Conference Abstracts

Abstract

Being extensively available and of high quality, groundwater is the primary source of freshwater in coastal regions globally. However, due to anthropogenic and natural drivers, groundwater salinisation is a growing threat to this resource’s long- and short-term viability. The causes and timescales of aquifer salinisation are complex and difficult to quantify, information essential for suitably timed mitigation strategies. One way to inform these strategies and develop storylines of future freshwater (un)availability is through 3D groundwater salinity modelling. These models can predict current groundwater distributions and quantitatively assess the impacts of a projected increase in groundwater extraction rates and sea-level rise. Until recently, detailed 3D models on this scale have been largely unattainable due to computational burdens and a shortage of in-situ data. Fortunately, recent developments in code parallelization, reproducible modelling techniques, and access to high-performance computing (e.g., via parallel SEAWAT) have made this feasible. Machine learning and data mining developments have also allowed an unprecedented opportunity to constrain and calibrate those models. With this in mind, we present our progress towards global 3D salinity modelling by showcasing a regional-scale model in the Mediterranean Sea area. This test case uses newly developed, automated geological and salinity interpolation methods to create initial conditions while implemented in a parallelized version of SEAWAT. The modelling outcomes highlight the potential of supra-regional scale modelling in the context of global (planetary) processes and localised anthropogenic effects.

Abstract

The Department of Water Affairs (DWA), Chief Directorate: Resource Directed Measures has developed guidelines over the past decade  in order  to  facilitate  proper implementation of the Groundwater   Resource   Directed   Measures   (GRDM)   (also   known   as   determination   of   the groundwater component of the Reserve). An intrinsic component of the GRDM is delineation of Integrated Units of Analysis (IUAs) from which the allocatable groundwater and surface water components are calculated, which essentially drives the allocation of water use licenses. Delineation typically follows a three-tiered approach, namely primary, secondary and tertiary level. Primary delineation is based on quaternary boundaries (considered to be the basic building block of the IUA); secondary follows geological, hydrogeological and hydrological boundaries, groundwater abstraction zones and baseflow contribution; and tertiary is dependent on management criteria. How then, do we undertake this challenging task of delineating IUAs to a level where it can be better managed and monitored? Complexities arise when hydrogeological data are scarce, hydrological and hydrogeological systems are not in sync, aquifers extend across a quaternary, water management area, provincial and administrative boundaries, surface water and groundwater interactions are not well understood, and legislation on protection of water resources differs greatly from one country to the next. Having undertaken delineation of IUAs in the Waterval Catchment (Upper Vaal WMA), Olifants WMA and Mvoti to Umzimkhulu WMA with the available datasets, the key criteria for the respective  WMAs  have  ultimately  been  management  class,  significant  aquifers,  groundwater– surface water interaction and groundwater stressed areas, and secondary catchment boundaries, followed by other hydrogeological, geological and management considerations.

Abstract

The way in which groundwater is utilized and managed in South Africa is currently being reconsidered, and injection wells offer numerous possibilities for the storage, disposal and abstraction of the groundwater resource for municipalities, rural communities, mining, oil and gas, and a multitude of other industries. This presentation is about the North Lee County Reverse Osmosis Water Treatment Plant Injection Deep Injection Well project in southwest Florida in the United States. Water is plentiful in Florida, but it is not drinking water quality when it comes out of the ground. As such, treating water from wells is an important part of water supply in the coastal regions of the state. One form of treatment is reverse osmosis (RO), which generates a brine concentrate waste. The concentrate must then be disposed of, and a preferred method of disposal is an injection well because the disposal is not visible to the general public. The injection well project was associated with the construction of a large water treatment plant. The emphasis of this presentation is on the drilling and technical work in the field for this injection well, and to illustrate the rigorous requirements of drilling, constructing and testing a Class I injection well. Class I injection wells are permitted by the United States Environmental Protection Agency (US EPA) for injecting hazardous waste, industrial non-hazardous liquid, and/or municipal wastewater beneath the lowermost Underground Source of Drinking Water (USDW). Aquifer storage and recovery (ASR) wells are permitted as Class V injection wells by the US EPA. The permitting of an injection well is rigorous and requires state and federal approval before, during and after the field portion of the project. {List only- not presented}

Abstract

Noble gases are used in this study to investigate the recharge thermometry and apparent groundwater residence time of the aquifers on the eastern slope of the Wasatch Mountains in the Snyderville Basin of Summit County, Utah. Recharge to and residence time for the basin aquifer in the Salt Lake Valley, Utah, from the western slope of the Wasatch Mountain range by 'mountain-block recharge' (MBR), is a significant source of subsurface flow based on noble gas and tritium (3H) data. The Snyderville Basin recharge thermometry from 15 wells and 2 springs indicates recharge temperatures fall within the temperature "lapse space" defined by the recharge thermometry determined in the study of MBR for the Salt Lake Valley and the mean annual lapse rate for the area. Groundwater residence times for the Snyderville Basin were obtained using tritium and helium-3 (3He). The initial 3H concentrations calculated for the samples were evaluated relative to the 3H levels in the early 1950s (pre-bomb) to categorize the waters as: (1) dominantly pre-bomb; (2) dominantly modern; or (3) a mixture of pre-bomb and modern. Apparent ages range from almost 6 years to more than 50 years. Terrigenic helium-4 (4He) is also used as a groundwater dating tool with the relationship between terrigenic 4He in Snyderville Basin aquifers and age based on the apparent 3H/3He ages of samples containing water from only one distinct time period. The 4He is then used to calculate groundwater residence times for samples that are too old to be dated using the 3H/3He method. The mean groundwater residence times calculated with both methods indicate the water yielded by wells and springs in the Snyderville Basin generally ranges from 6 to more than 50 years. In addition, the calculated terrigenic 4He age for the pre-bomb component of many samples was found to exceed 100 years. While terrigenic 4He residence times are not as definitive as those calculated with the 3H/3He method, or chlorofluorocarbons (CFCs), age dating with terrigenic 4He allows initial estimates to be made for groundwater residence times in the Snyderville Basin, and is an important tool for establishing groundwater residence times greater than 50 years. Historic water levels from production wells indicate a declining water table. This trend in conjunction with precipitation data for the area illustrates the decline in the water levels to be a function of pumping from the aquifers. Groundwater residence times in the Snyderville Basin and declining water levels support the need for a groundwater management program in the Snyderville Basin to effectively sustain the use of groundwater resources based on groundwater age. {List only- not presented}

Abstract

To control the impact of nitrate and its sustainable mitigation in groundwater systems used for drinking water production, it is crucial to understand and quantify sources as well as biochemical processes which (permanently) remove nitrate.

In an alluvial aquifer in Germany (Hessian Ried) that serves as major drinking water recourse for the Frankfurt metropolitan area, water quality is challenged by nitrate contamination from intensive agricultural land use locally by far exceeding the drinking water limits of 50 mg/L.

In order to evaluate the capability of the aquifer for natural mitigation of the nitrate contamination, we investigated the denitrification potential with respect to the availability of electron donors and the predominant reduction pathways in different sections of the aquifer. The content of sedimentary sulfide and organic carbon was quantified by solid-phase analyses of drill core samples from aquifer sediments. Water samples from vertical profiles gave access to information on the isotope-hydrochemical composition of the groundwater (multi-parameter profiles, major ions, nitrate isotope signature, sulfate isotope signature). Using this hydrochemical and isotope information in concert with the results of a groundwater flow model allowed determining the nitrate input and the average nitrate reduction kinetics along the flow path upstream of selected groundwater monitoring wells. Batch and column experiments provided detailed information on prevailing reaction pathways and the associated isotope fractionation pattern enabling the recognition and quantification of processes on field scale. Our results suggest that litho-autotrophic denitrification using sedimentary sulfide as an electron donor is preferably responsible for the nitrate degradation in the aquifer. However, due to the low sulfide content (max. 123 mg-S/kg), the potential for autotrophic denitrification is very limited. Consequently, if no active measures reducing the input of fertilizer-derived nitrate will be implemented in the near future, the limited potential for autotrophic denitrification will ultimately exhaust and a severe deterioration of the groundwater quality can be expected.

Abstract

Given the challenging global water outlook due to climate change and urbanisation, there is a heightened necessity for greater water resilience at critical facilities to tackle water disasters or disasters that lead to water crises. In 2017, the Western Cape Province of South Africa experienced an extended drought with the risk of acute water shortages. The Western Cape Government (WCG) developed business continuity plans and implemented a programme to ensure water supply to certain critical service delivery facilities, utilising the strategy of developing localised groundwater supply systems. The case study research of the WCG program enabled the development of an evaluation framework that assessed this strategy’s effectiveness in improving water resilience levels at critical facilities. From the lessons learnt in the WCG programme, the research also crystallised the critical success factors in sustainably implementing this strategy. The research showed that this is an effective strategy for its purposes and provides both current and future disaster preparedness planners with an improved understanding of the levels of water resilience achievable through this strategy and the methodology to achieve it best.

Abstract

National legislation is the outcome of processes, locally, provincial and nationally. Certain aspects of water management have first been the product of legal initiatives of the South African government, seeking  to  address  local  problems.  As  a  result,  the  National  Water  Act,  36  of  1998,  was promulgated. The Act is in line with the Constitution of the Republic of South Africa, 108 of 1996, which embrace human rights. The Water Services Act, 108 of 1997, regulates the accessibility of water and sanitation by domestic users. Groundwater, in many parts of South Africa, provides the sole  and/or  partial  water  supply  for  meeting  basic  human  needs.  With  an  increase  in  the dependency on groundwater usage, the need to properly and effectively protect, use, develop, conserve,  manage  and  control  groundwater  resources  has  become  a  national  priority  by  the custodian of all water resources: the National Department of Water Affairs. The question arises whether  or  not  the  current  groundwater  allocation  decision-making tools  are  enough  to  make informed  decisions  regarding  the  final  approval,  or  not,  of  groundwater  use  licenses,  and whether  a  proper  framework  that  includes  guidelines  together  with  licensing  conditions  are available  for  decision- making   in   complex  groundwater   scenario   situations   as   part   of   the groundwater license decision process. The current research contributes to answering this question and finding solutions in order to improve and make the groundwater use authorisation process more  effective.  The  groundwater  situation  will  be  discussed  on  a  comparative  basis  from international case studies regarding water legislation and groundwater resource management tools. A full evaluation and analysis of groundwater use authorisation process and decision-making tools on  regional and  national level  in  South  Africa will be done  and a Framework and tool for the evaluation, decision-making and determination of authorisation conditions of groundwater use authorisations, which includes existing lawful water use, general authorisations, and groundwater use licensing, will be developed. Scenarios and case studies are currently implemented.

Abstract

At a regional scale, groundwater recharge is often calculated using surface water models. Precipitation and surface water runoff are easier to measure than groundwater recharge, and evapotranspiration can be estimated with relative accuracy using indirect methods. In modelling, surface water measurements can be used for calibration, and groundwater is the residual term in the water balance of the catchment. This can give a good indication of regional trends, but provides limited scope for the accommodation of groundwater system characteristics and recharge processes. Recently, much research has been focused on the interaction of surface and groundwater models. The coupling of physically based surface and ground water models allows for calibration of the model using both surface and groundwater data while providing scope for improved insight into the processes which define the interaction of groundwater with the rest of the water cycle. For example: stream discharge, interflow, preferential flow through the unsaturated zone and interaction with surface water retained in dams and wetlands. One such model is GSflow (United States Geological Survey), which we are applying to the Upper Vaal Catchment. This model integrates the surface water model PRMS (Precipitation-Runoff Modelling System) with MODFLOW (Modular Groundwater Flow model). The model is initially being calibrated at quaternary catchment scale, starting with the surface water components and later adding the groundwater system. The quaternary catchment is subdivided into smaller, topologically defined hydrological response units. This scaling allows for a better understanding of how well the characteristics of the units are represented in the physical processes incorporated into the model, so that ultimately the sensitivity analysis can incorporate these processes. The results will be compared to current work on recharge being carried out using GRACE data and previous work done in the same area. Once the entire model has been calibrated, there will be scope to calculate future scenarios, allowing for climate and land-use changes. A brief overview of existing work as well as methods and initial results and sensitivity analysis will be presented.

Abstract

Simple and cost-effective techniques are needed for land managers to assess and quantify the environmental impacts of hydrocarbon contamination. During the case study, hydrocarbon plume delineation was carried out using hydrogeological and geophysical techniques at a retail filling station located in Gauteng.

Laboratory and controlled spill experiments, using fresh hydrocarbon product, indicate that fresh hydrocarbons generally have a high electrical resistivity, whilst biodegraded hydrocarbons have a lower resistivity. This is attributed to the changes from electrically resistive to conductive behaviour with time due to biodegradation. As such, it should be possible to effectively delineate the subsurface hydrocarbon plume using two-dimensional (2D) Electrical Resistivity Tomography (ERT). As part of the case study, two traverses were conducted using an Electric Resistivity Tomography (ERT) survey with an ABEM SAS1000 Lund imaging system. The resultant 2D tomographs were interpreted based on the resistivity characteristics and subsurface material properties to delineate the plume. Localised resistivity highs were measured in both models and are representative of fresh hydrocarbons whereas areas of low resistivity represented areas of biodegraded hydrocarbons.

More conventional plume delineation techniques in the form of intrusive soil vapour and groundwater vapour surveys as well as hydrochemical anlayses of the on-site monitoring wells were used to compare the results and to construct the detailed Conceptual Site Model. During the investigation, four existing monitoring wells located on the site and additional two wells were installed downgradient of the Underground Storage Tanks (USTs) in order to determine the extent of the plume.

In conclusion, a comparison was found between the groundwater results and geophysical data obtained during the case study and it was concluded that ERT added a significant contribution to the Conceptual Site Model.

Abstract

The North West Province has produced a large portion of South Africa’s inland alluvial diamonds. Kimberlite intrusions are typically the parent source for the alluvial diamonds. Diamondiferous kimberlite intrusions were eroded over time by surface run-off and streams which transport the diamondiferous sediments downstream to depositional regimes. The diamondiferous alluvial deposits around Schweizer- Reneke were mostly deposited on magmatic rock of the Ventersdorp Supergroup. Formal alluvial mining in the area often requires a considerable amount of overburden material to be removed in order to access the coarser gravel beds which contain the economic grade diamonds. Diamond production from secondary sources in this region totalled approximately 14.4 million carats up to 1984, and small scale production persists today.

The case study focuses on the impacts of alluvial diamond mining operations on surface- and groundwater resources in the North West Province, South Africa. To recover diamonds from the sediments, the industry is currently focussing on using modern processing methods and a more clinical approach to increase the sustainability of mining, therefore minimizing the impact on the environment. Wastewater from the screening and the fines management phase is delivered to the primary water treatment phase where up to 70% of process water is recirculated to the processing plant, minimising the volumes of fresh water required. The settled sludge or waste is deposited on a tailings storage facility. Alluvial diamond mining operations, unlike many other industrial processes and types of mining, have a lower environmental hazardous risk associated with waste material, however, it is a possibility that leachate emanating from tailings often have a high salt content. The process raw water to these operations are supplied from both surface- and groundwater sources from the local area. Supplying processing raw water in a sustainable manner is often a challenge in drought stricken areas with limited surface flow and low aquifer potential.

Abstract

Synthetic flocculants are widely used in water treatment for their efficiency when it comes to flocculation but pose a risk to the environment and human health. The need for an alternative flocculant was investigated in this study. Bioflocculants which are produced by microorganisms have the potential to flocculate fine suspended particles. The bioflocculant production by Bacillus sp. isolated from Umlalazi Estuary in Mtunzini, KwaZulu-Natal Province was evaluated. Optimum flocculation conditions were obtained with an inoculum size of 1% v/v (89%), carbon source which was glucose with a flocculating activity of 88%, a multiple nitrogen source with a flocculating activity of 88%, an optimum temperature of 400C with 95% flocculating activity, shaking speed of 120 rpm with 95% flocculating activity, K+ for the cations was optimum at 95% flocculating activity and the pH of 7 had the flocculating activity of 94%. In the time course assay optimum conditions were reached after 84 hours with the flocculating activity of 92% at pH 5.29 using 0.4% (w/v) kaolin suspension. After extraction and purification, a bioflocculant yield of 2.1g/L was recovered from a 1L fermentation broth. Water treatment without the risk to human health is now a reality.

Abstract

PFAS and pharmaceuticals in groundwater are two of many synthetic compounds currently under the attention of many researchers and environmental administration in Europe, especially in light of the revision of the EU Groundwater Directive 2006/118/EU. The two types of substances were first included in the voluntary groundwater watch list and were first formally regulated at the EU scale. This regulation implies that they will be obligatory to be monitored within national monitoring programmes for groundwater body status assessment procedures across the EU. While there is no doubt about the need to regulate the presence of these substances in groundwater, sampling procedures and QC/QA protocols may be challenging to implement as no official guidelines exist. Although scientific literature allows us to define protocols usually based on precautionary principle, these may be too difficult and expensive to implement at the national scale monitoring. This article describes a work that the Polish Geological Institute – National Research Institute undertook to define an optimal sampling process for PFAS and pharmaceuticals in groundwater. Experimentally tested factors included cleaning pumps between sampling sites, the need for using protective suits during sampling and the influence of ambient air on sample quality. Results showed that sampling protocols for PFAS and pharmaceuticals do not need to be modified concerning current protocols as these seem to be sufficient to protect groundwater samples from unintentional cross-contamination.

Abstract

The abstract presents a 2D modelling approach alternative to a 3D variable saturated groundwater model of solute or heat transport at the regional scale. We use FEFLOW to represent processes in the saturated zone, coupled with various models describing the unsaturated zone. The choice of the latter depends on modelling needs, i.e. simulation of the movement of seepage water and nitrate fate with respect to crop rotation patterns and dynamic characteristics of heat gradients, respectively. The flexibility of coupling specialized models of different subsurface compartments provides the opportunity to investigate the effects of land use changes on groundwater characteristics, considering the relevant drivers in sufficient detail, which is important in regions with intensive anthropogenic activities. The coupling can be operated either with (direct coupling) or without (sequential coupling) including the feedback between the saturated and the unsaturated zones depending on the depth of the groundwater table below the surface. Thus, the approach allows for reasonable computational times. The Westliches Leibnitzer Feld aquifer in Austria (43 km²; Klammler et al., 2013; Rock and Kupfersberger, 2018) will be presented as an example highlighting the needed input data, the modelling workflow and the validation against measurements.

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.

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

Abstract

This work is part of the AUVERWATCH project (AUVERgne WATer CHemistry), which aims to better characterise some Auvergne water bodies, specifically the alluvial hydrosystem of Allier River (France). Alluvial aquifers constitute worldwide a productive water resource, superficial and easily exploitable. In France, 45% of the groundwater use comes from these aquifers. The study site is a wellfield that withdraws 8.5 million m3 of water annually from an alluvial aquifer to produce domestic water for 80% of the local population. At the watershed scale, precipitations have decreased by -11.8 mm/y, air temperatures have increased by 0.06°C/y and the river flow has declined by 20.8 Mm3 /y on 2000 – 2020. In the summer period, at least 50% of the river flow is ensured by the Naussac dam (upstream catchment part), but the recent winter droughts have not allowed the dam to replenish. Thus, water stakeholders are concerned that the productivity of the wellfield could be soon compromised. Based on geological, geophysical, hydrochemical, and hydrodynamic surveys, a numerical model of the wellfield is being developed using MODFLOW. The calibration in natural flow regime is successful using a range of hydraulic conductivities going from 1×10-3 to 1×10-4 m/s (pilot points method), consistent with the pumping tests. Preliminary results show that the river entirely controls the groundwater levels at all observation points. The perspective is now to calibrate this model in a transient regime by integrating domestic water withdrawals to determine how low the river can go without affecting the wellfield productivity.

Abstract

The increase in awareness of environmental issues and the desire for a cleaner environment by the public has caused mining companies to place greater emphasis on the continuous rehabilitation of harmful effects caused by mining operations. Ongoing rehabilitation is also a requirement of the government departments involved in mining in South Africa. The biggest concern for the relevant government departments is the possible uncontrolled pollution of water resources in the vicinity of mines, after they have closed.

In  the  compilation  of  this  paper,  the  unique  nature  of  the  South  African  situation  has  been considered – this refers to a legally acceptable approach towards current legislation and policies. This study leads to the construction of a logical approach towards mine closure, specifically to understand issues around costs and financial liability. The final product of this approach should ultimately give more clarity on:

the principles followed to identify objectives for mine closure and groundwater assessment;

key steps to follow when assessing site hydrogeology and to determine related impacts, risks, closure costs and liabilities; and

an overview of methods that could be used for the mitigation of polluted aquifers and a brief site-specific application.

Abstract

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

Abstract

The increase in awareness of environmental issues and the desire for a cleaner environment by the public has caused mining companies to place greater emphasis on the continuous rehabilitation of harmful effects caused by mining operations. Ongoing rehabilitation is also a requirement of the government departments involved in mining in South Africa. The biggest concern for the relevant government departments is the possible uncontrolled pollution of water resources in the vicinity of mines, after they have closed. In  the  compilation  of  this  paper,  the  unique  nature  of  the  South  African  situation  has  been considered – this refers to a legally acceptable approach towards current legislation and policies. This study leads to the construction of a logical approach towards mine closure, specifically to understand issues around costs and financial liability. The final product of this approach should ultimately give more clarity on: 

the principles followed to identify objectives for mine closure and groundwater assessment;

key steps to follow when assessing site hydrogeology and to determine related impacts, risks, closure costs and liabilities; and an overview of methods that could be used for the mitigation of polluted aquifers and a brief site-specific application.

Abstract

Groundwater levels in E33F quaternary catchment are at their lowest level ever. The impact of climatic variation and increasing abstraction were determined to be the main factor. There are 115 registered groundwater users in E33F and the monthly abstraction volumes are not being measured. There is a need to use land use activities as well as the population to estimate groundwater use. The main objective is to use non-groundwater monitoring data to estimate groundwater use in order to protect the aquifer and ecosystem in general in varying climatic condition. Land use activities information was used to estimate groundwater use in E33F quaternary catchment. The estimated groundwater use volumes were compared to allocated and measured volumes. For domestic groundwater use estimation, population data and an estimation 100 litre per person per day were used. The water requirements for the types of crops being cultivated together with the area (m2) were used to estimate groundwater use volumes for irrigation. The number and type of live stocks were used with the water requirements for each livestock type to estimate the groundwater use volumes. 96 % of groundwater users are using groundwater for irrigation purposes with 9 966 105 m3/a allocated for irrigation. Mining, industries, domestic and livestock are allocated 100 200 m3/a. The estimated groundwater use volume for irrigation is 30 960 000 m3/a, which is three times higher than the allocated volume. Groundwater use volume for domestic use is estimated to be 38 225 m3/a which is higher than the 31 000 m3/a allocated. The total estimated groundwater use volume in E33F is estimated to be 30 998 225 m3/a, which is three times higher than the allocated groundwater use volume of 10 066 305 m3/a. This estimation could be higher as only registered boreholes were used and estimations from mining, Industries and live stocks were excluded due to lack of data

Abstract

atural water-rock interaction processes and anthropogenic inputs from various sources usually influence groundwater chemistry. There is a need to assess and characterise groundwater quality monitoring objectives and background values to improve groundwater resource monitoring, protection and management. This study aims to determine monitoring objectives and characterise monitoring background values for all monitoring points within the Soutpansberg region. This study used long-term groundwater quality monitoring data (1995- 2022) from 12 boreholes and 2 geothermal springs. Monitoring objectives were determined from land-use activities, allocated groundwater use, and water use sectors. Monitoring background values were determined from the physio-chemical parameters from each of the 14 monitoring points. This study determined monitoring objectives and background values of all monitoring points and all physio-chemical parameters in the Soutpansberg region. This study recommends reviewing the determined monitoring objectives and background values every 5 to 10 years to assess any change in land use, groundwater use and sector and monitoring data trends.

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.

Abstract

The Natural Background Level (NBL) of contaminants in groundwater is typically determined using regional-scale monitoring networks or site-specific studies. However, regional scale values are limited in their ability to capture natural heterogeneities that affect contaminant mobility at smaller scales, potentially leading to local over- or underestimation of the natural contaminant concentration. Conversely, site-specific studies can be expensive and time-consuming, with limited use outside the specified case study. To overcome this issue, a study was conducted in a 2600 km2 area, analyzing arsenic concentration values from monitoring networks of sites under remediation as an alternative source of information. The main drawbacks of the alternative dataset were the lack of information on monitoring procedures at the remediation sites or potential anthropogenic influences on the concentration data. However, these limitations were adequately managed with a thorough data pre-treatment procedure informed by a conceptual model of the study area. The NBLs estimated with the alternative dataset were more reliable than that from the regional monitoring network, which, in the worst case (i.e., in the area with the highest geological and geochemical heterogeneity), the NBL of one order of magnitude was underestimated. As a future step, the project seeks to incorporate geological and geochemical heterogeneities as secondary variables in a geostatistical analysis to produce a continuous distribution of arsenic concentrations at the mesoscale. This would provide a useful tool for managing contaminated sites and a reproducible protocol for NBL derivation in different areas, overcoming the scale issue.

Abstract

POSTER The poster presents the modified hydrogeologic conceptual model that was used to assess the dynamics of groundwater flooding in Cape Flat Aquifer (CFA). The groundwater flooding remains poorly understood in the context of urban hydrogeology of the developing countries such as South Africa. While engineering intervention are relevant to providing solution to such events, continue estimation of hydrogeologic parameters at local scale alongside field measurements remain paramount to plausible modeling the groundwater flooding scenarios that inform such engineering interventions. However, hydrogeologic conceptual model which informs numerical simulation has not been modified to include local scale variation in the CFA to reflect various groundwater units. The current study argues that modifying hydrogeologic conceptual model improves numerical simulations thereby enhancing certainty for engineering solutions. The current study developed groundwater units, set up site specific models and estimated aquifer parameters using pumping step-drawdown and constant rate pumping tests in order to produce a comprehensive modified hydrogeological conceptual model for CFA to inform groundwater modeling at catchment level for water sensitive cities.

Key Words: Aquifer parameters, Groundwater flooding, specific models, hydrogeologic conceptual model, groundwater units, numerical simulations, water sensitive cities, CFA

Abstract

Research on Fracking in the Karoo basin yielded results that, if not considered “unexpected”, can be considered as “should have been foreseen”. Some aspects substantially impacting research on fracking are often overlooked when undertaking scientific research on an emotional topic such as fracking. This presentation aims to provide insights and recommendations based on the experiences and outcomes of current research on hydraulic fracturing or “fracking” in the Karoo basin of South Africa. Fracking has been a subject of significant research and debate over the past decade. Topics, each with its challenges, include 1) The scale of exploration/production extent (Site specifics), 2) Importance of robust and independent research, 3) Need for stakeholder engagement and participation, 4) The complexity of environmental risks and impacts, 5) The need for a precautionary approach, 6) Regulatory and policy challenges. Several methodologies can be relied upon to compare outcomes of different aspects of fracking research in the Karoo, such as 1) Comparative analysis, 2) Meta-analysis, 3) Stakeholder mapping and analysis and 4) Data visualisation. A combination of these methodologies can be used to compare outcomes of different aspects of fracking research in the Karoo and provide insights and recommendations for future decision-making and planning. Ultimately, the decision to allow Fracking should be based on a balanced assessment of potential risks and benefits, considering long-term impacts on the environment, economy, and communities.

Abstract

Characterisation of fracture positions is important when dealing with groundwater monitoring, protection and management. Fractures are often good conduits for water and contaminants, leading to  high  flow  velocities  and  the  fast  spread  of  contaminants  in  these  conduits.  Best  practice guidelines related to groundwater sampling suggest that specific depth sampling with specialised bailers or low flow purging are the preferred methodologies to characterise a pollution source. These methods require knowledge about the fracture positions and, more importantly, flow zones in the boreholes. Down-the-hole geophysical and flow logging are expensive, complicated and time consuming. Not all fracture zones identified with geophysical logging seem to contribute to flow through   the   borehole.   An   efficient   and   cost-effective   methodology   is   required   for   the characterisation of position and flow in individual fractures. This research reviewed the use of Fluid Electrical Conductivity (FEC) logging to assist with the development of a monitoring protocol. FEC logging  proved  to  be  beneficial  as  it  provided  individual  fracture  positions,  fracture  yields  and vertical groundwater flow directions. FEC logging proved to be fast, cost-effective and practical in deep boreholes. The technique allows the development of a site-specific sampling protocol. The information so obtained assists with the identification of the appropriate sampling depths during monitoring.

Abstract

POSTER The Department of Transport and Public Works has been involved with the building and upgrading of schools in the Western Cape, as well as providing green areas for sports fields. Due to the excessive costs of using municipal water the option of using groundwater for irrigation was investigated by SRK Consulting. A number of successful boreholes have been scientifically sited, drilled and tested since 2011. The boreholes have been equipped with pumps and data loggers have been installed in several. These data loggers measure time-series water levels and temperature while the flow meters measure the discharge rate and the quantity of groundwater used. Currently groundwater is being abstracted to irrigate the sports fields. Initially some problems were encountered. Boreholes were not operating optimally due to incorrect pump sizes resulting in water levels to be at pump inlet depths and pumps were not being switched off for recovery. However, due to continuous monitoring, the pumping rates and times were adjusted accordingly. It is imperative that all boreholes are equipped with loggers and continuously monitored to ensure that the boreholes are being optimally and sustainably used. Monitoring groundwater abstraction and aquifer water levels provides critical information for proper groundwater resource management. It is envisaged that schools will become proactive and participate in the groundwater monitoring. The latter will assist with groundwater awareness and assist in the use of alternative water sources and ease the burden on already stretched conventional sources.

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.

Abstract

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

Abstract

The Western Cape of South Africa is rich in small stream sized rivers forming part of its water resources. The Lourens river and Eerste river, both situated in this region are the base for this study. Rivers are affected by their surrounding environments and the continuous development around these rivers could affect their health adversely. Diverse land-use patterns contribute to a wide range of pollutants with different characteristics. Indeed, some of the pollution levels in the Eerste and Lourens rivers were linked directly to specific land-use practices surrounding the rivers. However, the large change in weather during a seasonal cycle causes a significant difference in pollution levels too, because the transport of pollutants from the source to the rivers is primarily based on surface run-off, which in turn is predominantly dependent on the precipitation of the region.

A six months long monitoring in 2016 showed that processes like surface run- off, together with first flush events and dilution control the pollution concentrations in the Lourens river and Eerste river. Physicochemical parameters, major agricultural nutrients and industrially produced heavy metals all reacted differently to these processes, thus, providing an insight into the effects continuous development and climate change have on surface water as a national resource. Interestingly, both rivers included sections with substantial retention and/or reduction of pollutants. The natural riparian vegetation, hyporheic zone and microbial community present in these rivers are proposed to be the main drivers behind both rivers’ ability to reduce or retain pollutants. These drivers are sensitive to their environment and react differently depending on the weather, available nutrients, and physicochemical environment. With the effects of climate change becoming more apparent, it is important to study the impact of warmer temperatures, longer droughts, and heavier rain events, for instance, on the pollutant retaining capabilities of these streams.

Abstract

Faced with a burgeoning population and property growth, and in preparation for a future drier climate regime; the coastal town of Hermanus in the Western Cape has set up two wellfields to abstract groundwater from the underlying aquifer in order to augment the constrained surface water supply from the De Bos Dam.
Water Use Licences (WUL) were issued to the Overstrand Municipality in June 2011 and December 2013. The licences authorise a maximum annual abstraction of 1 600 Ml of water from the Gateway wellfield and 800 Ml of water from the Volmoed and Camphill wellfield via several boreholes. The water abstracted from the Gateway wellfield is pumped via a booster pump station to the Preekstoel Treatment Plant. The Volmoed and Camphill wellfield are situated at a higher altitude allowing for a gravity feed pipeline.
Earth Science Company, Umvoto Africa, has the responsibility to ensure Resource Quality Objectives are met which include balancing the need to protect the resource on the one hand; and the to develop sustainable utilisation of the Hermanus groundwater resources and compliance with the WUL on the other. The consultancy provides hydrogeological support, wellfield management and technical advice in operating the boreholes, pumps, boosters and related infrastructures.
Running the operations of the wellfield relies on a high-tech, semi-automated system, incorporating a remotely controlled, telemetry based structure. Vital parameters are monitored by electronic sensors, feeding data to processors which alters pump performance to maintain specified boundary levels. Data is simultaneously communicated via telemetry to a central control which uses data acquisition software to portray information to the operators. Warning alarms both alert operators via SMS and in certain instances auto-shut down the system.
To ensure ecological sustainability of the ground water resource, the wellfield also requires hydrogeological monitoring at far field locations within the recharge areas. Some of these locations are in remote areas making data download costly. The high-tech telemetry approach is used with positive results.
Any automated telemetry system is prone to malfunction and environmental hazards. The challenge lies in managing this and providing sufficient back up and duplication of systems.
The paper gives an overview of the components and flow of data based on the experiences gained during the evolution and development over 12 years of operation. Automation produces vast data bases which are often not sufficiently analysed, the premise that "once collected, the task is done". However data is only as good as the people who drive the systems and this paper provides a critical analysis of human intervention in an automated system and the decisive role of quality-checks. Finally the paper seeks to provide a pragmatic guideline for water users to comply with the WUL and institutional regulations.

Abstract

What are the key institutions, both formal and informal, that determine actual groundwater use in the Ramotswa aquifer? Are current institutions at regional, national and sub-national levels adequate to collaborate for equitable benefit-sharing for the future? These are the questions that the paper will address based on early findings of a project aimed at determining the role the Ramotswa aquifer can play in addressing multiple-level water insecurity, drought and flood proneness, and livelihood insecurity. Groundwater resources are critical in the SADC region

Abstract

Groundwater recharge assessment was undertaken in the crystalline aquifer of the Upper Crocodile River Basin, Johannesburg South Africa. The basin is characterised by the complex hydrogeological setting represented by weathered and fractured granitic gneisses overlain by quartzite, shale and dolostone. A number of recharge estimation methods including the Stable Isotope Enrichment Shift method, were tested. The measurement of δ 18O and δD in springsrevealed the presence of high elevation recharge or cold weather recharge that occurs prior to extreme evaporation, undergoing deep circulation and discharging at the contact between the Witwatersrand quartzite and the underlying shale. In the dolostones, recharge occurs after evaporation at higher elevation undergoing deeper circulation through the dissolution cavities.

The Water Table Fluctuation method in the dolostone resulted in the mean annual recharge of 99 mm/year, representing 14% of mean annual precipitation. The Reservoir Water Balance method revealed that the Pretoria Group shale aquifer contributes 16% of dam water outflow per year (groundwater discharge) which equates to 3 429 662 m3 on average, while 7% of dam inflow is lost to groundwater constituting groundwater recharge of average 2 084 131 m3 per annum. Baseflow Separation method applied gave an average recharge value of 9.4% for the entire catchment. The estimated average recharge for the entire catchment was found to be 13% corresponding to 91 mm, which equates to 374 Mm3 . The Stable Isotope Enrichment Shift Method resulted an average annual recharge of 26.1% in the aquifers composed of quartzites and 3% in the dolostones. The method is found to be promising for application in spring regimen however, a further development is recommended since small shifts exaggerate recharge while large shifts undermine it.

Abstract

The groundwater risk map for the Karoo aquifers has been developed by incorporating the major geological, hydro-geological and uranium concentration factors that affect and control the groundwater contamination using GIS-based DRIST model. This work demonstrates the potential of artificial intelligence to produce a map by using various spatially geo-referenced digital data layers that portray cumulative aquifer sensitivity ratings across the Karoo Uranium Province, South Africa. This provides a relative indication of groundwater risk to uranium contamination. The pollution index used in this analysis was the uranium concentration (expressed as ?g/L). The selection of this index was based not only on the fact that it constitutes the main contaminant that occurs naturally in the geology of the study area but also because it is a prime health hazard and its presence in concentrations that exceed the drinking water guidelines is a representative indicator of groundwater quality degradation. The methodology used for assessment of groundwater risk was based on an approach which was modified specifically for assessment of Uranium pollution at a regional Karoo Uranium Province, where the five DRIST maps were integrated to form an intrinsic vulnerability map. The results show that the high risk for contamination of groundwater by uranium covers the central and northern parts of the study area. The southern part is slightly less risky due to a combination of parameter settings which tend to favour attenuation as compared to transport of uranium in the subsurface. This parameter includes; rocks with good chemical attenuation properties, deeper groundwater table, and less yielding aquifers. The results were validated using the area under the curve approach and a high validation value of 0.737 was obtained. Thus, the groundwater risk map developed can be used for regional environmental planning and predictive groundwater management

Abstract

The availability of freshwater is one of the major development challenges that South Africa faces. South Africa is a water-scarce (semi-arid) country with rainfall distributed unevenly and away from the centres of major developments. The rainfall is tied to seasonal cycles that drive us repeatedly between floods and droughts. This paper serves to study the groundwater chemistry in light of the uranium mining that precedes shale gas fracking in the Karoo Uranium Province. The aim is to have groundwater baseline chemistry assessment before mining commence in order to be able to track mining effect on groundwater in the future. A total of 128 samples are dealt with in this work, 112 collected from groundwater, 9 collected from springs and 7 extracted from a database. The samples were analysed for physical parameters, cations, anions and metals. Redox potential was also determined as it plays a pivotal role because it controls the availability and form of uranium in a solution. Uranium is a radioactive actinide naturally occurring in the area. Therefore, this assessment will be crucial in order to understand how changing redox and pH conditions affect uranium solubility and to estimate the extent of uranium transport by water during and after mining. The effects of the redox potential and pH on uranium mobility have been examined in this work by means of computer modelling by using the Geochemist’s Workbench (GWB) 11.0. The composition of the water used for modelling resembled that of a typical bedrock groundwater of Karoo Uranium Province. The simulations were carried out under different redox potentials at different pH levels in the presence of ferrihydrite, dissolved organic matter and carbonates/bicarbonates to include the effects of uranium adsorption. The results show that the redox potential at which the uranium mineral (uraninite) dissolves varies depending on the pH of the groundwater.

Analysis of the simulation results indicated that the dissolution of uraninite takes place at a lower Redox condition with increasing pH (alkaline pH condition). This means higher redox conditions are needed for the dissolution of uraninite at low pH. Moreover, it is further concluded that the adsorption of uranium to ferrihydrite and carbonates is important at pH 6-10 and pH 5-8 respectively, which therefore play an important role in controlling the mobility of uranium in the modelled groundwater.

Abstract

The International Association of Hydrogeologists and UNESCO's International Hydrological Programme have established the Internationally Shared (transboundary) Aquifer Resource Management (ISARM) Programme. This multiagency cooperative program has launched a number of global and regional initiatives designed to delineate and analyze transboundary aquifer systems and to encourage riparian states to work cooperatively toward mutually beneficial, sustainable aquifer development and management. The Stampriet Transboundary Aquifer System was selected as one of the three case studies funded by UNESCO. The Stampriet Aquifer System is located in the arid part of the countries (Botswana, Namibia and South Africa) where groundwater is a sole provider for water resource. The area is characterised by the Kalahari (local unconfined aquifer) and Nossob confined aquifer

Abstract

The geochemical study of deep aquitard water in the southern Golan-Heights (GH), Israel, reveals the complex paleo-hydrological history affected by the intensive tectonic activity of the Dead Sea Rift (DSR). The sampled water collected from new research boreholes exhibits relatively high salinities (2,000-10,000 mg Cl/L), low Na/Cl ((HCO3 +SO4 )). δ18OV-SMOW and δDV-SMOW values are relatively depleted (~-7‰ and ~-42‰, respectively), while 87Sr/86Sr ratios are enriched compared to the host rocks. Lagoonary brines with similar characteristics (excluding the water isotopic compositions) are known to exist along the DSR. These brines formed 10-5 Ma ago from seawater that transgressed into the DSR and subsequently underwent evaporation, mineral precipitation and water-rock interactions. These hypersaline brines intruded into the rocks surrounding the DSR and based on the current study, also extended as far as the southern GH. Further, following their subsurface intrusion into the GH, the brines have been gradually diluted by isotopically depleted freshwater, leaving only traces of brines nowadays. The depleted isotopic composition suggests that the groundwater system is recharged at high elevations in the north. It is also shown that variable hydraulic conductivities in different formations controlled the dilution rates and subsequently the preservation of the entrapped brines. The paleo-hydrological reconstruction presented here shows that the flow direction has reversed over time. Brines that initially intruded from the rift have since been gradually flushed back to the rift by younger fresh groundwater.

Abstract

This study aims to investigate the groundwater circulation and hydrogeochemical evolution in the coastal zone of Xiamen, southeast China, which can provide a reference for the development of water resources and the protection of soil and water environment in the coastal areas. A close connection between mountains and the sea characterizes the southeast coast of China. Although rainfall is abundant, the topography limits it, and water resources quickly run into the sea. Coupled with a concentrated population, water is scarce. In addition, this area’s water and sediment environment are influenced by human activities and geological conditions. Its changing trend also needs further study. Therefore, using hydrochemical analysis, isotope technology, numerical simulation and other techniques, this study took Xiamen City on the southeast coast as an example to study the groundwater circulation and the environmental evolution of water and sediment. The results show that although the aquifer is thinner, there is still deep groundwater circulation, and the seawater intrusion range of deep aquifer is much further than that of shallow aquifer. In addition to geological causes, human activities have become the main factors affecting groundwater quality, especially nitrate and lead. The nitrate content even exceeds the content of the major ionic components. Introducing land-based pollutants has also contributed to declining seawater and sediment quality in the Bay area. In general, the main pollutants in coastal areas include nutrients, heavy metals and new pollutants.

Abstract

Drilling of five shallow (300m) boreholes was undertaken by the Council for Geoscience at Beaufort West. This was to characterise shallow aquifers and to determine the possible deeper aquifers linked to dolerite sills respectively. Furthermore, to determine the interconnectivity between shallow and deep aquifers. The five shallow boreholes B01H_BW, B02H_BW, B03H_BW, B04H_BW and B05H_BW have depths of 151m, 169m, 151m, 169m and 169m respectively. B02H_BW is currently used as a municipal production borehole and has produced volume of more than 134ML since inception February 2018, whilst the others are used for monitoring. Additionally, the two deep monitoring boreholes, R01-BW and R02-BW have depths of 1402m and 517m respectively. The seven boreholes drilled intersected the Poortjie Member, Abrahamskraal Formations (deep boreholes), Waterberg Formation and Tierberg Formation (R01_BW). An east-west striking dolerite sill that is dipping northwards was encountered during the drilling of the deep boreholes. Boreholes closer to this sill showed more brecciation and generally have a high yield, however, during drilling and pumping test there was no indication of water inflow related to the sill. Water strikes in brecciated rock were concentrated in borehole B03H-BW and reduce northward in borehole B02-BW and more rapidly southward in borehole B04H-BW. All the drilled boreholes except R01-BW that was not yielding enough were tested for aquifer parameters and sustainable yields. Interconnectivity between R02-BW and B04H-BW was confirmed when a drawdown response was observed in B04H-BW during pumping of R02-BW. The flow rate encountered in the boreholes indicates a strong yield in boreholes associated with the brecciated rock (B02H-BW, B03-BW, B04H-BW and R02-BW). Findings indicated that these boreholes are drilled in the same unconfined aquifer where the main water strikes are encountered on the contact between the Poortjie Member and the Abrahamskraal Formation.

Abstract

The occurrence of emerging organic contaminants (EOCs) in the aquatic environment is of no surprise since these are applied for various purposes daily. This study investigated the changes in EOCs concentrations in the water between 2019 and 2020. During rainy seasons, samples were collected from dams and surrounding boreholes in the Eastern Basin of the Witwatersrand Goldfields. During the first and second laboratory analyses, 24 and 11 analytes were screened in the water samples. The findings indicated that in 2020, compounds such as caffeine, sulfamethoxazole, atrazine and metolachlor displayed detection frequency exceeding 2019. This indicates that the occurrence of these compounds in the aquatic system has increased within a year. Whilst carbamazepine was still traced in 12 sites as previously observed in 2019, compounds estradiol, estrone, bisphenol A and ibuprofen were traced in fewer sites than they were detected in 2019. Compounds 4-nonylphenol, methylparaben, caffeine and atrazine were detected in all the samples analysed for 2019 and 2020, respectively. Antiretrovirals (ARVs) were analysed once and were detected in most sites, with efavirenz registering the highest (12/18) detection frequency. Assessing the occurrence of EOCs in boreholes according to the depth indicated that bisphenol A and estrone were traced in greater concentrations in deep than shallow aquifers, whilst the opposite was observed for atrazine. This study showed groundwater susceptibility to contamination by EOCs, with concentrations of most compounds increasing with time due to their high usage and improper sewer systems in the area.

Abstract

PMWIN5.3 has been one of the most commonly used software for groundwater modelling because of its free source and the adoption of the popular core program MODFLOW. However, the fixed formats required for data input and lack of GIS data support have posted big challenges for groundwater modellers who are dealing with large areas with complicated hydrogeological conditions. In South Africa, most geological and hydrogeological data have been captured and stored in GIS format during various national research projects such as WR2005, NGA, etc. Therefore, a proper linkage between PMWIN and ArcGIS is expected to do the pre-processing for modelling in PMWIN. Visual Basic for Application (VBA) embedded in ArcGIS 9.3 was used to develop the linkage. Based on the conceptualisation of the study area, the model dimension, discretisation and many value-setting processes can be easily carried out in ArcGIS other than directly in PMWIN. Then the grid specification file and other input files can be exported as the PMWIN-compatible files. The functions on the modification of model geometrics have also been integrated with the toolbar. The linkage can be used with a higher version of PMWIN or ArcGIS. It has been applied to several gold fields in the Witwatersrand gold basin to simulate the groundwater flow and mass transportation for various conditions and scenarios. One of the applications will be presented in this paper. It has been proven that the linkage is efficient and easy to use.

Abstract

An approach for evaluating the sustainability of managed aquifer recharge (MAR) has been developed and applied in Botswana. Numerical groundwater modelling, water supply security modelling (SWWM) and multi-criteria decision analysis (MCDA) are combined to thoroughly assess hydrogeological conditions, supply and demand over time and identify the most sustainable options. Botswana is experiencing water stress due to natural conditions, climate change and increasing water demand. MAR has been identified as a potential solution to increase water supply security, and the Palla Road aquifer, located 150 km northeast of the capital, Gaborone, has been identified as a potential site. To evaluate the potential of MAR and if it is suitable for improving water supply security, three full-scale MAR scenarios were evaluated based on their technical, economic, social and environmental performance relative to a scenario without MAR. The numerical groundwater model and the WSSM were used iteratively to provide necessary input data. The WSSM is a probabilistic and dynamic water balance model used to simulate the magnitude and probability of water shortages based on source water availability, dynamic storage in dams and aquifers, reliability of infrastructure components, and water demand. The modelling results were used as input to the MCDA to determine the sustainability of alternative MAR scenarios. The results provide useful decision support and show that MAR can increase water supply security. For the Palla Road aquifer, storage and recovery with a capacity of 40 000 m3 /d is the most sustainable option.

Abstract

Denmark is a small country in the northern part of Europe. The water supply in Denmark is solely reliant on groundwater. In the past 40 years Danish groundwater management has undergone a major development. A key aspect of this, which could be of relevance in South Africa, is The Danish Groundwater Vulnerability Mapping. During a 15 year period, Denmark has spent 2.7 billion DKK (App. 385 million USD) on mapping 40 % of Denmark, in order to conduct a thorough vulnerability mapping and proper delineation of catchment areas and groundwater protection zones. The mapping has been developed intensively through the years.

The approach includes development of key components as practice oriented guidance documents on all the professional areas of groundwater mapping, geophysical methods, groundwater modelling etc. As an example the airborne geophysical method of Sky-TEM which is a spin-off from the mapping can be mentioned. Other key tools in the groundwater mapping is geological modelling in GeoScene3D and groundwater modelling in GMS/MODFLOW and MIKE SHE. The foundation for Danish Groundwater Mapping is access to data. In Denmark almost all subsurface data is made available in publicly accessible databases. There are dedicated databases for; boreholes (JUPITER), geophysical data (GERDA), geological and groundwater models (Model database) and groundwater reports (Report database). In recent years Denmark has increased its focus on sharing this knowledge with other countries, including South Africa, China and the United States. Through the Strategic Water Sector Cooperation Program (SSC) on Water between the South African Department of Water and Sanitation and the Danish Ministry for Environment and Food, the Danish method of Groundwater Mapping is being tested on two case studies, in South Africa. One is of an alluvial aquifer in Western Cape, which has similarities to the Danish geological setting. The other is in a fractured rock setting which is widespread in South Africa, but seldom seen in Denmark.

Abstract

Floods result in significant human and economic losses worldwide every year. Urbanization leads to the conversion of natural or agricultural land covers to low-permeability surfaces, reducing the infiltration capacity of the land surface. This amplifies the severity and frequency of floods, increasing the vulnerability of communities. Drywells are subsurface structures built in the unsaturated zone that act as managed aquifer recharge facilities to capture stormwater runoff. They are particularly well-suited for the urban environment because of their low land occupancy. In this study, we utilized an integrated surface-subsurface flow modelling approach to evaluate the effectiveness of dry wells in reducing urban runoff at a catchment scale. We developed a 3D model with HydroGeoSphere, characterizing a synthetic unconfined aquifer covered by a layer of low-permeability materials. Sensitivity analyses of land surface conditions, aquifer properties, dry well designs, and rainfall conditions were performed. Model results indicated that dry wells are more effective in reducing runoff when the land surface has a higher Manning roughness coefficient or the aquifer material has a higher hydraulic conductivity. Dry wells should be situated beneath drainage routes with high runoff flux to achieve optimal performance. Increases in dry well radius or depth enhance the infiltration capacity, but deeper dry wells can contaminate groundwater through infiltrating stormwater. Dry well performance declines with higher rainfall intensity, emphasizing the need for local rainfall intensity–duration–frequency (IDF) data to inform the design level of dry wells in specific catchments.

Abstract

An end-member mixing analysis has been conducted for the hydrogeological system of the endorheic catchment of the Fuente de Piedra lagoon (Malaga, Southern Spain). Three end-members have been considered because of the three main groundwater types related to the different kinds of aquifers found in the catchment. The model’s objective is to help understand the distribution of the organic contaminants (including contaminants of emerging concern [CECs]) detected in groundwater samples from the catchment. Results suggest that some contaminants can be related to long groundwater residence time fluxes, where contaminant attenuation can be limited due to low oxygen levels and microbial activity. The three main aquifer types are: (i) unconfined carbonate aquifers with low mineralized water corresponding to two mountain ranges with no human activities over theirs surface; (ii) an unconfined porous aquifer formed by Quaternary and Miocene deposits, exposed to pollution from anthropogenic activities (agriculture and urban sources); and (iii) a karstic-type aquifer formed by blocks of limestones and dolostones confined by a clayey, marly and evaporite matrix from Upper Triassic. The groundwater monitoring campaign for the analysis of organic contaminants was carried out in March 2018. Target organic contaminants included pharmaceuticals, personal care products, polyaromatic hydrocarbons, pesticides, flame retardants and plasticizers. For the mixing model, a dataset was built with the hydrochemistry and isotopic results (δ2 H, δ18O) from the monitoring campaign conducted in March 2018 and from campaigns carried out in previous years and retrieved from the literature.

Abstract

Groundwater is an essential source of water worldwide. The increased reliance on groundwater has caused the mining of many aquifers, a situation compounded by climate change, rising surface-air temperature, declining precipitation, and reduced groundwater recharge in many regions. The global annual intensity of groundwater use rose from 128 to 155 m3 per capita between 1950 (when the world population was 2.5 billion people) and 2021 (when the population was 7.9 billion people) and is herein projected to rise to 178 m3 per capita by 2050 as the world’s population is projected to increase (to 9.7 billion people by 2050) throughout the rest of the 21st century and beyond. This study projects a global annual groundwater depletion of 1,008 km3 by 2050, representing a 256% rise from the estimated 2010 depletion. This projection is most likely a lower bound of the actual groundwater depletion that would be realized considering environmental flows, historical trends of global economic growth, and climate-change impacts, thus being a harbinger of rising environmental degradation (e.g., land subsidence, seawater intrusion, streamflow reduction, aridification). Measures to achieve groundwater sustainability are herein identified.

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.

Abstract

The Bauru Aquifer System (BAS) is a significant source of water supply in the urban area of Bauru city. Over the last decades, BAS has been widely affected by human activities. This study evaluates the nitrate plume in groundwater from 1999 to 2021 and how it relates to urbanization. The methods used were analysis of the data of 602 wells, survey of the sewer network and urbanization, and reassessment of nitrate concentration data. The seasonal analysis of 267 groundwater samples allowed the identification of concentrations up to 15.1 mg/L N-NO3 - mainly from the area’s central region, where the medium to high-density urban occupation dates back to 1910. Otherwise, the sewage system was installed before 1976. The reactions controlling the nitrogen species are oxidation of dissolved organic carbon, dissolution of carbonates, mineralization, and nitrification. Wells, with a nitrate-increasing trend, occur mainly in the central and northern regions, settled from 1910 to 1980-1990, when no legislation required the installation of the sewage network before urbanization. In turn, wells with stable or decreasing nitrate concentrations occupy the southwestern areas. Over the years, the concentrations of these wells have shown erratic behaviour, possibly caused by the wastewater that leaks from the sewer network. The bivariate statistical analysis confirms a high positive correlation between nitrate, sanitation age, and urban occupation density, which could serve as a basis for the solution of sustainable groundwater use in the region. Project supported by FAPESP (2020/15434-0) and IPA/SEMIL (SIMA.088890/2022-02).

Abstract

Water budget assessment and related recharge in karstified and fractured mountainous aquifers suffer a large uncertainty due to variable infiltration rates related to karst features. The KARMA project (karma-project.org), funded by the European Commission, has addressed this knowledge gap. The increase in human withdrawals and the effect of climate change can modify the recharge rate and, consequently, the spring discharge. The regional aquifer of Gran Sasso mountain, Central Italy, has been investigated by monitoring spring discharge isotope composition and calculating the inflow using a GIS approach on 100x100 m cells, considering local conditions, including karst features. The results for the 2000-2022 period highlight the preferential recharge area of the endorheic basin of Campo Imperatore (up to 75% of precipitation) and a mean infiltration of about 50% of rainfall. Different methods applied for recharge evaluation (Turc, Thornthwaite and APLIS) agree with a recharge rate close to 600 mm/year. This amount roughly corresponds to the spring discharge, evidencing: i) a “memory effect” in spring discharge, which is higher than previewed during dry years; ii) a variation in discharge due to rainy and drought year distribution, frequently recorded at springs with delay (1-2 years); iii) no significant trends of spring depletion since last 20 years; iv) the risk of lowering of snow contribution to recharge due to the temperature rise. The results provide updated information to the drinking water companies and the National Park Authority for sustainable management of the available groundwater resources.

Abstract

Groundwater in South Africa is an essential source of potable water for rural communities, farms and towns. Semi-arid conditions of South Africa, a growing population and surface water resources almost entirely being exploited to their limits, increase  the demand for groundwater resources. Therefore,  the  relation  between  the  geology  and  geohydrology  of  South  Africa  becomes  an important tool in locating groundwater resources that can provide sustainable quantities of water for South Africans. A document was therefore compiled, providing valuable geohydrological information  on  the  geological  formations  of  the  whole  of  South  Africa.  The  information  was gathered by means of interviews with experienced South African geohydrologists and reviewing of reports and articles of geohydrological studies. The geohydrological characteristics discussed include rock/aquifer parameters and behaviour, aquifer types (primary of secondary), groundwater quality, borehole yields and expected striking depths, and geological target features and the geophysical method  used  to  locate  these  targets.  Due  to  the  fact  that  90%  of  South  Africa’s  aquifers  are classified as secondary aquifer systems, groundwater occurrence within the rocks of South Africa is mainly controlled by secondary fractured systems; therefore, understanding the geology and geological processes (faulting, folding, intrusive dyke/sills and weathering) responsible for their development and how they relate, is important. However, the primary aquifers of South Africa (Coastal Cenozoic Deposits) should not be neglected as these aquifers can produce significant amounts of groundwater. Drilling success rates and possibility of striking higher yielding boreholes can be improved dramatically when an evaluation of the structural geology and geohydrological conditions of an area together with a suitable geophysical method is applied. The ability to locate groundwater has been originally considered (even today) a heavenly gift and can be dated back to the Biblical story of Moses striking the rock to get water: “behold, I will stand there before thee there upon the rocks thou shalt smite the rock and there shall come water out of it” (Exodus 17:6).