Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 201 - 250 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year	Keywords
Micro pore-pressure sensor (MEMs) and analysis technologies – towards a future of multi-scale groundwater monitoring	W	Timms	Australia	2023	multi-scale, pore pressure, sensors, analysis
Abstract Micro-electro-mechanical system (MEMs) technologies coupled with Python data analysis can provide in-situ, multiple-point monitoring of pore pressure at discrete and local scales for engineering projects. MEMs sensors are tiny, robust, inexpensive, and can provide wireless sensing measurements in many electrical and geomechanical engineering applications. We demonstrate the development of MEMs pressure sensors for pore pressure monitoring in open boreholes and grouted in piezometers. MEMs sensors with a 60 m hydraulic head range and centimetre vertical resolution were subject to stability and drawdown tests in open boreholes and in various sand and grouts (permeability 10-8 to 10-2 m/s). The resulting accuracy and precision of the MEMs sensors, with optimal calibration models, were similar to conventional pore pressure sensors. We also demonstrate a framework for estimating in-situ hydrogeological properties for analysis from vented pore pressure sensors. This framework method included Python code analysis of hourly pore pressure data at the millimetre vertical resolution, which was combined with barometric data and modelled earth tides for each borehole. Results for pore pressure analysis in confined boreholes (>50 m depth) included specific storage, horizontal hydraulic conductivity and geomechanical properties. Future improvements in the vertical resolution of MEMs pore pressure sensors and combined these two technologies will enable groundwater monitoring at multiple scales. This could include the deployment of numerous MEMs, at sub-meter discrete scale in boreholes and evaluating local site scale variations in pore pressure responses to recharge, groundwater pumping and excavations in complex sub-surface geological conditions.
The impact of storage and hydrogeological conditions on the design and recovery performance of small-scale urban ASR systems	Niels	Hartog	The Netherlands	2023	Urban Groundwater, Managed aquifer recharge, Aquifer Storage and Recovery, MAR, ASR
Abstract Aquifer storage and recovery (ASR) can play a vital role in sustaining water availability to cope with increasing weather extremes. In urban areas, ASR systems may provide flooding risk mitigation and support urban greenery. However, such systems are often relatively small and therefore, their recovery performance depends more strongly on site-specific storage conditions such as dispersion and displacement by ambient groundwater flow. In this study, we evaluated the impact of these factors by adapting and developing analytical solutions and numerical modelling, with recently established Urban ASR systems as a reference for a wide range of realistic field conditions. We validated the accuracy and usefulness of the analytical solutions for performance anticipation. Results showed that a simple, analytically derived formula describing dispersion losses solely based on the dispersion coefficient (α) and the hydraulic radius of the injected volume (Rh) provided a very good match for all conditions tested where α/Rh<0.2. An expansion of the formula to include the development of recovery efficiency with subsequent cycles (i) was also derived and in keeping with simulation results. Also, displacement losses were found to be significant at groundwater flow velocities that are typically considered negligible, particularly as displacement and dispersion losses disproportionally enforced each other. For specific conditions where the displacement losses are dominant, using a downgradient abstraction well, effectively resulting in an ASTR system, might be beneficial to increase recovery efficiencies despite increased construction costs and design uncertainty.
Highly productive geophysical mapping of groundwater systems in water-scare countries	D	Grombache	Africa	2023	Geophysics, Groundwater, Hydrogeology, transient electromagnetics
Abstract Groundwater is a hidden resource, so as part of making it more visible, geophysical methods can be very useful in inferring the delineation of aquifers and/or more productive zones to target in fractured rock environments. The most commonly used techniques to assist groundwater studies or exploration are still resistivity profiles or sections known as ERT or electrical resistivity tomography and vertical electrical soundings or VES. One of the limiting factors with this technique is the scale of what surveys can be conducted, resulting in, at best, some kilometers per day. The Hydrogeophysics group of Aarhus University have developed the towed transient electromagnetic (tTEM) system as a cost-efficient tool for characterizing regional hydrological systems to depths of up to 70 m as an alternative to these more traditional methods - which is highly productive in that collection of 40- to-80-line kilometers of data per day is feasible. The system is based on the transient electromagnetic (TEM) method, which involves using a transmitter and receiver coil to measure the electrical resistivity of the subsurface. The hydrological value in electrical resistivity images stems from the ability to delineate different hydrogeological units based on their contrasting electrical properties. Consequently, 3D electrical resistivity images can infer the subsurface hydrogeology and enhance the success of installing productive boreholes. This work presents case studies from several African countries (e.g., South Africa, Zimbabwe, Ethiopia, Senegal, and Togo). It demonstrates how the tTEM method can identify reliable drinking water sources in these countries.
Pock Marks as a Nature-based solution for enhancing water availability in African marginal drylands?	D	Kibirige	South Africa	2023	Pockmarks, Groundwater, nature-based solutions
Abstract Nearly 1.9 billion people live in marginal environments, including drylands, semiarid, arid, and hyperarid environments. Obscure but ubiquitous circular pockmark depressions dot these lands. These circular depressions can range from a few meters to kilometers, and the depth of these depressions varies from a few centimeters to over 10 m. However, the genesis of the circles has been investigated among scientists for many years because of their obscure nature. Some researchers believe that termites cause fairy circles, while others believe they are caused by plants competing for water and nutrients. This study documented the Africa-wide prevalence and extent of the pockmarks for the first time, and it further classified the pockmarks according to their genesis and hydrological roles. We further investigated their relevance in serving as nature-based solutions to overcome water scarcity in dryland regions. So far, field evidence in Ethiopia and Somalia showed that these features potentially have water security significance in a) organizing surface water flows over arid/semi-arid landscapes, b) serving as the site of temporary surface water storage, and c) serving as the site of focused groundwater recharge into the underlying aquifers. This presentation will highlight the spatial prevalence, extent, and genesis model of the pockmarks across the drylands in Africa (South Africa, Namibia, Somalia, Ethiopia, Kenya, Chad, Senegal, Mali, Niger, etc.).
Quantification of river-aquifer interactions using multiple measuring methods for improved water abstraction in the Lower Vaal River catchment, South Africa	Lucky	Baloyi	South Africa	2023	baseflow, discharge areas, Hydrochemistry, multi-methods approach, stable isotopes
Abstract Previous studies have shown that river-aquifer connectivity exists. However, an integrated approach that consists of multiple measuring methods to quantify and characterise such connectivity still needs improved scientific understanding due to the underlying principles and assumptions of such methods, mainly when such methods are applied in a semi-arid environment. Three techniques (hydrogeochemistry, stable water isotopes, and baseflow separations) were applied to quantify and characterize river-aquifer interactions. The study’s objective was to improve knowledge and understanding of the implications of the results from the three methods. Field measurement, laboratory assessment, and record review were used to collect primary and secondary data. Results showed that Na- HCO3 water type dominated the upper stream, discharging onto the surface and forming stream sources. Na-HCO3 water type was an outlier when the area’s geology and land use activities were assessed. The isotope results showed that the studied aquifer had 9% recently recharged water. Being the upstream, the freshwater in such a mountainous aquifer was expected. The baseflow index (BFI) results showed that the dependency of the total river flow to aquifer discharge contributed 7.24 % in the upper stream, 7.31% in the middle stream, and 7.32% in the lower stream. These findings provided empirical evidence that hydrochemistry, stable isotopes, and baseflow separation methods provide key insights into aquifer-stream connectivity. Such findings inform choosing appropriate and relevant measures for protecting, monitoring, and allocating water resources in the catchments.
Tracing mine water flows in a dolomite quarry, South Africa, using hydrochemistry and stable isotopes	Roger	Diamond	Mooiplaas Dolomite Quarry, Pretoria	2023	dewatering, Hydrochemistry, karst, mining, stable isotopes
Abstract Water resources, including groundwater, are under threat globally from abstraction and pollution, making studies of water flows ever more urgent. South Africa has a growing population, a relatively dry climate and abundant mining activity, all of which increase the importance of water management. Mooiplaas Dolomite Quarry, southeast of Pretoria, has been mining metallurgical grade dolomite since 1969 and is located in the productive karst aquifers of the Malmani Subgroup, Transvaal Supergroup. The site was investigated by sampling precipitation, surface water, groundwater and mine water for hydrochemical and stable isotope analysis from 2011 to 2017, totalling over 400 samples. Nitrate levels in groundwater and mine water were marginally above drinking water limits from explosives residues, and ammonia in the nearby Hennops River was unacceptably high due to municipal sewage outfalls, but otherwise, water quality was very good. Alkalinity from rock weathering, aided by the crushing of dolomite, was the main control on water chemistry. Combined analysis of dissolved matter (TDS, nitrate, Mg, etc.) suggested that the dewatering of the mine and resultant recharge from slime dams caused an aerated zone of groundwater, which mixed with regional groundwater flowing beneath the site. Stable isotopes, with an evaporated signature from mine open water bodies, also showed how mine operations cause recharge to groundwater and subsequent seepage back into the pit lakes. The mine appears not to contaminate the regional groundwater. However, mine designs should avoid situations where process water flows via groundwater back into pits, causing excessive dewatering costs.
Evaluation of the conditions that impact the spreading, impact and groundwater monitoring for the risk of brine leakage from wells into fresh groundwater aquifers	Niels	Hartog	The Netherlands	2023	Groundwater Contamination, brines, density-driven flow, groundwater monitoring, leakage risk
Abstract Contamination of fresh groundwater aquifers by leakage of saline water (brine) from wells may result from various activities, such as salt mining, wastewater or concentrate injection and geothermal heat production. Here, the brine transport and consequences for groundwater monitoring have been explored for a wide range of brine compositions, leakage and hydrogeological conditions using numerical simulations that considered buoyancy impacts from both temperature and density differences. Results show that at close distances to the leak (up to 3-5 meters away), breakthroughs of the salt ( at 1,000 mg/L) occurred within one month of leakage in all modelled scenarios. At a radial distance of 10 meters, with a leak rate of 2 m3 /d, it took three to six months in most cases. For the leakage of relatively warm brines, the heat transport is separated from the salinity due to thermal retardation resulting in monitoring the breakthrough of heat more closely to the depth of the leakage point than the salinity breakthrough. In summary, this study indicates that the mode of dispersion of leaking geothermal brine strongly depends on the brine properties and the leakage and hydrogeological conditions. At the same time, vertical monitoring of temperature and conductivity at a limited distance from brine injection wells (<5m) appears to be a robust method for detecting a possible leak relatively quickly (within a month) and after limited contamination. The monitoring signal in the event of leakage is also sufficiently distinctive to prevent false positives.
Variable-scale conceptual framework for shallow groundwater systems in the low-relief, water-limited Canadian Boreal Plains	K	Hokanson	Canada	2023	Groundwater-surface water interactions, long-term study, recharge, spatiotemporal scales, subsurface connectivity
Abstract Case studies illustrate a conceptual framework for shallow groundwater flow systems’ temporal and spatial variability with groundwater-surface water interactions in the Boreal Plains of Canada. The framework was developed using a twenty-year hydrometric dataset (e.g., climatological and streamflow data, hydraulic heads, vertical hydraulic head gradients, geochemical and isotopic signatures). The region is characterized by low-relief glacial landscapes, with a mosaic of forestlands and peatlands, and a subhumid climate, resulting in spatially heterogeneous storage and transmission properties, variable recharge and evapotranspiration potentials, and highly complex patterns of water movement. Two primary spatiotemporal scales were examined to create a holistic, variable-scale conceptual model of groundwater movement: the large scale (e.g., glacial landforms, regional topography, decadal climate cycles) and the small scale (e.g., individual landcover, local hummocks, annual moisture deficits). Water table behaviour, evapotranspiration rates, and runoff were controlled by a hierarchy of interactions between hydrological processes occurring at different spatiotemporal scales; however, the specific order of controls depends on the hydrogeological setting. The case studies, supported by empirical and numerical modelling, demonstrate that smaller-scale heterogeneities in geology and recharge can dominate over topographic controls, particularly in areas with high conductivity or hummocky terrain, where the climate, geology, and topographic relief are similar. Many hydrogeological studies rely on surface topography as a first‐order control; however, with field observations and modelling, this conceptual framework demonstrates the need to consider the potential dominance of subsurface characteristics and processes, plus climate, especially in landscapes with low recharge and low relief.
A stochastic data integration approach to generate geologically consistent hydrogeological models from geophysical and hydrogeological data	A	Neven	Switzerland	2023	Hydrogeophysics; Inversion; Data-Integration; Groundwater
Abstract This study presents a novel approach for developing geologically and hydrogeologically consistent groundwater models at large valley scales. Integrating geological, geophysical, and hydrogeological data into a single model is often challenging, but our methodology overcomes this challenge by combining the Ensemble Smoother with Multiple Data Assimilation algorithm (ESMDA) with a hierarchical geological modelling approach (ArchPy). The ESMDA framework assimilates geophysical and hydrogeological field data jointly. To diminish the computational cost, the forward geophysical and groundwater responses are computed in lower-dimensional spaces relevant to each physical problem, alleviating the computational burden and accelerating the inversion process. Combining multiple data sources and regional conceptual geological knowledge in a stochastic framework makes the resulting model accurate and incorporates robust uncertainty estimation. We demonstrate the applicability of our approach using actual data from the upper Aare Valley in Switzerland. Our results show that integrating different data types, each sensitive to different spatial dimensions enhances the global quality of the model within a reasonable computing time. This automatic generation of groundwater models with a robust uncertainty estimation has potential applications in a wide variety of hydrogeological issues. Our methodology provides a framework for efficiently integrating multiple data sources in geologically consistent models, facilitating the development of hydrogeological models that can inform sustainable water resource management.
A methodology for uncertainty quantification of dewatering volumes under the context of open-cast mining	C	Rivera Villarreyes		2023	FEFLOW, Groundwater Modelling, mining, PEST, PESTPP
Abstract Groundwater modelling at the mine sites involves assumptions from the geological model, mining stages, parametrization, and fractures, among others. Modelling work mainly focuses on calibrating against historical measurements before operations (pre-mining) or afterwards (transient calibration). Calibration is carried out mainly with gradient-based algorithms. However, the majorlimitation is the number of model runs, since the number of parameters can easily reach hundreds or more. PEST has become the common tool for parameter estimation. The Jacobin calculation required for the Levenberg Marquardt algorithm requires several model runs. This, a limited factor for the calibration and, subsequently, uncertainty quantification. The next generation of PEST, named PESTPP, is gained popularity in the groundwater community. The great advantage of PESTPP,, compared to the classical PEST, is its new module, Iterative Ensemble Smoother (IES). PESTPP-IES covers both parameter estimation and uncertainty quantification in one goal. Its empirical formulation of the Jacobian matrix reduces the number of runs; thus, the numerical bottleneck can be significantly reduced. PESTPP-IES has been extensively tested in an open-pit mine at the geological complex conditions in the Peruvian Andes. The work involves the task of model simplification, e.g., from a regional model to a detailed local pit model, calibration and uncertainty quantification of pit dewatering volumes. Detailed model was kept calibrated based on hydraulic-head measurements, and dewatering volumes were predicted. All these consider transient changes in the mining plan within the same FEFLOW model. Results validate the methodology and practicability in mining applications.
Evaluation of the impact of artificial recharge of groundwater by river replenishment in the North China Plain using a numerical model	Qichen	Hao	China	2023	artificial recharge, groundwater management, river water replenishment, the North China Plain
Abstract Since 2018, the North China Plain has started a large-scale ecological water replenishment project for rivers and lakes, with 17.5 billion cubic meters total from the South–North Water Transfer Project and other water sources. It is a key question of how much water infiltration into aquifers will affect groundwater and how to characterize and evaluate this effect quantitatively. The groundwater numerical model of the Beijing-Tianjin- Hebei region as the main part of the North China Plain was established using a numerical simulation method, and the groundwater level variation under the replenishment condition was simulated and predicted. By comparing the two scenarios, the relative rise method of groundwater level was proposed to characterize the influence of river water infiltration on groundwater level, and the unstructured grid method was used to refine cells near the river to improve simulation accuracy. Simulation results show that the groundwater level around some rivers has risen significantly in the past four years, especially in the alluvial fan regions with better infiltration properties. Accordingly, at the Piedmont alluvial fan region, there is also a large influence range on groundwater level. The maximum influence distance is more than 10km (0.1m relative rise of groundwater level was taken as the influential boundary). According to the prediction, if the water replenishment project continues, the range of influence can continue to expand, but the expansion rate will slow down due to the reduction of the hydraulic gradient.
Electromagnetic measurements in the Netherlands using an All Terrain Vehicle to rapidly characterize groundwater salinity and clay distribution in 3D	Jan	Gunnink	Netherlands	2023	3d-mapping, clay distribution, groundwater salinity
Abstract Electromagnetic (EM) techniques were used to map groundwater salinity and clay layers in the Netherlands. The EM method used the so-called time domain system, is towed behind an ATV and is therefore called towed TEM. The results revealed a detailed 3-dimensional insight into the subsurface’s sequence of clay and sandy layers. Also, shallow saline groundwater, far from the coast, has been detected related to a subsurface salt dome. The rapid, non-destructive data acquisition makes the tTEM a unique tool. Electromagnetic (EM) techniques detect electrical conductivity contrasts in the subsurface with depth. EM data can often be interpolated into a 3D model of electrical conductivity. Expert knowledge of the regional geohydrologist, together with existing (borehole) data, is paramount for the interpretation. The towed Transient Electro-Magnetic system (tTEM) is developed to acquire data up to 60-80m depth by driving a transmitter and a receiver behind an ATV. With a speed of 10-15 km/h, measurements are collected every 5m. On fields, the distance between lines is typically 20m, resulting in a dense network of data that is inverted into 1D resistivity models, showing the variation of conductivity with depth. Interpolating 1D resistivity models into a 3D model allows for further interpretation in terms of geology, lithology, and groundwater quality. The tTEM technique bridges the gap between point measurements and more expensive and lower-resolution airborne EM data collection. The technique is sensitive to disturbance by man-made conducting infrastructure.
Understanding the pattern of spatial and temporal variations of groundwater levels using long-term monitoring data	P	Fuku	South Africa	2023	Groundwater decline, Hydrological stresses, long-term monitoring data
Abstract Monitoring regional groundwater levels provides crucial information for quantifying groundwater depletion and assessing environmental impacts. Temporal variation of groundwater levels is the response of the groundwater system to natural and artificial stresses in terms of groundwater recharge and discharge. The complexity and extent of the variation rest on the nature and storage properties of the aquifer system. High groundwater levels are usually found in the recharge zones and low in the discharge zones, resulting in groundwater flow from recharge areas to discharge areas. Continuous decline of groundwater levels has been observed in some of the monitoring boreholes within the National Monitoring Network. Groundwater level decline has been caused either by over-exploitation or reduction of groundwater recharge. Generally, the pattern of spatial and temporal variations of groundwater levels is the consequence of incorporating climatic, hydrological, geological, ecological, topographical, and anthropogenic factors. Therefore, understanding the pattern of spatial and temporal variations in groundwater levels requires a combined approach. A combination approach of National long-term groundwater level monitoring data, Hydrological stresses, Anthropogenic interferences, and characteristics of the groundwater system was used to understand the continuous decline of groundwater levels in selected monitoring stations across the country.
Assessment of catchment scale groundwater-surface water interaction in a non-perennial river system, Heuningnes catchment, South Africa	Vincent	Banda	Bellville. Cape Town, South Africa	2023	Aquifer-river interaction, Environmental stable isotope, Geological fault, Hydrochemistry, South Africa
Abstract This study assessed aquifer-river interaction using a combination of geological, hydrological, environmental stable isotope, and hydrochemical data in a non-perennial river system in the Heuningnes catchment. Results showed the depth to groundwater levels ranging from 3 to 10 m below ground level and aquifer transmissivity values of 0.17 to 1.74 m2 /day. The analytical data indicated that Na-Cl-type water dominates most groundwater and river water samples. Environmental stable isotope data of river samples in upstream areas showed depleted δ18O (-4.3 to -5.12 ‰) and δ2H (-22.9 to -19.3 ‰) signatures similar to the groundwater data, indicating a continuous influx of groundwater into the river water. Conversely, high evaporative enrichment of δ18O (1.13 to 7.08 ‰) and δ2H (38.8 to 7.5 ‰) were evident in downstream river samples. It is evident from the local geological structures that the fault in the northeastern part of the study area passing Boskloof most likely acts as a conduit to groundwater flow in the NE-SW direction, thereby supplying water to upstream river flow. In contrast, the Bredasdorpberge fault likely impedes groundwater flow, resulting in hydraulic discontinuity between upstream and downstream areas. Relatively low conductive formation coupled with an average hydraulic gradient of 8.4 × 10−4 suggests a slow flow rate, resulting in less flushing and high groundwater salinisation in downstream areas. The results underscore the significance of using various data sets to understand groundwater-river interaction, providing a relevant water management platform for managing non-perennial river systems in water-stressed regions.
Distribution, Formation Conditions and Genesis of High-Quality Groundwater Containing Metasilicate in Zhaojue County, Southwest China	Shengzhang	Zou	Southwest China	2023	Groundwater; H2 SiO3 ; distribution; formation condition; Zhaojue County; Southwest China
Abstract The drinking water health issues have been considered due to improved living standards in recent years. Finding and developing high-quality groundwater with high-level minerals has become key to improving human health. The hydrochemical test data of 66 springs in Zhaojue County were analyzed using various methods, and the spatial distributions of H2 SiO3 -rich groundwater, hydrogeochemical characteristics, formation conditions and genesis were revealed. The main results including: 1) the groundwater with H2 SiO3 (≥25mg / L) was identified as the low salinity and alkaline water, which distributed in the six areas with the basement rocks of basalt,with a distribution area of about 79 square kilometers. The H2 SiO3 concentration was generally 25.74~46.04 mg/L; the low mineralization characterized the H2 SiO3 -rich groundwater of study area while the main hydrochemical types of groundwater are HCO3 - Ca·Mg, HCO3 -Ca, and HCO3 -Na; the Pearson correlation coefficient between the content of H2 SiO3 in groundwater and the content of pH is relatively high, indicating that the level of H2 SiO3 in groundwater in the study area is significantly affected by the pH value of the solution; the H2 SiO3 -rich groundwater was influenced by the water-rock interactions, the distribution range and solubility of silicate minerals ,the development of surrounding rock fissures, and water conservation and recharge conditions in the county, among which the water-rock interactions play a critical role. The results can provide a basis for the development of mineral water industry and the construction of urban and rural high-quality water sources in Zhaojue County.
Electrical Hydrogeology of Managed Aquifer Recharge from Meter to Kilometer Scales	Todd	Halihan	USA	2023	Byrds Mill Spring, carbonate, electrical resistivity imaging, enhanced aquifer recharge, Karst spring
Abstract While traditional well and spring sampling are limited to the integration of point data and the interpolation of the data across large scales. Electrical measurements of aquifers can be extended across a range of scales and integrated to provide an improved quantitative understanding of groundwater systems. At a site in Oklahoma, USA, a karst-managed aquifer recharge research site is being used to test electrical techniques for aquifer characterization on the kilometer scale and monitoring the aquifer on the meter scale. At the kilometer scale, the data illustrate fault locations, siphons in flow paths, and previously uncharacterized conduits. At the metre scale, the monitoring data illustrate porosity structure, flow paths, and potential biological changes in the subsurface. The results indicate that electrical approaches can significantly change aquifer conceptual models and provide targeted sampling locations in karstic bedrock aquifers.
Maximising groundwater value through innovation and technology - the power of membranes	Jean	Loock	South Africa	2023	Membrane Technology, quality, Reticulation, sustainability, Water treatment
Abstract The SADC region has vast potential to alleviate water scarcity and promote growth through the responsible development of groundwater resources. To achieve this, it is crucial to understand the resource’s value, implement sustainable abstraction programs, protect its quality, optimize its usage for regional development, and implement innovative aquifer management programs, including artificial recharge. Greenchain Group is a water treatment company that recognizes the value of water and strategically deploys its expertise to maximize the potential of each drop. As membrane technology specialists and local manufacturers of this advanced technology, we understand how to design integrated solutions to safeguard water quality and accessibility. Our wide range of filtration technologies allows us to select the technology suited to the application and regional groundwater context and to produce high-quality water from various sources, including groundwater. Additionally, by removing contaminants/unwanted constituents from groundwater, we enhance the value of each drop of water for local potable consumption, eliminate the need for overwatering in agriculture, and allow for the creation of new agriculture/industries in regions with poor groundwater quality. This same technology can also treat wastewater and remove contaminants (e.g. chemical of emerging concern, PFAS) and thus is critical to water reuse applications and responsible Managed Aquifer Recharge. Greenchain Group’s treatment systems have been used in various industries, including agriculture, mining, energy, medical, food and beverage, and remote and mobile settings.
Groundwater porosities and effective porosities: definitions, physical relevance, and scale issues	Alain	Dassargues	Belgium	2023	REV, drainage effective porosity, effective porosity, porosity, scale issue, transport effective Porosity
Abstract Porosity describes the ratio between the volume of pores, cracks, and fissures and the total volume of a studied geological medium. This notion implies a volume averaging of the medium characteristics using the concept of Representative Elementary Volume (REV). Small volumes can contain only pores, while larger volumes typically contain both pores and fissures. Porosity can be highly scale-dependent, and different porosity values can be measured for the same geological formation. Furthermore, groundwater in the pores and cracks can be partly immobile or mobile. So, the porosity actively involved in groundwater flow can be discussed. A ‘mobile water porosity’ can be defined, but this remains highly dependent on the existing pressure conditions in the geological medium. In unconfined conditions, the term ‘effective porosity’ usually corresponds to the drainage porosity corresponding to the specific yield or storage coefficient. When dealing with solute transport and remediation of contaminated sites, another ‘effective porosity’ is needed to describe the advection velocity of the contaminant. This ‘mobile water porosity’ acting in solute transport processes typically takes lower values than drainage’s ‘effective porosity’. Scale issues must also be expected, as shown by field and lab tracer tests. The term ‘Darcy velocity’ will be banished herein because it induces much confusion. For clarity, we propose to distinguish ‘drainage effective porosity’ and ‘transport effective porosity’. The physical meaning of both terms is discussed, and examples of supporting observations are presented for illustration and discussion.
Regional Scale Groundwater Monitoring Status Reporting: A mapping series within the Vanrhynsdorp aquifer system	Ashton	van Niekerk	South Africa	2023	Aquifer scale, groundwater availability, Groundwater Quality, spatial-temporal, trend analysis
Abstract A mapping series was generated using the Vanrhynsdorp aquifer system to illustrate an improved standardization groundwater monitoring status reporting, that includes a progressive conceptual site model linked with spatial and temporal groundwater monitoring network assessment on an aquifer scale. The report consists of 4 segments: Base map provides a conceptual site model of a groundwater resource unit (GRU) delineating an area of 1456 km2 representing the geology and geological structures that make up the Vanrhynsdorp aquifer system. The Groundwater Availability Map illustrated over a long-term trend analysis, the measured water levels indicate an 83% decreasing trend over an average period of 21.83 years, the water levels have declined by an average linear progression of 11.54 m (ranging 0.48-35.76 m) or 0.64 m per year, which equates to an estimated decline in storage of 218 Tm3 - 21 Mm3 within the GRU. The Groundwater EC map illustrated over the long-term analysis of an average period 24 years the average EC ranged between 57 - 791 mS/m, with certain areas tracking at a constant increasing trend beyond 1200 mS/m. The Groundwater Quality Characterization map provides EC contours and spatial Stiff diagram plots. The Stiff diagrams illustrate three aquifer water types namely, Na-Cl (Table Mountain Group Sandstones), Na-Cl with high SO4 concentration (Blouport and Aties Formation) and Na-Cl-HCO3 (Widouw Formation). These four segments of information products inform Resource Quality Objectives and the need for surveillance monitoring in conjunction with annual compliance monitoring and enforcement groundwater use audits.
Impact of Engineered Tree Plantations on Water Transfer Through the Upper Vadose Zone and Implications on Vertical Groundwater Recharge	Hendrik	Botha	National	2021	Poster, tree plantations, impact, vertical recharge, water transfer, vadose zone, water balance
Abstract The main purpose of this paper is to present a case study where soil moisture and rainfall data were evaluated for engineered tree plantations, to understand the potential impact on vertical groundwater recharge. Soil moisture for probes within the tree plantation root zones and reference sites within the same soil types were evaluated, in context to site rainfall patterns. Water transfer from shallow to deeper soil zones for a dataset of 2 years are presented. Observations in terms of water movement in the root zone are made. A water balance is presented in the effort to conceptualise the impact on water transfer through the upper vadose zone and to quantify the significance in terms of potential vertical groundwater recharge reduction.
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.
Conjunctive use of water resources	Jan	KÜrstein	Saldanaha Bay	2021	Groundwater protection; recharge, Drawdown
Abstract Surface water has traditionally been the primary resource for water supply in South Africa. While relatively easy to assess and utilise, the surface water resource is vulnerable to climatic conditions, where prolonged periods of drought can lead to an over-exploitation and eventually water shortness and supply failure. Following the drought in 2018, more focus has been given to the groundwater resource to supplement the water supply in South Africa. In the Saldanha Bay municipality the water supply is based on a combination of surface water and groundwater, with plans to supplement this with desalination and managed aquifer recharge (MAR) in the future. For an efficient and sustainable utilisation of the different water resources, a Water Supply Management System is developed that can be used to manage water mix from multiple resources. The system builds on top of a flexible WaterManager system developed for operation of complex water supply infrastructures, which in the study is extended by implementing operational rules for optimal management. The operational rules provide recommendations for the day-to-day management, but also consider seasonal and long-term utilisations. To achieve this, the rules will rely on real-time monitoring data combined with results from hydrological modelling, providing estimated system response to selected scenarios to which the water supply must be resilient. In the present study the combined Water Supply Management System is developed and tested using synthetic data, which will be presented in the paper.
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.
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.
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.
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
Testing Danish groundwater mapping methodologies in South Africa, Case Ladysmith, South Africa	Jan	KÜrstein	Ladysmith, South Africa, Denmark	2021	Mapping methodologies, 3D models
Abstract Vermaak, N; Fourie, F; Awodwa, A; Metcalf, D; Pedersen, PG; Linneberg, MS; Madsen, T The Strategic Water Sector Cooperation (SSC) between Denmark and South Africa is a long-term bilateral cooperation, which amongst others are contributing to the South African water sector by demonstrating and testing different Danish groundwater mapping methodologies in South Africa in order to add long term value to the South African work on optimizing the utilization of groundwater and to increase the resilience against drought. One key aspect is to develop a South African groundwater mapping methodology, based on the detailed Danish methodology and South African specialized knowledge of the South African hydrogeology. In this case, the SSC has contributed to the work done by Umgeni Water in The District Municipality of uThukela in the KwaZulu-Natal (KZN) province of South Africa. The methodology that has been used is integrated modelling using 3-geological models built in GeoScene3D and groundwater modelling, which was based on existing data from Umgeni Water and Department of Water and Sanitation (DWS). Based on the outcome of the 3-D geological voxel model both known aquifers where the boundary has been adjusted, as well as new aquifers has been outlined. Good places for drilling production boreholes have been identified, followed by groundwater modelling of sustainable abstraction rates from existing and new potential well fields. Finally, recommendations were made for new data collection and how to modify the Danish mapping approach for use in South Africa, taking the differences in geology and water management into consideration. The Danish methodology for groundwater mapping is adaptable to South African conditions but it requires Danish and South African experts works closely together. The project has also shown that integrated 3-D geological modeling and hydrological modelling can contribute to a sustainable development of groundwater in South Africa, as well as the Danish methodology for modelling and monitoring sustainable abstraction rates.4
Science-Policy Nexus: Assessing role of groundwater resource directed measures in water resources protection practice, case of Schoonspruit-Koekemoerspruit River Catchment, South Africa	Stanley	Nzama	Gauteng, North West	2021	RDM, aquifer protection, knowledge sharing, policy implementation
Abstract The argument in this paper is that improved understanding of science-policy integration, where physical bases of natural science is combined with practice in managing water resource challenges, becomes critical in translating scientific knowledge into effective and sustainability solutions linked to groundwater resource protection. Such hypothesis should be attested at locally relevant scale where water resources reside and where water utilization takes place. This paper provides a practical case-study of how science-policy integration can directly impacts groundwater resource protection practice from a local, and national perspective using strategies of groundwater resources directed measures. A combination of literature surveys, and desktop record review methods were used for the purpose of data collection from published literature and publicly accessible national databases of the Department of Water and Sanitation (DWS). Collected data were analysed using document analysis, descriptive statistics, and case study analysis methods. Based on the analysis, three types of science-policy nexus theoretical models exist in practice, namely, 1) science-policy integration, 2) policy-science integration, and 3) mixed integration. From a national perspective, the analysis showed that South Africa is able to practically apply science-policy nexus in policy implementation practice for water resources protection, and that such practice depicts a mixed integration model of the nexus. Case study analysis of the Schoonspruit-Koekemoerspruit River Catchment provided insight on how localized operationalization of groundwater resource directed measures facilitates sustained groundwater resources protection for water availability and sustainable utilization. This study provides an exemplary for collaborations between researchers and/or scientists and policy makers to ensure that science research is answering policy-relevant questions and that results from scientific work are readily available for policy implementation. In addition, there is adequate evidence to indicate that science-policy nexus can be designed and prioritized to support sustainable development agenda on groundwater resilience, and visibility at various levels.
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.
The Seven Deadly Sins of Numerical Modelling	Andries	Wilke	South Africa	2021	numerical modelling, recharge
Abstract Pope Gregory defined the seven deadly sins in order to guide the Catholic Church in the 6th century. The past 20 odd years in the industry has shown that there are several mistakes that are repeatedly made by numerical modelers. Although we all acknowledge that any numerical model is a non-unique solution, and that there exists and infinite number of solutions, there are several sins that will prevent the model from giving an accurate representation. This paper will provide the most common mistakes made in a format that is accessible to numerical modelers as well as other practitioners. Issues covered will include boundary conditions, model complexity and recharge.
Assessment of Concentration levels of contaminants in groundwater of Soutpansberg Region, Limpopo Province, South Africa	Lindelani	Lalumbe	Limpopo	2021	community supply, Drinking water standards, Groundwater Quality, skills transfer, knowledge sharing, health, Food security
Abstract Kanyerere, T Groundwater contribution towards improved food security and human health depend on the level of contaminants in the groundwater resource. In rural areas, many people use groundwater for drinking and irrigation purposes without treatment and have no knowledge of contaminants levels in such waters. The reason for such lack of treatment and knowledge is due to the parachute type of research which emphasizes on scientific knowledge and records only and do not develop skills and outputs on groundwater quality for improved human health and food security in communities. This study argued that parachute research type exposes groundwater users to health hazards and threaten food security of communities. Concentration levels of contaminants were measured to ascertain suitability of groundwater for drinking and irrigation use. 124 groundwater quality samples from 12 boreholes and 2 springs with physiochemical data from 1995 to 2017 were assessed. This study found high concentration levels of contaminants such F-, NO3-, Cl- and TDS in certain parts of the studied area when compared to international and national water quality standards. In general, groundwater was deemed suitable for drinking purposes in most part of the studied area. Combined calculated values of SAR, Na%, MH, PI, RSC and TDS determined that groundwater is suitable for irrigation purposes. The discussion in this paper showed that scientific knowledge generated on groundwater quality is not aimed at developing skills and outputs for improved human health and food security but rather for scientific publication and record keeping leaving communities where such knowledge has been taken devoid of knowledge and skills about the groundwater quality. In this study, it was recommended that skills and outputs on groundwater quality should be developed and shared with groundwater users through various initiatives as it will enhance the achievement of SDG’s.
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.
The Importance Of Reliable Monitoring Data	Shuaib	Dustay	National	2021	data management, numerical model, poor data
Abstract Imrie, S “Monitoring rounds”, “logging”, “quality checking”, “data collation” and “reporting” are terms all too familiar to groundwater field specialists. Yet, a full understanding of the true worth and the full lifecycle of data is often not appreciated. Field data form critical “ingredients” to groundwater conceptual and numerical models. Unfortunately, if can often be the case that the quality of field data is only tested once it has been processed and input to the model, which may be many years following collection. This case study highlights the time-consuming, budget-consuming and groundwater management difficulties that can arise from poor quality data, such as poor monitoring network designs, inconsistent data capturing, erroneous logging, poor borehole construction and gaps in data. The study area is an industrial complex with a highly contaminated groundwater system. The site is located on fractured sandstone and tillite, with major cross-cutting fault zones. The objectives of the numerical groundwater model are to assess the efficacy of the current remediation measures, likelihood of seepage due to artificial (contaminated) recharge, and prediction of the future potential contaminant plume footprint. Setbacks were encountered in the early stages of building the model. Although the site has a monitoring network of over 300 boreholes, less than 50 of these boreholes could be considered for model calibration, with those remaining including data with high uncertainty and multiple assumptions. The poor data resulted in lower calibration statistics which translated into lower model confidence levels. The modelling exercise proved useful for informing updates to the monitoring programme and identification of critical gaps where future drilling and testing will be focussed. However, the lack of reliable monitoring data led to a model of low confidence and high uncertainty, subsequently impacting the level of groundwater management, and thus impeding remediation efforts and future protection of our precious groundwater resource.
Analyzing the effects of episodic groundwater recharge caused by extreme events in a semi-arid region: a case study in Beaufort West, South Africa.	Aarifah	Williams	Beaufort West	2021	recharge
Abstract On a global scale, groundwater is seen as an essential resource for freshwater used in both socioeconomic and environmental systems; therefore forming a critical buffer when droughts occur. Due to its location in a dry and semi-arid part of South Africa, Beaufort West relies on groundwater as a crucial source of fresh water. Thus, proper management of their groundwater resources is vital to ensure its protection and preservation for future generations. Although fluctuations have occurred over the years, groundwater levels in the area have progressively dropped due to abstraction in well fields. However, in 2011, an episodic flooding event resulted in extreme groundwater recharge with groundwater levels North-East of Beaufort West recovering tremendously. This led to the overall groundwater levels of Beaufort West becoming relatively higher. The general flow of groundwater in the town, which is from the Nuweveld Mountains in the North to the town dyke in the South, is dictated by dykes occurring in the area. This study aims to expand on the understanding of episodic groundwater recharge around extreme climatic conditions of high precipitation events in a semi-arid region. This was done by analyzing historical data for the Gamka Dam spanning over 30 years; estimating recharge in the Beaufort West well fields caused by the flooding event; as well as studying the hydrogeological setting and lineaments in the area. It was found that sufficiently elevated recharge around the observed flooding event only occurred in areas where the correct climatic (precipitation, evaporation), geological and geographical conditions were met. Ultimately, gaining a better understanding of these recharge events should aid in the assessment of the groundwater development potential of Beaufort West.
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.
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.
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.
Towards a conceptual understanding of groundwater-ecosystems interactions in the Tuli-Karoo transboundary aquifer	Kwazikwakhe	Majola	Karoo	2021	Ecosystem, TBAs, Dependent, Aquatic, Vegetation, Wetlands, Interactions, Transboundary flow, Integration, recharge, Discharge, conceptualisation
Abstract Xu,Y; Kanyerere, T Currently, there is little understanding of the nature and extent of groundwater-dependent ecosystems (GDEs) at catchment or aquifer scale globally, making it difficult to protect and incorporate them in integrated groundwater resources management plans. Groundwater levels fluctuations could alter groundwater accessibility patterns to GDEs, potentially resulting in groundwater quality deterioration too. The understanding of groundwater-ecosystems interactions is generally poor since most historical research has been skewed to surface water-related ecosystems. There exists a research need towards the understanding of groundwater processes that control the maintenance of GDEs at local level, through conceptual modelling. A study has been initiated in the Tuli-Karoo transboundary aquifer (TBA) – shared between Botswana, South Africa and Zimbabwe in the Limpopo Basin - to address this scientific knowledge gap because of possible cross-border negative impacts on respective groundwater resources attributed to interlinked aquifer systems’ nature between riparian countries. Ecosystems’ protective measures here are country-specific, disregarding neighbouring countries activities and based on low-flow requirements through baseflow, largely excluding terrestrial GDEs. Groundwater resource co-management agreements are also non-existent among sharing countries, warranting a collaborative approach to research. Potential GDEs in this TBA include riparian vegetation along the main stem Limpopo River and its major tributaries (Shashe and Mzingwane); terrestrial vegetation of Mopane bioregion of the Savanna Biome; and seasonal and permanent wetlands, pans and springs. Isotope analysis have ascertained dependency partly in one country and therefore extended to cover the TBA. Tuli-Karoo is characterized by shallow unconfined alluvium aquifer systems of the Karoo sandstones and basalts of shallow to medium depths. A conceptual model developed will demonstrate interactions between groundwater, surface water and ecosystems; allowing for assessments of impacts on GDEs to ensure resilience. Although TBA focused, the findings will be applicable to similar national aquifers in terms of lithology, geology, geohydrology and ecosystems types.
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.
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.
Unconventional Gas Regulations for Water Use by DWS Unconventional gas	Lebogang	Malefane	South Africa	2021	Unconventional gas, UCG, CMB, contamination, Regulations, NWA 1998
Abstract Unconventional gas development in South Africa consists of but not limited to shale gas extraction commonly known as “fracking”, Underground Coal Gasification (UCG), Coalbed Methane (CBM), to extract natural gas from geological formations is a new, rapidly expanding industry in the world and in South Africa. However, there are general concerns that these operations could have large negative impacts such as groundwater contamination. This article maps out the development of regulations for unconventional gas operations, according to Section 26(1) (9) of the National Water Act, 1998 (NWA) and read together with Government Notice 999 (Government Gazette No.: 39299, of 16 October 2015). The objectives of the published DWS regulations include, augmenting the NWA and its existing regulatory framework, providing for a step-wise process for authorising all unconventional gas operations to allow for informed decision making, to set prohibitions and restrictions for protection of water resources, and requirements for disclosure on chemicals to be used during the operations. The objectives of DWS regulations are aligned to the NEMA, and MPRDA requirements for exploration and production of these operations, and are further supplemented by the minimum information requirements for water use licensing application and as part of integrated water resource management. In conclusion, DWS proposes thoroughly consulted and fit-for-purpose regulatory framework that seeks to propose water use law and requirements for unconventional gas operations based on the National Water Act (1998). With these proposed regulations DWS ensures that it plays its critical role in the development of a regulatory framework for unconventional gas operations.
The onset of iron biofouling in boreholes in and around Cape Town	Roger	Parsons	Cape Town	2021	Iron biofouling, Drought, Monitoring
Abstract Iron biofouling in boreholes drilled into the Table Mountain Group has been documented, with groundwater abstracted for the Klein Karoo Rural Water Supply Scheme and irrigation in the Koo Valley hampered by clogged boreholes, pumps and pipes. A similar phenomenon has been experienced at some boreholes drilled and operationalised by the Western Cape Government in response to the onset of the crippling drought in 2017. Monitoring of groundwater levels and pumping rates has yielded data showing a gradual decrease in groundwater level as the pumping rate reduced in response to the pump becoming biofouled, with possibly the same negative impact on the borehole itself. Methods are available to rehabilitate the boreholes (mechanical scrubbing, chemical treatment and jetting), but it seems difficult to destroy the bacteria and re-occurrence of biofouling appears inevitable. In the absence of better solutions, current experience suggests an annual borehole maintenance and rehabilitation budget of R 100 000 per borehole is required. This paper presents three case studies of boreholes drilled into the Malmesbury Group and Table Mountain Group and explores possible triggers of biofouling and its manifestation in the monitoring data.
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.
A changing environment focussing on drought	Fanus	Fourie	Northern Cape	2021	Drought, community supply, groundwater behaviour, Pumping
Abstract The western part of South Africa is experiencing a prolonged drought. In many cases, the effects of drought have been noticed since 2011, putting the western part of the Northern Cape under severe stress to provide water to the communities. In the past 10 years, rainfall has also decreased, and in most cases, the catchments did not receive rain to help with the recharge of 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 what we are noticing in the environment that impacts the way we think groundwater behaves. The changes include the change in rainfall: patterns, lines, and type of rainfall. The collapsing of boreholes with water strikes closing when being over-pumped occurs more often in the last 3 years. Pump test recommendation changes with water level change – deployment output. A combination of the factors mentioned puts more stress on groundwater resources, and a mindset change is needed to give assurance of future supply to the communities.
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.
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.
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.
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.
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.