Conference Abstracts
Title | Presenter Name | Presenter Surname | Area Sort ascending | Conference year | Keywords | ||||||
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Per and Polyfluoroalkyl Substances (PFAS) Groundwater Toolkit | Fern | Beetle-Moorcrof | western United States | 2023 | PFAS, fate and transport, Groundwater, sampling | ||||||
AbstractPer and Polyfluoroalkyl substances (PFAS) are ubiquitous on our planet and in aquifers. Understanding PFAS transport in aquifers is critical but can be highly uncertain due to unknown or variable source conditions, hydrophobic sorption to solid organic aquifer matter, ionic sorption on mineral surfaces, changing regulatory requirements, and unprecedentedly low drinking water standards. Thus, a PFAS toolkit has been developed to enable decision makers to collect the hydrogeologic data necessary to understand and better predict PFAS transport in aquifers for the purpose of managing water resources. This toolkit has been tested at a significant alluvial aquifer system in the western United States, which provides water for 50,000 people. Here, the toolkit has provided decision makers with the data necessary to optimize water pumping, treatment and distribution systems. The toolkit describes (1) the design and implementation of a sentinel well network to measure and track PFAS concentrations in the alluvial aquifer over time in response to variable pumping conditions, (2) data collection used to empirically derive input parameters for groundwater fate and transport models, which include the collection of paired aquifer matrix and groundwater samples, to measure PFAS distribution coefficients (Kds) and modified borehole dilution tests to measure groundwater flux (Darcy Velocity) and (3) the use of data collection techniques to reduce cross contamination, including PFAS-free, disposable bailers and a triple-rinse decontamination procedure for reusable equipment. The PRAS transport toolkit has the potential to assist decision makers responsible for managing PFAS contaminated aquifers. |
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Complementary use of electromagnetic frequency domain and electroseimic survey methods in groundwater exploration in Zimbabwe. | Joseph M | Zulu | Zimbabwe | 2015 | |||||||
AbstractComplementary use of electromagnetic frequency domain and electrosiesmic geophysical exploration methods in groundwater exploration in Zimbabwe. |
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Can Groundwater Sustain The Future Development Of Rural Zimbabwe? | Jeffery | Davies | Zimbabwe | 2013 | Groundwater, development, Rural development | ||||||
AbstractZimbabwe occupies a tectonically stable plateau underlain by ancient Precambrian crystalline basement rocks. These form a central craton bounded by east-west trending mobile belts; the Zambezi mobile belt to the north and the Limpopo mobile belt to the south. Zimbabwe receives generally low and variable quantities of seasonal rainfall within a semi-arid to savannah type climate characterised by moderate to high temperatures. Evaporation commonly exceeds rainfall so that recharge to the thin near surface aquifers is generally low and in some years non-existent. The groundwater resources of the weathered and fractured basement aquifers that underlie more than 60% of the country are of limited potential, typically sufficient to supply the needs of small villages and cattle ranches. However, within the central plateau area of the African to Post-African erosion surfaces, the weathered and fractured basement may exceed 60 m in thickness. The thickness of this zone diminishes towards the main valley systems where subsequent cycles of erosion have stripped the weathered zone away, leaving only a shallow surface fractured zone that may only be 20-30 m thick. Groundwater resources have been developed extensively in Zimbabwe since the 1920s. During 1991/92 drought abstraction from urban boreholes within the southern Harare area caused yield decline and ultimate failure of numerous boreholes. It is now time to question the long-term viability of groundwater development within the basement aquifers in Zimbabwe given the uncertainty in groundwater resources, the complexities of the climate–groundwater interactions and the projected demands of a growing rural population.
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Integration of geophysical and well monitoring techniques in the evaluation of the groundwater potential for the Urban Bulawayo | Innocent | Muchingami | Zimbabwe | 2015 | |||||||
AbstractPOSTER Most developing urban areas in semi-arid regions of Sub Saharan Africa are often forced to utilise groundwater as an alternate source of domestic water supplies. As such groundwater evaluations strategies often face dual challenges in terms of resource quantification and their quality evaluation. However, groundwater potential assessment and aquifer yield evaluations often present a challenge when the system is of crystalline basement nature where groundwater potential is highly spatially variable and cases of dry holes and seasonal wells have been reported. This study demonstrate the integrated combination of geophysical techniques, (namely, vertical electrical sounding, electrical resistivity tomography, magnetic mapping, and seismic refraction tomography) with both borehole monitoring and infiltration techniques in the groundwater prospecting and spatial yield analysis of the Urban Bulawayo crystalline basement aquifer. The Bulawayo Metropolitan Province of Zimbabwe is located in the semi-arid region of Zimbabwe with an average annual rainfall of below 500 mm and has had a prolonged dry spell has resulted in the dwindling of the existing surface water resources. The aquifer system consists of syenite granite and fractured basaltic greenstone crystalline basement complexes. Provisional geophysical results have shown that the thickness of the fractured zone sharply varies in terms of spatial distribution and often some sections are characterized by shallow surface fractured zone that may only be 20-30 m thick and some sections have a reported regolith of up to 60m in thickness. Borehole yield assessments and chemical analysis techniques will be done on drilled wells in order to come out with detailed spatial variation in the borehole yield and water quality variations across the aquifer system. All the technical evaluations are then integrated to produce a detailed hydro-geophysical map of the system that can be used in the technical groundwater management of the urban Bulawayo aquifer. |
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Characterisation And Development Of A Carbonate Rock Aquifer For Large Scale Irrigation In Zambia (A Case Study) | Kobus | Troskie | Zambia | 2013 | aquifer, case study, Groundwater | ||||||
AbstractLimestones and dolomites form an important aquifer system in Zambia. The municipal water supplies for Lusaka and several population centres on the Copperbelt all depend on the carbonates for a substantial proportion of their water supply. Currently 155,912 ha of land are irrigated in Zambia, which is about 30 percent of the economical irrigation potential. Development of large scale irrigation schemes from carbonate rock aquifers proves to be a viable groundwater resource in Zambia. The Katanga carbonate rock aquifers are considered to have good groundwater potential, with high yielding anomalies of up to 60l/s common in certain areas of the country. A phased approach was adopted to characterise the Katanga Carbonates by means of quantifying the volume of groundwater available for abstraction within the geological boundaries. The first phases included geophysical surveys (mainly electrical resistivity and magnetic methods), exploration drilling and aquifer testing. Later phases included the drilling of production boreholes and wellfield development. Lessons learned during the exploration included the identification of high yielding drilling targets and the role of anomaly frequency in target selection. Further development of the Katanga aquifers for production provided challenges regarding production borehole construction and design. The feasibility of the optimum design of production boreholes versus the initial capital cost of the development of these carbonates proved to be an important consideration in this regard. |
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Regional-scale identification of recharge or discharge using remote sensing and GIS: Implications towards groundwater-surface water interactions | Kawawa | Banda | Zambia | 2023 | Barotse Floodplain, Groundwater-Surface water, Zambezi River, Zambia, Ecosystems | ||||||
AbstractIdentifying groundwater recharge and discharge areas across catchments is critical for implementing effective strategies for salinity mitigation, surface water and groundwater resource management, and ecosystem protection. This study seeks to identify potential GW-SW discharge and recharge areas around the Barotse Floodplain. The results of remote sensing analysis using the Normalised Difference Vegetation Index (NDVI) show that the vegetation is sensitive to the dynamics of groundwater level, with shallower levels (< 10 m) in the lower reaches compared to deeper levels (>10 m) in the upper catchment). These zones are further investigated and likely represent geological variability, aquifer confinement and the degree of GW-SW interactions. GW-SW interactions likely are influenced by an interplay of factors such as water levels in the groundwater and surface level and hydrogeological conditions. Based on the findings, the wetland hosts riparian vegetation species responsive to the groundwater dynamic. NDVI can thus be used as a proxy to infer groundwater in the catchment. Therefore, effective water resources management of the floodplain should be implemented through conjunctive management of groundwater and surface water. |
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Correlation Between Rainfall, Streamflow And Groundwater Levels For The Zachariashoek Sub‐Catchment Near Wemmershoek, Western Cape | Nicolette | Vermaak | Zachariashoek, Western Cape | 2013 | Rainfall, streamflow, Groundwater levels, Geohydrological | ||||||
AbstractZachariashoek catchment was one of the study areas looking into the hydrological characteristics of winter rainfall catchments in the Western Cape. Nearly thirty years of historical data are available for the Zachariashoek area. This data include rainfall, gauge plate readings for the weirs, and water levels for the boreholes in the area. Numerous articles and reports had been written about the research done in the area, concentrating mostly on the effects of fire on streamflow and vegetation. This article will look at patterns that can be observed from the data record and correlate the different data sets for the Zachariashoek sub‐catchment. It will use the data from the two weirs, three rain gauges and at least three of the boreholes that was drilled in this sub‐catchment. The information gained from this comparison can then be used to evaluate possible future hydrological patterns and the interaction between the various components of the hydrological system. |
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Isotopic Study Of Water Resources In Wonderfonteinspruit Valley, North-Western, South Africa | Naziha | Mokadem | Wonderfonteinspruit Valley, North-West | 2019 | Water resources Groundwater, Wonderfonteinspruit Valley, South Africa | ||||||
AbstractStable Hydrogen and Oxygen isotopic technique were used in studying the water resources interaction in Wonderfonteinspruit Valley, North-western South Africa. The objective of this study is to refine the understanding of recharge processes in typical watersheds representative for karstic semiarid areas. This study investigated the isotopic composition of 35 boreholes, 5 surface water, 4 Dams, 4 springs, 1 canal, 2 pipelines, 1 cave and 4 rain stations for two periods October and Mars. Oxygen-18 (?18O?SMOW) and deuterium (?D?SMOW) isotopic data of the karst aquifer reflects the identification of different sources of recharge controlled mainly by the rainfall for the majority of samples and by bank filtration of the main rivers (Wonderfonteinspruit, Middelvieinspruit, Renfonteinspruit) for some samples. Stable isotopes, |
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Vulnerability of South African water resources to emerging organic contaminants: a case study of the Witwatersrand Goldfields, Eastern Basin | L | Ligavha-Mbelengwa1 | Witwatersrand Goldfields, Eastern Basin | 2023 | bisphenol A, caffeine, emerging organic contaminants, estrone, Groundwater | ||||||
AbstractThe occurrence of emerging organic contaminants (EOCs) in the aquatic environment is of no surprise since these are applied for various purposes daily. This study investigated the changes in EOCs concentrations in the water between 2019 and 2020. During rainy seasons, samples were collected from dams and surrounding boreholes in the Eastern Basin of the Witwatersrand Goldfields. During the first and second laboratory analyses, 24 and 11 analytes were screened in the water samples. The findings indicated that in 2020, compounds such as caffeine, sulfamethoxazole, atrazine and metolachlor displayed detection frequency exceeding 2019. This indicates that the occurrence of these compounds in the aquatic system has increased within a year. Whilst carbamazepine was still traced in 12 sites as previously observed in 2019, compounds estradiol, estrone, bisphenol A and ibuprofen were traced in fewer sites than they were detected in 2019. Compounds 4-nonylphenol, methylparaben, caffeine and atrazine were detected in all the samples analysed for 2019 and 2020, respectively. Antiretrovirals (ARVs) were analysed once and were detected in most sites, with efavirenz registering the highest (12/18) detection frequency. Assessing the occurrence of EOCs in boreholes according to the depth indicated that bisphenol A and estrone were traced in greater concentrations in deep than shallow aquifers, whilst the opposite was observed for atrazine. This study showed groundwater susceptibility to contamination by EOCs, with concentrations of most compounds increasing with time due to their high usage and improper sewer systems in the area. |
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Witwatersrand Mine Voids – Their Hydrochemistry And Hydrodynamic Characteristics | Eddie | van Wyk | Witwatersrand | 2013 | Hydrochemistry, hydrodynamics | ||||||
AbstractGold mining on the Witwatersrand has started in the late nineteenth century as sporadic open cast mining and ceased in the late twentieth century, leaving a complex network of haulages, tunnels and ultra-deep vertical shafts/sub-vertical shafts. At least three ore bodies (conglomeritic horizons) were mined down to a depth in excess of 3 000 m from surface. Three large mining basins resulted from the mining methodology applied, namely the Western, Central and Eastern (Rand) Basins. In the early days of mining on the Witwatersrand reefs, gold mine companies realised that dewatering of their mine workings is required to secure mining operations at deeper levels and decades of pumping and treatment of pumped mine water followed. As the majority of deep gold mines on the Witwatersrand ceased operations since 1970, the deeper portions of the mine voids became flooded and led to a new era in the mining history in the Witwatersrand. Rewatering of the mine voids is a combination between excessive surface water ingress generated by surface runoff, and to lesser degree recharge from an overlying fractured and weathered aquifer system (where developed). The flow regime in the mine voids from a scattering of ingress/direct recharge points and single discharge points are complex and is driven by shallow (<100 m) and probably deep (>1 000 m) man-made preferential pathways. The high concentrations of iron sulphide minerals (pyrite. for example FeS2) content, three percent (by weight), of the mined reefs/backfilled stopes and surrounding waste rock piles/tailings dams mobilised significant levels of sulphates (SO4) and ferrous iron (Fe2+) producing an acidic mine-void water (<3 pH). Monitoring of the rewatering mine void hydrological regime became necessary following the first acid-mine water decant from a borehole in the West Rand Basin, and the Department initiated a mine-void water table elevation trend and water quality monitoring programme. Results from this monitoring programme will be illustrated and discussed in this paper with some views on the future water quality and discharge scenarios. |
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Acid mine drainage in the Witwatersrand: Unanswered questions | Henk | Coetzee | Witwatersrand | 2015 | |||||||
AbstractSince the first decant of acid mine drainage in the West Rand in 2002, a great deal of effort has gone into researching the challenges which it poses there and in the adjacent Central Rand and East Rand Gold Fields. Short-term interventions have been implemented to maintain water at conservatively-determined safe levels and remove the worst contaminants from the water pumped from the mined. A feasibility study, looking at the long-term options has proposed treatment of water to a much higher standard, identifying a number of potential end-users of the treated water and highlighted the extremely high costs involved in responsible management. During the second half of 2010, a team of experts was convened to assess problems related to acid mine drainage in the Witwatersrand and propose solutions. A number of recommendations were made and the most urgent - the need for a short-term intervention to bring things under control and the the feasibility study for long-term management of the problems were undertaken. Nevertheless, despite the intense focus on the problem, a number of questions have remained unanswered. Throughout the period of min flooding, no detailed systematic monitoring of surface water flow has been undertaken, preventing the detailed apportionment of pollution between underground and surface sources. Ingress control measures have been proposed, but funding mechanisms, regulatory hurdles and challenges relating to long-term management have not all been comprehensively addressed. On a more positive note, the installation and operation of pumps to control the water level in the Western and Central Basins will start to provide valuable data regarding the response of the flooded mine workings to pumping, assisting in the characterisation of the hydraulic properties and behaviour of the large voids. This will facilitate the optimisation of pumping strategies and the refinement of environmental critical levels and assist in the development of more sustainable management options. |
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Numerical modelling of mine dewatering and flooding in the Evander Gold Basin, South Africa | Kai T | Witthueser | Witwatersrand | 2013 | gold mining, mine water rebound | ||||||
AbstractThe assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in the Witwatersrand basin, South Africa. The cessation of dewatering lead to large volumes of contaminated surface discharges in the western parts of the basin. Towards the eastern extremity of the Witwatersrand basin the detached Evander Goldfield basin has been mined since the early 1950s at depths between 400 and 2000 metres below ground, while overlain by shallower coal mining operations. The hydrogeology of the Evander basin can be categorised by a shallow weathered-fractured rock aquifer comprising of the glacial and deltaic sediments of the Karoo Supergroup, while the deeper historically confined fractured bedrock aquifer consist predominantly of quartzite with subordinate lava, shale and conglomerate of the Witwatersrand Supergroup. The deep Witwatersrand aquifer has been actively been dewatered for the last 60 years with a peak rate of 60 Ml per day in the mid late 1960s. Modelling the impacts of mine dewatering and flooding on a regional scale as for the Evander basin entails challenges like the appropriate discretisation of mine voids and the accurate modelling of layered aquifer systems with different free groundwater surfaces on a regional scale. To predict the environmental impacts of both the historic and future deep mining operations, the detailed conceptual model of the aquifers systems and a 3-dimensional model of the mine voids were incorporated into a numerical groundwater model to simulate the dewatering and post-closure rebound of the water tables for the basin. The presented model could serve as an example for the successful modelling of mine dewatering and flooding scenarios for other parts of the Witwatersrand basin. |
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Geochemical reaction modelling as a tool to quantify gold mining impacts on shallow groundwater resources in the East Rand Basin | Robert | Hansen | Witwatersrand | 2015 | |||||||
AbstractIn recent years acid mine drainage (AMD) has become the focus on many mine sites throughout the world. The Witwatersrand gold mines have been the main focus of AMD in South Africa due to their extensive impact on especially groundwater resources. The Witwatersrand Basin is a regional geological feature containing the world-famous auriferous conglomerate horizons. It is divided into sub-basins and the East Rand Basin is one of them. Due to the regional scale of the East Rand Basin AMD issues, a systems approach is required to provide a useful tool to understand the pollution source term and fate and transport dynamics and to aid in environmental decision making and to evaluate the geochemical impact of mitigation measures and evaluate future scenarios. |
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Numerical modelling of groundwater contributions to wetlands | Kai T | Witthueser | Witbank | 2015 | groundwater flow model | ||||||
AbstractIn order to meet the increasing national and international demand for coal, substantial expansion plans for existing as well as new coal mines were put forward in recent years. The mine developments are often proposed in environmentally sensitive areas and require an appropriate assessment of potential environmental impacts, including impacts on groundwater dependent ecosystems. This paper describes the development of a conceptual and numerical groundwater model as part of a wetland reserve determination in the Witbank coalfields. The model was used to assess potential mining related impacts on the shallow groundwater flow, including surface seepages and spring discharges feeding hill slope and valley bottom wetlands as well as pans. A number of shallow monitoring boreholes were sited, drilled and tested in the focus area around a pan to characterise the shallow perched and weathered aquifers. While these aquifers were generally found to be very low to low yielding, higher yields were encountered in a coarser grit layer intersected by two of the eight boreholes. The grit layer represents a potential preferential groundwater flow path towards the pan and was subsequently further delineated based on the exploration drilling logs from the mine. The different aquifers, the target coal seam, and over 60 mapped hill slope and valley bottom wetlands as well as pans, were incorporated into a numerical groundwater flow model. A free seepage boundary was assigned to the entire surface area to evaluate if the model is able to represent the observed seepages and spring discharges. The simulation of unsaturated flow processes (Richard's equation) was found to be crucial for the representation of discharges from perched aquifers. Following a satisfactory calibration of the model, different open cast mine layouts were then incorporated into the model to assess their impacts on the groundwater contribution to wetlands. The presented quantitative simulation of groundwater contributions towards wetlands and pans based on site specific groundwater investigations and data is considered a best practice example in assessing the groundwater component for a wetland reserve determination. |
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Baseline concentrations of radionuclides in groundwater of the Namibian Uranium Province, Namib Desert, western Namibia | Ester | Gustavo | Western Namibia | Namib Desert, baseline, Groundwater, radionuclides, uranium province | |||||||
AbstractThe Namibian uranium province, located in the Namib Desert, derives its name from the local presence of almost ten uranium tenements. The mines conduct monitoring of natural radionuclide concentrations of Ra226, Ra228, Pb210, U234, U238, Th232 and Po210 in local aquifers. This data is useful in mine rehabilitation and developing closure criteria, as only radiation doses additional to natural doses are usually considered ‘controllable’ for radiation protection purposes. An accredited laboratory analyzed the baseline data collected through quarterly groundwater sampling with submersible pumps. The uranium deposits are hosted in Damara age granites or as secondary mineralization in Tertiary calcareous paleochannels. The analysis of the long-term baseline data provides the background radionuclide concentrations of three aquifer types in the province, i.e., the Quaternary saturated alluvium of the Khan and Swakop ephemeral Rivers, the Tertiary paleochannel sediments, and Proterozoic basement aquifers. The ephemeral rivers are important because they supply groundwater downstream of the mines for agricultural use. The analysis demonstrated that the alluvial aquifers have the lowest natural radionuclide content, with the U234 concentrations ranging between 0.03 and 3.4 Bq/l, while paleochannel and basement aquifers show intermittent U234 concentrations ranging between 0.25 and 5.1 Bq/l. The groundwater in the immediate ore zones shows the highest U234 concentrations, ranging between 44.8 and 86.3 Bq/l, exceedingly higher than the WHO standards of 1 Bq/l. This study illuminates that radioactivity is a natural phenomenon and that groundwater baseline data is paramount to groundwater protection. |
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Investigating Methods to Identify Groundwater Dependent Ecosystems and Assess Potential Impacts of Shale Gas Developments in the South Western Karoo, South Africa | Louelle Chelsea | Philander | Western Karoo, South Africa | 2017 | Dependent Ecosystems, Shale Gas Developments | ||||||
AbstractThe need to diversify energy resources for South Africa has brought developing shale gas to the forefront. Consequently, the semi-desert Karoo basin in South Africa is being explored as a potential source for shale gas resources. South Africa’s limited water resources have caused concern because groundwater resources are the main source of water for irrigation, drinking and for sustaining groundwater dependent ecosystems. Groundwater dependent ecosystems are found across the South |
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Development of Table Mountain Group aquifer wellfields and monitoring networks for the City of Cape Town (Western Cape, South Africa) | Dylan | Blake | Western Cape, South Africa | 2023 | Critical Zone, Table Mountain Group aquifers, environmental monitoring, wellfield development, “no-regrets” approach | ||||||
AbstractThe City of Cape Town (CCT) initiated its “New Water Programme” in 2017 (during the major 2015-2018 “Day Zero” drought) to diversify its bulk water supply, thereby improving longterm water security and resilience against future droughts. This includes bulk groundwater abstraction from the major fractured Peninsula and Nardouw Aquifers of the Table Mountain Group (TMG) in the mountain catchments east of the CCT. The TMG aquifers are essential in sustaining groundwater-dependent ecosystems associated with the Cape Floral Kingdom – a global biodiversity (but also extinction) hotspot with exceptional endemic diversity. A strong geoethical, “no-regrets” approach is therefore required to develop TMG wellfield schemes for the CCT (and other towns/cities in the Western/Eastern Cape) to reduce the risk of any negative ecological and environmental impacts while still enhancing the drought resilience of the city, providing water for future urban growth, and meeting Sustainable Development Goals 6 and 11. To this extent, the CCT has developed an extensive regional (and local, in terms of Steenbras Wellfield) environmental monitoring network, incorporating a range of in-situ and remote sensing-based measurements across the Earth’s “Critical Zone” – this includes current groundwater, surface water, ecological, soil and meteorological monitoring stations, and future seismo-geodetic monitoring. An ongoing ambition is to include this CCT TMG monitoring network into the “Greater Cape Town Landscape”, which is currently in development as one of six national South African landscapes under the “Expanded Freshwater and Terrestrial Environmental Observation Network” (EFTEON) platform being hosted by the South African Environmental Observation Network. |
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Keep the flow: Applying a HOPE model | Jacqueline | Goldin | Western Cape, South Africa | 2023 | community engagement, Governance, social justice, transformative | ||||||
AbstractTop-down governance systems are not well designed to secure the protection, use and management of groundwater at the local level and, on the contrary, perpetuate ‘wicked’ problems of poor groundwater management and protection. Citizen science promises solutions to these ‘wicked’ problems. We present findings from a project in the Hout Catchment, Limpopo, where citizen scientists monitor water in wells in remote rural settings. We redress the bias towards the natural sciences and pay attention to human systems as it is through engaging with people’s ‘ordinary’ citizens that they will protect their environment for better planetary health. To better understand these human systems that impact groundwater, we emphasise diversity and difference and argue for a HOPE model (heralding optimal participatory equity). HOPE has intrinsic and extrinsic value (equity) (addressing a hydrological void and understanding groundwater features). To achieve this, we open up a toolkit providing very practical methods. Using these tools, we propose that citizen science - taking science away from remote institutions, out of libraries and laboratories - and bringing it close to people is emancipatory and addresses new ways of understanding polycentric governance. Citizen science is transformative; citizens move from a passive state of non-engagement with science to acting as scientists. Disempowered people now have a sense of being part of the betterment of their world and improved water resources management. Narrowing the natural and social sciences divide is crucial for improved polycentric governance. |
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Using passive sampling to identify trends in aquatic pesticide pollution in the Western Cape, South Africa | Emma | Davies | Western Cape, South Africa | 2023 | Imidacloprid, passive water sampling, pesticide, South Africa, surface water, Sustainable Development Goal | ||||||
AbstractSouth Africa is the leading user of pesticides in Sub-Saharan Africa, but data on pesticide occurrence in (ground)water is limited. Consequently, there is a need to improve knowledge on transport pathways that cause pesticides to enter the aquatic environment. This research monitored pesticide concentrations in three agricultural catchments in the Western Cape, South Africa, including Grabouw (pome fruit), Hex River Valley (table grapes), and Piketberg (wheat). Passive samplers were deployed in rivers from March 2022- March 2023, adding to a 2017-2019 dataset of analytical and pesticide application data. Field and laboratory methods were developed at Stellenbosch University to measure pesticides using Liquid Chromatography-Mass Spectrometry. For quality control, duplicate samples were analyzed at Eawag, Switzerland. 30 compounds were detected, yet two/three comprise most of the total mass, including an analyte not considered in earlier investigations (dimethomorph). Rainfall-flow relationships and agricultural application could only partially explain detection levels, suggesting that other factors, including non-agricultural application or groundwater input, might influence detections. Two compounds exceeded European Environmental Quality Standards (chlorpyrifos and imidacloprid). Imidacloprid is particularly concerning because it exceeded consistently despite few recorded applications. 2017-2022 imidacloprid data indicates a decreasing concentration trend in Hex River Valley and increasing trends in Piketberg and Grabouw. Consistently high detections during wet and dry periods suggest groundwater input. However, such pesticide transport pathways are poorly understood due to a lack of local evidence. Local authorities must establish a long-term monitoring program to understand better the risk pesticides pose to the aquatic environment and human health. |
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Western Cape Groundwater Status Amid Times Of Severe Drought - Selected Case Studies. | Julian E | Conrad | Western Cape | 2019 | Drought | ||||||
AbstractThe rainfall situation in the Western Cape became a focal point in 2015; 2016 and 2017. The rainfall in 2015 was half the long term average; in 2016 it was still below the long-term average and in 2017 it was again about half the long-term average. In 2018 the rainfall was better and was about the same as the long term average. These consecutive years of low rainfall were really problematic and with the declaration of the "Day Zero" campaign the media brought the plight of the City of Cape Town into the global headlines. However it was not only the City of Cape Town that was under dire stress but the whole of the Western Cape Province (and beyond). The neighbouring District Municipalities (DM) also embarked on frantic groundwater development and augmentation programmes. GEOSS South Africa (Pty) Ltd was fortunate to be involved in the DMs surrounding the City of Cape Town. This presentation focusses more on the groundwater aspects per se rather than the technical; aspects of boreholes; pumps etc, with specific reference to case studies including the Sandveld; Saldanha Bay Local Municipality and the Stellenbosch Local Municipality (specifically the Franschhoek area). The Sandveld (which is within the Berg River District Municipality) has a significant agricultural sector and 25 years of regional groundwater monitoring indicates that even with significant groundwater abstraction for the agricultural activities within the area, the groundwater volumes are robust enough to support further development of groundwater to meet the increasing water requirements for the town supply of Graafwater and Lamberts Bay. This expansion is currently underway. The West Coast District Municipality (specifically the Saldanha Bay Local Municipality) committed significant resources to groundwater development in the times of the drought. The Langebaan Road Aquifer wellfield was expanded with additional production boreholes and a new wellfield, known as the Hopefield Wellfield was also fully developed and equipped with all infrastructure in place. The wellfields have also set up to implement Managed Aquifer Recharge. Although these schemes are not yet operational, the groundwater levels held up well during the drought, indicating these wellfields should play a major role in times of future drought. Groundwater within the Franschhoek area (Winelands District Municipality) is utilized by many sectors and from detailed and long term monitoring the drought had little impact on the resources supporting the development of groundwater supply schemes for Municipal augmentation. From widespread work in the Western Cape Province it is evident that the drought had little impact on the groundwater levels of the region and it bodes well as a resource to be utilised in times of severe stress, so long as it is properly authorised, monitored and managed. |
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A conceptual model for methane occurrences in the Western Karoo as part of a geochemical baseline for shale gas development | Danita | Hohne | Western Cape | 2023 | Western Karoo, shale gas development, shallow and deep groundwater, thermogenic and biogenic methane; isotopes | ||||||
AbstractAlthough methane occurrences have been documented in Karoo groundwater in the past, the advent of possible unconventional oil and gas extraction now made it important to determine the type and origin of this methane to assess the possibility of shallow-deep groundwater interaction. During groundwater surveys from 2016-2021, methane was detected at three sites in the Western Karoo: the Soekor sites KL1/65, QU1/65 and an unidentified shallow groundwater borehole (BHA). The Soekor wells were drilled in the 1960-1970s to depths of between 2500-3500 meters in South Africa’s search for oil. On the other hand, Borehole BHA was drilled in 1998 and only up to a depth of 298m. This study aimed to determine methane’s origin through gas and isotope analyses. To do this, groundwater, rock and soil samples were analysed to determine whether the methane is thermogenic or biogenic and its origin. We determined that methane was both thermogenic and biogenic and probably originated from different layers of the Karoo formations and that mixing occurs between deep and shallow aquifer systems at these Soekor sites. This information was used to develop a final conceptual model of what the Karoo underground system might look like and to make recommendations for establishing a groundwater baseline. |
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Feasibility of iron and manganese removal by in-situ ozonation - Atlantis Aquifer Case Study | Kate | Robey | Western Cape | 2015 | |||||||
AbstractThe development of groundwater supply schemes is on the increase in South Africa. However, the sustainability of many of these wellfields is threatened due to the presence of iron (Fe2+) and manganese (Mn2+) ions in the groundwater. Their occurrence can manifest in problems with water quality and supply to consumers. The World Health Organisation recommends the removal of iron and manganese to below 0.3 mg/? and 0.1 mg/? respectively, to circumvent water quality risks. However, production borehole clogging is of greatest concern in the operation of wellfields due to the severe cost implications associated with reduced production. Clogging is caused by the precipitation of iron- and manganese-oxides at the borehole screen initiated by biogeochemical processes. Since Fe2+ and Mn2+ ions and the bacterial populations are naturally present in anoxic/anaerobic aquifer systems and the ingress of oxygen through pumping cannot be entirely prevented. The only approach to controlling borehole clogging is through management and rehabilitation procedures. Locally, these procedures have been implemented and in severe clogging cases the Blended Chemical Heat Treatment method has been applied. However, the effectiveness of rehabilitation has been limited. This can be ascribed to factors such as the incorrect production borehole design |
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Western Cape Coastal Groundwater Resources: Potential For Artificial Recharge And Conjunctive Use | Sumaya | Israel | Western Cape | 2017 | groundwater potential, artificial recharge, mixed use | ||||||
AbstractWestern Cape groundwater resources are often considered in isolation, per quaternary or aquifer depending on the level of management. This is an attempt to look at groundwater resources in its entirety for the major aquifer areas of the Western Cape. Atlantis in the Western Cape has been successfully operating for about 4 decades using artificial recharge, recycling of treated waste water and storm water. It is currently under used due to clogging of borehole screens and pumps with iron. However, there is no question of the potential for use and the volumes of water that the aquifer is able to supply. The Cape Flats Aquifer (CFA) has been identified in the past as a potential source to augment Cape Town’s municipal water supplies. Studies to assess the viability of the aquifer as a water supply to the Cape Metropolitan area all concluded that the CFA is a viable resource that can supply a projected sustainable yield of about 18 Mm3/a of bulk water. Artificial recharge was tested in the Cape Flats and showed great promise. The Langebaan area along the West Coast has an existing well field supply, which is able to supply the town. Artificial recharge was tested in Langebaan Road during 2009, and showed promise for the Langebaan area. In essence, the Western Cape has a large volume of untapped resources which could improve the water situation. Climatic data, groundwater levels, and chemistry for these areas are explored to consider the potential for artificial recharge, abstraction and use and the extent to which artificially recharged and existing resources can supply the coastal areas of the Western Cape. |
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GIS and Groundwater Monitoring | Freda | Jonck | Western Cape | 2017 | monitoring network, resource assessment | ||||||
AbstractThe Department of Water Affairs and Sanitation is the custodian of the Water Resources in South Africa. The Western Cape Provincial Office, Geotechnical Services (Geohydrology) Sub Directorate, is responsible for management of groundwater resources in two Water Management Areas (WMA), Berg Olifants and Breede- Gouritz. Thirty-eight monitoring routes comprising 700 sites in total are monitored across the Western Cape Province. The purpose of this paper is to show the use of GIS as a management tool for groundwater monitoring in the Western Cape. This is to assist and support the scientists, technicians, managers, external stakeholders and/or general public. The main question that needs to be answered is: “What is the current groundwater monitoring and data management situation in the Provincial office” With GIS as platform, geographical information was generated from existing data bases to answer questions such as, what is being monitored, where is it being monitored, who is monitoring it, why is it being monitored, when is it being monitored, are instruments installed, what instruments are installed, what equipment is involved and what energy source is used? These questions are applicable to the Region, Water Management Areas, the relevant monitoring route and geosites. Generated geographical information showed the gaps, hot spots and what is still needed for all the facets of groundwater management (from data acquisition to information dissemination) processes. The result showed the status of data bases, need for data in areas of possible neglect, training gaps, inadequate structure and capacity, instrumentation challenges, need for improvement of commitment and discipline, as well as many other issues. The information generated proves to be an easy tool for Scientists, Technicians and Data Administrators to assist them to be on top of the groundwater resource management in their area of responsibility. The expansion of the use of GIS as a groundwater management tool is highly recommended. This will ensure better understanding of the “The Hidden Treasure” resource. |
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Existing Springs in City of Cape Town and Environs: Spring Use Strategy | Louise | Soltau | Western Cape | 2015 | |||||||
AbstractCape Town... Home to over 3 and a half million people, the second most populated city in South Africa was born in the shadow of the Table Mountain. The mountain offered all the elements vital for human settlement... most importantly WATER. The reports of the abundance of fresh water and fertile land at the foot of the mountain and surrounds inspired the VOC to set up a refreshment station at the Cape. By the late-1800s, spring water was solely used for domestic supply to the settlers of Cape Town. Until the 1930s, the Stadsfontein or Main Spring was still being used as a source of drinking water but because of on-going concerns about the safety of the water for human consumption, and sufficient water being available from the new schemes like Steenbras and Wemmershoek, a decision was taken to discontinue using the Stadsfontein for drinking water purposes. Since then most of the water joined the stormwater to the sea, until 2010 when the City recommenced using the water for irrigation at Green Point Stadium and the Commons. City of Cape Town faces a number of water supply challenges. These include managing the ever increasing demands on the current water supply. The City of Cape Town Springs Study was born from this 2001 Water Demand Management study and it aims primarily to examine the possibility of using spring water as an alternative source of water for non-potable supply. Of these, the springs which hold the most potential for use are found in two areas - the CBD area of Oranjezicht, home to the Field of Springs |
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The presence and concentration of antiretroviral drugs in different water bodies around the Western Cape | Phumelele | Maphumulo | Western Cape | 2021 | Antiretroviral, chemical formulas | ||||||
AbstractThis study is based on the presence and concentration of antiretroviral drugs in water bodies around the Western Cape Province in South Africa, these areas include wastewater treatment plants, water treatment plants, stormwater, and landfill boreholes. South Africa has the highest rate of HIV and AIDS in the entire world, statistics from 2018 show that 7.7 million South Africans are infected with HIV/AIDS and 68% of them are on antiretroviral treatment (UNAIDS). South Africa has the largest antiretroviral treatment program (ART) in the world, due to the lack of proper water and sanitation these drugs are deposited in the environment poorly and reach water bodies, therefore, contaminating them. This study involves the collection of samples from areas such as Mitchell’s Plain, Khayelitsha, Athlone, Cape Flats, and Atlantis around the western cape, these samples are analyzed to determine the presence of 5 antiretroviral drugs used in South Africa which are Efavirens, Lopinavir, Nevirapine, Ritonavir, and Tenofovir. Water samples are prepared for analysis by filtering 2.5ml water through a 1µm glass fiber filter, the sample is then placed into sample vials and analyzed on HPLC-QTOF/MS. Mass Hunter software is used to identify the specific ARVs in the water samples analyzed, by searching for the compounds via their chemical formulas. With a match made if their chemical formula, retention time and mass to charge ratio of the compounds correspond. Concentrations range between 0.0855ng/ml Nevapine to 4.3289ng/ml Lopinavir, this analysis has determined that all the mentioned antiretroviral drugs are indeed present in different water bodies around the identified areas within the Western Cape in varying concentrations. |
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Unravelling the complex geohydrological structure of the Elandsfontein aquifer unit | Kezia | Smith | Western Cape | 2015 | |||||||
AbstractThe Elandsfontein aquifer is currently under investigation to assist with the management of the system and to ensure the protection of the associated Langebaan lagoon RAMSAR site. The Elandfontein aquifer unit is situated adjacent to the Langebaan Road aquifer in the Lower Berg River Region and is bounded by the Langebaan Lagoon, possible boundary towards Langebaan Road aquifer, the Groen River bedrock high and the Darling batholith. The study will investigate the boundaries and hydraulic characteristics of the different aquifers and aquitards (Elandsfontein clay layer) in the Elandsfontein unit and their relationship to the Langebaan Lagoon. A literature review and baseline study has been completed to determine groundwater flow patterns and the general distribution of water quality, using historic data to characterize the different aquifers and aquitards of the system. An initial conceptual model has been formulated based on this data. Pumping tests will be used to acquire hydraulic characteristics of the Elandsfontein aquifer where data gaps exist, together with water quality and stable isotope sampling. Future plans are to construct a groundwater numerical flow model of the Elandsfontein system to assist with the management of the complex relationships between the recharge areas, flow paths through the different aquifer layers and aquitards towards the Langebaan Lagoon discharge. Results will be presented using graphical methods such as time series graphs amongst the monitoring boreholes over the years, piper diagrams to show water type characterization (Na-Cl type water) and initial results from the groundwater flow model. The expected results are envisaged to advance knowledge on groundwater availability and quality to inform the decision about water resource protection and utilization. Therefore this study is designed to provide large-scale background information that will improve the knowledge and understanding of the Elandsfontein aquifer unit and provide a basis for potential future studies of a more-detailed nature. |
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Community Involvement In Groundwater Management In The Western Cape: The Sandveld Case Study | Ayuk Juveta | Nchoung | Western Cape | 2013 | groundwater management, case study, Groundwater, Water treatment | ||||||
AbstractGroundwater is a reliable freshwater resource. Its location underground prevents it from evaporative forces. Thus it serves as storage of most of the world’s liquid fresh water. Being enclosed in the ground it is not also easily contaminated. Since groundwater can be used wherever it exists without costly treatments, there is over-dependence on the resource. Though in the past it was mainly used by rural dwellers for domestic water supply, presently, due to effects of climate change on surface water resources, pressures of population growth leading to expansion of towns and cities, groundwater is also supplied for agriculture and industrial purposes. But, the resulting effect from these additional users is the vulnerability of groundwater resources to reduction and pollution. Its importance in sustaining livelihood and development has been highly credited and its management is looked upon as a prerogative. To enhance groundwater management in the Sandveld, a qualitative content analysis approach was used to evaluate six factors considered to be highly needed in groundwater management. This background was used to find out how institutional arrangement in South Africa facilitates or constraints groundwater management in the Sandveld, a highly groundwater dependent area in the West Coast of the Western Cape. The results showed that all six factors are present, but three facilitate groundwater management while three others constrain management. The community involvement which ranked first, is deficient. Thus, institutional weaknesses that need to be strengthened have been identified. |
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Why is groundwater a Cinderella Water Resource? | Roger | Parsons | Western Cape | 2019 | Awareness, development | ||||||
AbstractFor years hydrogeologists have bemoaned the fact the groundwater is often pushed aside in favour of surface water resources being developed for water supply purposes. This is despite the advantages of groundwater being less vulnerable to the impact of drought, generally significantly cheaper to develop and being ubiquitous in character. The intangible character of groundwater was thought to be a major factor in water resources engineers favouring surface water resource development, as well their limited appreciation of the character, exploration, development and management of the resource. But is this really the case? Recent experiences in developing groundwater as an alternative source of water across the Western Cape Province in the face of failing municipal water supplies has highlighted poor communication being a central issue. It was observed that the hydrogeologists had little appreciation of the controls and constraints that govern getting groundwater to the user. Further, their recommendations around the use of groundwater were at times confusing to the uninitiated. Engineers, on the other hand, were found to not adhere to recommended pumping regimes nor appreciate groundwater management requirements. The treatment of groundwater emerged as a constraint that added greatly to the complexity of developing these supplies and requiring ongoing operation and maintenance efforts. |
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Isotope Constraints On The Source And Residence Time Of Spring Water From The Table Mountain Group Aquifer, Paarl, South Africa | Jodie | Miller | Western Cape | 2017 | large-scale abstraction, urban water supply, fractured rock, springs, Tritium, residence time | ||||||
AbstractLarge scale groundwater abstraction is increasingly being used to support large urban centres particularly in areas of low rainfall but presents particular challenges in the management and sustainability of the groundwater system. The Table Mountain Group (TMG) Aquifer is one of the largest and most important aquifer systems in South Africa and is currently being considered as an alternative source of potable water for the City of Cape Town, a metropolis of over four million people. The TMG aquifer is a fractured rock aquifer hosted primarily in super mature sandstones, quartzites and quartz arenites. The groundwater naturally emanates from numerous springs throughout the cape region. One set of springs were examined to assess the source and residence time of the spring water. Oxygen and hydrogen isotopes indicate that the spring water has not been subject to evaporation and implies that recharge to the spring systems is via coastal precipitation. Although rainfall in the Cape is usually modelled on orographic rainfall, δ18O and δ2H values of some rainfall samples are strongly positive indicating a stratiform component as well. Comparing the spring water δ18O and δ2H values with that of local rainfall, indicates that the springs are likely derived from continuous bulk recharge over the immediate hinterland to the springs and not through large and/or heavy downpours. Noble gas concentrations, combined with tritium activities indicate that the residence time of the TMG groundwater in this area is decadal in age with a probable maximum upper limit of ~40 years. This residence time is probably a reflection of the slow flow rate through the fractured rock aquifer and hence indicates that the interconnectedness of the fractures is the most important factor controlling groundwater flow. The short residence time of the groundwater suggest that recharge to the springs and the Table Mountain Group Aquifer as a whole is vulnerable to climate change and reductions in regional precipitation. Any plans for large-scale abstraction to supplement the City of Cape Town water supply would need to factor this in to models of maximum sustainable yield. |
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The use of boreholes for the infiltration of treated effluent - Pearly Beach Waste Water Treatment Works - A case study. | Dale | Barrow | Western Cape | 2015 | monitoring network | ||||||
AbstractA Waste Water Treatment Works (WWTW) is being constructed at Pearly Beach. A geohydrological assessment was conducted to assess the potential discharge of treated effluent above and below the subsurface calcrete layers. A hydrocensus has been completed of the area to confirm there is no use of groundwater down-gradient of the WWTW and there is no likely impact on ecosystem functioning. Based on existing boreholes, infiltration above the calcrete layer in the vadose zone was found to be more efficient. A geophysical study was conducted to determine the optimal locations of boreholes for disposal of the treated effluent. The geophysics included an extensive electromagnetic (EM) survey. Resistivity data were acquired along a single resistivity profile to use as calibration for the EM data. This information has been correlated with borehole information from the monitoring boreholes that were drilled at the proposed WWTW site. From this information it would seem that the areas with higher conductivity (lower resistivity) can be targeted for drilling boreholes to dispose of the treated effluent. Also, the higher conductivity areas are interpreted as the areas with increased porosity. However, the change in conductivity could result from an increase in salinity or changes in calcrete content in the subsurface. The expected depth of the unconsolidated sand formations is generally less than 10 m based on the interpreted depth of the saturated formation from the resistivity data. Drilling will target the unconsolidated sands, as well as potential higher porosity zones beneath the calcrete. The geophysics data should then be calibrated with the information obtained from drilling the first borehole. The other sites can then be confirmed or reviewed based on the information. The boreholes are to be drilled soon and pump tested. The obvious concern is that the boreholes may clog, however measures will be put in place to minimise this risk. A detailed monitoring network will also be established. On-going monitoring is crucial to ensure the success of the scheme. The full conference paper will include the drilling and pump testing results and infiltration tests. This method of disposal needs to be taken into consideration especially if such schemes can be run successfully so that another option is available for the disposal of treated effluent. {List only- not presented} |
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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 | ||||||
AbstractMonitored 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. |
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Cape Town: Where sweet waters meet the sea | Matthys A | Dippenaar | Western Cape | 2017 | Tourism, Drought, Hydrological Heritage Overview | ||||||
AbstractThe City of Cape Town is a favourite tourist destination. With Table Mountain being one of the new seven natural wonders of the world, Cape Town is also uniquely positioned where the Benguela and Atlantic ocean currents meet. Proximate environs play home to some of the most unique biodiversity found in the world with the fynbos biome protected in numerous reserves such as the Cape Peninsula, Table Mountain and Kogelberg Nature Reserves. Cape Town is also South Africa’s cultural heartbeat where artists, film makers, designers and wine connoisseurs contribute to the tourism of the country. The recent drought and increasing demands through urbanisation are raising concerns regarding water scarcity and supply. Will the city be able to supply this growing demand, notably with additional stress due to climate change? The Hydrological Heritage Overview aims to address the important power water has over Mankind and how we can harness that to our benefit without compromising the environment. The selection of Cape Town (following completion of Pretoria and Johannesburg) supplies the opportunity to address the mechanical impacts of water: Table Mountain formed through the action of water, and was shaped into its characteristic landform due to subsequent erosion by water action. Additional emphasis on the power of water relates to aspects of hydropower, the impacts of floods and droughts, and additionally of the power of water as it is harnessed as a vital life supporting resource and as a means of recreation. As the final deliverable of this project, a short 12-minute documentary film has been made for the information of the general public and interested parties. The film showcases the water history of the City of Cape Town, emphasising supply from springs, dams and, more recently, artificial groundwater recharge. Although not a technical presentation, showcasing of the film will advance citizen science and public appreciation for the value of water. |
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Parameter Estimation For Artesian Aquifer In Table Mountain Group Aquifers By Analytical Method | Xiaobin | Sun | Western Cape | 2013 | aquifer, artesian conditions | ||||||
AbstractAccurate parameter estimation for fractured-rock aquifers is very challenging, due to the complexity of fracture connectivity, particularly when it comes to artesian flow systems where the potentiometric is above the ground level, such as semi-confined, partially confined and weak confined aquifers in Table Mountain Group (TMG) Aquifer. The parameter estimates of these types of aquifers are largely made through constant-head and recovery test methods. However, such tests are seldom carried out in the Table Mountain Group Aquifer in South Africa due to the lack of a proper testing unit made available for data capturing and an appropriate method for data interpretation. An artesian borehole of BH-1 drilled in TMG Peninsula Formation on the Gevonden farm in Western Cape Province was chosen as a case study. The potentiometric surface is above the ground level in the rainy season, while it drops to below ground level during the dry season. A special testing unit was designed and implemented in BH-1 to measure and record the flow rate during the free-flowing period, and the pressure changes during the recovery period. All the data were captured at a function of time for data interpretation at later stage. Curve-fitting software developed with VBA (Visual Basic Application) in Excel was adopted for parameter estimation based on the constant-head and recovery tests theories. The results indicate that a negative skin zone exists in the immediate vicinity of the artesian borehole in Rawsonville, and the hydraulic parameters estimates of transmissivity (T) ranging from 6.9 to 14.7 m2/d and storativity (S) ranging from 2.1×10-5 to 2.1×10-4 appear to be reasonable with measured data collected from early times. The effective radius is estimated to be 0.5 to 1.58 m. However, due to formation losses, the analytical method failed to interpret the data collected at later times. Consequently the analysed results by analytical solution with later stage data are less reliable for this case. Numerical modelling is proposed to address the issue in future. |
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Nutrient Retention In Stream Sized Rivers, Related To Riparian Land Development And Climatic Change | Reuben | Lazarus | Western Cape | 2017 | Seasonal cycles, Pollution, physicochemical environment | ||||||
AbstractThe Western Cape of South Africa is rich in small stream sized rivers forming part of its water resources. The Lourens river and Eerste river, both situated in this region are the base for this study. Rivers are affected by their surrounding environments and the continuous development around these rivers could affect their health adversely. Diverse land-use patterns contribute to a wide range of pollutants with different characteristics. Indeed, some of the pollution levels in the Eerste and Lourens rivers were linked directly to specific land-use practices surrounding the rivers. However, the large change in weather during a seasonal cycle causes a significant difference in pollution levels too, because the transport of pollutants from the source to the rivers is primarily based on surface run-off, which in turn is predominantly dependent on the precipitation of the region. A six months long monitoring in 2016 showed that processes like surface run- off, together with first flush events and dilution control the pollution concentrations in the Lourens river and Eerste river. Physicochemical parameters, major agricultural nutrients and industrially produced heavy metals all reacted differently to these processes, thus, providing an insight into the effects continuous development and climate change have on surface water as a national resource. Interestingly, both rivers included sections with substantial retention and/or reduction of pollutants. The natural riparian vegetation, hyporheic zone and microbial community present in these rivers are proposed to be the main drivers behind both rivers’ ability to reduce or retain pollutants. These drivers are sensitive to their environment and react differently depending on the weather, available nutrients, and physicochemical environment. With the effects of climate change becoming more apparent, it is important to study the impact of warmer temperatures, longer droughts, and heavier rain events, for instance, on the pollutant retaining capabilities of these streams. |
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Are Farmers Drying Out The Cederberg? Deep Groundwater Flow And Isotopes In The Table Mountain Group. | Roger E | Diamond | Western Cape | 2017 | TMG, Isotopes | ||||||
AbstractThe 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. |
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Strategy For Groundwater Testing And Management In A Confined Artesian Basin: Oudtshoorn Area | Chris JH | Hartnady | Western Cape | 2013 | groundwater management, strategy | ||||||
AbstractThe Deep Artesian Groundwater Exploration for Oudtshoorn Supply (DAGEOS) Project is culminating in development of the Blossoms Well-field (C1 Target Zone), about 20 km south of the town. The target Peninsula Aquifer is located at depths >300 m below ground level, geopressured to ~800 kPa (8 bar) artesian head. Each production well has to be uniquely designed for site-specific hydrogeological, hydrochemical and aquifer hydraulic conditions. Hydrostratigraphy rather than stratigraphy must inform the final well design. It is a recipe for unnecessary expense and deleterious consequences for aquifer management, to design and commence the drilling of wide-diameter production wells without the data and information provided by necessary exploration and essential pilot boreholes, yielding broader hydrogeological insights. During discovery exploration at the C1b Target Site Area (TSA), drilling of a 715 m-deep diamond-core exploration borehole (C1b2) was essential for the proper siting and safe design of a production well (C1b3). Following confirmation of the artesian nature of the Peninsula Aquifer, the C1b2 borehole was equipped for monitoring, prior to the drilling of the nearby (~25 m distant) C1b3 production well, which was piloted with a core borehole down to a low level (~290 m) within the Goudini Aquitard, where it became marginally artesian and was then plugged and sealed. This pilot borehole was reamed with wide-diameter percussion tools to a depth where casing could be firmly cemented within the Goudini, above a solid, relatively unfractured zone. The final stage of drilling into the Peninsula Aquifer, using the Wassara water-hammer method, was thereafter continuously monitored from the C1b2 site, and the subsequent recovery history of C1b3 is comprehensively documented. The DAGEOS drilling and deep-groundwater monitoring provides significant experience in solving technological problems likely to be encountered in the future development of shale-gas in the main Karoo basin. The confined, artesian aquifer behaves very differently to other, conventional groundwater schemes and requires a different management approach that focuses on managing the artesian pressure within the basin and its response to abstraction. The potential adverse influences of high and/or extended abstraction on the Peninsula Aquifer may be divided into two general categories: 1) depletion or degradation of the groundwater resource, and 2) environmental or ecological consequences. Depletion in the case of a confined aquifer refers to depletion in storage capacity due to non-elastic behaviour. Environmental/ecological impacts of groundwater extraction arise only when the ‘radius-of-influence’, defined by the distance from the centroid of a well-field to the perimeter of the cone of depression in the ‘potentiometric surface’ (surface of pressure potential in the aquifer), reaches recharge and or discharge boundaries. The new Oudtshoorn Groundwater Scheme affords an opportunity to stage a transition from an increasingly risky reliance on surface water that is prone to severe reduction through climate change, to a deep groundwater resource that is capable of acting as a sustainable buffer against water-scarcity through drought intervals that may endure over decades rather than years, and can be operated without electricity supply by utilising the artesian pressure in the aquifer. This approach was demonstrated in a 3- month artesian flow test during 2009.
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Groundwater Quality And Potability | Roger | Parsons | Western Cape | 2019 | quality | ||||||
AbstractThe quality of groundwater is, in part, controlled by the character of the rock in which it is stored and the water - rock contact time. Rainfall (or recharge) is also a contributing factor as the mineralisation of groundwater increases from east to west across South Africa. It is well established that groundwater is more mineralised than surface water, and with most of South Africa's domestic supplies being sourced from dams, municipal water supplies are generally of low salinity. The exception to this is where water supplies are sourced from groundwater - such as in the Karoo and along the West Coast. The assessment of water potability is based on both the South African National Standard 241 and the Department of Water and Sanitation guidelines, with the former being a legal requirement. Previously, SANS 241 had two classes of water with the lower class only being allowed for a limited period. In 2015, Class II water was done away with and only a single class of water is now specified. While this may have been done to conform to World Health Organisation standards, it disregarded the realities of a resource-strapped South Africa where in large parts the municipal water supplies simply cannot meet the SANS241 standard. This paper examines the implications of the SANS 241 standard on efforts to establish emergency groundwater supplies during the drought impacting the Western Cape Province. |
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Identifying Potential Managed Aquifer Recharge Zones In West Coast Aquifers, Western Cape | Ashleigh | Tomlinson | Western Cape | 2019 | Poster, recharge, MAR | ||||||
AbstractThe overexploitation of water resources has resulted in a global decline in groundwater levels. Managed aquifer recharge (MAR) is a globally acceptable practice to manage the depletion of water in overexploited aquifers in regions with limited water availability. The West Coast of South Africa experiences a semi-arid climate with predominantly dry summers. This study aims to identify potential areas suitable for MAR in the Saldanha Bay area to maximize the water available to these areas during the dry season. This will be done through the delineation of the aquifer(s) units to determine the distribution of suitable aquifers, understanding the aquifer(s) hydraulic and hydrogeological characterises and investigate the water quality. This study focuses on 1) Frequency domain electromagnetic and electrical resistivity geophysical methods to characterise the subsurface; 2) Aquifer testing, to estimate the hydraulic properties of the aquifer(s); 3) Water quality sampling and analysis for water quality investigations. Practical considerations like distance from suitable water sources will also be considered. The expectations for this study, based on the results that should be obtained from these methods, should include the identification of several zones that would allow for MAR practices |
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The Use Of Derivative Analysis To Choose And Refine Conceptual Models Of Groundwater Flow Systems | Thokozani | Kanyerere | Western Cape | 2019 | modelling, flow systems | ||||||
AbstractGroundwater flow system responses have been understood using derivative analysis. The argument is that the use of derivative analysis derived from pumping test data improves the understanding of aquifer types and curve matching in a hydrogeologic setting. The different aquifer systems encountered in Western Cape Government Business Continuity Programme (WCBCP) of South Africa was used as case study where the analysis of the time versus draw-down derivative plots were applied to validate the aquifer characteristics to explaining the groundwater flow systems. Key findings showed that analysis from the time versus draw-down derivative plots can be used to infer conditions within the wellbore, groundwater flow to boreholes and boundary conditions within the aquifer to provide insights. In addition, results confirmed that the archetypal time vs draw-down responses enabled characterizing the aquifer types and such analysis showed unique responses to the pumping. Lastly, long term operation of boreholes for water supply were ascertained when the analysis was interpreted. The analysis was enhanced when the geological information that was collected during drilling operations, were added to the conceptual understanding of groundwater flow studied aquifer system. However, due to costs implications of conducting long-term aquifer hydraulic pumping tests, deviations from the conventional draw-down responses are expected. In this study, it is suggested that due to complexities associated with heterogeneous flow in aquifer types, it is essential to combine derivative analysis with pumping methods to improve interpretation and assessing long term operation of boreholes for water supply |
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Comparing The Influence Of Aquifer Heterogeneity On Borehole Design, Test Pump Results And Interpretations Between The Primary Cape Flats And Atlantis Aquifers Of The Western Cape, South Africa. | Luke | Towers | Western Cape | 2019 | Heterogeneity, development, Management | ||||||
AbstractThe recent Western Cape drought initiated large scale development of the Cape Flats Aquifer (CFA) and refurbishment of the Atlantis Water Resource Management Scheme (AWRMS). Both aquifers are comprised of primary sediments of the Sandveld Group. Lithologies and depositional environments of the two aquifers are often directly compared and linked, but recent borehole drilling in these two aquifers is highlighting their inherent differences. The use of conventional mud rotary drilling techniques in these aquifers and changing nomenclature over time, has created uncertainty in their lithological character, leading to complications in borehole design and interpretation of test pumping results. Sonic drilling - Atlantis (20) and CFA (25) - was undertaken and incorporated with approximately 200 mud rotary borehole drill logs and geophysical survey results to investigate aquifer geometry and hydro-lithological characteristics. Results to date indicate the CFA is more heterogenous and has greater lateral variation compared to the Atlantis Aquifer. The CFA is interspersed with clay lenses, organic rich layers, calcrete and thick basal shell units. Whilst the Atlantis Aquifer displays a more homogeneous character with limited clay lenses, minor organic layers, interspersed calcrete and a near non-existent basal shell layer. Results of the sonic drilling have led to increased confidence in boreholes design, test pump analyses and numerical model results. The influence of CFA's heterogeneity on test pumping interpretation is displayed in the results through a variety of unconfined, confined, semi-confined and leaky type curves. Atlantis however, typically displays unconfined Neuman-type curves. Delayed gravity drainage signals, test pump duration, varying hydraulic conductivities of different lithological units and other boundary effects not only have an economic impact on test pump design, but can lead to the misinterpretation of test pump data which greatly influences planning for the aquifers' response to large scale abstraction and Managed Aquifer Recharge (MAR) alike. |
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Developing Groundwater Supplies To Supplement The Water Supply Of Ladismith, Western Cape Province | Roger | Parsons | Western Cape | 2015 | |||||||
AbstractLadismith was established in 1852 at a point where freshwater springs discharge from the Swartberg mountains. Growth of the town required building of the Goewerments Dam in 1920 and the Jan F le Grange Dam in 1978. However, water demand now matches supply, and water shortages are being experienced. Poor management and recent droughts exacerbated the situation. A project was initiated to address problems with the existing water supply and identify additional sources of water. Groundwater is an obvious option, with the regionally extensive Cango-Baviaanskloof fault being located directly north of the town. The west-east trending fault juxtaposes the highly productive Table Mountain Group aquifer with less productive argillaceous rocks of the lower Witteberg Group. This paper presents the results of initial geohydrological exploratory work and examines the role groundwater can play in the future water supply to the town. |
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Evaluating changes in groundwater storage during the 2015-2018 drought in the Western Cape using GRACE data | Ritshidze | Nenweli | Western Cape | 2021 | Poster, Drought, GRACE, Groundwater storage | ||||||
AbstractThe frequency, intensity, and duration of droughts are increasing globally, putting severe pressure on water supply systems worldwide. The Western Cape Province suffered from a period of severe water shortages that began around January 2015 and lasted until about July 2018. During this recent drought, there was a forced reduction in water use, predominantly from the agricultural sector. Citizens also reduced water use and increasingly tapped into groundwater for their needs irrespective of whether the hydrogeology was considered favourable or not. Unmonitored and unregulated abstraction of groundwater, especially under unstable climatic conditions, poses a significant risk to the future water security of the Western Cape. While there is data on surface water use during the drought, the impact on groundwater resources has yet to be evaluated. However, the accurate assessment of groundwater use is difficult, especially in data-scarce regions, such as South Africa. In our study, we combine remote sensing from NASA’s Gravity Recovery and Climate Experiment (GRACE), the Global Land Data Assimilation Systems, groundwater level measurements from the National Groundwater Archive, and ancillary datasets from the City of Cape Town’s weekly water dashboard to assess the total change in groundwater storage in the Cape Town Metropolitan area and surrounding cities over an 8-year period, from 2012 to 2020. Preliminary results from GRACE data analysis show a steady decline in aquifer saturated thickness over the drought, indicative of an increase in groundwater use. |
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Assessment Of Groundwater Iron Concentration In Aquifers With Focus On Geological, Hydrogeological And Hydrogeochemical Conditions For Its Occurrence, Western Cape, South Africa | Presanta | Bissonram | Western Cape | 2019 | Poster, hydrochemical, iron | ||||||
AbstractDue to the recent drought in the Western Cape province of South Africa, surface water can no longer meet our current demand of water and as a result groundwater usage has increased. High iron concentration in groundwater is a problem which results in iron encrustation and iron clogging. This results in decreased borehole yields, decreased water quality and expensive treatments to remove iron encrustation or the drilling of entirely new boreholes. From both international and local literature there are two common factors which stand out which is that high concentration of iron in groundwater is a global issue, the second common factor is that the occurrence and influencing factors of high iron concentrations are site specific. Boreholes drilled for drought relief in health facilities across the Western Cape have reported increased concentrations of iron. Understanding of the geology, hydrogeology and hydrogeochemical conditions that cause the increased iron concentrations in groundwater at these specific locations is required. The objectives of this research project are to: 1) Assess spatial and temporal variations in iron and manganese concentrations; 2) Establish site specific processes that control the concentration of iron in groundwater; and 3) model the geochemical processes that impact iron levels in groundwater. These objectives will be achieved through historical groundwater quality data analysis, geochemical modeling, field work where samples will be collected and laboratory analysis of the samples collected. The information provided from this research project will allow for the effective management decisions to be made in terms of iron removal from groundwater and early preventative measures that can be made to ensure iron clogging and encrustation does not occur. The study is currently ongoing and there are currently no results available at this point however, at the time of the conference there will be information ready to share. |
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Assessment Of The Spatial Coverage Of Groundwater Dependent Ecosystems In A Semi-Arid To Arid River Gouritz River Basin | T | Mbandezi | Western Cape | 2017 | Shallow groundwater, groundwater dependant ecosystems, remote sensing | ||||||
AbstractThe presence of shallow groundwater at locations with limited spatial coverage in drylands have since time immemorial supported plant and animal communities. These locations often have in comparison to the surrounding dry landscapes high biomass production and biodiversity. The presence of groundwater makes these locations attractive for development of groundwater dependent human activities such as irrigated crop production, and livestock production. Groundwater abstractions from locations that are not necessarily close to these plant and animal communities, but tapping into the same aquifer systems have also a potential to affect the availability of water to these ecosystems which is critical for their existence. The importance of these groundwater dependent ecosystems is not well understood due to limited knowledge about their spatial coverage. Some of the groundwater dependent ecosystems occur in areas that are not accessible such as mountain slopes, or in remote areas. The long-term impact of groundwater usage on some of these ecosystems has not been evaluated, with most of the knowledge about these impacts being based on anecdotal information obtained from the respective land owners. Remote sensing offers an opportunity to map the spatial coverage of groundwater dependent ecosystems in drylands. A distinguishing characteristic of these systems is the active plant growth especially during periods when throughout the landscape, there is limited or no water to support plant growth. Monitoring plant growth during the dry season using indices such as the NDVI enables detection of groundwater dependent ecosystems. Knowledge about the rates of actual evapotranspiration at locations with these ecosystems enables an estimation of the amount of water required to support them during the dry season. The MODIS 16 actual evapotranspiration rates (ETA) which are globally available can be used for evaluating water use by groundwater dependent ecosystems. This paper explores the mapping of the spatial coverage of groundwater dependent ecosystems using remote sensing based vegetation indices in parts of the Gourizt River basin in South Africa. The rates of waters use by the identified groundwater dependent ecosystems are estimated using actual evapotranspiration rates based on MODIS 16. The paper also examines possible long-term changes to the spatial coverage of groundwater dependent ecosystems. |
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Development and testing of a hydrogeological multilevel sampling device and analysis of water chemistry through hydrochemical parameters | Lesedi | Sipuka | Western Cape | 2021 | Poster, Groundwater Sampling, Hydrochemistry | ||||||
Abstract |
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Comparison of Topographical and Seasonal Variation of Geochemical Parameters in the Kuils River and Steenbras River | G.D. | Rezelman | Western Cape | 2017 | geochemical parameters, Topographical Variation | ||||||
AbstractWater resources are a great concern in South Africa, more specifically the Western Cape. Therefore, a need has developed to understand the processes that may affect these precious resources. In the Western Cape large proportions of these resources are in the form of streams originating in untouched mountainous areas. However, as these streams continue towards the ocean they are faced by many threats. Alien vegetation, the destruction of river beds and abstraction from streams and boreholes threaten to dry up these resources. Additionally, pollution from fertilizers, sewage treatment plants as well as urban and industrial run-off contaminate these resources. The influx of pollutants, such as fertilizers, usually varies between seasons as it is only applied at certain times of the year. However, pollutant concentrations are not only linked to riparian land-use but are largely affected by climate changes as well. Processes such as surface run-off, along with first flush events and dilution control the nutrient concentrations in the streams. Although water is a renewable resource, it is not replaceable. This project will look at the streams’ self-purification potential. This refers to the processes within the rivers that lead to an in situ reduction of contaminants and pollutants. For example, contaminants and pollutants in rivers can be reduced by particle settling, plant and microbial uptake as well as chemical processes such as redox reactions and complex formation. For this project, pollution will be categorized into two different groups: nutrients and major ions from both point sources and non-point sources. The relevant nutrients analysed in this study are: nitrate, ammonium, phosphate and sulphate; and the major ions analysed are: Calcium (Ca), Sodium (Na), Potassium (K), Aluminium (Al), Iron (Fe) and Manganese (Mn). These will be analysed in conjunction with several physico-chemical parameters: temperature, pH, conductivity, total dissolved solids (TDS), salinity, oxidation reduction potential (ORP) and alkalinity. Analysing these parameters will allow us to measure the effects these processes have on pollution concentrations in the rivers and how climate changes facilitate these processes. For this study, the polluted Kuils River will be analysed and compared to the Steenbras River, which lacks major direct contaminants. This stream will this mainly serve as a ‘control’. Since this study will only be completed at the end of 2017, full conclusions have not been drawn yet. Therefore, this paper will highlight the findings thus far. |
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Mountain Catchment Studies and Catchment Management | Nicolette | Vermaak | Western Cape | 2015 | catchment management | ||||||
AbstractThe mountain catchments of the Western Cape winter rainfall area were identified as areas needing more study in the early 1960s and so the Mountain Catchment studies were born. A number of study areas were suggested for these studies, but it was finally narrowed down to three sites. The studies in Jonkershoek had already started in 1935, with Zachariashoek and Jakkalsrivier added on in the 1960s. The Zachariashoek site was the only one that included groundwater as part of the experimental setup. A number of publications had been written about the work done in Zachariashoek. Most of the publications focused on changes in runoff after deforestation and fires, as well as the recovery patterns of the vegetation. The studies in Zachariashoek were done from 1964 till its termination in 1991 because of a lack of funding. The groundwater component consisted of 14 boreholes, with recorders on the five boreholes near the five weirs. The Zachariashoek area is made up of three catchments, Zachariashoek, Bakkerskloof and Kasteelkloof. It is adjacent to the Wemmershoek catchment. Bakkerskloof was the control catchment, while different burn cycles were part of the experimental setup of the two other catchments. The vegetation of Kasteelkloof was burned every 6 years with a 12 year cycle for Zachariashoek. Monitoring of the 5 weirs, 14 boreholes and the 9 rain gauges was done every week, with recorders on all five weirs, five of the 14 boreholes and at least 4 of the rain gauges. This data was entered into the data bases of the Department of Water and Sanitation, stretching from 1964 to 1986, with a complete record contained in 10 small field books. In this publication, we will look at the experiments done in Zachariashoek to see how this long term monitoring data can assist in managing the water resources within a catchment, taking into account the effects of deforestation and fires on surface water, groundwater and recharge to groundwater, the interaction between groundwater and surface water, as well as climate change. |
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Flow Test Analysis And Monitoring Of The Deep Confined Peninsula Aquifer In Blossoms (Oudtshoorn), Western Cape, South Africa | David | McGibbon | Western Cape | 2015 | |||||||
AbstractThe Oudtshoorn Groundwater Project aims to target deep groundwater as a long-term option to augment the water supply to the greater Oudtshoorn Local Municipality. Located 15 km south of Oudtshoorn towards the Outeniqua Mountain range, the Blossoms Wellfield lies within a potentially high-yielding artesian basin. The Peninsula Formation (of the Table Mountain Group (TMG), hydrostratigraphically known as the Peninsula Aquifer, is exposed in the Outeniqua Mountains (high rainfall recharge area), and is deeply confined northwards by the overlying Bokkeveld Group. |
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Urbanization effects on the channel morphological changes in the Kuils River, Western Cape | Naeem | Davids | Western Cape | 2015 | |||||||
AbstractPOSTER The human interferences in river catchments includes impoundment construction, sediment mining, bank revetment and artificial cutoff, which eventually leads to changes in the hydrology system and channel transportation ability, and may reduce channel stability. In past 10 years the Kuils River had been upgraded between Van Riebeeck Road and the Stellenbosch Arterial route to reduce flood levels. The stretch of the river between the R300 and Van Riebeeck Road was also upgraded: reducing any possibility of flooding, by concrete-lining of some areas of the river that are within the Kuilsrivier Municipal Area. Producing a cross-section of a river channel is of great importance in river studies. To determine the discharge one should survey the profile of a feature such as a meander or riffle, it is necessary to produce a cross-section of the river. In order to focus on restoration requirements of a river, a map of the river is needed. This provides an indication of what exactly the river currently is. Habitat mapping is intended to access the stream. Woody debris, substrate, aquatic vegetation is measured continuously throughout a river, to be able to identify conservation and restoration needs. The cross section 1.3 of site 1 indicates that the channel width from January 2002 is almost similar in width of September 2012. The depth of the channel is about 0.5m deeper when compared to January 2002. The Kuils River banks are covered in grassy vegetation, with some trees with deep and large roots that provide protection against undercutting along rivers. The banks of Site 1 are covered long weeds and annual grasses with shallow root systems, which don't provide stability when the banks were saturated after high rainfall. The Kuils River area is used for various types of land uses and this also impacts the channels eg. Urban, Industrial and Agricultural use. Because of canalization occurring upstream one can see evidently the changes within the channel. |