irrigation, training, Water security
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.
Expanding the boundaries of the Eastern Kalahari Karoo Transboundary Aquifer (EKK-TBA) shared between Botswana and Zambia: A governance challenge	Kevin C	Pietersen	Karoo, Botswana, Zambia	2021	transboundary, joint management
Abstract The EKK-TBA is significant in anchoring Gross Domestic Product growth and development in both countries is heavily reliant on groundwater. Recently a transboundary diagnostic analysis (TDA) and a strategic action plan (SAP) for the EKK-TBA was completed. The analysis resulted in a three-fold expansion of the EKK-TBA boundary. The new EKK-TBA boundary overlaps part of the Okavango and Zambezi River Basins and now also includes major wellfields in Botswana and Zimbabwe (Nyamandlovu and Epping Forest) as well as the Makgadikgadi Pans which act as the surface water and groundwater discharge zone. An analysis of institutional arrangements was carried out to enhance effective and efficient management of the EKK-TBA. Noting the complexity of the EKK-TBA. the initial institutional response could potentially be the development of a bilateral agreement between Botswana and Zimbabwe for cooperation and coordination to support the management of the TBA. This agreement would seek to establish a Joint Permanent Technical Committee (JPTC) that would also co-opt in members from the two shared watercourse commissions. Such a JPTC would enable improved coordination across the varying transboundary dimensions and would align with the precepts of the Revised Protocol on Shared Watercourses. This would include such principles including sustainable utilization, equitable and reasonable utilisation and participation, prevention, and co-operation, as well as aspects of data and information exchange and prior notification.
The Application of Machine Learning for Groundwater Level Prediction in the Steenkoppies Compartment of the Gauteng and North West Dolomite Aquifer, South Africa	Kirsty	Gibson	Gauteng, North West	2021	Steenkoppies Compartment, agriculture, NNAR, groundwater level, predictions
Abstract Groundwater in the Steenkoppies compartment of the Gauteng and North West dolomite aquifer is extensively used for agricultural practices that can potentially lead to groundwater storage depletion, threatening groundwater sustainability in the compartment. Groundwater levels represent the response of an aquifer to changes in storage, recharge, discharge, and hydrological stresses. Therefore, groundwater levels are useful for identifying limits and unacceptable impacts on an aquifer and using this information to implement sustainable groundwater management decisions. The use of machine learning techniques for groundwater modelling is relatively novel in South Africa. Conventionally, numerical techniques are used for groundwater modelling. Unlike traditional numerical models, machine learning models are data-driven and learn the behaviour of the aquifer system from measured values without needing an understanding of the internal structure and physical processes of an aquifer. In this study, Neural Network Autoregression (NNAR) was applied to obtain groundwater level predictions in the Steenkoppies compartment of the Gauteng and North West Dolomite Aquifer in South Africa. Multiple variables (rainfall, temperature, groundwater usage and spring discharge) were chosen as input parameters to facilitate groundwater level predictions. The importance of each of these inputs to aid the prediction of groundwater levels was assessed using the mutual information index (MI). The NNAR model was further used to predict groundwater levels under scenarios of change (increase or decrease in recharge and abstraction). The results showed that the NNAR could predict groundwater levels in 18 boreholes across the Steenkoppies aquifer and make predictions for scenarios of change. Overall, the NNAR performed well in predicting and simulating groundwater levels in the Steenkoppies aquifer. The transferability of the NNAR to model groundwater levels in different aquifer systems or groundwater levels at different temporal resolutions requires further investigation to confirm the robustness of the NNAR to predict groundwater levels.
Optimized Groundwater Monitoring Design for Managed Aquifer Recharge Using Hybrid Numerical, Geophysical and Chemical modelling approach	Clinton W	Andries	West Coast, Western Cape	2021	MAR, AHP, Monitoring network design
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.
Analysis of groundwater sampling methods used within uranium-rich fractured rock aquifers of the Beaufort West region	James	Berkland	Beaufort West	2021	Poster, Monitoring, sampling, protocol, fractured rock
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.
An innovative approach to dealing with elevated iron concentrations at the Knysna Hospital	Roger	Parsons	Knysna	2021	Iron treatment, TMG, pumping rates
Abstract In response to the drought which started in 2017, the Western Cape Government set about securing water supplies to key facilities across the province, including the Knysna Hospital. Drilling and testing of two boreholes at the facility indicated it to be viable to establish a groundwater supply of 66 KL/d from the underlying Table Mountain Group Aquifer. Iron concentrations were low and the initial water chemistry analyses pointed to concentrations below the SANS 241 aesthetic limit. However, further to the implementation and operationalization of the groundwater supply schemes, significantly elevated iron concentrations of up to 6 mg/L were observed. This contributed to the difficulty in getting the Knysna Hospital’s alternative water supply operational. Best practice requires that as little oxygen as possible gets introduced into the groundwater system; and this can be achieved by pumping the borehole continuously at the lowest rate possible. It is not always possible to do this under operational conditions when the water demand varies. To counter the iron problem in the potable water and to prevent or retard an increase in the iron concentration in the abstracted groundwater, iron treatment was added to the treatment train and a dual pumping regime was adopted. Using the variable speed drives that had been installed with the pumps, two pumping rates were adopted – with the rate controlled by the level in the treated water storage tank. When the tank level is low, the borehole is pumped at a rate of 0.9 L/s. However, when the level fills to 70%, the pumping rate is reduced to 0.35 L/s and continues pumping even if the tank is full. The modified system was brought into operation in August 2019 and has continued to meet the water demand of the hospital.
Prefeasibility Study for Managed Aquifer Recharge within the Greater Kruger National Park, Limpopo Province, South Africa.	Michael	Holloway	Limpopo, KNP	2021	MAR, Doleritic Dyke Swarms, Prefeasability Study
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.
The fate and occurrence of pharmaceuticals in Cape Town’s water network	Mikyle	Cloete	Cape Town	2021	Poster, CECs, micropollutants, pathways, contamination, pharmaceuticals
Abstract Israel, S Thousands of pharmaceuticals, pesticides and microplastics are consumed and disposed of directly or indirectly into various waterbodies globally. They are collectively termed “contaminants of emerging concern” or CECs. Contaminants of emerging concerns are defined as micropollutants that are present in the environment that are not regulated and that can pose a risk to the health of both humans and wildlife. The spread of these CEC’s in water systems is not isolated to a specific place and is on the rise all over the world. This study aims to investigate the spatial and temporal distribution pattern of pharmaceuticals in Cape Town’s water network, in order to assess the occurrence, concentration levels and distribution of pharmaceuticals in various water bodies. The study focuses on the occurrence of eight pharmaceuticals which are most frequently used and occurs in various water bodies around the world, namely acetaminophen, diclofenac, carbamazepine, naproxen, rifampicin, tenofovir, progesterone, sulfamethoxazole. The research sites include six waste water treatment plants in Cape Town with receiving rivers and borehole sites nearby and downstream from the waste water treatment works. Liquid chromatography combined with mass spectrometry is the selected method used to analyse the analytes of interest in the collected samples. Preliminary results obtained during the summer period (January 2021) showed that pharmaceuticals had indeed spread from waste water treatment plants into receiving water bodies with concentrations ranging from 0.8 to ≤ 6400 ng/L in both surface and groundwater due to the inefficient removal of these compounds. Continued research will conclusively address the concentration levels as a function of time, and consider the spatial distribution and its seasonality. It can be concluded from the preliminary results, that pathways of contamination from waste water discharge points to surface water and groundwater do indeed exist for the 8 pharmaceuticals considered.
"But is it 'pollution'?" - determining appropriate site-specific regulatory limit values for groundwater quality.	Carin	Bosman	National	2021	Groundwater Quality, WSA 108 of 1997, SANS, law, policy, Methodology
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.
What is in a - groundwater - map?	Nicolette	Vermaak	South Africa various	2021	Mapping methodologies
Abstract A map is a symbolic or diagrammatic representation of an area of land or sea, showing physical features and the relationship between these elements. It often reduces a three-dimensional world to two dimensions. Maps are generally static – fixed to paper or some other medium. Maps are produced for different reasons, leading to different types of maps, e.g., roadmaps, topo-cadastral maps and the groundwater maps – with the latter the topic of this article. There is a lot of work going into maps. This includes collecting all the data, doing evaluation and analysis of the data and selecting the data to use on the map. It is not possible to present all the information on a map and maps are often a generalisation. Different kinds of groundwater maps include availability, quality, vulnerability and protection. The selection of symbols to represent the information and the rendering of the maps are important in producing understandable, useful maps, but need explanations. The success in representing the information on a map will determine the usefulness of a map, but it is still often misused. At the end of this long and tedious process where conflict management skills were well developed, you may find that the information on the map is outdated before the ink on the map is dried properly. The production of maps should be an iterative process, where new data can be incorporated as soon as it becomes available. It is an expensive process and cannot be repeated too often. This article will look at the processes that helped to shape the current series of hydrogeology maps of South Africa, and how to use it optimally while mindful of limitations. It will also briefly touch on recent research that aims to help with the production of improved groundwater maps for South Africa.
Evaluating changes in groundwater storage during the 2015-2018 drought in the Western Cape using GRACE data	Ritshidze	Nenweli	Western Cape	2021	Poster, Drought, GRACE, Groundwater storage
Abstract The frequency, intensity, and duration of droughts are increasing globally, putting severe pressure on water supply systems worldwide. The Western Cape Province suffered from a period of severe water shortages that began around January 2015 and lasted until about July 2018. During this recent drought, there was a forced reduction in water use, predominantly from the agricultural sector. Citizens also reduced water use and increasingly tapped into groundwater for their needs irrespective of whether the hydrogeology was considered favourable or not. Unmonitored and unregulated abstraction of groundwater, especially under unstable climatic conditions, poses a significant risk to the future water security of the Western Cape. We hypothesize that groundwater enabled the municipalities, residents, and industries of the Western Cape to survive the recent drought. Our aim is to evaluate the change in groundwater storage during the 2015 to 2018 drought and its subsequent recovery. To achieve this, we must gain a comprehensive understanding of the dynamics of separate components of the water cycle, as well as the overall water balance. While there is data on surface water use during the drought, the impact on groundwater resources has yet to be evaluated. However, the accurate assessment of groundwater use is difficult, especially in data-scarce regions, such as South Africa. In our study, we combine remote sensing from NASA’s Gravity Recovery and Climate Experiment (GRACE), the Global Land Data Assimilation Systems, groundwater level measurements from the National Groundwater Archive, and ancillary datasets from the City of Cape Town’s weekly water dashboard to assess the total change in groundwater storage in the Cape Town Metropolitan area and surrounding cities over an 8-year period, from 2012 to 2020. Preliminary results from GRACE data analysis show a steady decline in aquifer saturated thickness over the drought, indicative of an increase in groundwater use.
Assuring supply during a changing environment focussing on drought	Danita	Hohne	National	2021	Drought, community supply, operating rules
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.
Measuring Hydraulic Conductivity Across Different Scales Using Varying Methods To Develop A Hydraulic Conductivity Model	Sispho	Dlakiya	Cape Town	2021	Poster, hudraulic conductivity, methods, scales, infiltrometer, vertical infiltration
Abstract This paper describes the calibration and testing processes of three methods of measuring hydraulic conductivity (slug test, mini disk infiltrometer and particle size distribution (sieves)) across varying scales (field and lab). The methods used in the field are the slug test and sieves which were used in four different wells of the Rietvlei wetland in Cape town and the mini disk infiltrometer was used in a grid developed in one of the Nelson Mandela University Reserve salt pans. The mini disk infiltrometer and the slug test are used to determine the saturated hydraulic conductivity (Ks) of altered or unaltered soil samples under controlled conditions in a laboratory, and that is a key parameter to understand the movement of water through a porous medium. The mini disk infiltrometer requires a small volume of water and has a compact size which makes it convenient for laboratory soil specimens, especially when studying vertical infiltration. Infiltration shows a dependence on the compaction and saturation of soil while hydraulic conductivity increases with depth in a simulated aquifer.
Transport and attenuation of microplastics in saturated sands	Sabastian	Stenzl		2021	Microplastics
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.
Latest approaches and examples illustrating the key role of numerical modelling in sustainable groundwater use in South Africa	Annalisa Sagra	Vicente	South Africa various	2021	numerical modelling, recharge
Abstract Imrie, S. Groundwater in South Africa has great potential to supplement our country’s water demands. Currently, studies show that less than 10% by volume of the Average Groundwater Exploitation Potential is abstracted on an annual basis. The 2017 drought has aided in creating awareness of the importance of this resource towards building water resilience. If managed correctly, groundwater is commonly viewed as a sustainable source. Oftentimes, the ‘sustainability’ of a groundwater resource is an ‘open-ended’ definition based on the hydrogeologist’s interpretation of aquifer pumping test data alone. This approach often discounts the cumulative impact of environmental factors (including drought and climate change) and other users on groundwater. The use of numerical groundwater models to support and inform the conceptual models provides the mechanism to bridge this gap. This paper discusses various approaches and examples of where numerical modelling plays a key role in supporting groundwater usage in a sustainable and informed manner. In particular, this includes: •Inclusion of impact from other anthropogenic activities and groundwater users, with model scenarios that show the potential impact of each on the other, as well as the combined result to groundwater (levels and water quality) •Consideration of extreme climatic events (e.g. 1 in 100-year drought and/or flood), including the use of uncertainty analysis and consideration of dynamic groundwater management, such as the possible varying of sustainable pumping rates to suit the prevailing conditions •Identification of groundwater receptors and appropriate assessment of potential impacts to those receptors from groundwater usage, including “target-audience” thinking in the post-processing and reporting of numerical model results, so as to convey clear messages to the interested and effected parties and stakeholders •Use of multiple methods and technologies to calculate and model surface water / groundwater interaction and recharge, including uncertainty analysis, and intelligent challenging of traditional methods of estimating groundwater recharge
HALF FULL OR HALF EMPTY ? Groundwater surface water interactions – An ever-increasing focus for water resource management.	Sonia	Veltman	South Africa various	2021	Gw-Sw interaction, wellfield testing, resource management, numerical model
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
Hydrocarbon groundwater analyses: a Karoo case study	Danita	Hohne	Karoo	2021	Hydrocarbon, Water level, contamination, Artisan borehole, Methane concentration, Natural gas, Dolrites, quality, Fracturing
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.
Managed aquifer recharge - evaluating the efficiency of the unsaturated zone to reduce contaminants. A case study of Atlantis aquifer	Londiwe	Ntshangase	Atlantis	2021	MAR, contaminants removal, unsaturated zone, prevention strategies
Abstract Surface water resources are under threat of depletion and quality deterioration due to various factors such as climate change, urbanization, and population expansion. Managed aquifer recharge (MAR) is a technique that has been successfully implemented over the last 4 decades to sustain the balance between water demand and availability. The unsaturated zone, where source water is introduced during infiltration, plays a major role in the reduction of contaminants present in water before it naturally percolates and reaches the aquifer. This research aims to evaluate the removal efficiency of contaminants by the unsaturated zone. Three objectives to be accomplished are; to determine and classify the chemical composition of the source water. Secondly, to determine the hydraulic properties of the soil in the area of interest. Lastly to evaluate the contaminants removal efficiency, by tracing the quality of water at the point of recharge and discharge. The Atlantis water resource management scheme in the Western Cape will be used as a case study, in order to assess the relationship between the unsaturated zone and the reduction of contaminants. The current study argues that during the artificial recharge of aquifers, contaminants present in the source water filter through the unsaturated zone, where natural processes, as well as resident microbes, reduce their concentrations to acceptable levels. Assessing the ability of the unsaturated zone to reduce contaminants, will allow for the early warnings of contamination potential and the execution of informed prevention strategies that can be used in decision making of the management and protection of water resources. Additionally, the advanced understanding of the role that the unsaturated zone plays in eliminating contaminants can be used to account for satisfactory groundwater quality in areas where groundwater is not constantly monitored and artificial remedies are not applied.
Test pumping derivative analysis to improve conceptual understanding in a complex aquifer: Steenbras Wellfield.	Kevin	De Bruin	Steenbras Wellfield, Cape Town	2021	flow regime analysis, flow models, test-pumping, drawdown derivative curve, hydraulic conductivity, Derivative data
Abstract Test-pumping drawdown curves are not always sufficiently indicative of aquifer characteristics and geometry. In fact, drawdown curves should never be analysed and interpreted alone. The derivative analysis (Bourdet et al., 1983) and flow dimension theory (Barker, 1988) make it possible to infer the regional geometries and flow characteristics of fractured aquifers which are otherwise often unknown or inconclusive when interpreting point-source borehole logs. The propagation of the drawdown and/or pressure front through the aquifer reaches distal hydrogeological objects which influence the flow regime and imprints signatures in the drawdown derivative curves. The conjunctive interpretation of these flow regime sequences and geological data results in a robust, well-informed conceptual model which is vital for resource management. A methodology similar to that of A. Ferroud, S. Rafini and R. Chesnaux (2018) was applied to the test-pumping data of 14 confined and unconfined Nardouw Aquifer boreholes in the Steenbras area, Cape Town, which has been under exploratory investigation since the early 2000’s. The Steenbras wellfield was developed following the major 2017-2018 Western Cape drought. The NE-SW trending open folds and dextral strike-slip Steenbras-Brandvlei Megafault Zone (with crosscutting faults and dykes) make the aquifer hydrogeologically complex. It is due to these complexities that the sequential flow regime analysis was undertaken to enhance the current conceptual understanding. The analyses reveal domains of flow models which include open vertical fracture, T-shaped channel, double(triple) porosity model, and leaky/recharge boundary amongst others. Poor data quality and noise issues are also highlighted. The outcomes of the sequential flow regime analysis allow for identification of applicable flow models for type curve fitting to avoid erroneous aquifer parameter estimations; improvement of the hydrogeological understanding of the aquifer; enhancements of the current conceptual model in order to inform on subsequent numerical modelling, groundwater resource management and ecological protection.