Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 51 - 100 of 795 results

Title	Presenter Name	Presenter Surname	Area Sort ascending	Conference year	Keywords
Can Palaeochannels Be Used To Enhance Groundwater Recharge? A Case Study: Langebaan Road Aquifer	Awodwa	Magingi	Western Cape	2017	Palaeochannels, hydraulic parameters, Drought, artificial recharge
Abstract The assumed interconnection between palaeochannels and subsurface water resources is described. This paper (poster) discusses the different methods that can be used to indicate the significance of palaeochannels into groundwater recharge. Hydraulic parameters such as permeability and transmissivity of the layer underlying the palaeochannel act as the main dependents of groundwater recharge on palaeochannels. Considering the drastic drought from which South Africa is recovering or has recovered the importance of artificial recharge through palaeochannels is explained. The Langebaan Road Aquifer with its palaeochannel is used as a practical example and a detailed explanation on how palaeochannels can be used to enhance groundwater recharge is further demonstrated. Enhancement of recharge would ensure groundwater sustainability and augmentation to surface water especially during drought periods.
Characterisation of submarine groundwater discharge into False Bay (Western Cape)	Eric	Petermann	Western Cape	2015
Abstract In this paper we present results of a field study that focused on the characterisation of submarine groundwater discharge (SGD) into False Bay (Western Cape) with emphasis on its localisation. SGD is defined here as any flow of water from the seabed to the ocean. Thus, it includes (1) advective flow of fresh terrestrial groundwater as well as (2) seawater that is re-circulated across the ocean / sediment interface. Groundwater discharge into the coastal sea is of general interest for two reasons: (i) it is a potential pathway of contaminant and nutrient flux into the ocean, and (ii) it may result in the "loss" of significant volumes of freshwater. In our investigation we applied environmental aquatic tracers, namely radionuclides of radon (222-Rn) and radium (223-Ra, 224-Ra), as well as physical water parameters (salinity and temperature). The concentrations of radon and radium can be used as tracers for groundwater discharge since radon and radium are highly enriched in groundwater relative to seawater. We conducted discrete point measurements of seawater and of terrestrial groundwater as well as continuous radon time-series measurements of near-coastal seawater. A large-scale survey was performed along the entire shoreline of False Bay and revealed distinct positive anomalies of radon in the area of Strand/Gordons Bay and a rather diffuse anomaly along the Cape Flats, which is indicating possible groundwater discharge in these areas. The location of these anomalies remained constant to a large extent throughout several surveys that were performed during different seasons, although these anomalies varied with regard to their magnitude and clearness. Further detailed studies were undertaken in the area of Strand/Gordons Bay including radon time-series measurements in the coastal sea at a fixed location in order to estimate the quantity of SGD and its variability on a tidal time scale. The results indicate that groundwater discharge rates are significantly elevated during low tide. Furthermore, the distribution of radium isotopes (224-Ra/223-Ra ratios) in the Strand/Gordons Bay area indicate a "groundwater" residence time of less than 10 days within a distance of 5 km from the shore. In summary, we found spatially considerable constant SGD locations during different field campaigns. Additionally, we gained a rough understanding of the SGD dynamics on a tidal time scale, its magnitude and groundwater residence time within the inner bay after discharge. These results can be beneficial to trace back contamination in near-coastal waters or to find potential locations for groundwater abstraction.
Geohydrological update and numerical modelling of the Langebaan and Elandsfontein Aquifer Systems	Julian E	Conrad	Western Cape	2015	Elandsfontyn Aquifer System, Langebaan Road Aquifer Systemaquifer systems, numerical modelling
Abstract The Saldanha / Langebaan area is expanding at a significant rate, increasing the water demand for the area. The expansion comes from the industrial, residential and tourism sector. In addition there are economically viable deposits of silica and phosphate in the area. Ecosystem functioning in the area is also to a degree dependent on groundwater. All of these factors require an improved understanding of the geohydrology of the area. The geology of the area consists of basement Cape Granite and Malmesbury Group rocks that underlie the sediments of the Sandveld Group. The unconsolidated formations present, are (in order of oldest to youngest) as follows: - Elandsfontyn Formation (oldest): This formation overlies the bedrock in depressions and palaeo-channels in the bedrock. This formation is about 40 m thick and is composed of upward fining quartz sediments. - Varswater Formation: This formation is composed of marine deposits and is restricted to the western (seaward) parts of a bedrock depression to the east of the Langebaan Lagoon and Saldanha. The formation is characterized by rounded quartz grains. - Langebaan Formation: This formation consists of calc-arenites. The sediments are generally grey to cream coloured and consist of quartz and shell fragments, the grain size ranges from coarse to fine and the consolidation is variable. - Witzand Formation (youngest). This formation consists of light-coloured, calcareous, coastal dune sand that can be distinguished from the underlying consolidated Langebaan Formation. The Elandsfontyn Aquifer System (EAS) and the Langebaan Road Aquifer System (LRAS) are the main aquifer systems in the area. These aquifer systems are defined by palaeo-channels that have been filled with gravels of the Elandsfontyn Formation and represent preferred groundwater flow paths. Within each of these aquifer systems (EAS and LRAS) two aquifer units are present. Namely, the confined Lower Aquifer Unit (LAU) geologically consisting of the basal gravels of the Elandsfontyn Formation and the Upper Aquifer Unit (UAU) composed of consolidated sands and calcrete. The two units are separated by a clay aquitard. A numerical model has been established for the area, and extends from the Berg River to the Langebaan Lagoon. Granite outcrop and river system define the other boundaries of the model. Extensive logging of groundwater levels by the Department of Water and Sanitation (DWS) has enabled the accurate establishment of a model. In addition extensive field work and a detailed hydrocensus, as well as the capture of a lot of historical information has resulted in a comprehensive GIS which assists with the refinement of the numerical model. The model provides a valuable tool in modelling potential impacts whether they been from planned groundwater abstraction or artificial recharge. {List only- not presented}
Are Farmers Drying Out The Cederberg? Deep Groundwater Flow And Isotopes In The Table Mountain Group.	Roger E	Diamond	Western Cape	2017	TMG, Isotopes
Abstract The Table Mountain Group is a major fractured rock aquifer system throughout the Western Cape, with many interconnected but semi-independent parts, each having its own recharge area, flow paths and discharge area. Groundwater is known to travel long distances and reach great depths, including through the Olifants River syncline, such as at The Baths hot spring near Citrusdal. Stable isotope compositions of rain and groundwater in the Cederberg and Olifants River Mountains were measured over a period of 2-3 years. Rainfall in the Cederberg averaged -22‰ and -4.7‰ for D and  18O respectively, whereas rainfall in the Olifants River Mountains averaged -11‰ and -3.0‰ similarly. Groundwater used by farmers in the Olifants River Mountains averaged -13‰ and -2.9‰ similarly. The similarity between groundwater and rainfall isotope compositions in the Olifants River Mountains suggests local groundwater movement. It was concluded that the source of groundwater abstracted by farmers in the Olifants River Mountains is from the peaks west of the Olifants River with little to no contribution from the Cederberg, east of the Olifants River syncline. Geological evidence (thinning of the Olifants River syncline and increased faulting northwards) supports this conclusion.
Identifying Potential Managed Aquifer Recharge Zones In West Coast Aquifers, Western Cape	Ashleigh	Tomlinson	Western Cape	2019	Poster, recharge, MAR
Abstract The 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
Water Supply Boreholes must be Test Pumped	John	Weaver	Western Cape	2017	Drought, sustainable yield
Abstract This past drought (summer of 2016/17) in the Western Cape has resulted in a number of boreholes “failing” and desperate farmers calling for more boreholes to be drilled. A closer look shows that many, if not most, of these boreholes were tested by the long-discredited “Maximum drawdown-yield at end of 48 hours x 60% = yield” method. A prime example was a borehole drilled and tested by the “old” method in 1983. This borehole was the main borehole supplying a stud horse farming operation. The borehole was equipped with a large capacity pump set at depth for paddock irrigation, plus a low capacity pump set above for drinking water supply. Using the existing main pump the author carried out a step-test in 2012. The borehole appeared to be sustainable. When re-tested in the middle of the drought of 2017 it hit pump- suction in 8 hours, i.e. it is not sustainable. Two radical examples of water supply boreholes are examined: a borehole with air-lift yield of 10 to 15 L/sec for which the sustainable yield was determined to be 0.5 L/sec, and a borehole with an air-lift yield of 0.5 to 0.7 L/sec for which the sustainable yield was determined to be 7.5 L/sec. Conclusion: In order to determine the sustainable yield of a borehole, especially in the fractured rock environment of Southern Africa, do not rely on the driller’s report of air- lift yield, and use the proper method of test-pumping a borehole. If not you may be in trouble.
Transport and Fate of chemical and microbial tracers at UWC campus site, Cape Flats aquifer of South Africa	Erin	Haricombe	Western Cape	2015	biological tracers, chemical tracers
Abstract Different biological and chemical transport results are evaluated in this study. Ecoli and PDR1 were selected as the biological tracers with salt and rhodamine as chemical tracers. The transport experiments were evaluated through the primary aquifer material found at the University of the Western Cape research site. A series of controlled experiments under laboratory and field conditions was conducted. Each provides a different kind of data and information. The results from laboratory studies could be used to better design the field studies. In both cases, the data collected was to provide information on fate and transport of microbes in groundwater. The field design phase of the experiment was an up-scaling of the laboratory phase of this project. The amount injected into the aquifer was increased in proportion to the size of the research site. Tracer tests using chemical and microbial tracers were carried out simultaneously. Results of laboratory tests show a 5 times slower transport of microbes, compared to salts.. The salts at field scale show a breakthrough occurring after 2 days whereas the microbes never managed to breakthrough with the experiment stopped after 45 days. A new borehole was drilled closer to reduce distance/ travel time, but this had no effect on field results for the microbes. {List only- not presented}
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
Abstract Large 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.
Urbanization effects on the channel morphological changes in the Kuils River, Western Cape	Naeem	Davids	Western Cape	2015
Abstract POSTER 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.
Developing Groundwater Supplies To Supplement The Water Supply Of Ladismith, Western Cape Province	Roger	Parsons	Western Cape	2015
Abstract Ladismith 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. {List only- not presented} KEYWORDS groundwater, exploration, water supply, Ladismith
Mountain Catchment Studies and Catchment Management	Nicolette	Vermaak	Western Cape	2015	catchment management
Abstract The 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.
Assessing groundwater dependence of wetlands and streams within the Table Mountain Group Aquifer: A Case Study from the Kogelberg	Dale	Barrow	Western Cape	2021	Ecosystems, datasets, conceptualisation, Monitoring
Abstract Ewart Smith, J; Snaddon, K; de Beer, J; Murray, K; Harillal, Z; Frenzel, P; Lasher-Scheepers, C Various analysis techniques are available for assessing the groundwater dependence of ecosystems. Hydrogeological monitoring within the Kogelberg and greater Table Mountain Group (TMG) aquifer has provided various datasets from multiple scientific disciplines (hydrological, hydrogeological, geochemical, climatic, ecological and botanical). Using a variety of analysis techniques, and using the Kogelberg as a case study, this paper assesses the groundwater dependence of several ecological sites (wetlands and streams). The starting point is a sound geological and hydrogeological conceptualisation of the site. The approach involves conceptualisation and analysis within each scientific discipline, but also requires bridging between areas of specialisation and analysis of a variety of datasets. This paper presents the data and analyses undertaken and the relevant results as they pertain to several sites within the Kogelberg.
Conceptualization Of Groundwater Flow System In Heuningnes Catchment	Vincent	Banda	Western Cape	2017	hydrochemical, groundwater flow
Abstract Records review and field based methods were used to collect and interpret groundwater level and hydro- chemical data to characterise groundwater occurrence and flow system in the Heuningnes catchment, Western Cape Province of South Africa. Our research outcome indicates that the study area has alluvial and fractured rock aquifers. The groundwater system has a rainfall driven recharge mechanisms resulting in freshwater in higher altitudes situated in the northern and western parts of the catchment. Highly saline waters are found in low-lying areas. Few samples showing high salinity water exhibit a signature of seawater although in many instances the groundwater chemistry is by and large governed by the geological formation. Groundwater potentiometric surface map shows that the general groundwater flow direction is southwards. In relation to the surface water bodies, groundwater mainly flows towards the Nuwejaars River especially in the northern and north-west part of the study area resulting in fresh water in this part of the river. As this is an ongoing study, these preliminary findings provide the required insight for further analysis and investigation. Future work will involve carrying out aquifer hydraulic tests and collection of water samples for analysis of major ions and stable isotopes. Further discussion will wait for the validation of these results to inform a meaningful implication of such findings.
Assessment of Plume Stability in Monitored Natural Attenuation Assessments Using the Centre of Mass and Total Plume Mass Approach	Samuel D	Mohr	Western Cape	2017	Monitored natural attenuation, petroleum, Hydrocarbon, plumes, monitoring network
Abstract Monitored natural attenuation (MNA) is becoming a commonly employed sustainable site remediation strategy for sites with petroleum hydrocarbon groundwater impacts. Natural attenuation is essentially the reduction in contaminant concentration, mass or mobility due to naturally occurring processes within the environment. Aromatic compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX) are common compounds of concern in the context of petroleum hydrocarbon related investigations because of their relative mobility and toxicity characteristics. Despite this, these compounds have historically displayed a strong affinity towards attenuating temporally and spatially away from the source areas. Evaluating plume stability is an important element of evaluating the overall attenuation of groundwater plumes and numerous methods have been developed in order to assess plume stability including graphical and statistical methods. It is often the case however that these analyses focus on single wells in isolation and do not take an integrated approach to evaluate the attenuation of contaminant mass over the entire plume. The authors present a case study where historical trends in plume characteristics have been used to assess overall plume stability. Trends in parameters such as average plume concentration, total plume contaminant mass, plume area and plume centre of mass were statistically assessed to determine whether the groundwater plume was expanding, stable, or shrinking. The methods employed in the plume stability analysis were found to be effective tools in demonstrating the occurrence of natural attenuation of contaminant plumes. It is important to note that a good quality dataset is required, in terms of a spatially representative monitoring well network and adequate time series data, in order to conduct analyses that will yield meaningful conclusions.
Assessing Spatial, Temporal Depth Variation Of Groundwater Salinity Variation, Cape Flats Aquifer, South Africa	Danica	Carnow	Western Cape	2017	sampling, Salinity, Irrigation, Water quality, unconfined aquifer, urban
Abstract The use of specific-depth sampling technique to demonstrate groundwater quality variation different groundwater units of unconfined aquifers has not been widely published. To demonstrate the feasibility of such technique, the unconfined Cape Flats Aquifer (CFA) in Cape Town of South Africa was studied. The aquifer underlies an urbanised area which is vulnerable to contamination from industrial and agricultural activities, waste disposal sites, landfill sites, and formal and informal settlements. The study assessed Spatio-temporal and depth variation salinity levels in CFA using electrical conductivity (EC) as an indicator of salinity. Groundwater samples were collected using specific-depth sampling, and analysed using multi-parameters probes and standard laboratory methods for EC, temperature, pH and major ionic concentrations. Statistical analysis was used to compare mean concentrations of selected parameters to guidelines set by Department of Water and Sanitation and Food and Agricultural Organization to establish fitness for irrigation use. The results showed high EC levels (212.26 mS/m) at shallow depths (9m) and low EC levels (78.53 mS/m) at greater depths (39m) proposing anthropogenic influence. Potassium, sodium, chloride, and the Sodium Adsorption Ratio (SAR) exceeded permissible ranges set for irrigation water suggesting that groundwater be used with caution. A conceptual diagram was developed to explain sources and processes contributing to groundwater salinization of the aquifer. The diagram illustrated that irrigation return flow, in residential and agricultural areas, contributed significantly to salinity levels. In conclusion, groundwater in the CFA is suitable for irrigation use but should be used with caution as shallow depths contain groundwater with elevated salinity levels. It is recommended that the specific-depth sampling technique be used to understand how the physical, chemical and microbiological constituents vary with depth in these groundwater units.
Why is groundwater a Cinderella Water Resource?	Roger	Parsons	Western Cape	2019	Awareness, development
Abstract For 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.
Feasibility of iron and manganese removal by in-situ ozonation - Atlantis Aquifer Case Study	Kate	Robey	Western Cape	2015
Abstract The 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
Western Cape Coastal Groundwater Resources: Potential For Artificial Recharge And Conjunctive Use	Sumaya	Israel	Western Cape	2017	groundwater potential, artificial recharge, mixed use
Abstract Western 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.
Suitability of drilling techniques for geological interpretation and borehole design within the Cape Flats Aquifer, Western Cape.	Sasha Dean	Singh	Western Cape	2021	Bulk water supply, MAR, Drilling, facies analysis
Abstract McGibbon, D; Riemann, K The Cape Flats Aquifer Management Scheme (CFAMS) includes both abstraction of groundwater and managed aquifer recharge (MAR) as part of the City of Cape Towns (CoCT) New Water Programme to diversify their bulk water supply and build resilience against future droughts. Since the project was initiated in early 2018, over 250 boreholes have been drilled for exploration, monitoring, abstraction, and MAR. Rotary mud drilling was used for most of the drilling due to its suitability in unconsolidated geological material, typical of the CFA. As effective as rotary mud drilling is for large scale development, it lacks in accuracy for detailed geological interpretation used for borehole siting and design (gravel pack and screen aperture size and screen position). This is due to the mixing of material and the circulation of the drilling mud washing away fine sediment which can skew grain size analysis results and obscure the vertical position and thickness of thin confining clay or organic rich lenses. The clay and organic rich layers can cause surface flooding during injection as they act as confining layers which effects borehole design and more importantly siting of MAR boreholes. To overcome this, two additional drilling techniques were explored, sonic and air core. Air core was disregarded early on due to the air creating a cavity in the underlying unconsolidated sediments. Sonic drilling, however, was successful in retrieving a continuous undisturbed core log through high resonant energy that liquefies the sediments, which are then brought to surface in a core barrel. The undisturbed continuous nature of the log allows for accurate grain size analysis and detailed vertical geological logging which can be used for facies analysis to interpret the paleoenvironment and predict the lateral extent of clay or organic rich layers that influence borehole siting, design, and the hydrochemistry.
Groundwater and surface water interaction in farming areas in the Rawsonville area of the Western Cape.	Siphumelelo	Mbali	Western Cape	2015
Abstract The understanding of groundwater and surface water interaction is important for the planning of water resources in particular for farming areas. The interactions between groundwater and surface water are complex. To understand the relationship of groundwater and surface water interactions it is important to have a good understanding of the relation of climate, landform, geology, and biotic factors, a sound hydrogeoecological framework. Surface-water and groundwater ecosystems are viewed as linked components of a hydrologic continuum leading to related sustainability issues. In this study the Gevonden farm in Rawsonville will be used as the study site. This study site forms part of the Table Mountain Group (TMG). The methods to establish the relationship of groundwater and surface water interaction are collection of rainfall data monthly, river channel parameters at the farm such as the discharge on a monthly bases, chemistry of the water in the stream and groundwater were also be analyzed and pumping tests will be conducted twice to get the hydraulic parameters of the aquifer. The aquifer parameters will be analyzed using the Theis and Cooper-Jacob methods. The river has lower water levels in the summer months and this is also the case in the water levels in the boreholes on the farm, however in winter the opposite is true. The chemical analyses which are identical indicate that there is groundwater and surface water interaction in the farm. The degree of the interaction differs throughout the year. The results show that the interaction is influenced by the rainfall. The results clearly suggests that the farmers need to construct dams and drill pumping borehole in order to have enough water to water their crops in the summer season as by that time the river is almost dry. {List only- not presented}
Knowledge comes with trial, error and time: The Langebaan Road story	Nicolette	Vermaak	Western Cape	2015
Abstract When planning an experimental setup in the laboratory, it is very important and possible to control all the variables so that one can manipulate particular variables at a given time. Experimental setups under natural conditions could be a challenging task. The success of an experiment depends to a large extent on the correct understanding of the functioning of a natural system. If the conceptual understanding of the natural system is erroneous, it is likely that unexpected results could be achieved. This was the case with the artificial recharge pilot project that was done in 2008 and 2009 at the Langebaan Road wellfield just outside Hopefield in the Western Cape. Years of research gave scientists a fairly good idea of the way in which the aquifer system functioned, especially since the establishment of the well field. This provided information of the response of the aquifer unit to large scale abstraction. The Langebaan Road aquifer unit is a multilayered system with a lower aquifer composed of Elandsfontyn gravel overlaying a bedrock layer of either granite of the Vredenburg or Darling plutons of the Cape Granite Suite or Malmesbury shale. The bedrock was considered impermeable. The upper aquifer layer was composed of mostly the Varswater Formation with peat and clay of the Elandsfontyn Formation forming the confining layer between the two aquifer layers. The extent of the different layers of the aquifer unit was plotted with a fair amount of accuracy and the clay layer was considered to be continuous between the two aquifer layers. Monitoring data for the area was done since 1974 with a gap in data-set between 1991 and 2001. Despite all the data from geophysical work, boreholes drilled, and the monitoring record, the research done prior and during the artificial recharge pilot project in 2008 and 2009 the aquifer units did not respond quite as anticipated. The Artificial Recharge (AR) pilot project team concluded that the aquifer units responded in a particular manner as opposed to the expected response according to the data and conceptual model at hand. It was thus clear that there are gaps in the conceptual model of the aquifer systems in the bigger Lower Berg River Valley that include the Langebaan Road, Elandsfontein and other aquifers that needed to bridge before another pilot test is attempted. Although the artificial recharge pilot project did not yield the expected results, valuable lessons were learned. This article will look at the conclusions and recommendations of the research done on the pilot project and attempt to evaluate the monitoring data (water levels, chemistry and rainfall) from the period just before the beginning of the AR pilot project. The monitoring data would be manipulated using the following techniques
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 This study investigates and elaborates the development and testing of a multilevel sampling device. The primary purpose of this device is to achieve multilevel sampling in a well simultaneously, producing samples that are representative of the in situ groundwater. The device has been designed to have four different depths from which extraction of groundwater samples can be performed. Testing of the device involves a two-part process. A laboratory based testing and field based testing. The laboratory testing was done in a simulated well where three water tests were performed; normal tap water, salt water and hot boiling water. The field based testing was done on existing boreholes in the Rietvlei Wetland Reserve in the Western Cape. In the two processes involved, hydrochemical parameters were used to test for the efficiency of the device in terms of its working performance and to furthermore analyse the water chemistry which enables us to determine the water quality.
Flow Test Analysis And Monitoring Of The Deep Confined Peninsula Aquifer In Blossoms (Oudtshoorn), Western Cape, South Africa	David	McGibbon	Western Cape	2015
Abstract The 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. The project is currently emerging from an exploration phase, with eight existing boreholes that target the deep confined Peninsula Aquifer, and three boreholes that monitor the shallower Nardouw (Skurweberg) Aquifer. Estimation of the aquifer's productive and sustainable groundwater potential involves determining its hydraulic properties by stressing the aquifer through flow and pumping tests and accurately monitoring flow rates, the potentiometric surface level (PSL) during flow, and PSL recovery thereafter. Free-flow and pumping tests were carried out on four boreholes between the 12th May 2014 and the 29th June 2014. The boreholes were all equipped with data-loggers to record pressure and flow-meters to determine the flow-rate. Recovery of the aquifer after the testing is still being continuously monitored. Results from the month and a half flow-test show that there is no interaction between the deep confined Peninsula Aquifer and the shallower Nardouw Aquifer beneath the southern part of the wellfield. Because the water-use licence stipulates that there can be no negative impact from Peninsula Aquifer abstraction on the Nardouw Aquifer, which is utilised by farmers in the region, this issue is of paramount importance. The hydrochemical signature of the two aquifers is also different. Recovery monitoring emphasised that the northern block is better inter-connected through fracture systems than the southern block, because those boreholes recovered to their original potentiometric surface almost immediately, whereas the southern boreholes took days for recovery. Two boreholes in the south are still recovering eight months later, which is most likely due to their being drilled into the limb of folded rock systems and not the more fractured hinge zone (as with the more connected boreholes). Using the drawdown and recovery curves ('Horner plots'), the transmissivity and storativity of the aquifer is calculated analytically by the Theis equation. The results show a large variation in storativity (1.0E-1 to 1.46E-4) and transmissivity (9-20 m2/day) between the various boreholes, emphasising the heterogeneity of the aquifer. The aquifer properties gained from this testing are essential in better understanding the aquifer system, and developing numerical models for future wellfield testing and model simulation.
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
Abstract The 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.
Findings from nearly three decades of groundwater monitoring in an area of intensive agriculture: Sandveld, West Coast, South Africa	Julian E	Conrad	Western Cape	2023	groundwater monitoring agricultural impact
Abstract The Sandveld (Western Cape, South Africa) is a critical potato production area on the national production scale, especially for table potatoes. As the area is situated on the continent’s West Coast, it is a dry area of low rainfall (less than 300 mm /a). The bulk of the irrigation water for agriculture in the region is derived from groundwater. Approximately 60 Mm3 /a of groundwater is abstracted for irrigation of potatoes in the broader Sandveld, assuming a 4-year rotation cycle. The abstraction of groundwater is a sensitive issue in the Sandveld as groundwater also plays a critical role in supplying water to towns in the area, water for domestic use, and it also plays a critical role in sustaining sensitive ecosystems (such as the coastal lake Velorenvlei). The groundwater resources have been monitored for nearly thirty years now. The results indicate areas where a slow but consistent decline in groundwater levels and groundwater quality is occurring. The trends can also predict when the aquifers will become depleted, and the groundwater will become too saline for use. This is critical information for management interventions to be implemented now to protect the area from irreversible damage.
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
Abstract A 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}
Evaluating changes in groundwater storage during the 2015-2018 drought in the Western Cape using GRACE data	Ritshidze	Nenweli	Western Cape	2021	Poster, Drought, GRACE, Groundwater storage
Abstract The frequency, intensity, and duration of droughts are increasing globally, putting severe pressure on water supply systems worldwide. The Western Cape Province suffered from a period of severe water shortages that began around January 2015 and lasted until about July 2018. During this recent drought, there was a forced reduction in water use, predominantly from the agricultural sector. Citizens also reduced water use and increasingly tapped into groundwater for their needs irrespective of whether the hydrogeology was considered favourable or not. Unmonitored and unregulated abstraction of groundwater, especially under unstable climatic conditions, poses a significant risk to the future water security of the Western Cape. We hypothesize that groundwater enabled the municipalities, residents, and industries of the Western Cape to survive the recent drought. Our aim is to evaluate the change in groundwater storage during the 2015 to 2018 drought and its subsequent recovery. To achieve this, we must gain a comprehensive understanding of the dynamics of separate components of the water cycle, as well as the overall water balance. While there is data on surface water use during the drought, the impact on groundwater resources has yet to be evaluated. However, the accurate assessment of groundwater use is difficult, especially in data-scarce regions, such as South Africa. In our study, we combine remote sensing from NASA’s Gravity Recovery and Climate Experiment (GRACE), the Global Land Data Assimilation Systems, groundwater level measurements from the National Groundwater Archive, and ancillary datasets from the City of Cape Town’s weekly water dashboard to assess the total change in groundwater storage in the Cape Town Metropolitan area and surrounding cities over an 8-year period, from 2012 to 2020. Preliminary results from GRACE data analysis show a steady decline in aquifer saturated thickness over the drought, indicative of an increase in groundwater use.
Application of multivariate statistical analysis to investigate the hydrochemistry of groundwater Upper Berg River Catchment, We	Tebogo	Madlala	Western Cape	2015
Abstract The present study applied multivariate statistical analysis (MSA) to investigate the status of the hydrochemistry of groundwater Upper Berg River Catchment, Western Cape, South Africa. Factors that influence the quality of groundwater are well established. The aim of the present study was to characterize groundwater quality in the Upper Berg River Catchment, using multivariate statistical analysis methods in order to establish the evolution and suitability of such waters for agricultural use in addition to confirming major factors that explain groundwater quality in the study area. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (CA) were applied to groundwater physicochemical data that were collected from 30 boreholes. Data collection and analysis followed standard procedure. The use of a Piper Diagram showed that Na-Cl water types were the predominant groundwater facies. Furthermore, PCA extracted five major factors that explained 83.11 % of the variation in the physicochemical characteristics of groundwater. Using Varimax rotation, two main factors, namely, surface water recharge and rock-water interactions, were extracted which collectively explained 60.81% of the variation in the groundwater physicochemical data. The two factors indicate that the predominant factors affecting groundwater quality in the study area are natural (biochemical) processes in the subsurface as well as interactions between the rock matrix and passing water. Cluster Analysis extracted three major groundwater clusters based on dissimilarities in groundwater physicochemical characteristics in different sites. The first cluster included 7 borehole sites located in the Franschhoek Valley area and 14 borehole sites located in the Robertsvlei Saddle area as well as the upper catchment (behind the Berg River Dam). The second and third clusters collectively included 9 groundwater sites within the Franschhoek Valley area. These sites were located on agricultural land where extensive vineyard and orchid cultivation is done. Groundwater quality in the Upper Berg River Catchment mainly reflects the influence of natural process of recharge, rock-water interactions and microbial activity. The quality of groundwater fell within Target Water Quality Guidelines for agricultural water use published by the Department of Water and Forestry Affairs meaning such waters are suitable for agricultural use. Key words: Dendrogram, Groundwater quality, Hierarchical Cluster Analysis, Principal Component Analysis, Physicochemical, Spatial.
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
Abstract Although 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.
Arsenic In The West-African Water Reserves: Investigation Into Sources Of The Contaminant Through Case Studies In The Region	Andre	van Coller	Western Africa	2013	Contaminant, investigations, Groundwater reserve
Abstract The mineral-rich basin of the West African region has vast reserves of gold, diamond as well as iron ore deposits. Throughout the regional geological setting characterised by structural variations and intrusive belts with metamorphic mineral-rich sequences covered by saprolite soils, one common chemical constituent remains a constant in the water reserves. Arsenic is in high concentrations throughout the region with chemical ranges commonly above the various country guidelines as well as international IFC and WHO standards. The aqueous chemical species is associated with arsenopyrite-rich mineralogy of the regional greenstone belts and highly weathered soils. This conference presentation investigates the natural source of the arsenic through baseline data, as well as the effect of mining on the already high concentrations of arsenic in both the groundwater and surface water. Natural levels of various chemical species in the regional area are already high at baseline level. One of the main research questions is thus whether mining and other anthropogenic activities will have an impact on the environment or will the changes to concentrations be so insignificant to allow the ecosystems and water users to continue in their current ways without any effect. Various case studies in Burkina Faso, Liberia, Sierra Leone and other countries have been combined to investigate the arsenic-rich resources of the West African region through groundwater specialist investigative methods with emphasis on geochemical modelling of the fluid–rock and fluid–fluid interactions leading to the aqueous chemical conditions in the region.
Identifying And Modelling Sustainable Groundwater Inflows Into The Verlorenvlei Coastal Estuarine System In South Africa	Jodie	Miller	West Coast, Western Cape	2017	estuarine system, agriculture, hydrochemical, baseflow
Abstract The Verlorenvlei estuarine lake is one of only two freshwater estuarine systems in South Africa. Whilst being important ecologically it is also a critical agricultural region, supporting a significant proportion of South African potato crops as well as a number of other diverse crops. The vlei itself is fed by the Verloren River which is thought to be fed by surface water inflows and baseflow throughout the year along several tributaries, namely the Krom Antonies, Hol, Berg Vallei and Kruismans. Each of these tributaries has a distinct hydrochemical character defined by cation and anion concentrations, as well as O, H and Sr isotopes. Simulated discharge from each tributary suggests that all tributaries contribute to the chemistry of the Verloren River. The Krom Antonies which has the freshest water has the highest discharge at around 50% of surface water inflows, whilst the Hol with the highest EC values contributes around 35% of surface water inflows. In spite of this, the surface water hydrochemistry in the Verloren River, is remarkedly fresh and very similar in character to the surface water of the Krom Antonies. Sr isotopes in each of the tributaries are distinct and support mixing of different components of each tributary above the confluence. However, below the confluence, they drop significantly which indicates mixing with another unidentified Sr-source. This source was thought to be baseflow from the deeper groundwater system, but the Sr isotope composition of deeper groundwater indicates that it is not the contributing component. Recent years have seen dramatic reductions in precipitation, while increases in pumping for agricultural purposes potentially exceeds the long-term sustainable yield of the aquifer system. Identification of this unknown component has therefore become a priority for groundwater management in the area as it is unclear how vulnerable this component will be to climate change and hence what impact climate change will have on the vlei.
Optimized Groundwater Monitoring Design for Managed Aquifer Recharge Using Hybrid Numerical, Geophysical and Chemical modelling approach	Clinton W	Andries	West Coast, Western Cape	2021	MAR, AHP, Monitoring network design
Abstract Israel, S; Kanyerere, T Globally, surface waters are severely unsustainably exploited and under pressure in semi-arid coastal regions, which results in increasing demand for groundwater resources. Currently, Cape Town and its neighbouring towns along the West Coast of South Africa are facing water shortage related problems. Managed Aquifer Recharge (MAR) is a nature based solution to improve groundwater security in drought prone regions such as the West Coast. The objective of this study was to design a groundwater monitoring network using a hybrid hydrochemical, geophysical and numerical modelling approach to assess and mitigate the potential impacts of MAR for the West Coast Aquifer System (WCAS). An Analytical Hierarchy Process method was used to perform a Multi-criteria analysis employed in GIS (ArcMap 10.3). The factors of importance for optimized groundwater monitoring network design were based on available data and consultations with hydrogeologists and environmental scientist at stakeholder workshops. The factors which were considered included: elevation (m), geology, density of existing boreholes (wells/km2), electrical conductivity (mS/m), water rise (m), water level decline (m), transmissivity (m/day), saturation indices and lithological thickness (m). Factors were weighted based on their level of importance for the design of the groundwater monitoring network using Analytical Hierarchy Process (AHP). Priorities were calculated from pairwise comparisons using the AHP with Eigen vector method. The Consistency Ratio (CR) calculated was 5.2% which deems the weighting coefficients statistically acceptable. The results show that high priority monitoring areas occurs in the areas where there are fresh groundwater, high borehole density, elevated topography, higher recharge rates and decline in water levels are found. The monitoring network will include boreholes from the low priority areas to ensure that hydrogeological conditions are monitored and impacts are not worsened. Geophysical, numerical and chemical modelling aspects of the methodological approach will be incorporated into the initial groundwater monitoring network design.
Understanding Natural Groundwater Recharge Systems In The Lower Berg River Catchment, West Coast, Western Cape	Clinton W	Andries	West Coast, Western Cape	2017	MAR, geochemical, Lower Berg River Catchment, conceptual model
Abstract The CSIR has embarked on a study to investigate the potential for additional water in the West Coast, Western Cape through the application of Managed Aquifer Recharge (MAR). The benefits of MAR is that it may generate additional water supplies from sources that may otherwise be wasted with the recharged water stored in the aquifer to meet water supply in times of high demand. Determining recharge is the most important aspect of hydrological system. However, the accurate estimation of recharge remains one of the biggest challenges for groundwater investigators. Numerous studies have been conducted using geochemical methods to estimate and distinguish sources of recharge in different groundwater units of unconfined and confined aquifers internationally. The application of geochemical methods to produce accurate conceptual model describing natural recharge in aquifer units of Lower Berg River Region has not been widely published. The Lower Berg River catchment, consisting of 4 primary aquifer units (Adamboerskraal, Langebaan Road, Elandsfontein and Grootwater) will be used to demonstrate the applicability of such methods. The aim of the study is to estimate recharge in the lower berg river catchment, and develop a conceptual natural recharge model that will improve understanding of the aquifer system and be an indicator for water availability in the Lower Berg River Catchment. The objectives in developing the conceptual model includes establish groundwater recharge sources, groundwater flow paths, recharge mechanism and potential mixing of groundwater by using environmental isotopes; and obtain a reliable estimation of its recharge amount using the Chloride Mass Balance. As this study is still in progress, this publication will focus on reviewing literature and the outcomes envisioned from the project as to provide a complete understanding of the complex geology. This will lead to a better understanding of the functioning of natural recharge of the aquifer units in the Lower Berg River Catchment.
The most valuable resource	Nicolette	Vermaak	West Coast, Western Cape	2015	resource economics
Abstract Mining is becoming a problem in the Western Cape - different kinds of mining and other resources, different problems than in other parts of the country. The West Coast had been declared a development corridor and a mining priority area. It is an arid to semi-arid area, where surface water is scarce, and rainfall relatively low and decreasing as one moves north. Some areas have significant volumes of good quality groundwater available, with potential impacts by the mining activities. This would play the importance of different resources off against the other. Most see resources as minerals, such as gold, silver, phosphate, and others where the value of these resources is measurable. Resources are also human capital, time, water, air, a healthy environment. It is more difficult to measure the value of the second group, as some of them have more than just a Rand and cent value. The value of resources is mostly done by measuring its monetary value, i.e. how much you will get when you sell the resource to a customer, providing the way the value of most resources is measured, i.e. resource economics. Economics is an area that most scientists are not familiar with as it contains a way thinking, of rules and laws unrelated to the way they have been taught. Supply and demand determines the value of a commodity, with scarce resources normally fetching higher prices. The value of the second group of resources is more difficult to determine. When does a resource become a strategic resource? This would be a resource that has a limited supply, does not get regenerated through natural processes and that is needed for defence, energy supply and others important for the stability of a country. There are also a category of resources we cannot live without such as water, and air - pure, fresh air and water. Without it life on this planet will cease to exist. This could be termed critical resources. What do you do if the occurrence of two very important critical resources overlaps, where the extraction of the one will lead to irreparable damage to the other? This article will look at one site where a strategic resource occurs at the same site as an important water resource. It will compare the potential value of the mineral resource with the value of the water resource in the aquifer measured at the current value of water as available to the public. It will also take into account the value of the water resource from the perspective of a healthy functioning ecosystem and a RAMSAR site. This analysis becomes more valuable when considering the potential effects of climate change in the area and the cost of desalination.
Identifying suitable sites for Managed Aquifer Recharge within the Saldanha Bay Local Municipality, situated in the West Coast of South Africa	Ashleigh	Tomlinson	West Coast, Western Cape	2021	MAR
Abstract The West Coast in the Western Cape of South Africa is a water-scarce area. With pressure from population and industrial growth, recurring droughts and climate change, there is increasing urgency in the West Coast to protect groundwater resources. Saldanha Bay is dependent on groundwater as part of its bulk water supply system. Where the natural groundwater recharge is no longer sufficient to meet the growing groundwater needs, practices such as Managed Aquifer Recharge (MAR) can be used to ensure the sustainability of these groundwater resources. This study aims to identify areas within the Saldanha Bay Local Municipality suitable for Managed Aquifer Recharge to maximize the water available during periods of limited surface water supply. As such, the MAR study site identification requires a comprehensive geohydrological assessment of the Saldanha Bay aquifer. This includes an understanding of the quality and quantity of the source water available for recharge, the aquifer structure and hydraulic properties, the space available to store water, and the compatibility of the recharged water with the groundwater. MAR research methods included Time Domain Electromagnetic (TDEM) airborne geophysical surveys, infiltration tests, pumping tests and hydrochemical analysis. TDEM surveys provided clarity on the various aquifer geological properties. Infiltration and pumping tests shed light on the horizontal and vertical hydraulic properties of the aquifer. PhreeqC modelling outputs helped predict the outcome of the mixing between groundwater and potential MAR water resources. Geological features were delineated through TDEM surveys and inferred five suitable MAR sites where clay layers were missing. Infiltration and pumping tests showed that Langebaan Road is better suited to borehole injection, whereas Hopefield has the benefit of infiltration MAR techniques as an additional option. PhreeqC outputs exhibit that both pipeline and Berg River water show promising results as potential source water resources for MAR as compared to other resources.
The Geohydrological Setting Of The Elandsfontein Phosphate Mine, West Coast	Julian E	Conrad	West Coast, Western Cape	2017	Phosphate mine, numerical modelling, dewatering, injection system
Abstract The Elandsfontein Phosphate Mine is situated midway between the Langebaan Lagoon and the town of Hopefield. It is located on the Cape West Coast, within the Saldanha Bay Municipality. The mine is positioned within the Elandsfontein Aquifer Unit – which comprises an upper and lower aquifer separated by an aquitard. The economic phosphate layer is situated within the saturated zone of the Upper Aquifer Unit. There are fresh water inflows into the Langebaan Lagoon and all measures must be taken to ensure the natural geohydrological flows are not impacted. Numerous groundwater studies and numerical modelling was carried out to optimize the best way of minimizing the impact on the geohydrology of the area. The dewatering system that has been designed includes re-injection of the groundwater approximately 2 km down-gradient of the open pit. This paper reviews the geological and geohydrological setting of the area and the outcomes of the dewatering and injection systems in place.
An Investigation Of The Natural Groundwater Recharge And Discharge Of The West Coast Aquifer Systems	Aqeela	Parker	West Coast Aquifer Systems	2019	Poster, recharge, Discharge
Abstract Groundwater in the West Coast has been utilised for many years as there are not many surface water resources in the area, and is therefore extremely important. Despite studies being conducted on the aquifer systems since 1976, they are still poorly understood especially with regards to their recharge and discharge processes. This means that the amount of water entering and leaving these systems are unknown, which may lead to over abstraction. It is therefore important to investigate these systems to prevent overexploitation of the groundwater as it will have adverse effects for both humans and ecosystems dependent on it. As part of a managed aquifer recharge (MAR) project for the Saldanha Bay Municipality, this study aims at providing better insight and understanding on the natural resource volumes. The study focusses on groundwater recharge, flow paths and discharge processes and aims at quantifying the volume of water related to each. The study will be conducted by identifying aquifer characteristics through Frequency Domain Electromagnetic and Electrical resistivity geophysical methods. Groundwater flow paths through the unsaturated zone, into the groundwater and towards the discharge area will be determined using Chloride Mass Balance calculations and water isotope analyses. The mass balance equations along with isotope analyses will then aid in the identification of natural recharge and discharge areas of the West Coast aquifer systems, as well as quantifying the volume of water moving through each aquifer. Temperature profiles will also be generated to identify specific layers of the aquifer systems and to determine their groundwater-surface water interactions. The aquifer characteristics will be used in numerical models to test the conceptual understanding of recharge and flow through the systems as well as assessing the volumes of water available to the users of the system.
Geochemical investigations to improve the prediction of mine water impacts: A case study in the Elandsfontein Aquifer System, West Coast.	Angelo	Johnson	West Coast	2021	Phosphate mine, waste sreams, mine water impacts, PHREEQC, geochemical
Abstract The impact of the future closure of the KROPZ phosphate mine in the West Coast on the various potential receptors including the underlying Elandsfontein Aquifer System (EAS), Langebaan Lagoon (RAMSAR-site) and wetlands were assessed. This abstract/paper describes the geochemical characterization and management options related to the waste streams from the mining activity, to assess the post closure contribution to groundwater flow from the mine towards potential receptors. The PHREEQC geochemical modelling code was used to predict potential mine water impacts. The input water quality parameters used in the model included: background groundwater quality, pit water and processed water generated from phosphate separation process at the mine. Various scenarios were simulated combining the different process water streams with the tailings and soft stockpile material at the mine. The geochemical predictions showed some management options that should be prevented, while also providing guidance to promising options where most of the chemical parameters does not exceed the WUL stage 1 thresholds. There is however, an increase in sulphate concentrations that need attending to before the mine goes into production phase. Currently there seems to be no immediate concern on the Lagoon relating to the prediction of mine water impacts post mine closure. Some of the management scenarios do however show low levels of potential impacts on SANParks property 100 years post closure. These predictions do however correlate to areas where limited calibration data is available. At the time of this abstract the sites for new boreholes have been selected and the initial boreholes are being drilled to confirm aquifer properties in areas with limited data.
Arsenic In The West-African Water Reserves: Investigation Into Sources Of The Contaminant Through Case Studies In The Region	André	van Coller	West African region	2013	Contaminant, case study
Abstract The mineral-rich basin of the West African region has vast reserves of gold, diamond as well as iron ore deposits. Throughout the regional geological setting characterised by structural variations and intrusive belts with metamorphic mineral-rich sequences covered by saprolite soils, one common chemical constituent remains a constant in the water reserves. Arsenic is in high concentrations throughout the region with chemical ranges commonly above the various country guidelines as well as international IFC and WHO standards. The aqueous chemical species is associated with arsenopyrite-rich mineralogy of the regional greenstone belts and highly weathered soils. This conference presentation investigates the natural source of the arsenic through baseline data, as well as the effect of mining on the already high concentrations of arsenic in both the groundwater and surface water. Natural levels of various chemical species in the regional area are already high at baseline level. One of the main research questions is thus whether mining and other anthropogenic activities will have an impact on the environment or will the changes to concentrations be so insignificant to allow the ecosystems and water users to continue in their current ways without any effect. Various case studies in Burkina Faso, Liberia, Sierra Leone and other countries have been combined to investigate the arsenic-rich resources of the West African region through groundwater specialist investigative methods with emphasis on geochemical modelling of the fluid–rock and fluid–fluid interactions leading to the aqueous chemical conditions in the region.
Groundwater and mining on the West African shield: application of mineralogical and weathering profiling	David	Love	West Africa	2015
Abstract The Birimian and Tarkwaian rocks of the Paleoproterozoic West African Shield host some of the most important gold reserves in the world, with Ghana the world's 10th largest gold producer and the region collectively producing more gold than all but five countries in the world. The gold was deposited during successive hydrothermal sulphide alteration events, which were channelled by shear zones and thrusts formed during the regional progressive Eburnean tectono-thermal deformation event. The hydrothermal fluids were auriferous and sulphide-rich, resulting in two distinct types of gold and sulphide mineralisation: (1) gold-bearing quartz- and quartz-ankerite veins, occurring in NNE-SSW trending shear zones or thrust folds, usually in Birimian metasediments, with associated sulphides deposited on the fragmented wall rock and (2) disseminated gold-bearing pyrite and arsenopyrite, occurring in halos within the same shear zones or thrust folds as the quartz veins. The sulphidic nature of the gold deposit leads to a high risk of acid rock drainage (ARD). During operations, inflowing groundwater may carry the ARD into underground workings and opencast pits. Post-closure, as the groundwater rebounds, there is a risk of acidic pit lakes forming or acidic decant of underground mines. However, the occurrence of ARD in such systems can be predicted by a combination of weathering profiling, mineralogical profiling and conventional acid base accounting (ABA). The weathering profile can be divided into three zones, readily distinguishable in borehole core: (i) Oxide Zone, from which both the acid-generating sulphide minerals and the acid-neutralising carbonate minerals have been largely leached, (ii) Transitional Zone, from which the carbonate minerals have been largely leached but the sulphide minerals remain, (iii) a Fresh/Primary Zone, where both sulphide and carbonate minerals occur. The Oxide Zone is generally non acid-generating, the Transitional Zone is acid-generating and the Fresh Zone is potentially acid-generating, depending upon the balance of sulphide vs carbonate minerals. Mineralogical profiles can be prepared from the relative abundance of macroscopic sulphide and carbonate minerals in the borehole core, again providing an assessment of ARD risk. Combined logs can then be prepared from these profiles with acid-generation and neutralisation data from ABAs, illustrating in space where the highest ARD risk zones are located. Using this information, groundwater and mine water management options can be developed for operations and closure, such as prioritisation of open pit backfilling or which levels of an underground mine water should be preferentially excluded from.
Arsenic in the west-African water reserves: Investigation into sources of the contaminant through case studies in the region	Andre	van Coller	West Africa	2015	Arsenic
Abstract The mineral rich basin of the West African region has vast reserves of gold, diamond as well as iron ore deposits. Throughout the regional geological setting characterised by structural variations and intrusive belts with metamorphic mineral rich sequences covered by saprolite soils, one common chemical constituent remains a constant in the water reserves. Arsenic is in high concentrations throughout the region with chemical ranges commonly above the various country guidelines as well as international IFC and WHO standards. The aqueous chemical species is associated with arsenopyrite rich mineralogy of the regional greenstone belts and highly weathered soils. This conference article and presentation investigates the natural source of the arsenic through baseline data as well as the effect of mining on the already high concentrations of arsenic in both the groundwater and surface water. Natural levels of various chemical species in the regional area are already high at baseline level. One of the main research questions is thus whether mining and other anthropogenic activities will have an impact on the environment or will the changes to concentrations be so insignificant to allow the ecosystems and water users to continue in their current ways without any effect. Various case studies in Burkina Faso, Liberia, Sierra Leone and other countries have been combined to investigate the arsenic-rich resources of the West African region through groundwater specialist investigative methods with emphasis on geochemical modelling of the fluid-rock and fluid-fluid interactions leading to the water quality in the region.
The role of groundwater in urban resilience	Adrian	Healy	Wales	2023	Groundwater, Governance, household, Resilience, urban
Abstract The potential role of groundwater in supporting the resilience of human societies is garnering increased attention in the context of climate change. Much of this attention focuses on the resilience of the groundwater resource itself. Less attention has been given to the way that groundwater is used by society and how this may influence human-centred resilience outcomes, particularly in urban settings. In this paper, I explore how questions of scale are fundamental to the role of groundwater in the resilience of urban areas, from the scale of individual households to more regional and catchment-based notions of scale. It is these variations in the geographies of urban groundwater exploitation that provide for the challenges of groundwater governance. Drawing on the practices revealed across 5 diverse cities in sub-Saharan Africa; the paper highlights the variety of ways that groundwater promotes the resilience of urban areas to water stress. The paper finds that groundwater can accommodate a prevalence of ‘self-supply’ and market-based models as urban populations seek to counter failings in public supply provision. Whilst these actions promote the resilience of the urban setting in the short to medium term, they raise important questions for the longer-term sustainability of the resource. The paper considers the implications of these questions for the future governance of resilient groundwater resources and the role of groundwater as part of a wider strategy for urban resilience.
Making the Invisible Visible: Do Aquifers Have Agency?	Adrian	Healy	Wales	2023	agency, Groundwater, more-than-human, social, socio-hydrogeology
Abstract In the social sciences, there has been a ‘posthuman’ turn, which seeks to emphasise the role of non-human agents as co-determining social behaviours. In adopting a ‘more-than-human’ approach, the academy seeks to avoid claims of human exceptionalism and extend the social to other entities. In this paper, we explore the extent to which the more-than-human approach might be applied to groundwater and aquifers and the implications that this may have for groundwater science. The role of groundwater in complex adaptive socio-ecological systems at different scales is increasingly well-documented. Access to groundwater resources positively influences societal welfare and economic development opportunities, particularly in areas where surface waters are scarce. The potential adverse effects of human activities on the quantity or quality of groundwaters are also widely reported. Adopting a ‘properties’ approach, traditional social science perspectives typically describe aquifers as structuring the agency of human actors. To what extent might aquifers also have agency, exhibited in their capacity to act and exert power? Drawing on insights from 5 cities across sub-Saharan Africa, we argue for the agency of aquifers in light of their capacity to evoke change and response in human societies. In doing so, we draw on the concept of the more-than-human to argue for a more conscious consideration of the interaction between the human and non-human water worlds whilst acknowledging the critical role played by researchers in shaping these interactions.
Using geophysics to detect water-hosting fractures in the Vredefort Dome: A training opportunity	Stephanie	Enslin	Vredefort Dome, Gauteng	2021	Field School, fractures, geophysical methods
Abstract Tamilo, T; Webb, S.J. The Vredefort Dome 120 km southwest of Johannesburg is a meteorite impact crater that formed at approximately 2 Ga. The region hosts farmland, and the town of Parys is situated in the northwestern part of the dome. The dome is the location of the annual Wits University/AfricaArray Geophysical Field School. The aim of the field school is to teach geoscience students several geophysical techniques while conducting scientific research in the area. A geophysical survey during the 2019 field school over an open field just outside of Parys revealed a buried fracture that hosts ground water. A 150 m long magnetic profile over the fractures shows a magnetic low (approximately 500 nT) that correlates with a low resistivity region on the inverted electrical resistivity data (dipole-dipole method). Euler deconvolution depth estimates and magnetic modelling estimate an overburden thickness of around 10 m and a similar fracture thickness. The magnetic low of the fracture is due to weathering and removal of any magnetic material in the granites in the region. Two existing boreholes that lie 618m due south and at a 10 m lower elevation have water levels of around 6.4 m. Both boreholes lie near a riverbed and vegetation, and appear to lie along an extension to the fracture. This fractures detected using geophysical methods seems to form part of a larger fracture system within the Vredefort Dome, that is linked to the formation of the dome. These fractures provide a vital source of water for the local farming community.
The impact of groundwater temperature on water quality in the urban aquifer of the city of Vienna	E	Kaminsky	Vienna	2023	groundwater temperature, groundwater-surface water interaction, trends, Water chemistry
Abstract Rising shallow groundwater temperatures are observed in many cities worldwide and are expected to increase further over the next century due to anthropogenic activities and climate change. The impact of groundwater temperature increase on groundwater quality is poorly understood. This study conducted two high-spatial-resolution campaigns in Vienna (Austria, autumn 2021/ spring 2022). At 150 wells, a comprehensive parameter set (e.g. major ions, nutrients, and water stable isotopes) was analyzed in groundwater collected, and at 812 wells, the water temperature was measured. Results are compared to available long-term data on groundwater chemistry (1991-2020). In theory, temperature triggers a cascade of effects, where, finally, the depletion of dissolved oxygen (DO) causes a switch to anaerobic microbial processes and a deterioration of water quality. No direct relation between DO and water temperature was observed between 10 and 20 °C. However, many wells delivered anoxic groundwater, including the one with the highest measured temperature (27 °C). The highest temperatures were consistently observed near potential heat sources (local scale), with a rapid decrease in temperature with increasing distance from these sources. Long-term data from particular high-temperature wells revealed decreased dissolved oxygen after sudden temperature changes of > 5 K. On a regional scale, it is observed that groundwater-surface water interactions and aquifer properties play a pivotal role in oxygen availability and redox conditions. In conclusion, high-spatial-resolution sampling combined with long-term data analysis is needed to determine the impact of temperature on water quality.
Water Quality Assessment And Water Use Practices Of Groundwater In Vhembe District, South Africa.	Joshua	Edokpayi	Vhembe District	2019	quality
Abstract Groundwater is often used as an alternative source of drinking water in many places of the world mostly in rural areas. There is a perceived claim that groundwater is clean and safe. This study was carried out to assess the quality of various groundwater sources in the Vhembe District of South Africa. Questionnaires were distributed to residents of the area to evaluate the water use practices. Water quality indices were employed to estimate the usefulness of the groundwater water resources. Heavy metals and major ions were analysed using ICP-MS. E. coli and total coliforms were determined using membrane filtration method. Health risk of the heavy metals in the water was estimated using standard protocol. The results of the study showed that most of the metals complied with the South Africa National Standards. Some of the anions exceeded the recommended limit. Majority of the groundwater sources were fit for other uses except drinking due to the levels of E. coli determined. Sources of contamination determined were both natural and anthropogenic. Adequate monitoring of groundwater resources is recommended to avoid possible risk to public health.
3-D electrical conductivity image as a decision-aiding tool in the post-closure management of a South African colliery	Lize	Wessels	Vereniging	2015
Abstract The colliery is situated in the Vereeniging-Sasolburg Coalfield, immediately southwest of Sasolburg in the Republic of South Africa. The stratigraphy of this coal field is typical of the coal-bearing strata of the Karoo Sequence. The succession consists of pre-Karoo rocks (dolomites of the Chuniespoort Group of the Transvaal Sequence) overlain by the Dwyka Formation, followed by the Ecca Group sediments, of which the Vryheid Formation is the coal-bearing horizon. Mainly the lava of the Ventersdorp and Hekpoort Groups underlie the coal. The Karoo Formation is present over the whole area and consists mainly of sandstone, shale and coal of varying thickness. The underground mine was flooded after mining was ceased at the colliery in 2004. The colliery is in the fortunate position that it has a very complete and concise monitoring programme in place and over 200 boreholes were drilled in and around the mine throughout the life of the mine. To stabilise mine workings located beneath main roads in the area, an ashfilling project was undertaken by the colliery since 1999. A key issue is if the mine will eventually decant, and what the quality of the water will be. This is important for the future planning of the company, as this will determine if a water treatment plant is necessary, and what the specifications for such a plant will be, if needed. Therefore it was decided to do a down-the-hole chemical profile of each available and accessible borehole with a multi-parameter probe with the aim of observing any visible stratification. Over 90 boreholes were accessible and chemical profiles were created of them. From the data collected a three - dimensional image was created from the electrical conductivity values at different depths to see if any stratification was visible in the shallow aquifer. The ash-filling operations disturbed the normal aquifer conditions, and this created different pressures than normally expected at a deeper underground colliery. From the three-dimensional image created it was observed that no stratification was visible in the shallow aquifer, which lead to the conclusion that in the event that if decant should occur, the water quality of the decanting water will still be of very good quality unless external factors such as ash-filling activities is introduced. It is not often that it is possible to create chemical profiles of such a large number of boreholes for a single colliery and as a result a very complete and informative three-dimensional electrical conductivity image was created. This image is very helpful in aiding the decision making process in the future management of the colliery and eventually obtaining a closure certificate, and also to determine whether ash-filling is a viable option in discarding the ash.
Application Of A Numerical Groundwater Flow Model Towards The Development Of An Excavation Pit Dewatering Strategy In Vereeniging, South Africa	Jacqueline	Stapelberg	Vereeniging	2019	flow model, dewatering

Vanwyksvlei: Water provisioning and the Blue Drop system - how effective is this?	Danita	Hohne	Vanwyksvlei	2015	Blue drop standards, water supply challenges
Abstract POSTER Vanwyksvlei had always experienced problems with water supply and quality of drinking water. The town relies on 6 boreholes to supply the town with drinking water. Since 2011 the town was told not to use the water that was supplied from the borehole called Soutgat. This meant that the town could now rely only on the water being supplied from the other 5 boreholes.From 2011 till present the town has experienced a lot of problems regarding water supply, due to the fact that the Soutgat could not be used anymore. Extra stress was put on the other boreholes and these were pumped almost dry. The two aquifers are currently failing and monitoring data since 2009 shows that the water levels of the town are decreasing. Due to low rainfall, recharge to the boreholes are much lower, which exacerbates the problem. This poster will examine the effectiveness of using the Blue Drop system in small towns with limited water supply, at the hand of a case study of Vanwyksvlei. This review will take into account factors such as the point at which water quality is tested in the water supply system, the type of water treatment available for the town and a review the usefulness of certain standards in the Blue Drop system which may indicate failure of supply sources.
Establishment Of A Database And A Representative Groundwater Monitoring Network For The Vanrhynsdorp Water User Association	Brian	Dyason	Vanrhynsdorp, Western Cape	2013	groundwater monitoring, Geohydrological
Abstract The aim of this project was to establish a detailed geohydrological database and monitoring network for the karst aquifer within the boundaries of the Vanrhynsdorp Water User Association. An adequate monitoring network is necessary for the Vanrhynsdorp Water User Association to implement sustainable water use management as well as for the Department Water Affairs to ensure its mandate as trustee of all water resources. Hydrocensus projects were conducted in phases as the project escalated from historic town supply during 1978 towards a catchment driven water user association after implementation of the new National Water Act in October 1998 (Act 36 of 1998). With the successive hydrocensuses conducted, the monitoring network also evolved in regard to area monitored, point locations, monitoring schedules and parameters measured. Hydrocensus data were captured on the National Groundwater Archive, time series data on the Hydstra database and chemical analysis on the Water Management System. Time series graphs were compiled to analyse the monitoring data and to create a conceptual model of the karst aquifer. The study showed a general decline in groundwater levels and quality in the study area. The conclusion is that the aquifer is over exploited. It is recommended that an extensive management plan is developed and implemented to ensure sustainable use of this sensitive water resource. The installation and monitoring of flow meters on all production boreholes should be seen as urgent and stipulated as such in licensing conditions. This will ensure the effective management and regulation of this valuable groundwater resource.