Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 101 - 150 of 795 results

Title	Presenter Name Sort ascending	Presenter Surname	Area	Conference year	Keywords
Groundwater and surface water interaction in farming areas in the Rawsonville area of the Western Cape.	Siphumelelo	Mbali	Western Cape	2015
Abstract The understanding of groundwater and surface water interaction is important for the planning of water resources in particular for farming areas. The interactions between groundwater and surface water are complex. To understand the relationship of groundwater and surface water interactions it is important to have a good understanding of the relation of climate, landform, geology, and biotic factors, a sound hydrogeoecological framework. Surface-water and groundwater ecosystems are viewed as linked components of a hydrologic continuum leading to related sustainability issues. In this study the Gevonden farm in Rawsonville will be used as the study site. This study site forms part of the Table Mountain Group (TMG). The methods to establish the relationship of groundwater and surface water interaction are collection of rainfall data monthly, river channel parameters at the farm such as the discharge on a monthly bases, chemistry of the water in the stream and groundwater were also be analyzed and pumping tests will be conducted twice to get the hydraulic parameters of the aquifer. The aquifer parameters will be analyzed using the Theis and Cooper-Jacob methods. The river has lower water levels in the summer months and this is also the case in the water levels in the boreholes on the farm, however in winter the opposite is true. The chemical analyses which are identical indicate that there is groundwater and surface water interaction in the farm. The degree of the interaction differs throughout the year. The results show that the interaction is influenced by the rainfall. The results clearly suggests that the farmers need to construct dams and drill pumping borehole in order to have enough water to water their crops in the summer season as by that time the river is almost dry. {List only- not presented}
Groundwater Contamination In The Cape Flats	Sinazo	Mnyaka	Cape Flats, Cape Town, Western Cape	2013	Groundwater Contamination, Groundwater, aquifer protection, Water treatment, groundwater protection
Abstract Groundwater is the water that is found beneath the surface of the ground in a saturated zone (Bear 1979). Groundwater contamination refers to the groundwater that has been polluted commonly by human activities to the extent that it has higher concentrations of dissolved or suspended constituents. The scale of the potential supply of groundwater from the Cape Flats Aquifer Unit (CFAU) is very significant due to the increase of the population in Cape Town that leads to limited water resources (Maclear 1995). Groundwater contamination is a threat in the Cape Flats. This is because sand is more susceptible to pollution as a result of urbanisation, industrialisation, intense land use area for waste disposal and agricultural activities (Adelana 2010). The aim of this paper is to evaluate groundwater contamination and assess possible prevention and treatment measures in the CFAU. Pumping tests were done in UWC site in Borehole 5 (pumping borehole) and Borehole 4 (observation borehole) for six hours; three hours was for the pumping and the other three hours for recovery. This was done in order to see how the aquifer recovers after pumping. Water samples were also taken and analysed in the lab. This was done to find the type of contamination, whether it is degradable or non-degradable. The Borehole 5 drawdown plot is showing a straight line. This suggests a linear flow and that there is no confining bed beneath. This is because straight lines are showing the Cooper-Jacob type curve, which is for unconfined aquifers. The curve of Borehole 4 can be fitted to a Theis-type curve. This suggests a radial flow pattern indicating homogeneous characteristics in the deeply weathered zone and that there is a confining bed beneath. This is because aquifers responding in the same manner as the Theis-type curve, are confined aquifers (Hiscock 2005).The groundwater samples are showing a TDS range of 260 to 1 600 mg/l. This could be the result of the waste water treatment plant that is near UWC and the industries that are near the airport and at Bellville South. In conclusion, the geology of the CFAU is very susceptible to groundwater contamination, which is due to agricultural, industrial and human activities.
Development Of A Conceptual Understanding Of Hydrogeological Relationship Between The Skurweberg Aquifer And Wetlands In The Steenbras Catchment	Sinawo	Jack	Skurweberg Aquifer, Steenbras Catchment	2019	Drought, City of Cape Town, Steenbras, Skuweberg Aquifer, Groundwater Abstraction, Ecosystems
Abstract The City of Cape Town (CoCT) commenced a study into the feasibility of the Table Mountain Group aquifers (TMGA) for augmenting the water supply to the city in 2002. It comprised drilling of exploration boreholes in several target areas and the establishment of a hydrogeological and ecological monitoring network. Due to the prolonged drought and associated water crisis, the CoCT decided to fast-track the TMGA development in 2017. The first wellfield is currently developed within the catchment area of the Steenbras Dam comprising production boreholes targeting the Skurweberg and the Peninsula aquifers of the TMGA. Since groundwater abstraction from the Peninsula and Skuweberg aquifers might have a short-term or long-term impact on aquatic ecosystems (i.e. streams and wetlands) that are linked to the TMGA. As a result, evaluation of the potential impact of groundwater abstraction from this aquifer system requires an understanding of the nature and extent of groundwater dependency of the ecosystems. A variety of data sets and parameters have been measured over the last decade at ecological monitoring sites across the study area, of which two sites are located within the Steenbras catchment that are probably connected to the Skurweberg Aquifer. Recently further boreholes and monitoring sites have been added. This paper describes the various methods used and results of the analysis towards a conceptual understanding and quantification of the groundwater dependency of the selected ecosystems. While groundwater contribution is only one factor in ecosystem functioning, sustainable and adaptive management of the groundwater use must be based on the conceptual model and ongoing monitoring of the ecosystem responses.
Natural methane in the Karoo: Its occurrence and isotope clues to its origin	Siep	Talma	Karoo	2013	Methane concentration
Abstract The possible future exploitation of methane in the Karoo has stimulated work from various disciplines to examine its occurrence, exploitability and exploitation risks. Groundwater issues are vital in this context because of its possible use during exploration and exploitation, and more important, to understand the risks of its pollution during and after all these activities. This paper presents the experiences of the authors to document the presence of methane in the Karoo based on data from boreholes, springs, tunneling and deep drilling. There have been frequent anecdotal reports of explosive gas in boreholes, both dry and wet, in the Karoo. In some cases the gas is identified as methane. Thermal spring waters in the Karoo invariably contain some amounts of methane. Methane pockets have been found in the Karoo during tunneling projects and in some deep Soekor boreholes. A groundwater study in the vicinity of the Gariep Dam indicated substantial quantities of methane in warm groundwater and an association with helium. The isotope concentrations of carbon and hydrogen in methane characterise the methane-forming processes. Such analyses in samples from the central Karoo basin are consistent with that of thermogenic gas found elsewhere in the world. Towards the edges of the basin, lower 13C-values indicate that methane there is produced by microbial processes at shallower depths. The presence of thermogenic methane together with helium on the surface is likely to give clues to pathways from depth.
An investigation into the effectiveness of underground water pollution mitigation policies	Sibanda	Kin		2015
Abstract Pollution of underground water is fast becoming a global problem and South Africa is not immune to this problem. The principal objective of this paper is to investigate the effectiveness of laws and policies put in place to mitigate underground water pollution. The paper also seeks to examine the causes and types of underground water pollution followed by a closer look into the laws and policies in place to mitigate the pollution levels. Finally, the paper seeks to ascertain whether the current policies are properly implemented. The paper follows content analysis (desk research) to achieve the objectives. Policy recommendations are given based on the findings. {List only- not presented}
Rigorous Methodology For Sustainable Yield Estimation Using Groundwater Numerical Modelling Validation To Detailed Long Term Pumping Test Data	Shuaib	Dustay	Port Alfred	2017	numerical modelling, WUL, large-scale abstraction, Monitoring
Abstract Groundwater numerical models are commonly used to determine the impact that groundwater abstraction has on the ability of surrounding areas to supply water, and thus to inform Water Use Licence (WUL) Applications. However, data available is often limited to that generated by relatively short-term geohydrological studies and pumping tests. In most cases this data and the degree of defined uncertainty in the model results are sufficient. However, for large scale abstractions (such as municipal abstraction) and in sensitive or complex geological areas, a more rigorous approach to calculating the impact from pumping is recommendable. The study area is located on a syncline consisting of two sandstone aquifers. However, there was a lack of data to quantify the connectivity between the two aquifers. SRK Consulting (South Africa) (Pty) Ltd undertook a rigorous, long-term approach, which included a 3- year monitoring plan of the area, input from stakeholders, extending the hydrocensus to the entire catchment and monitoring of pumping in the area. Using this comprehensive data set, the existing numerical groundwater model was updated, re-calibrated and validated such that predictive scenarios could be run to assess the long-term potential impact of the municipal wellfield. These results were submitted for the final allocation of the WUL. Along with mitigation measures, recommendations could also be made on where to focus monitoring and future testing. This rigorous methodology and the use of long- term comprehensive monitoring data is recommended for future use in similarly complex environments to decrease uncertainty on the expected impacted area from large-scale abstractions.
Implementation Of Protection Zoning	Shuaib	Dustay	National	2013	Protection, development
Abstract Currently limited progress is made in South Africa (and Africa) on the protection of groundwater quality. To achieve the objective of water for growth and development and to provide socio- economic and environmental benefits of communities using groundwater, significant aquifers and well-fields must be adequately protected. Groundwater protection zoning is seen as an important step in this regard. Till today, only one case study of groundwater protection zoning exists in Africa. Protection zone delineation can be done using published reports and database data. However, due to the complexity of the fractured rock at the research site, more data are required. This data can be collected by conducting a hydro census and through aquifer tests. An inventory of the activities that can potentially impact water quality was done and aquifer characteristics such as transmissivity and hydraulic conductivity were determined through various types of aquifer testing. Fracture positions were identified using fluid-logging and fracture flow rates were also measured using fluid-logging data. A conceptual model and basic 3D numerical model were created to try to understand groundwater movement at the research site. The improved information will be used to build a more detailed numerical model and implement a trustworthy groundwater protection plan, using protection zoning. The expected results will have applicability to groundwater management in general. The protection plan developed during this project can be used as case study to update and improve policy implementation.
Groundwater Protection Zoning- A case study of the Rawsonville research site.	Shuaib	Dustay		2015	groundwater protection zones
Abstract Currently limited progress is made in South Africa (and Africa) on the protection of groundwater used for drinking water. To achieve the objective of water for growth and development and to provide socio-economic and environmental benefits of communities using groundwater, significant aquifers and well fields must be adequately protected. Groundwater protection zoning is seen as an important step in this regard. Till today, limited case studies of groundwater protection zoning exists in Africa. A case study at the Rawsonville research site is conducted in this research project. Generic protection zones can be delineated at the site using published reports and database data. However, due to the complexity of the fractured rock at the research site, these would be of limited value and would not provide adequate protection for the well field Baseline data was collected by conducting a hydro census and through aquifer tests. An inventory of the activities that can potentially impact water quality was done and aquifer characteristics such as transmissivity and hydraulic conductivity were determined through various types of aquifer testing. Fracture positions were identified using fluid logging and fracture flow rates were also measured using fluid logging data. A conceptual model and preliminary 3D numerical model were created to try to understand groundwater movement at the research site. The knowledge gained will be used to guide information gathering and monitoring that can be used to build a more detailed numerical model and implement a trustworthy groundwater protection plan at a later stage. The expected results will have applicability to groundwater management in general. The protection plan developed during this project can be used as a case study to update and improve policy implementation. {List only- not presented}
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.
Assessment of hydrochemistry and heavy metal contamination in the groundwater around an abandoned Copper Mine area in Klein Aub, Namibia	Shoopala	Uugulu	Namibia	2023	contamination, Copper, Heavy metal, Klein Aub
Abstract The long mining history in Namibia has resulted in numerous abandoned mines scattered throughout the country. Past research around the Klein Aub abandoned Copper mine highlighted environmental concerns related to past mining. Considering that residents of Klein Aub depend solely on groundwater, there is a need to thoroughly investigate groundwater quality in the area to ascertain the extent of the contamination. This study made considerable effort to characterise groundwater quality using a comprehensive approach of quality assessment and geostatistical analysis. Onsite parameters reveal that pH ranges between 6.82-7.8, electrical conductivity ranges between 678 - 2270 μS/cm, and dissolved oxygen ranges between 1.4 -5.77 mg/L. With an exemption of two samples, the onsite parameters indicate that water is of excellent quality according to the Namibian guidelines. The stable isotopic composition ranges from −7.26 to -5.82‰ and −45.1 to -35.9‰ for δ18O and δ2H, respectively—the groundwater plots on and above the Global Meteoric Water Line, implying no evaporation effect. Hydrochemical analyses show bicarbonate and chloride as dominant anions, while calcium and sodium are dominant cations, indicating groundwater dissolving halite and mixing with water from a recharge zone. The heavy metal pollution index of the groundwater is far below the threshold value of 100, which signals pollution; it contrasts the heavy metal evaluation index, which clustered around 3, implying that the heavy metals moderately affected groundwater. Copper, lead and Arsenic were the main contributors to the values of the indices.
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.
'Best Practice' Approach To Undertaking Detailed Groundwater Impact Assessment Studies For Proposed Solar Energy Plants	Sheila	Imrie	Jacobsdal, Free State	2015	Solar energy, EIA, best practice, groundwater management
Abstract South Africa is a country at the forefront of the solar energy revolution. Each solar energy plant implementation results in further supply of clean renewable energy to the South African electric grid, thus playing a part in helping South Africa meet its renewable energy targets, in addition to stimulating long-term economic development and creating new jobs. Active solar techniques include the use of photovoltaic systems, concentrated solar power and solar water heating to harness the energy. Particular focus has recently been on the use of concentrated solar power technology which is better able to address the issues of scalability and electric storage. The process includes the use of a liquid salt solution and also requires a reliable water source. When applying for a new solar energy plant, a geohydrological assessment is required to inform the Environmental Impact Assessment. SolarReserve South Africa (Pty) Ltd responsibly take this one step further by requesting detailed geohydrological assessments including drilling and field testing, numerical modelling and simulations, and detailed impact analysis. Of particular consideration in these assessments is the potential for groundwater to meet the plants water needs, as well as the assessment of risk and potential groundwater contamination impact from failure in the lining of the evaporation ponds. This paper describes the 'best practice' approach that has been formulated and undertaken for some previously proposed sites, and is now recommended for future use in the groundwater impact assessment of future proposed solar energy plants in South Africa. It makes use of a SolarReserve case study example, located at the farm Kalkaar near Jacobsdal in the Free State Province, to explain the main steps in the process and how the results of using this approach are important inputs in the assessment of impacts, decision-making regarding go/no-go, technology used, infrastructure and site layout, and responsible management and monitoring of the groundwater in the future.
Hydrogeochemical And Environmental Isotope Characteristics Of The Thyspunt Area, Eastern Cape, South Africa.	Seeke	Mohuba	Thyspunt, Eastern Cape	2019	Environmental Isotopes, Hydrogeochemistry, Seawater Intrusion, Hydrochemical Evolution, Regional Recharge And Hydraulic Link
Abstract Hydrogeochemical and environmental isotope investigation of the Thyspunt area, located in Eastern Cape South Africa, has been undertaken to understand the hydrogeological conditions in the area. Fifty-nine water samples from springs, wells, streams and ocean were collected for major ions, metals, and environmental isotope analyses. The hydrogeochemical and environmental isotope signatures were used to identify the interaction between various waters bodies, major hydrogeochemical processes, and possible sources of moisture in the Thyspunt area. The groundwater is characterised by electrical conductivity (EC) that varies between 286 and 7040 ?S/cm, dominant alkaline pH conditions and calcium-magnesium-bicarbonate hydrochemical water type. Hydrochemical evolution of groundwater is observed along the groundwater flow direction (west to east), from fresh calcium-magnesium-bicarbonate water type to saline sodium-chloride water type. Furthermore, mixing of calcium-magnesium-bicarbonate and sodium-chloride type groundwater is apparent in the analysed spring samples, indicating deep circulation. Gibbs plot of major ion hydrochemical data indicates that the groundwater hydrochemistry is primarily controlled by water-rock interactions (mineral dissolution) and evaporation processes. Isotopically, water samples from springs and wells have depleted isotope signatures indicative of rainfall recharge from either high attitude moisture source or recharge during colder seasons or both. None of the groundwater samples have isotope signatures similar to ocean water, signifying that there is no seawater intrusion in any of the sampled aquifers. Deuterium excess values range between -0.71 ? and 22.64 ?, suggesting the presence of numerous moisture sources. Tritium activity in groundwater varies between 0.2 T.U and 3.2 T.U, showing submodern to modern (5 - 10 years) recharge. Hydrochemical and environmental isotope similarities between spring and borehole samples confirm the fact that springs are a surface manifestation of the local groundwater flow conditions.
The effect of geology on the mobility and rebound of light non-aqueous phase liquids	Sedzani Elia	Muravha		2015	LNAPLS
Abstract Hydrogeological environments are commonly determined by the type of underlying geology; these environments may have a tremendous effect on the mobility and recovery of LNAPLs. Hydrogeological environment include intergranular sediments and bedrocks of contrasting permeability and porosity. This paper synthesizes several case studies and conceptual models of different hydrological environments and illustrates how they affect the flow characteristics and rebound of LNAPLs.
Comparative use of groundwater by invasive alien PROSOPIS SPP and co-occurring indigenous V. Karoo in a semi-arid catchment	Sebinasi	Dzikiti		2015
Abstract Groundwater is a vital source of water for many communities in South Africa and elsewhere. Besides the changing climate, rapidly spreading invasive alien plants with deep roots e.g. Prosopis spp, pose a serious threat to this water source. Dense impenetrable thickets of Prosopis occur in the drier parts of the country mainly along river channels in the Northern, Eastern and Western Cape Provinces. Few studies have quantified the actual water use by this species outside of the USA where it is native. Consequently the impacts of Prosopis invasions on groundwater resources are not well documented in South Africa. The aim of this study was to quantify the actual volumes of water used by Prosopis invasions and to establish the effects on groundwater. Because deep rooted indigenous trees that normally replace Prosopis once it has been cleared also use groundwater, we sought to quantify the incremental water use by Prosopis over and above that used by indigenous trees in order to determine the true impacts on groundwater. The study was conducted at a site densely invaded by Prosopis at Brandkop farm near the groundwater dependent town of Nieuwoudtville in the Northern Cape. One in seven trees at the site is the Vachellia karroo (formerly A. karroo) which is the dominant deep rooted indigenous tree species. Actual transpiration rates by five Prosopis and five V. karroo are being measured using the heat pulse velocity (HPV) sap flow technique. Additional HPV sensors were installed on the tap and lateral roots to study the water uptake dynamics of the trees. Groundwater levels are being monitored in four boreholes drilled across the site while sources of water used by the trees (i.e. whether soil or groundwater) is being determined using O/H stable isotopes. For similar size trees, V. karroo had higher transpiration rates than Prosopis because of the larger sapwood to heartwood ratio in V. karroo than in Prosopis. However, at the stand level Prosopis consumed significantly larger amounts of water than V. karroo. This is because Prosopis invasions had a much higher tree density than V. karroo. From August 2013 to July 2014, annual stand transpiration for Prosopis (~ 372 mm) was more than 4 times higher than that of V. karroo (~ 84 mm). Tree water uptake was correlated to changes in groundwater levels (R2 ~ 0.42) with groundwater abstractions of ~ 2600 m3/ha/y by Prosopis compared to ~ 610 m3/ha/y for V. karroo. In addition, Prosopis showed evidence of hydraulic redistribution of groundwater wherein groundwater was deposited in the shallow soil layers while V. karroo did not. Results of this study suggest that clearing of Prosopis to salvage groundwater should target dense stands while less dense stands should be prevented from getting dense. {List only- not presented}
Isotope geochemistry disentangles interactions between water and carbon cycle in Mediterranean peatland	Sebastien	Santoni	Mediterranean peatland	2023	Groundwater-Dependent Ecosystem, origin of carbon, peatland-atmosphere interface, peatland-carbon-water system, sources and sinks of carbon
Abstract This research aims to evaluate the carbon storage function of a Mediterranean peatland in changing climate conditions. The scientific strategy relies on a seasonal geochemical survey sourcing the carbon origin by considering the hydrosphere, lithosphere, biosphere, and atmosphere. This unprecedented research on a Mediterranean peatland reveals the seasonality of dissolved carbon inputs from primary production, organic matter oxidation, and time-changing recharge components within the catchment (rainwater, river water, shallow groundwater, deep groundwater). Based on the mixing proportions of all recharge water components, the study applies a reverse end-member mixing analysis to define the theoretical peat water d13CDIC value and compare it to the measured ones. The model explains 65 % of the data, demonstrating the water flow influence on peatland carbon content. In 35% of the cases, peatland processes such as primary production and organic matter oxidation drive the peat water’s carbon content. Peat organic and inorganic properties, d13CTOC, and d13CCO2 data demonstrate the role of groundwater as a CO2 source and the dominance of in situ primary production that argues in favour of carbon storage within such Mediterranean peatland. This research proves the relevance of geochemistry and isotope hydrology tools to disentangle and rank peatland water and carbon processes within peatland hydro-ecosystems. Overall, it reveals the necessity to take into account the interactions between water and carbon cycle processes, with particular consideration for groundwater as a CO2 source at the peatland-atmosphere interface, to build better models for the future evolution of the global climate.
Modelling The Progression Of AMD Plume In Karst Aquifer Using Complex Resistivity Tomography Model	Sbonelo	Zulu		2019	modelling, AMD
Abstract The costs of acid mine drainage (AMD) monitoring result in the quest for alternative non-invasive method that can provide qualitative data on the progression of the pollution plume and ground geophysics was the ideal solution. However, the monitoring of AMD plume progression by ground geophysics (time-lapse electrical resistance) proves to be non-invasive but also time consuming. This gave way to a study that focuses on the modeling of different scenarios of the karstic aquifer. The models use the field parameters such as the electrical resistivity of the host rock and the target rock, depth to the target, noise level and electrode configuration in order to ensure that the model outcomes represent the field data as much as possible. This geoelectric modeling process uses Complex Resistivity Model (CRMod) and Complex Resistivity Tomography (CRTomo) to generate geoelectric subsurface images. Different resistivity values are applied to targets in order to assess the difference against the baseline model for each target scenario. The model resistivity difference is reduced to the smallest difference possible between the reference and new models in order to gauge the lowest percentage change in the model at which the background noises start to have impact on the results. The study shows that the behavior of targets (aquifer) could be clearly detected through resistivity difference tomography rather than inversion tomography. The electrode array plays a significant part in the detection of target areas and their differences in resistance because of its sensitivity. This therefore indicates that the electrode array should be chosen according to study requirements. Furthermore, the model geometry also plays a role and this can be seen with the modelling of different target sizes, alignments and shapes. Future studies that can provide a correlation between the field quantitative data from sampling and the model outcomes have the ability to add to the knowledge field of geophysical modelling therefore reducing costs associated with field based plume AMD monitoring300-500 words without references; reach your conclusions rather than only delivering promises.
Investigating The Hydrochemical Character Of The Cape Flats Aquifer In Support Of Bulk Supply To The City Of Cape Town, South Africa.	Sasha Dean	Singh	Cape Town	2019	hydrochemical
Abstract The City of Cape Town (CoCT) and surrounding areas in the Western Cape is experiencing one of the worst droughts recorded in over a century and has been declared a disaster area. The need to develop the underlying, shallow Cape Flats Aquifer (CFA) has become of utmost importance to increase the resilience of the CoCT during times of drought. Since early 2018, over 180 boreholes have been drilled into the CFA and undergone test pumping and hydrochemical sampling. Hydrochemical analyses include macrochemical, dissolved metal and microbiological analytes to investigate the hydrochemical character of the CFA, identify potential contamination sources and better understand rock and groundwater interactions. In recent times, Contaminants of Emerging Concern (CEC) have become an important role player in groundwater hydrochemistry. Limited CEC data in South Africa prompted detailed investigations and analyses of CEC within the CFA. Groundwater within the CFA can be characterised into 3 types, predominantly linked to aquifer heterogeneity: Ca-HCO3 type (Mitchells Plain WWTW-Strandfontein), Na-Cl type (Philippi-Hanover Park) and Ca-Na-HCO3 (Bishop Lavis-Swartklip). Water quality varies across the aquifer with some areas being poor and highly contaminated, not meeting SANS 241:2015 drinking water standard. Exceedances include EC, TDS, sodium, chloride, sulphate, ammonia and TOC. Dissolved metals which exceed the standards are aluminium, iron, manganese, chromium and arsenic. These pose considerable risks to ecological functioning of the CFA and to human health if not properly treated, managed and monitored. Poor water quality within the CFA is predominantly a result of anthropogenic contamination, such as industrial pollution, unlined WWTW, leaking canals and sewage lines, agricultural fertilizers and irrigation return flow. Further sampling of surrounding surface water bodies and groundwater from boreholes will lead to the identification of contamination sources and an understanding of temporal changes in water quality to inform treatment options and costs when considering bulk supply
Suitability of drilling techniques for geological interpretation and borehole design within the Cape Flats Aquifer, Western Cape.	Sasha Dean	Singh	Western Cape	2021	Bulk water supply, MAR, Drilling, facies analysis
Abstract McGibbon, D; Riemann, K The Cape Flats Aquifer Management Scheme (CFAMS) includes both abstraction of groundwater and managed aquifer recharge (MAR) as part of the City of Cape Towns (CoCT) New Water Programme to diversify their bulk water supply and build resilience against future droughts. Since the project was initiated in early 2018, over 250 boreholes have been drilled for exploration, monitoring, abstraction, and MAR. Rotary mud drilling was used for most of the drilling due to its suitability in unconsolidated geological material, typical of the CFA. As effective as rotary mud drilling is for large scale development, it lacks in accuracy for detailed geological interpretation used for borehole siting and design (gravel pack and screen aperture size and screen position). This is due to the mixing of material and the circulation of the drilling mud washing away fine sediment which can skew grain size analysis results and obscure the vertical position and thickness of thin confining clay or organic rich lenses. The clay and organic rich layers can cause surface flooding during injection as they act as confining layers which effects borehole design and more importantly siting of MAR boreholes. To overcome this, two additional drilling techniques were explored, sonic and air core. Air core was disregarded early on due to the air creating a cavity in the underlying unconsolidated sediments. Sonic drilling, however, was successful in retrieving a continuous undisturbed core log through high resonant energy that liquefies the sediments, which are then brought to surface in a core barrel. The undisturbed continuous nature of the log allows for accurate grain size analysis and detailed vertical geological logging which can be used for facies analysis to interpret the paleoenvironment and predict the lateral extent of clay or organic rich layers that influence borehole siting, design, and the hydrochemistry.
A Methodology To Assess The Movement Of Hydrocarbons And Associated Remediation Thereof	Sascha	Roopa	National	2013	Methodology, Hydrocarbon, remediation, contamination
Abstract POSTER Water is an invaluable resource without which life would cease to exist. Supply in South Africa has become limited due to increases in demand brought upon by population growth, urbanisation and industrialisation. In Southern Africa, water systems are considerably degraded by mining, industry, urbanisation and agricultural activity and a large amount of the fresh surface water has already been utilised. The stresses on this resource will unlikely make the current usage sustainable in years to come. In order to provide for basic needs for the future, groundwater as a resource will have to play a major role. It is for this reason that groundwater integrity needs to be preserved. Hydrocarbon contamination is a huge threat to groundwater as it contains toxic substances that are insoluble in water. These toxins are carcinogenic and mutagenic, and have a major impact on human health and ecosystem stability. When spilled, hydrocarbons will move downward through the unsaturated zone under the influence of gravity and capillary forces, trapping small amounts in the pore spaces. Accumulation will result in added weight along the water table, forcing the entire surface to be displaced downward. Some of the components can dissolve in the groundwater and move as a plume of contaminated water by diffusion and advection within the saturated zone. The transport of contaminants from petroleum hydrocarbon spills needs to be described in terms of a multiphase flow system in the unsaturated zone, taking into account contaminant movement in each of the three phases: air, water and free light non-aqueous phase liquid. Petroleum hydrocarbon behaviour in the subsurface is additionally complicated by the presence of multiple compounds, each with different properties. The net result is that some hydrocarbon fractions are transported faster than others and a contamination plume of varying intensity may spread over a large area. The aim of this study is to develop a methodology to map and simulate the movement of groundwater that has been contaminated by hydrocarbons and to determine the fate of the water quality through decomposition. Associated remediation options will be determined thereafter.
Hydrogeological Conceptual Model of Kinsevere Mine	Sarah	Mahlangu	Africa	2023	Groundwater; Conceptual Model; Copperbelt; Dewatering; Hydrogeology
Abstract Kinsevere Mine is an open pit copper mine located within the Central African Copper Belt, experiencing common water challenges as mining occurs below the natural water table. The site’s conceptual model is developed and updated as one of the tools to manage and overcome the water challenges at and around the mining operations. The natural groundwater level mimics topography but is also affected by the operations. The pits act as sinks. The water table is raised below the waste dumps due to recharge in these areas, and the general groundwater flow direction is to the east. The site is drained by the Kifumashi River, located to the north of the site. Water levels from dewatering boreholes and natural surface water bodies define the site’s piezometric surface. The geological model is adopted to define the aquifers and groundwater controls. The Cherty Dolomites, a highly fractured Laminated Magnesite Unit, contribute the highest inflows into the mine workings. The Central Pit Shear Zone acts as a conduit and compartment for groundwater between Mashi and Central Pits. Hydraulic tests have been conducted over the years, and these data are used to estimate possible aquifer property values. The high-yielding aquifer on the west is dewatered using vertical wells, and the low-yielding breccia on the east is depressurized using horizontal drain holes. The site’s water management strategy is reviewed and improved through refinement of the conceptual model.
Surface Water-Groundwater Interaction Using Tritium and Stable Water Isotopes: A Case Study of Middelburg, South Africa	Sarah	Mahlangu	Middelburg	2019	Tritium, stable water isotopes, cemetery, surface water
Abstract With an increasing population, development of the country and a changing climate, an increased demand for fresh water, coupled with negatively impacted natural water resources, are observed. One impacted component of the water resource may have an impact on another, due to the interaction between water resource components in the water cycle. All water resource components need to be well-managed and protected to ensure their availability and sustainability. Studies on water quantities, flow dynamics, quality, and contamination are essential in this regard. Isotopes are used as a tool in these studies to define the interconnection between different water resource components. The information gained from isotope studies is valuable in the planning of activities in areas where interacting water resource components may potentially be affected. A study in Middleburg comprised a literature review and field investigations at and around a cemetery, as part of a Water Research Commission project on impacts on the water resource from large scale burials. A seasonal wetland is located downgradient of the cemetery, between the cemetery and a stream that flows past the cemetery. In order to assess possible flow pathways from the cemetery to the stream, monthly monitoring of surface and groundwater quality and level fluctuations was carried out on the stream, as well as existing and newly installed boreholes at the site. The water samples were analysed for inorganic constituents, tritium, and stable water isotopes. The isotope results - revealed the comparative influence of rainfall and shallow groundwater contributions to streamflow, while groundwater provides base-flows as the stream levels recede. The depth to groundwater reduced with increasing rainfall, indicating direct recharge. The difference in concentrations of some inorganic parameters in the stream compared to the groundwater at the cemetery revealed the effect of natural attenuation and the wetland acting as a filter to improve the water quality of the shallow interflow.
First Nations Communities as Partners in Hydrogeology	Sarah	Bourke	Australia	2023	Cultural Water Values, First Nations Groundwater Connections, Social Hydrogeology
Abstract Aboriginal and Torres Strait Islander people have inhabited the lands now known as Australia for over 65,000 years. Their communities are intricately connected to the land and waters through culture and tradition. However, there are few examples of integrated water resource management that serve Aboriginal and Torres Strait Islander communities or cultural interests. This is particularly the case for groundwater. In Australia, Indigenous connections to groundwater have historically been overlooked or, in some cases, assumed not to exist. On the contrary, many Aboriginal and Torres Strait Islander cultures have longstanding physical and spiritual connections to a range of artesian and subartesian groundwater resources. These cultures also house accurate records of groundwater systems. Despite this, groundwater management in Australia remains dominated by Western scientific perspectives, and the groundwater sector poorly integrates Indigenous stakeholder concerns or knowledge into groundwater management and planning. IAH Australia has prepared and signed an Indigenous Groundwater Declaration intending to raise awareness among the groundwater community of the value of Indigenous perspectives and knowledge of groundwater systems. This Declaration can be viewed and signed at http://declaration.iah.org.au. This presentation provides examples of effective partnerships between Indigenous Communities and Government or Academic groundwater professionals. While progress has been made, challenges must be overcome to integrate Indigenous knowledge and connections into groundwater resource management.
New challenges for low-enthalpy geothermal resource management at the urban scale	Sara	Barbieri	Milan, Italy	2023	MODFLOW-USG, geothermal energy, heat transport, numerical modelling, resource management
Abstract The study focuses on the overlapping effects of low-enthalpy geothermal plants in urbanized areas, showing the importance of quantifying thermal groundwater exploitation to manage the resource adequately. Geothermal energy connects groundwater use to one of the ever-growing needs nowadays: energy. For low-temperature geothermal, the form of energy we can harness is thermal energy for building heating or cooling, one of the most polluting sectors, representing 34% of CO2 emissions in Europe. As in the main European cities, geothermal energy use is constantly growing, and understanding the status of groundwater exploitation for geothermal purposes is essential for proper resource management. To this end, the study’s first phase focused on quantifying geothermal use in the study area selected in Milan city-Italy. Knowing the characteristics of geothermal plants in the area allows us to understand the extent of the resource exploitation and the consequences of its mismanagement at a large scale. In fact, the plant designers often focus on the local scale, not considering the presence of neighbouring plants, which risks decreasing the plant’s efficiency or amplifying its subsurface thermal effect. To minimize the thermal effects/interferences of geothermal plants in the subsoil, the study of the application of D-ATES systems (Dynamic Aquifer Thermal Energy Storage) with significant groundwater flow is promising. A numerical model of the study area is then implemented with MODFLOW-USG for thermal transport in porous media to evaluate the advantages of installing D-ATES systems instead of typical open-loop systems.
Assessing The Role Of Oxygen In The Attenuation Of Petroleum Hydrocarbon Vapours In The Vadose Zone	Samuel D	Möhr	National	2013	Hydrocarbon, petroleum
Abstract Vapour intrusion (VI) is the term used to define the encroachment of vapour phase contaminants from subsurface sources into structures such as buildings and basements. It is widely recognised that VI often forms the principal risk of exposure to receptors at petroleum release sites. Petroleum VI (PVI) generally occurs where a release of petroleum hydrocarbon product migrates from its source (for example, from a leaking underground storage tank) to the groundwater table at which point, given favourable conditions, the hydrocarbon plume may migrate laterally beneath an adjacent building or structure. Subsequent volatilisation of the petroleum product results in the upward diffusion of vapours towards the surface where the vapours may enter into the building or structure at concentrations which may be harmful to human health. The subject of PVI with regards to its fate and transport mechanisms, as well as associated mitigation measures, is rapidly gaining attention on a global scale, although to date this exposure pathway remains largely unassessed in South Africa, with no regulatory guidance currently available. In the late 1990s and early 2000s focus was placed on the development of VI screening criteria by which sites could be screened with respect to their hydrogeological conditions and contamination status so as to determine whether VI may be a potential exposure pathway of concern, with much of the early work being completed by the United States Environmental Protection Agency. For the past decade the majority of the available screening criteria and guidance has not, or has only partially accounted for biodegradation processes associated with VI, which has led to doubt over the application of such screening criteria in many cases. Furthermore, recent research conducted abroad has highlighted the importance of the role of oxygen in the vadose zone in the natural attenuation of petroleum hydrocarbon vapours as they diffuse through the soil profile. This research is pointing towards the notion that currently applied screening criteria may be overly conservative when applied to petroleum impacted sites, leading to many unnecessary PVI investigations being conducted to the disruption of occupants of the buildings, and at great cost. Over the last two years ERM has compiled a dataset of PVI results from numerous investigations it has conducted throughout Southern Africa and in this paper the authors present data that supports the growing global trend towards recognising the role that oxygen plays in attenuating petroleum hydrocarbon vapours in the vadose zone. The data also support the notion that confirmed cases of PVI into buildings have generally been found to be the exception to the rule and not the norm.
Flowing Fluid Electrical Conductivity Profiling – An Inventive And Cost-Effective Alternative To Conventional Downhole Hydraulic Profiling Techniques	Samuel D	Möhr	National	2013	Electrical conductivity, Hydraulic profiling
Abstract Flowing fluid electrical conductivity (FFEC) profiling provides a simple and inexpensive way to characterise a borehole with regards to the vertical location of transmissive zones, the hydraulic properties of the various transmissive zones and the intra-well flow conditions which may be present in the well under ambient conditions. The method essentially involves analysing the time evolution of fluid electrical conductivities in a borehole under pumped and ambient conditions using a down-hole conductivity/temperature data logger. The premise of the method is that the borehole column of water has its electrical conductivity altered by adding saline water into the borehole. This results in a contrast in electrical conductivity (EC) between the water in the borehole and the water in the adjacent formation. At depths where transmissive zones are present, decreases in EC values in the FFEC profile will be observed where formation water with a lower EC (relative to the borehole water column) enters into the well, whilst pumping at low abstraction rates (between 500 ml and 1 liter per minute). By altering the EC of the well-borewater and maintaining a constant pumping rate, the sequence of FFEC profiles depicts the dynamic flow and transport response which is dependent upon the hydraulic properties of the formation. In this paper the authors present several examples where FFEC profiling has been used to identify transmissive zones in boreholes where no information existed with regards to the vertical distribution of transmissive zones. Furthermore, the authors present case studies where FFEC profiling has been employed as an alternative technology to more conventional hydraulic profiling techniques. This includes a comparative technology case study where down-hole impeller flow meter technology was employed in addition to FFEC profiling and a multi-rate FFEC profile test which was used to determine discrete fracture transmissivity values in a borehole where packer testing equipment could not be installed. Within the context of groundwater contamination investigations, the method holds several attractions as it generates minimal waste water to be managed and disposed of, is inexpensive and can be completed within a relatively short time period.
Assessment of Plume Stability in Monitored Natural Attenuation Assessments Using the Centre of Mass and Total Plume Mass Approach	Samuel D	Mohr	Western Cape	2017	Monitored natural attenuation, petroleum, Hydrocarbon, plumes, monitoring network
Abstract Monitored natural attenuation (MNA) is becoming a commonly employed sustainable site remediation strategy for sites with petroleum hydrocarbon groundwater impacts. Natural attenuation is essentially the reduction in contaminant concentration, mass or mobility due to naturally occurring processes within the environment. Aromatic compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX) are common compounds of concern in the context of petroleum hydrocarbon related investigations because of their relative mobility and toxicity characteristics. Despite this, these compounds have historically displayed a strong affinity towards attenuating temporally and spatially away from the source areas. Evaluating plume stability is an important element of evaluating the overall attenuation of groundwater plumes and numerous methods have been developed in order to assess plume stability including graphical and statistical methods. It is often the case however that these analyses focus on single wells in isolation and do not take an integrated approach to evaluate the attenuation of contaminant mass over the entire plume. The authors present a case study where historical trends in plume characteristics have been used to assess overall plume stability. Trends in parameters such as average plume concentration, total plume contaminant mass, plume area and plume centre of mass were statistically assessed to determine whether the groundwater plume was expanding, stable, or shrinking. The methods employed in the plume stability analysis were found to be effective tools in demonstrating the occurrence of natural attenuation of contaminant plumes. It is important to note that a good quality dataset is required, in terms of a spatially representative monitoring well network and adequate time series data, in order to conduct analyses that will yield meaningful conclusions.
High Resolution Site Characterisation (HRSC) In South Africa: Challenges, Successes And Lessons Learned	Samuel D	Mohr		2015
Abstract Inadequate characterization of contaminated sites often leads to the development of poorly constructed conceptual site models and consequently, the design and implementation of inappropriate risk management strategies. As a result, the required remedial objectives are not achieved or are inefficient in addressing the identified risks. Unfortunately, it is all too common to find remedial intervention strategies that run for lengthy periods of time at great cost while generating little environmental benefit due to inadequate characterization of site conditions. High resolution site characterization (HRSC) can provide the necessary level of information to allow for development of rigorous conceptual site models, which can be used to develop and implement appropriate risk management solutions for environmental problems. At the outset, the HRSC approach generally has comparatively higher costs than traditional state-of-the-practice assessment methods. However, the project lifecycle costs can be substantially reduced due to development of optimal risk management strategies. In developing countries where there is a lack of legislation relating to soil and groundwater contamination or, a lack of enforcement of legislation which is present, the long-term liabilities related to contaminated sites are often not immediately apparent to the parties responsible for the sites. This often creates a reticence to employ HRSC techniques due to their increased cost, especially when much of the technology must be imported on a project specific basis from either Europe or the United States. The Authors provide information from several case studies conducted in South Africa where HRSC techniques have been employed to gain a greater understanding of subsurface conditions. Techniques employed have included surface-based geophysical techniques such as electrical resistivity tomography (ERT) and multi-channel analysis of seismic waves (MASW), passive soil gas surveys, deployment of Flexible Underground Technologies (FLUTe?) liners, diamond core drilling, fluid electrical conductivity profiling, downhole geophysical logging tools, the Waterloo Advanced Profiling System (APS), and the use of field laboratories. Several of the techniques required importing equipment and personnel from Europe or the US, and in several case studies, were a first to be employed in South Africa, or the continent of Africa for that matter. The Authors present data obtained using the HRSC techniques from the case studies and elaborate on how the information obtained was used to drive effective decision making in terms of managing long term environmental risks at the various sites, which has been positively embraced by local clients. The authors also highlight key challenges in conducting HRSC investigations in an emerging market context.
Assessing The Role Of Oxygen In The Attenuation Of Petroleum Hydrocarbon Vapours In The Vadose Zone	Samuel	Samuel M?hr		2015
Abstract Vapour intrusion (VI) is the term used to define the encroachment of vapour phase contaminants from subsurface sources into structures such as buildings and basements. It is widely recognized that VI often forms the principal risk of exposure to receptors at petroleum release sites. Petroleum VI (PVI) generally occurs where a release of petroleum hydrocarbon product migrates from its source (e.g. from a leaking underground storage tank) to the groundwater table at which point, given favourable conditions, the hydrocarbon plume may migrate laterally beneath an adjacent building or structure. Subsequent volatilisation of the petroleum product results in the upward diffusion of vapours towards the surface where the vapours may enter into the building or structure at concentrations which may be harmful to human health. The subject of PVI with regards to its fate and transport mechanisms, as well as associated mitigation measures is rapidly gaining attention on a global scale, although to date this exposure pathway remains largely un-assessed in South Africa, with no regulatory guidance currently available. In the late 1990's and early 2000's focus was placed on the development of VI screening criteria by which sites could be screened with respect to their hydrogeological conditions and contamination status so as to determine whether VI could be a potential exposure pathway of concern, with much of the early work being completed by the United States Environmental Protection Agency. For the past decade the majority of the available screening criteria and guidance has had a partially incomplete understanding of hydrocarbon vapour fate and transport processes associated with VI, which has led to doubt over the application of such screening criteria in many cases. Furthermore, recent research conducted abroad has highlighted the importance of the role of oxygen in the vadose zone in the natural attenuation of petroleum hydrocarbon vapours as they diffuse through the soil profile. This research is pointing towards the notion that currently applied screening criteria may be overly conservative, leading to many unnecessary PVI investigations being conducted to the disruption of occupants of the buildings, and at great cost. Over the last two years ERM has compiled a dataset of PVI results from numerous investigations it has conducted throughout Southern Africa and in this paper the authors present data that supports the growing global trend towards recognizing the role that oxygen plays in attenuating petroleum hydrocarbon vapours in the vadose zone. The data also supports the notion that confirmed cases of PVI into buildings have generally been found to be the exception to the rule and not the norm.
Groundwater Vulnerability Assessment Of A Sedimentary Basin In South Western Nigeria	Saheed	Oke	Nigeria	2015
Abstract The Dahomey Basin is a transboundary sedimentary basin with its eastern half in south western Nigeria. The vulnerability assessment of the basin was carried out to ascertain the degree of the shallow unconfined aquifers sensitive to groundwater contamination through the investigations of the intrinsic properties of lithology over the unconfined aquifer systems. The basin is a multi-layered aquifer system hosting large population densities particularly in Lagos where nearly half of the population rely on the groundwater for domestics and industrial purposes. The vulnerability evaluation involves determining the protective cover and infiltration condition of the unsaturated zone in the basin. This was achieved using the PI vulnerability method of the European vulnerability approach. The PI method specifically measures the protection cover and the degree to which the protective cover is bypassed. Intrinsic parameters assessed were the subsoil, lithology, topsoil, recharge and fracturing for the protective cover. While, the saturated hydraulic conductivity of topsoil, infiltration processes and the lateral surface and subsurface flow were evaluated for the infiltration bypassed. The results were depicted in vulnerability maps. Map of the protective cover ranges from high to very high. This means a very effective cover over the groundwater resources. The I map revealed a low to very low degree of bypass. The final vulnerability map shows that the Dahomey Basin vulnerability ranges from moderate to very low vulnerability areas. Low vulnerability areas were characterised by lithology with massive sandstone and limestone, sub soils of sandy loam texture, high slopes and high depth to water table. The moderate vulnerability areas were characterised by high rainfall and high recharge, low water table, unconsolidated sandstones and alluvium lithology. The vulnerability map was validated with hydrochemical properties of the groundwater. Chloride and TDS concentration of the groundwater reveals high chloride concentration for low groundwater vulnerability areas while low chloride concentrations were observed for moderate vulnerability areas. Low to moderate groundwater vulnerability areas show low TDS concentrations according to the WHO standards except for the coastal areas with relatively higher TDS concentrations. The groundwater vulnerability maps will be a useful tool for planning land use activities which will minimise groundwater contamination and enhance the protection of the Dahomey Basin groundwater resources. {List only- not presented} Keywords: PI method, Dahomey Basin, aquifer vulnerability, protective cover, groundwater resources.
The Challenges Facing Delineation Of Integrated Units Of Analysis Within Context Of The Groundwater Resources Directed Measures	Sagadevan	Kisten	National	2013	groundwater resource directed measures
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.
Transport and attenuation of microplastics in saturated sands	Sabastian	Stenzl		2021	Microplastics
Abstract Globally, cumulative plastic production since 1950 is estimated to have reached 2500 Mt of plastic. It is estimated up 60% of this plastic is either resting in landfills or the natural environment, including groundwater settings. Microplastics are small pieces of plastic ranging between 1μm – 5mm in size and have been found in every ecosystem and environment on the planet. Much of the available literature on microplastics is focused on marine environments with few in comparison focused on freshwater environments, and even fewer on groundwater settings. The aim of this study is therefore to investigate the attenuation process responsible for influencing microplastic transport in saturated sands. This research will adapt colloid transport theory and experiments to better understand the movement of microplastics through sandy media. Saturated aquifer conditions will be set up and simulated using modified Darcy column experiments adapted from Freeze & Cherry (1979). Modified microplastics will be injected into the columns as tracers and the effluent concentrations measured by Fourier-transform infrared spectroscopy (FTIR). Breakthrough curves will then be plotted using the effluent concentrations to determine the attachment efficiency (α). It is expected the attachment efficiency will vary by microplastic type and size range. The Ionic strength of the solution flowing through the column and the surface charges of both microplastics and sandy surfaces are likely to influence the degree of attenuation observed. The relationship between different types of microplastics and collector surfaces from a charge perspective and their influence on the degree of attenuation will be evaluated. Given the lack of literature, its ubiquitous presence and postulated effects on human health, this research is significant. Through this research, the transport and attenuation of microplastics through sandy aquifers can be better understood, and in the process inform future research and water resource management.
Development of an Artificial Neural Network for the Prediction of Mine Dewatering	S.	Ngoie	Democratic Republic of the Congo.	2017	neural network, mine dewatering
Abstract Open pit mines often experience problems related to groundwater inflows. To perform mineral extractionin safe conditions with high productivity, it is essential to have dry working conditions. For this reason, the groundwater table is often lowered below the elevation of the floors of the pits by using various dewatering schemes. Numerical groundwater models are powerful tools that can be used to simulate the behaviour of aquifers during dewatering operations. However, these models typically require a lot of geohydrological data which are often expensive and time-consuming to collect. When geohydrological input data are limited, artificial neural networks (ANNs) provide an alternative approach of predicting the behaviour of the groundwater system during dewatering. This study investigated the possibility of predicting the impacts of pit dewatering on the aquifer system in the vicinity of open pit mines where geohydrological inputs are limited, using ANNs. First, the performance of the ANNs in predicting hydraulic head responses was evaluated by using synthetic data sets generated by a numerical groundwater model developed for a fictional mine. The synthetic data sets were then used to both train and evaluate the performance of the ANNs. The ANN found to give the best predictions of the hydraulic heads had an architecture of 2-6-1 (input-hidden-output layers) and was based on the hyperbolic tangent transfer function. This network was selected to predict the hydraulic heads at a number of piezometers installed at two open pit mines in the Democratic Republic of the Congo. The only input to the ANN was the recorded hydraulics heads and the time of recording. A portion of the real data set was used to train the ANN, while the remaining portion was used to evaluate the performance of the ANN in predicting the hydraulic heads. The results of the performance analyses indicated that the ANN successfully predicted the general behaviour of the aquifer system under dewatering conditions, using only limited input data. The results of this investigation therefore illustrate the great potential of using ANNs to predict aquifer responses during dewatering operations in the absence of comprehensive geohydrological data sets. Since these networks recognise patterns in the training data sets without considering the underlying physical principles that govern the processes, the responses of complex systems that are dependent on numerous parameters may be predicted.
Balancing qualitative and quantitative issues of the groundwater extraction at the drinking water production site of Velm (Central Belgium)	S	Van den Broeck	Belgium	2023	Belgium, Drinking water, Drought, Pollution, sustainability, time series analysis
Abstract Recent findings allow a better insight into the interaction between two aquifers and their vulnerabilities at the groundwater extraction site of Velm, which produces drinking water for around 55,000 households. The shallow aquifer that is exploited is situated in the Formation of Hannut. This aquifer is vulnerable to pollution, especially from the agricultural lands close to the extraction site and is sensitive to natural recharge. In this case, the groundwater is captured in a basin via a naturally occurring spring flow. The second aquifer is situated in the Cretaceous at 50 to 100 m below the surface and is pumped by four wells. The drinking water quality is guaranteed by mixing and treating these two waters. To optimize the central decalcification and the pollution risks, the production volume in the deep aquifer was increased from 2017 to 2021 at the expense of the shallow aquifer. This led to a decrease in the available volumes of the shallow aquifer, which indicated a leakage from the shallow to the deeper aquifer, which was unexpected. Groundwater modelling and time series analysis have been used to assess the impact of the increased production volumes and the longer dry periods. Based on this data, a maximum production volume of 1,000,000 m3 /year is considered best for the cretaceous aquifer. With this extraction rate in the Cretaceous, it is possible to supply sufficient drinking water and limit the impact on the Formation of Hannut.
onitoring a deep fresh-saline water interface using repeatVertical Electrical Soundings measurements	S	Meekes	The Netherlands	2023	Fresh-saline interface, Geo-electrical, Monitoring, Vertical Electrical Sounding
Abstract Monitoring deep (~100 – 200 m) fresh-saline water interface is a challenge because of the low spatial density of deep boreholes. In this project, Vertical Electrical Soundings measurements were used to evaluate changes in the depth of the interface over various decades. Water quality monitoring is a well-known application of geo-electrical measurements but generally applies to the relatively shallow subsurface. In this case study, the saline groundwater interface is around 120 -200 m deep, and the time interval between the measurements is several tens of years. Several locations showing good-quality existing VES-measurements acquired in the last century were selected to see whether repeat measurements could be performed. The number of locations where a repeat measurement could be performed was limited due to the construction of new neighbourhoods and greenhouse complexes. When interpreting the measurements for the change in the depth of the fresh-salt interface, it is assumed that the transition from fresh to saline groundwater occurs over a small depth range and that the electrical conductivity of the fresh water above this interface has not changed. However, it turned out that the ion concentration of the groundwater in the layers above the fresh-saline interface had increased sharply at almost all locations. This complicated the approach, but still, useful results could be obtained. Based on the measurements, it can be said that the fresh-saline water interface has shifted downwards at 3 locations, and hardly any change has occurred at 5 locations.
Understanding the influence of Artefacts on the Darcy Velocity Estimations from Point Dilution Tracer Tests	S	Mofokeng	South Africa	2023	Contaminant transport, Darcy velocity, Groundwater, horizontal groundwater flow, point, dilution tracer test
Abstract Darcy Velocity (Vd) is often estimated through a single-borehole Point Dilution Tracer Test (PDTT). Vd is used in the investigation of contaminant transport and distribution in aquifers. The tracer dilution rate in groundwater is controlled by horizontal groundwater flux. However, it can be affected by other artefacts, such as diffusion and density effects. Although there are studies on tracer tests, there has not been much done to gain an understanding of how these artefacts affect the correct Vd estimation. This study, therefore, aims to investigate and provide an understanding of the influence of artefacts on the PDTT through laboratory experiments conducted using a physical model representing a porous media. A total of 18 experiments were performed with different NaCl tracer concentrations under constant horizontal groundwater flow and no-flow conditions. The study results show that the density sinking effect affects an early period of tracer dilution, which can lead to overestimation of Vd; therefore, these stages should not be used to estimate Vd. The study, therefore, proposes a way in which PDTT data should be analysed to understand the effects of artefacts on Darcy velocity estimation.
ion of multivariate statistical analysis as a support for the delineation of groundwater bodies: a case study in coastal plain areas of Campania Region (Southern Italy)	S	Stevenazzi	Southern Italy	2023	coastal aquifers, statistical analysis, volcanic areas, Water chemistry
Abstract The identification of hydrogeological boundaries and the assessment of groundwater’s quantitative and qualitative status are necessary for delineating groundwater bodies, according to the European Guidelines. In this context, this study tries to verify the current delineation of groundwater bodies (GWBs) through hydrogeochemical methods and multicriteria statistical analyses. The areas of interest are three GWBs located in the northern part of Campania Region (Southern Italy): the Volturno Plain, a coastal plain constituted of fluvial, pyroclastic and marine sediments; the Plain of Naples, an innermost plain of fluvial and pyroclastic sediments and the Phlegrean Fields, an active volcanic area with a series of monogenic volcanic edifices. Hydrogeochemical methods (i.e., classical and modified Piper Diagram) and multivariate statistical analyses (i.e., factor analysis, FA) were performed to differentiate among the main hydrochemical processes occurring in the area. FA allowed the handling many geochemical and physical parameters measured in groundwater samples collected at about 200 sampling points in the decade of the 2010s. Results reveal five hydrogeochemical processes variably influencing the chemical characteristics of the three GWBs: salinization, carbonate rocks dissolution, natural or anthropogenic inputs, redox conditions, and volcanic product contribution. Hydrogeochemical methods and FA allow the identification of areas characterised by one or more hydrogeochemical processes, mostly reflecting known processes and highlighting the influence of groundwater flow paths on water chemistry. According to the current delineation of the three GWBs, some processes are peculiar to one GWB, but others are in common between two or more GWBs.
Enhancing resilience to hydrological extremes in the Limpopo River Basin: a collaborative modelling approach	S	Mustafa	Limpopo	2023	opo River Basin, climate resilience, collaborative modelling approach, hydrological extremes and stakeholders workshops
Abstract The Limpopo River Basin (LRB) is highly vulnerable to recurrent floods and droughts, significantly threatening its water and food security. Sustainable groundwater management is necessary to improve resilience. Scientists and stakeholders must collaborate to evaluate management scenarios that can identify sustainable practices. A transboundary basin-scale management instrument was developed using a multisector collaborative modelling approach to identify the role of groundwater in building resilience. The approach used an integrated hydro(geo)logical model, co-created through stakeholder workshops. The model assessed management scenarios identified during a series of local, national and transboundary stakeholders workshops, focusing on improving groundwater storage during wet periods for use during dry periods in a context of population growth and increasing groundwater reliance across the basin. Management scenarios: (1) increasing groundwater abstraction; (2) deforestation; (3) afforestation; and (4) managed aquifer recharge (MAR) using injection wells capturing excess water from major dams, rainwater harvesting through local ponds/ wells, and small water reservoirs. Analysis of scenario outputs suggested that local groundwater storage techniques, especially water harvesting and storage through small-scale water well recharge, were the most effective strategy in reducing the risk and impact of floods and drought at the basin scale. Upscaling this strategy can significantly increase groundwater levels across the basin, supporting increasing groundwater reliance. The study showed that the multisector collaborative modelling approach effectively co-creates management strategies and identifies appropriate and inclusive strategies to improve resilience in data-limiting conditions. The proposed modelling outcomes are useful in making informed decisions regarding water management and transboundary cooperation in the LRB.
Use of krypton-81 to constrain the reliability of carbon-14 in estimating groundwater ages	S	Lu	China	2023	groundwater dating, krypton-81 isotope, radiocarbon
Abstract Advances in groundwater age dating provide key information for groundwater recharge history and rates, which is of great significance for groundwater sustainable development and management. By far the, radioisotope 14C is the most frequently used in routine investigations. However, groundwater age can be misinterpreted given its dating range of up to 40 ka and its chemically active in nature. In comparison, 81Kr is less frequently used but chemically inert with a dating range of up to 1,300 ka, which overcomes the limit of 14C. Although it is not as precise as 14C when the groundwater age is younger than 40 ka, it may be helpful to determine the reliability of 14C dating results. In this study, we collected eight field samples from coastal aquifers in Nantong, China and analyzed them for 81Kr, 85Kr, and 14C. The 14C results show that all groundwater ages range from 2,400 to 35,300 years, with different correction methods yielding uncertainties of 1,500 to 3,300 years. Four of the 81Kr ages provided upper bounds, while three yielded groundwater ages which are consistent with the 14C dating results within measurement uncertainties. Interestingly, one 81Kr result gave an age of 189+11 - 12ka, whereas the corresponding corrected 14C age was less than 29,200 years. The great difference may indicate modern contamination in the sampling process or mixing between young and old groundwaters. Further investigation is needed to shed more lights in this case. Moreover, it shows the benefits of introducing 81Kr in routine hydrogeological investigations and the groundwater studies.
Testing Potential Reservoir Connectivity Using Isotopes	S	Dlakavu	Karoo	2017	Shale gas, hydraulic connectivity, geochemical, Isotopes, contamination
Abstract Anticipated Shale Gas Development could intensify possible natural hydraulic connectivity between deep groundwater reservoirs and shallow aquifers in the Karoo. This project attempts to test geochemical evidence of natural mixing between old groundwater from deep aquifers and young groundwater from shallow aquifers using selected isotopic signatures in conjunction with borehole yields. Borehole yields were determined using slug tests. All isotopes (δ18O, δ2H, δ13C, 3H and 14C) were analysed in the laboratory of Environmental Isotope Group of iThemba Laboratories in Gauteng. To date, results from four water samples collected in Jansenville reveal these average isotope signatures: δ18O = -3.02 ‰, δ 2H = -21.17 ‰, δ 13C = 12.46 ‰ 3H = 0.45 TU and 14C = 65.38 pMC. The δ18O-δ 2H relationship for the groundwater has a gradient of 4.48. This demonstrates that the groundwater has experienced evaporation before or during recharge. The unevaporated isotopic signature of the water is -5.86 ‰ and -33.89 ‰ for δ18O and δ2H, respectively. The enriched δ13CDIC signature suggests that methanogenesis has influenced the groundwater. The unstable isotopes (3H and 14C) suggest that there is groundwater mixing in Jansenville between younger water from shallow aquifers and older water likely from deeper aquifers. Borehole yields increase with decreasing radioactive isotope concentrations. This suggests that high yielding boreholes are areas of potential contamination because they are associated with mixed groundwater.
Exploring the Role of Land Use evolution in Groundwater Modeling for Sustainable Management: A Case Study of the Lille Metropolitan Area	Ryma	Aissat	France	2023	Land use change, groundwater flow modelling, groundwater sustainability, recharge, runof
Abstract Groundwater represents a crucial source of drinking water in the Lille metropolitan area. Despite its importance, the resource is vulnerable to the potential evolution of land use: recharge, runoff and evapotranspiration processes in a soil-sealing context and changes in cultural practices. As a result, stakeholders emphasized the importance of exploring the influence of land use on groundwater to ensure sustainable resource management and enhance territorial planning. The 3D hydrodynamic model helped manage groundwater resources, but the (MARTHE code) has a significant limitation in that it does not consider the impact of land use evolution. We propose to investigate the contribution of a hydrological distributed numerical approach incorporating land cover data in groundwater modelling compared to a global approach at the scale of a peri-urban territory. To do so, we use the HELP code by considering the temporal and spatial evolution of land use and their associated characteristics, such as vegetation and soil properties, to detail recharge and runoff over more than 20 years that we incorporate into the initial groundwater model. The two approaches yielded comparable global water balance results. However, at the local scale, the model accounting for land use showed significantly different hydric components. Choosing the appropriate model depends on the specific research question and spatial scale, and considering land use evolution is crucial for accurate urban planning impact assessments, especially at the district level.
Teaching Machines Hydrogeology: Demonstrating The Use Of Machine Learning In Groundwater Science And Management	Rui	Hugman		2019	Machine learning, AI
Abstract The advent of the 'Big Data' age has fast tracked advances in automated data analytics, with significant breakthroughs in the application of artificial intelligence (AI). Machine learning (ML), a branch of AI, brings together statistics and computer science, enabling computers to learn how to complete given tasks without the need for explicit programming. ML algorithms learn to recognize and describe complex patterns and relationships in data - making them useful tools for prediction and data-driven discovery. The fields of environmental sciences, water resources and geosciences have seen a proliferation of the use of AI and ML techniques. Yet, despite practical and commercial successes, ML remains a niche field with many under-explored research opportunities in the hydrogeological sciences. Currently physical-process based models are widely applied for groundwater research and management, being the dominant tool for describing and understanding processes governing groundwater flow and transport. However, they are limited in terms of the high data requirements, costly development and run time. By comparison, ML algorithms are data-driven models that establish relationships between an input (e.g. climate data) and an output (e.g. groundwater level) without the need to understand the underlying physical process, making them most suitable for cases in which data is plentiful but the underlying processes are poorly understood. Combining data-driven and process-based models can provide opportunities to compensate for the limitations of each of these methodologies. We present applications of ML algorithms as knowledge discovery tools and explore the potential and limitations of ML to fill in data gaps and forecast groundwater levels based on climate data and predictions. Results represent the first step in on-going work applying ML as an additional tool in the study and management of groundwater resources, alongside and enhancing conventional techniques such as numerical modelling.
Investigation of Sustainable Groundwater Resource Supply in the Crystalline Basement Aquifer at Matoks (Mokomene) ,in Molemole Municipality, Limpopo Province, South Africa.	Ronald	Ramathieledza	Molemole Municipality, Limpopo, South Africa	2017	Groundwater resource supply, crystalline basement aquifers, geophysical techniques, magnetic anomalies, borehole yield, water quality.
Abstract Water is an essential resource for livelihood (humans, animals and plants) and without water there is no life on earth. Worldwide over 1.1 billion people do not have access to safe water and more than 1 billion people are living in water stressed areas. The scarcity of water is more intense in developing countries where statistics show that 67% of the rural population have no access to safe water supply. Detailed geohydrological investigation and chemical analysis were conducted in crystalline basement rocks at Matoks in Capricorn District, Limpopo province of South Africa to determine the groundwater availability and its quality for human consumption. Groundwater potential was identified by the use of geophysical techniques (electromagnetic profiling, magnetic profiling). Traverse lines were set based on the information acquired from the desktop studies (DWS-mapped structures such as faults, joins or lineaments, Topographical map, Google Earth and geological mapping). Drilling positions were configured based on the magnetic anomalies, followed by the drilling of selected targets. Water strikes ranges were at 20 – 36 mbgl, these showed that the area has shallow aquifers. The aquifer response under applied pressure produced a blow yield ranging from 3-20 l/s. The recommended borehole yields ranges from 1 – 6 l/s which makes about 2 747.52 m³/day and the average transmissivity was 41.04 m²/day. Water samples were analysed through the use of various techniques, namely: AAS, IC, IC-PMS, water quality from the study area ranges from class I to class IV, which is good to poor water quality according to South African National Standards. The aquifers at Matoks can meet the present water abstraction demand and the aquifers are having good to poor water quality.
A review of slug tests analysis on South African aquifers in potential yield and transmissivity estimations	Rolene	Lubbe	South African	2023	Slug test; Potential yield; Transmissivity; Limitations; Modelling
Abstract Slug tests are preliminary tests applied to determine the hydraulic conductivity and whether it is necessary to perform a pumping test on the borehole under investigation and should never be recommended as a substitute for a pumping test. For this reason, slug tests cannot be related to sustainable yield because slug tests cannot detect boundary conditions. The aim was to develop a methodology to relate slug tests to a potential yield estimation, investigating and reviewing the applicability and accuracy of the slug test methodology in South Africa, applied on fractured rock aquifers as established in 1995. The aim was achieved by reviewing the methodology applied for slug tests that are related to potential yield estimations, identifying the limitations of slug tests, investigating the possibility of updating the potential yield estimation method of 1995, and investigating the possibility of relating slug tests, to potential yield and transmissivity estimations through groundwater modelling. The investigation revealed that using transmissivity values determined through slug test homogenous modelling can be utilised to estimate the potential yield of a borehole under investigation by implementing correlation statistics. Note that this is not an absolute and is subject to limitations.
Interannual variability in rainfall isotope composition as a tracer of spring water flow.	Roger E	Diamond	Western Cape	2015	Table Mountain Group, springs, rainfall isotopes
Abstract Table Mountain reaches 1086m elevation, the upper half of which comprises Table Mountain Group (TMG) quartzite with extensive fracture porosity. The lower half of the mountain comprises a mixture of Cape Granite intruded into Malmesbury Group metapelites, both of which are poor aquifers, but are in places overlain by scree slopes predominantly composed of TMG quartzite boulders. The region experiences a Mediterranean climate with warm, dry summers and cold, wet winters, with rainfall ranging from 600-1600mm/a depending largely on proximity to the mountain. Several springs issue from the slopes of the mountain, ranging in elevation from 15-410masl and in flow from non-perennial to 30L/s. Water chemistry reveals very little about spring water flow, as the waters have very low dissolved solids. Samples of 10 of these springs were taken twice per year for 3 years while rainwater was sampled at 120masl at the University of Cape Town (UCT) and at 1074masl at the Upper Cableway Station. These samples were analysed for oxygen and hydrogen stable isotope composition, mostly by mass spectrometer, but also by laser spectroscopy. The isotope results reveal an altitude gradient between the two rainfall stations of -0.075?/100m for ?D and -0.48?/100m for ?18O. Employing this isotope gradient, the average recharge altitude for the springs is 304masl, compared to an average discharge altitude of 156masl. Using this difference in altitude and the average slope of the terrain, a typical flow path of 1km from recharge to discharge point can be derived. Additionally, there are shifts in the weighted annual mean isotope composition of rainfall at UCT. For the years 2010-2012, the shifts are paralleled by similar shifts in the mean isotope composition at the springs for each of those years. This suggests rainfall discharges in the same winter season it has been recharged. In combination with the evidence for long term reliability of some of the springs over the dry season and during droughts, this suggests a layered flow of groundwater in the scree aquifer, allowing both long term steady discharge of deeper groundwater, as well as short term discharge of recently recharged rain. In combination with the flow path derived above, hydraulic conductivities in the realm of 10-20m/d can be calculated for the scree aquifers.
Are Farmers Drying Out The Cederberg? Deep Groundwater Flow And Isotopes In The Table Mountain Group.	Roger E	Diamond	Western Cape	2017	TMG, Isotopes
Abstract The Table Mountain Group is a major fractured rock aquifer system throughout the Western Cape, with many interconnected but semi-independent parts, each having its own recharge area, flow paths and discharge area. Groundwater is known to travel long distances and reach great depths, including through the Olifants River syncline, such as at The Baths hot spring near Citrusdal. Stable isotope compositions of rain and groundwater in the Cederberg and Olifants River Mountains were measured over a period of 2-3 years. Rainfall in the Cederberg averaged -22‰ and -4.7‰ for D and  18O respectively, whereas rainfall in the Olifants River Mountains averaged -11‰ and -3.0‰ similarly. Groundwater used by farmers in the Olifants River Mountains averaged -13‰ and -2.9‰ similarly. The similarity between groundwater and rainfall isotope compositions in the Olifants River Mountains suggests local groundwater movement. It was concluded that the source of groundwater abstracted by farmers in the Olifants River Mountains is from the peaks west of the Olifants River with little to no contribution from the Cederberg, east of the Olifants River syncline. Geological evidence (thinning of the Olifants River syncline and increased faulting northwards) supports this conclusion.
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.
Assessing the Endorheic Character of Groenvlei Using Four Independent Hydrogeological Tools	Roger	Parsons	Groenvlei, South Africa.	2017	Endorheic, Hydrogeological
Abstract It has been claimed that Groenvlei, a shallow lacustrine wetland on the southern Cape coast of South Africa, is endorheic. This characterisation was based solely on the inward sloping topography immediately surrounding the wetland and an absence of any surface water outflow. However, four independent hydrogeological tools were used to confirm that water discharges from the wetland into the aquifer along its southern banks, thus invalidating the endorheic characterisation. These tools included contouring of groundwater levels, interpretation of the hydrochemical character of groundwater, electrical conductivity depth profiling and a comparison of natural environmental isotopes in surface and groundwater. This case study supports the need for an integrated approach when characterising and assessing water bodies.
A scientific method of assessing the groundwater contribution to lakes and wetlands	Roger	Parsons		2015
Abstract The intangible nature of groundwater provides challenges when trying to understand and quantify the role of groundwater in the hydrology of lakes and wetlands. This task is made even more difficult by the frequent absence of data. However, by adopting a scientific approach, it is possible to assess the hydrogeological contribution
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.