Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 101 - 150 of 795 results
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Abstract

Understanding the sensitivity of groundwater resources to surface pollution and changing climatic conditions is essential to ensure its quality and sustainable use. However, it can be difficult to predict the vulnerability of groundwater where no contamination has taken place or where data are limited. This is particularly true in the western Sahel of Africa, which has a rapidly growing population and increasing water demands. To investigate aquifer vulnerability in the Sahel, we have used over 1200 measurements of tritium (3H) in groundwater with random forest modelling to create an aquifer vulnerability map of the region.

In addition, more detailed vulnerability maps were made separately of the areas around Senegal (low vulnerability), Burkina Faso (high vulnerability) and Lake Chad (mixed vulnerability). Model results indicate that areas with greater aridity, precipitation seasonality, permeability, and a deeper water table are generally less vulnerable to surface pollution or near-term climate change. Although well depth could not be used to create an aquifer vulnerability map due to being point data, its inclusion improves model performance only slightly as the influence of water table depth appears to be captured by the other spatially continuous variables.

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.

Abstract

Worldwide, more than 400 transboundary aquifers (TBAs) have been identified. Only a small number of these aquifers have been assessed in detail. Consequently, little is known about (potential) transboundary impacts. Changes in transboundary groundwater fluxes can indicate potential transboundary impacts as groundwater abstractions can affect such fluxes, indicating potential risks of transboundary contamination. To our knowledge, a quantitative assessment of transboundary aquifer fluxes (TBAFs) is not available because national groundwater models (if existing) often lack a good interaction with surrounding countries. In recent years, a high-resolution global groundwater model (GGM) has been developed as part of the PCR-GLOBWB family of models, having a 5 arcmin (~10*10km2 ) resolution. PCR-GLOBWB has previously been used to quantify environmental flows, assess global droughts, and assess climate impacts on global water resources. Recently the 5 arcmin GGM has been updated to 30 arcsec (~1*1km2 ) using high performance computing (referred to as GLOBGM). We present an application of GLOBGM to assess TBAFs of major TBAs. Results show that even though hydrogeological data are often scarce, a rough order of magnitude of the TBAFs can be assessed. TBA fluxes are compared with groundwater recharge. Although GLOBGM cannot replace assessments of TBAs based on local hydrogeological information and information on groundwater use, the analysis provides valuable information. GLOBGM can be used to quantify the relevance of TBAFs in relation to other fluxes such as from rivers or (future) abstractions. TBAF analyses can also assist in prioritising scarce funds and capacity between TBAs

Abstract

It has been claimed that Groenvlei, a shallow lacustrine wetland on the southern Cape coast of South Africa, is endorheic. This characterisation was based solely on the inward sloping topography immediately surrounding the wetland and an absence of any surface water outflow. However, four independent hydrogeological tools were used to confirm that water discharges from the wetland into the aquifer along its southern banks, thus invalidating the endorheic characterisation. These tools included contouring of groundwater levels, interpretation of the hydrochemical character of groundwater, electrical conductivity depth profiling and a comparison of natural environmental isotopes in surface and groundwater. This case study supports the need for an integrated approach when characterising and assessing water bodies.

Abstract

Springs are examples of groundwater discharges. This paper reports on findings from cold springs groundwater discharges that have served as important water sources for sustaining domestic and agricultural supply. This study assessed the hydrogeology of springs to inform practical measures for the protection, utilization, and governance of such discharges. The research assessed the hydrogeology of springs in terms of conditions in the subsurface responsible for occurrences of springs spatially and their flow paths to the surface. Spring locations were mapped and validated for spatiotemporal assessment. The study examined the flow dynamics and hydrogeochemistry of spring discharges. In-situ and laboratory measurements of spring discharges were carried out using standard methods. Results showed that shallow and deep circulating systems of springs existed in the study area, being controlled by lithology and faults. All springs had fresh water of Na-Cl type, and rock-water interaction was the dominant geochemical process that influenced spring water chemistry. Radon-222 analysis showed high values detected in spring waters that confirmed recent groundwater seepage on the surface. The drum-and-stopwatch technique was used to estimate yield from spring discharges because it’s only effective and reliable for yields of less than 2 l/s. Results suggest that some springs were locally recharged with some regionally recharged. Based on results from estimated yield and quality, it was concluded that spring waters had low discharges. A comprehensive assessment of spring discharges should be conducted to generate large datasets to inform practical measures for protection, utilization, and governance.

Abstract

Due to the recent drought in the Western Cape province of South Africa, surface water can no longer meet our current demand of water and as a result groundwater usage has increased. High iron concentration in groundwater is a problem which results in iron encrustation and iron clogging. This results in decreased borehole yields, decreased water quality and expensive treatments to remove iron encrustation or the drilling of entirely new boreholes. From both international and local literature there are two common factors which stand out which is that high concentration of iron in groundwater is a global issue, the second common factor is that the occurrence and influencing factors of high iron concentrations are site specific. Boreholes drilled for drought relief in health facilities across the Western Cape have reported increased concentrations of iron. Understanding of the geology, hydrogeology and hydrogeochemical conditions that cause the increased iron concentrations in groundwater at these specific locations is required. The objectives of this research project are to: 1) Assess spatial and temporal variations in iron and manganese concentrations; 2) Establish site specific processes that control the concentration of iron in groundwater; and 3) model the geochemical processes that impact iron levels in groundwater. These objectives will be achieved through historical groundwater quality data analysis, geochemical modeling, field work where samples will be collected and laboratory analysis of the samples collected. The information provided from this research project will allow for the effective management decisions to be made in terms of iron removal from groundwater and early preventative measures that can be made to ensure iron clogging and encrustation does not occur. The study is currently ongoing and there are currently no results available at this point however, at the time of the conference there will be information ready to share.

Abstract

Quantification of hydrological processes is required for many projects related to potential groundwater recharge. Thus, investigation on various hydrogeologic conditions is paramount. Changes of climate can affect the hydrological cycle by altering groundwater recharge. As a result, an understanding of the hydrological conditions is essential to make sensible predictions of the possible groundwater recharge. Thus WetSpass, which yields spatially varying groundwater recharge using hydrological inputs, can be used together with a geographical information system to quantify the environmentally acceptable flow regime of the catchment area. This paper presents an overview on the use of WetSpass in combination with GIS on quantification of groundwater potential which will assist to sustainable groundwater development in the catchment area. Previous applications are presented.

Abstract

The presence of shallow groundwater at locations with limited spatial coverage in drylands have since time immemorial supported plant and animal communities. These locations often have in comparison to the surrounding dry landscapes high biomass production and biodiversity. The presence of groundwater makes these locations attractive for development of groundwater dependent human activities such as irrigated crop production, and livestock production. Groundwater abstractions from locations that are not necessarily close to these plant and animal communities, but tapping into the same aquifer systems have also a potential to affect the availability of water to these ecosystems which is critical for their existence. The importance of these groundwater dependent ecosystems is not well understood due to limited knowledge about their spatial coverage. Some of the groundwater dependent ecosystems occur in areas that are not accessible such as mountain slopes, or in remote areas. The long-term impact of groundwater usage on some of these ecosystems has not been evaluated, with most of the knowledge about these impacts being based on anecdotal information obtained from the respective land owners.

Remote sensing offers an opportunity to map the spatial coverage of groundwater dependent ecosystems in drylands. A distinguishing characteristic of these systems is the active plant growth especially during periods when throughout the landscape, there is limited or no water to support plant growth. Monitoring plant growth during the dry season using indices such as the NDVI enables detection of groundwater dependent ecosystems. Knowledge about the rates of actual evapotranspiration at locations with these ecosystems enables an estimation of the amount of water required to support them during the dry season. The MODIS 16 actual evapotranspiration rates (ETA) which are globally available can be used for evaluating water use by groundwater dependent ecosystems.

This paper explores the mapping of the spatial coverage of groundwater dependent ecosystems using remote sensing based vegetation indices in parts of the Gourizt River basin in South Africa. The rates of waters use by the identified groundwater dependent ecosystems are estimated using actual evapotranspiration rates based on MODIS 16. The paper also examines possible long-term changes to the spatial coverage of groundwater dependent ecosystems.

Abstract

Kanyerere, T

Groundwater contribution towards improved food security and human health depend on the level of contaminants in the groundwater resource. In rural areas, many people use groundwater for drinking and irrigation purposes without treatment and have no knowledge of contaminants levels in such waters. The reason for such lack of treatment and knowledge is due to the parachute type of research which emphasizes on scientific knowledge and records only and do not develop skills and outputs on groundwater quality for improved human health and food security in communities. This study argued that parachute research type exposes groundwater users to health hazards and threaten food security of communities. Concentration levels of contaminants were measured to ascertain suitability of groundwater for drinking and irrigation use. 124 groundwater quality samples from 12 boreholes and 2 springs with physiochemical data from 1995 to 2017 were assessed. This study found high concentration levels of contaminants such F-, NO3-, Cl- and TDS in certain parts of the studied area when compared to international and national water quality standards. In general, groundwater was deemed suitable for drinking purposes in most part of the studied area. Combined calculated values of SAR, Na%, MH, PI, RSC and TDS determined that groundwater is suitable for irrigation purposes. The discussion in this paper showed that scientific knowledge generated on groundwater quality is not aimed at developing skills and outputs for improved human health and food security but rather for scientific publication and record keeping leaving communities where such knowledge has been taken devoid of knowledge and skills about the groundwater quality. In this study, it was recommended that skills and outputs on groundwater quality should be developed and shared with groundwater users through various initiatives as it will enhance the achievement of SDG’s.

Abstract

Groundwater forms an important part of the water resources of South Africa, especially in Karoo region, where groundwater is an important source of fresh water. Beaufort West is a town that uses groundwater as a major source of municipal and private water supply. Groundwater samples were collected from a network of 43 boreholes, between November 2015 to December 2018 within Beaufort West town and 10km radius surrounding. The water samples were analysed for inorganics, organics, stable isotopes and radioactive isotopes. The hydrogeochemical results indicate that all the boreholes onsite are collecting water from the shallow aquifer with neutral pH. From the 228 groundwater samples analyses, the total dissolved solids (TDS) concentrations averaged 1041 mg/L. This falls within the SANS 241:2015 guideline standard of ? 1200 mg/L for TDS. The high nitrates and sulphates in the water indicate that shallow aquifer has aerobic conditions. Generally, the water type is Calcium Magnesium Bicarbonate and Magnesium Sulphate. Both the inorganic chemistry and the stable isotopes have a signature of water that is recently recharged. The carbon dating results indicate that water has been underground for no more than 3 000 years. The groundwater samples generally show no contamination of organic compounds with the exception of boreholes located in the Karoo National Park, which showed high amounts of organic compounds (xylene and ethylbenzene). The interaction of the known uraniferous deposit of the Poortjie Formation in the Beaufort West area has possibly influenced the groundwater. This has resulted in groundwater with elevated average amount 17.58 ?g/L of uranium against background values of 10 ?g/L. This is however below the SANS 241:2015 standard of 30 ?g/L.

Abstract

This study was carried out in Lagos State, southwestern Nigeria. It is a coastal city that lies approximately between longitude 30 13’30”E and 30 17’15”E and between latitude 60 28’N to 6 0 42’N. The study assessed the groundwater pollution risk using geophysical methods and the concepts of Dar Zarrouk parameters as veritable tools. Resistivity measurement was taken at twelve (12) vertical electrical sounding (VES) stations and along eight (8) 2D resistivity profiles using the Schlumberger array and dipole-dipole array respectively. The VES data were processed using IP2Win computer iteration software. The geoelectric model from the interpretation revealed four/five geo-electric layers. These include: Top sandy layer with resistivity and thicknesses ranging from 2.29-1915 Ωm and from 0.46-4.55 m respectively. The second layer is mostly clay soil of varying degree of saturation which is obvious from its resistivity behavior. This layer has a minimum resistivity of 3.52 Ωm at VES1 and maximum resistivity of 20 Ωm at VES6. Also, the thickness of this layer varies from 1.85 m at VES9 to 7.32 m at VES6. The third/fouth layers delineated are clay and clayey sand/sandy clay. However, the highest thickness value of 43.1m for clay occurred at the third layer at VES10. The apparent resistivity of this layer varies from 1.61 Ωm to 265 Ωm and varies inversely with the clay content from 16.3 m to 33.3 m. Also the thickness of this layer varies from 4.8 m to 45.3 m. The 2D resistivity data (dipole-dipole) acquired along Oniru, Elegushi, and Adeniji were processed using RES2D. Along Oniru traverse 1, low resistivity zones diagnostic of contaminant plume was observe at distances between 12 m to 30 m and also, an isolated plume of contaminants deducible from low resistivity occur along traverse 3 at depth below 30 m. At Elegushi , vertically migrating plumes of contaminant indicated by low resistivity zones equally occur at distance between 320 m along traverse 1 and spread towards the centre from the western and eastern parts of the traverse respectively. Furthermore, pockets of contaminants are also observed all along the distance between traverse 2. However, at Adeniji, a plume was only observed at 384 m along the same traverse. The longitudinal conductance and the corresponding vulnerability of the lithologies delineated in the study area shows that the longitudinal conductance and protective capacity of clay is maximum at VES10 with a value of 26.7702 Ω-1 at a depth of 65.6 m. Therefore, the sand aquifer confined by clay is the least vulnerable in the study area. This is because the highly impervious clayey overburden, characterized by relatively high longitudinal conductance, offers protective shield to the underling aquifer. However, sand being the most vulnerable,has the least values of longitudinal conductance ranging from 0.6884 Ω-1 at VES11 to 0.0006 Ω-1 at VES2. The vulnerability sandy clay/clayed sand are of intermediate value and the risk improves/reduces with increasing clay content.

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.

Abstract

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

Abstract

This study assessed aquifer-river interaction using a combination of geological, hydrological, environmental stable isotope, and hydrochemical data in a non-perennial river system in the Heuningnes catchment. Results showed the depth to groundwater levels ranging from 3 to 10 m below ground level and aquifer transmissivity values of 0.17 to 1.74 m2 /day. The analytical data indicated that Na-Cl-type water dominates most groundwater and river water samples. Environmental stable isotope data of river samples in upstream areas showed depleted δ18O (-4.3 to -5.12 ‰) and δ2H (-22.9 to -19.3 ‰) signatures similar to the groundwater data, indicating a continuous influx of groundwater into the river water. Conversely, high evaporative enrichment of δ18O (1.13 to 7.08 ‰) and δ2H (38.8 to 7.5 ‰) were evident in downstream river samples.

It is evident from the local geological structures that the fault in the northeastern part of the study area passing Boskloof most likely acts as a conduit to groundwater flow in the NE-SW direction, thereby supplying water to upstream river flow. In contrast, the Bredasdorpberge fault likely impedes groundwater flow, resulting in hydraulic discontinuity between upstream and downstream areas. Relatively low conductive formation coupled with an average hydraulic gradient of 8.4 × 10−4 suggests a slow flow rate, resulting in less flushing and high groundwater salinisation in downstream areas. The results underscore the significance of using various data sets to understand groundwater-river interaction, providing a relevant water management platform for managing non-perennial river systems in water-stressed regions.

Abstract

The Kavango West and East regions are situated in a semi-arid area northeast of Namibia and bounded by the perennial Okavango River on the northern border. Groundwater in the area is the main source of water supply for the inhabitants living further from the river. In addition, most bulk water users along the river have boreholes for their water supply. With a semi-arid climate, drought in the regions is common and inflicts devastating effects on local communities. More drought relief boreholes are being drilled to sustain communities, increasing the dependency of the inhabitants on groundwater. The complexity of the behaviour and nature of the groundwater in the regions is poorly understood, and there are no strategies to manage these aquifers properly. As a result, an attempt was made to better understand the groundwater potential by examining several hydrogeological factors involved. A basic water-balance approach was used in determining the groundwater potential of the middle and lower Kalahari aquifers. The total resource potential for the entire region is estimated at 144 447.16 x 106 m3 /a, demonstrating great resource potential with significant storage space.

The greatest potential is shown in the middle Kalahari aquifers, comprising about 94% of the total resource. Groundwater recharge, as one of the hydrogeological factors, was determined using the chloride mass balance method, giving an average of 6.03 mm/a for the entire study area. If utilized sustainably, the Kalahari aquifers can sustain most communities within the two regions, especially those further from the Okavango River.

Abstract

The long mining history in Namibia has resulted in numerous abandoned mines scattered throughout the country. Past research around the Klein Aub abandoned Copper mine highlighted environmental concerns related to past mining. Considering that residents of Klein Aub depend solely on groundwater, there is a need to thoroughly investigate groundwater quality in the area to ascertain the extent of the contamination. This study made considerable effort to characterise groundwater quality using a comprehensive approach of quality assessment and geostatistical analysis. Onsite parameters reveal that pH ranges between 6.82-7.8, electrical conductivity ranges between 678 - 2270 μS/cm, and dissolved oxygen ranges between 1.4 -5.77 mg/L. With an exemption of two samples, the onsite parameters indicate that water is of excellent quality according to the Namibian guidelines. The stable isotopic composition ranges from −7.26 to -5.82‰ and −45.1 to -35.9‰ for δ18O and δ2H, respectively—the groundwater plots on and above the Global Meteoric Water Line, implying no evaporation effect. Hydrochemical analyses show bicarbonate and chloride as dominant anions, while calcium and sodium are dominant cations, indicating groundwater dissolving halite and mixing with water from a recharge zone.

The heavy metal pollution index of the groundwater is far below the threshold value of 100, which signals pollution; it contrasts the heavy metal evaluation index, which clustered around 3, implying that the heavy metals moderately affected groundwater. Copper, lead and Arsenic were the main contributors to the values of the indices.

Abstract

Water is regarded as a source of life and access to potable water supply delivery remains the building block to improving and maintaining the community member’s health and productive life. The demand for water supply has been increasing due to population growth and climate change phenomena. Hence, there is need to assess the current state of potable water supply system in selected rural areas of Vhembe District Municipality (VDM), South Africa. About 14 villages in VDM were visited to assess the state of water supply. Interview were held with three municipal officials who deals with water supply systems and 14 focus group discussions were held in each village with the communities and their leaders. 448 head of households, 14 councillors completed the questionnaires on potable water supply situation in their area. The results indicated that the main sources of water supply are boreholes followed by tap water from dams. In areas where the two sources are not available, the rivers, fountain and the water tankers were also the main sources. In terms of water usage, the boreholes recorded the highest responses of 45% from households, followed by the tap water from dams at 35%, 4% from rivers, 5% from fountain and 10% from water tankers. In addition, about 53.6% of participants collect water once a week from the main source (boreholes and tap water from dams). Rural communities of Vhembe District Municipality were not satisfied with the quantity, distance and reliability of boreholes. Therefore, this article recommended that the municipality, communities, councillors and traditional leaders should work together in addressing the pressing water issues. Part of which include provision of more sources of water to complement growing population. In addition, village water committees need to be established to assist in water provision management.

Abstract

Fourie, F

Communities reacted differently to the drought. In some cases, you would notice a proactive approach and good management of the wellfields. In other cases, communities have been under a misconception that they received good rainfall for a recharge which did not reflect in monitoring data, and lastly, you get the communities that are mismanaging the groundwater. Various lessons were learned from the change in the climate and environment. But a lot can be done to minimise the impact of these changes on the water supply to communities. This paper addresses the changes that we can apply to deal with the changing environment around us to provide a sustainable water supply. The changes can include relooking at operating rules to ensure better management on the aquifer and borehole level. Recharge determined during pump test must be considered periods low to no recharge. Methods to enhance the recharge to the aquifer will ensure recharge occur during low rainfall events By implementing these rules, groundwater can be sustainably managed for future use.

Abstract

Artificial Intelligence (AI) has been used in a variety of problems in the fields of science and engineering in particular automation of many processes due to their self-learning capabilities as well as their noise-immunity. In this paper, we describe a study of the applicability of one of the popular branch of AI (Artificial Neural Network (ANN)) as an alternative approach to automate modelling of one-dimensional geoelectrical resistivity sounding data. The methodology involves two ANNs; first one for curve type identification and the other one for model parameter estimation. A three-layer feedforward neural network that was trained from geoelectrical resistivity data taken at boreholes with geology logs was used to predict earth models from measured data without the need to guess the initial model parameters or use synthetic data as is done with most conventional inversion approaches. The motivation for using the ANN for geophysical inversion is that they are adaptive systems that perform a non-linear mapping between two sets of data from a given domain. For network training, we use the back-propagation algorithm. An example using data from southern Malawi shows that the ANN results outperforms the conventional approaches as the results after adequate training, produce reasonably accurate earth models which are in agreement with borehole log data.

Abstract

Recent findings allow a better insight into the interaction between two aquifers and their vulnerabilities at the groundwater extraction site of Velm, which produces drinking water for around 55,000 households. The shallow aquifer that is exploited is situated in the Formation of Hannut. This aquifer is vulnerable to pollution, especially from the agricultural lands close to the extraction site and is sensitive to natural recharge. In this case, the groundwater is captured in a basin via a naturally occurring spring flow. The second aquifer is situated in the Cretaceous at 50 to 100 m below the surface and is pumped by four wells. The drinking water quality is guaranteed by mixing and treating these two waters. To optimize the central decalcification and the pollution risks, the production volume in the deep aquifer was increased from 2017 to 2021 at the expense of the shallow aquifer. This led to a decrease in the available volumes of the shallow aquifer, which indicated a leakage from the shallow to the deeper aquifer, which was unexpected. Groundwater modelling and time series analysis have been used to assess the impact of the increased production volumes and the longer dry periods. Based on this data, a maximum production volume of 1,000,000 m3 /year is considered best for the cretaceous aquifer. With this extraction rate in the Cretaceous, it is possible to supply sufficient drinking water and limit the impact on the Formation of Hannut.

Abstract

Groundwater recharge is of strategic importance in groundwater research both globally and locally in South Africa as it ensures that the development of groundwater does not exceed the systems rate of renewal, protecting the integrity of these resources. The Table Mountain Group (TMG) system is considered to a potential source of future bulk water supply with a recharge potential ranging from 7 to 23% of Mean Annual Precipitation (MAP). However, estimation of true groundwater recharge is challenging as groundwater recharge is affected by many factors which influence the ability of water to reach the water table. Various studies have been carried out within the Jonkershoek Nature Reserve which investigated the response of a catchment’s hydrological functioning and biodiversity to land use management and disturbance regimes such as fires. Previous studies assessed the effect of fire on the hydrology of the catchment, highlighting the associated increase in streamflow components and hydrological response of catchments due to the development of soil water repellency which generated rapid runoff but do not discuss the possible effects on the recharge potential to the groundwater system. The present study investigated the possible effects of wildfire disturbances on local groundwater recharge system of the TMG aquifer system in Jonkershoek Valley, Western Cape Province of South Africa using baseflow as a proxy for groundwater recharge. The possible effects of wildfire disturbance on groundwater recharge processes were determined through review of literature, lithological logs and geological maps. Baseflow separation of hydrographs was conducted using the Recursive Digital Filter Method. It was found that the baseflow response to rainfall events following the March 2015 fire remained unchanged for the Tierkloof sub-catchment of Jonkershoek whereas Langrivier experienced a decline in baseflow response following the winter rainfall period later that 2015. The findings suggest that wildfire to some extent influences groundwater recharge but not all times thereby providing insight on the extent of influence of a vegetation cover on groundwater recharge and confirming findings from previous studies. The present study recommends long term studies on the influence of wildfire on groundwater recharge and the use of both direct and indirect methods for investigating groundwater response to fires. 

Abstract

The Namibian uranium province, located in the Namib Desert, derives its name from the local presence of almost ten uranium tenements. The mines conduct monitoring of natural radionuclide concentrations of Ra226, Ra228, Pb210, U234, U238, Th232 and Po210 in local aquifers. This data is useful in mine rehabilitation and developing closure criteria, as only radiation doses additional to natural doses are usually considered ‘controllable’ for radiation protection purposes. An accredited laboratory analyzed the baseline data collected through quarterly groundwater sampling with submersible pumps. The uranium deposits are hosted in Damara age granites or as secondary mineralization in Tertiary calcareous paleochannels. The analysis of the long-term baseline data provides the background radionuclide concentrations of three aquifer types in the province, i.e., the Quaternary saturated alluvium of the Khan and Swakop ephemeral Rivers, the Tertiary paleochannel sediments, and Proterozoic basement aquifers. The ephemeral rivers are important because they supply groundwater downstream of the mines for agricultural use. The analysis demonstrated that the alluvial aquifers have the lowest natural radionuclide content, with the U234 concentrations ranging between 0.03 and 3.4 Bq/l, while paleochannel and basement aquifers show intermittent U234 concentrations ranging between 0.25 and 5.1 Bq/l. The groundwater in the immediate ore zones shows the highest U234 concentrations, ranging between 44.8 and 86.3 Bq/l, exceedingly higher than the WHO standards of 1 Bq/l. This study illuminates that radioactivity is a natural phenomenon and that groundwater baseline data is paramount to groundwater protection.

Abstract

A conceptual water budget model is required to “make groundwater visible” in the shared transboundary area of Estonia and Latvia, which doesn’t face any significant water management issues. Despite having a water management agreement since 2003, it wasn’t until 2018 that cooperation on groundwater began. In the EU-WATERRES project, the water balance modelling of the ~9,500 km2 transboundary (TB) area with MODFLOW 6 was performed. Based on budget calculations, the area’s average precipitation is 203 m3 /s, with ~50% (102 m3 /s) of it discharging to the sea as surface water. The infiltration share (7%, 14.4 m3/s) is a small fraction of overall precipitation, but as an average, it forms ~14% of surface water flow, with 98% of infiltrated groundwater forming the baseflow. Modelling produced two main conclusions: surface water and groundwater form a joint system in the upper ~150 m cross-section depth, and there is no preferred regional TB flow direction due to flat topography. This makes cross-border flow highly dependent on pumping close to the border area. The results of recent studies provide valuable information on groundwater’s importance in EE-LV TB areas and a basis for simple conceptual models to make groundwater visible to the general audience and decision-makers. These findings are critical for specialists in managing water resources in the region and will inform decisions related to the use and protection of groundwater in transboundary areas.

Abstract

Basin-scale studies addressing the transfer of pollutants among groundwater and surface water bodies are essential to support local authorities in the sustainable management of freshwater resources. This work revealed that, in the hydro-system of the Oglio River basin (Northern Italy), nitrate pollution in groundwater, originated by overfertilization, is transferred downstream to surface water bodies via outflow through lowland springs and baseflow to gaining rivers. Downstream groundwater is unaffected due to reducing conditions that facilitate denitrification. It follows that efficient measures to reduce nitrate pollution in surface water bodies should not be applied solely to rivers/streams but, instead, they should include the upstream groundwater body. The work aimed at understanding nitrate pollution dynamics in an intensively irrigated hydro-system, focusing on the role played by the complex interaction among irrigation water, surface water and groundwater. The study relied on nitrate concentration, Cl/Br ratio, stable isotopic composition of water, nitrate and boron in groundwater, river, lake, spring, and rainwater samples. Results highlighted a well-defined spatial distribution of nitrate concentrations in groundwater, mainly driven by irrigation practices: (1) where groundwater-fed irrigation is done, return flow promotes high nitrate concentrations (>50 mg/L) due to groundwater recirculation; (2) where intensive surface-water-irrigation is practised, fed by low-nitrate river water, return flow generates lower nitrate concentrations (<50 mg/L) due to dilution. This work highlighted the importance of a holistic approach jointly investigating surface water, groundwater, and irrigation water when nitrate pollution is examined at a basin scale.

Abstract

Managed Aquifer Recharge (MAR) provides an integrated water governance solution that improves water security for communities and farmers by storing water in aquifers and managing groundwater extractions to ensure water supplies are available during droughts. Quantitative analysis of levelised costs and benefit-cost ratios (BCRs) of 21 MAR schemes from 15 countries and qualitative assessment of additional social and environmental benefits demonstrates the benefits of MAR compared to water supply alternatives. Cost-benefit analysis provides a systematic method for comparing alternative water infrastructure options. Levelised cost is a widely accepted method of comparing MAR with alternative water infrastructure solutions when market valuations of water are unavailable.

The benefits of MAR can be estimated by the cost of the cheapest alternative source of supply or the production value using water recovered from aquifer storage. MAR schemes recharging aquifers with natural water using infiltration basins or riverbank filtration are relatively cheap with high BCRs. Schemes using recycled water and/or requiring wells with substantial drilling infrastructure and or water treatment are more expensive while offering positive BCRs. Most MAR schemes have positive or neutral effects on aquifer conditions, water levels, water quality, and environmental flows. Energy requirements are competitive with alternative sources of supply. This analysis demonstrates strong returns to investment in the reported MAR schemes. MAR provides valuable social and environmental benefits and contributes to sustaining groundwater resources where extraction is managed.

Abstract

Preventing the spread of seepage from tailings storage facilities (TSF's) in groundwater is necessary as it often contains toxic contaminants. Experience has shown that seepage from TSFs is inevitable and that zero seepage remains difficult even with complex liner systems. Multiple seepage control methods are often required to minimise seepage to ensure that environmental regulations are met. Control methods can be grouped into either barrier or collection systems. Barrier systems are used to hinder seepage whereas collection systems are used to intercept seepage. A blast curtain, which is the focus of this article, is a type of collection system that is still at a conceptual level but has seen little or no application worldwide. It works in principle, similarly to a curtain drain, but is typically extended to greater depths depending on the aquifer vulnerability. Numerical modeling has shown that this mitigation measure could add another line of defence for seepage control. The depth and effectiveness of the curtain can be optimized with a numerical model to ensure optimal interception of contaminated seepage around the TSF. Depths of up to 30 m in fractured aquifers have been simulated in this study. A blast curtain is constructed by drilling a set of boreholes around a TSF in close proximity to one another and then fracturing the rock using either explosives or fracking methods to create a more permeable zone. This is then combined with a series of scavenger wells or natural seepage to abstract the contaminated water. Numerical simulation has shown that blast curtains are effective especially if groundwater flow is horizontal. The effectiveness decreases if the vertical flow component is significant. A blast curtain can result in the lowering of the water table, however, local depression is a less of a concern than potential groundwater contamination. {List only- not presented}

Abstract

Millions of tons of coal ash are produced across the globe, during coal combustion for power generation. South Africa relies largely on coal for electricity generation. The current disposal methods of coal ash are not sustainable, due to landfill space limitations and operational costs. One way/means of disposing of coal ash that could provide environmental and financial benefits; is to backfill opencast mines with the ash. However, a limited number of studies have been conducted to assess the feasibility of this method in South Africa. Thus the aim of the experiment is to monitor bulk ash disposal under field conditions to improve the understanding of the geochemical and hydrogeological processes occurring during the actual deposition of coal ash in opencast coal mines. To achieve the aim (1) a gravity lysimeter will be built containing both mine spoils and coal ash representing field conditions; (2) the factors (CO2, water level and moisture content) affecting acid mine drainage will be monitored in the lysimeter and (3) the change in the quantity and quality of the discharge released from the lysimeter.

Abstract

Water resources worldwide are stressed, and the number of groundwater professionals required to manage those resources is not being generated in sufficient numbers. Groundwater educational resources must be placed in schools to generate excitement and raise awareness. Additionally, people entering the workforce need training throughout their professional careers. Oklahoma State University partnered with the U.S. National Ground Water Association to develop a framework for providing education and training programs in groundwater that allow for interactive online education at all levels. The Awesome Aquifer 360 program targets grades 5-8, allowing students to conceptually explore aquifers and the people who manage them. The Drilling Basics Online program provides a 40-hour basic safety and drilling training to recruit professionals into the groundwater industry and reinforce safe operations. These programs and future plans for the technique will be discussed.

Abstract

Deploying a participatory approach for surveying the complex geohydrological system and defining the status of the groundwater resources in the Kunzila catchment area has crucial importance towards conjunctive use of its water and land resources for sustainable economic growth, social well-being, and environmental protection. Several initiatives are being undertaken to pilot the ‘Integrated Landscape Management and WASH’ project in this community to implement evidence-based approaches. A comprehensive hydrogeological study has been carried out to understand the hydrogeological system, propose ecosystem restoration measures, identify suitable locations for drilling boreholes and design a groundwater and surface water monitoring network.

The first results pointed out the central area of the catchment as holding the best potential for groundwater abstraction, a productive Late Quaternary basalt aquifer. As this area is in use by private floriculture farms, several other borehole locations were sited to meet the domestic and livelihood demand across the watershed. In addition to the drinking water supply goals, the project proposed catchment intervention for soil and water conservation based on the Landscape Approach and 3R measures implementation - Retain, Recharge, Reuse. Such measures include but were not limited to riparian vegetation restoration, terracing and contour bunds, agroforestry, controlled grazing, etc. A telemetric monitoring network has been designed and installed to support the conjunctive management of shallow and deep groundwater water resources, streams and Lake Tana, together with a functional dashboard for data registrations and sharing. The monitoring program gauges the impact of groundwater abstraction and the quality parameters.

Abstract

Cadmium is a highly mobile and bioavailable non-essential element that is toxic to plants, and is an animal and human carcinogen (affecting the kidneys and bones in vertebrates). Since the late-1970s the effects of cadmium on the environment have become a global issue of concern, and many countries have conducted evaluations on the exposure of their populations to cadmium in phosphate fertilizer (a major non-point source of anthropogenic cadmium). A scoping project, funded by the Water Research Commission, aimed to review cadmium contamination of South African aquifer groundwater systems (predominantly) via phosphate fertilizer use. Topics reviewed included fertilizer composition and types, metal speciation, metal mobility in soil and groundwater systems, metal bioavailability, health and environmental effects, and local South African contamination case studies. A preliminary study site, namely the greater Hermanus region, was identified for trace metal and groundwater quality studies (which incorporated urban and agricultural areas in various hydrogeological settings). Hermanus was selected due to: 1) the discovery of cadmium concentrations of 20 ?g/l (in comparison to the SANS 241-1:2011 cadmium limit of 3 ?g/l) in a golf estate irrigation borehole, during drilling and test-pumping of the borehole at the end of 2012

Abstract

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

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

Abstract

Zimbabwe occupies a tectonically stable plateau underlain by ancient Precambrian crystalline basement rocks. These  form a central craton bounded by east-west trending mobile belts; the Zambezi mobile belt to the north and the Limpopo mobile belt to the south. Zimbabwe receives generally low and variable quantities of seasonal rainfall within a semi-arid to savannah type climate characterised by moderate to high temperatures. Evaporation commonly exceeds rainfall so that recharge to the thin near surface aquifers is generally low and in some years non-existent. The groundwater resources of the weathered and fractured basement aquifers that underlie more than 60% of the country are of limited potential, typically sufficient to supply the needs of small villages and cattle ranches. However, within the central plateau area of the African to Post-African erosion surfaces, the weathered and fractured basement may exceed 60 m in thickness. The thickness of this zone diminishes towards the main valley systems where subsequent cycles of erosion have stripped the weathered zone away, leaving only a shallow surface fractured zone that may only be 20-30 m thick. Groundwater resources have been developed extensively in Zimbabwe since the 1920s. During 1991/92 drought abstraction from urban boreholes within the southern Harare area caused yield decline and ultimate failure of numerous boreholes. It is now time to question the long-term viability of groundwater development within the basement aquifers in Zimbabwe given the uncertainty in groundwater resources, the complexities of the climate–groundwater interactions and the projected demands of a growing rural population.

 

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.

Abstract

The lack of reliable groundwater level monitoring data hinders the comprehensive understanding and sustainable management of our aquifers. New remotely sensed data products could present novel possibilities to fill in situ data gaps. For example, continuous monthly groundwater storage anomaly estimates at a spatial resolution of 0.25° (28 km) are made available through the Global Data Assimilation System Version 2.2 (GLDAS-2.2) data products that assimilate Gravity Recovery and Climate Experiment (GRACE) data. In this study, it was hypothesised that the open-source, higher resolution Climate Hazards Group InfraRed Precipitation With Station Data (CHIRPS) precipitation data and Moderate Resolution Imaging Spectroradiometer (MODIS) evapotranspiration data could be used to downscale groundwater storage anomalies (GWSA) for local scale investigations. Using an intergranular and fractured aquifer, as well as a karst aquifer as case studies, both enclosed within the Steenkoppies Catchment (A21F), two respective random forest regression (RFR) models were developed to downscale GLDAS-2.2 GWSA. Sampling monthly training data without accounting for temporal lagging resulted in an increased correlation, index of agreement (IA) and improved RMSE for the intergranular and fractured aquifer. Where the correlation between the observed groundwater storage changes and the GLDAS-2.2 groundwater storage estimates were weaker, however, accounting for the temporal lags resulted in an improved RMSE. The final product is a 0.05° (5.5 km) grid of monthly time-series GWSA estimates that can improve groundwater resource assessments, understanding aquifer recharge, modelling accuracies and better overall decision-making regarding Integrated Water Resource Management (IWRM).

Abstract

In response to the Western Cape’s worst drought experienced during 2015-2018, the City of Cape Town implemented various projects to augment its water supply, including desalination, re-use and groundwater. The Cape Flats Aquifer Management Scheme (CFAMS) forms one of the groundwater projects that includes groundwater abstraction and managed aquifer recharge (MAR). The Cape Flats Aquifer (CFA) is a coastal, unconfined, primary aquifer within an urban and peri-urban environment. As such, it is well situated to take advantage of enhanced recharge using high-quality advanced treated effluent but also has challenges related to seawater intrusion (SWI) and risk of contamination. MAR is currently being tested and implemented with a three-fold purpose: (1) to create hydraulic barriers against seawater intrusion and other contamination sources, (2) to protect groundwater-dependent ecosystems harbouring biodiversity, and (3) to increase storage and improve water quality to enhance resilience to effects of drought. As no legislation for MAR exists in South Africa, international guidelines are used to determine water quality requirements related to clogging environmental and health concerns. Further consideration includes aquifer-scale design, the interaction of multiple abstraction and injection wellfields within an area, and the design of individual boreholes to enhance yield and limit clogging. We aim to present progress made to date that includes exploration, wellfield development, monitoring, numerical modelling, aquifer protection, and the lessons learnt.

Abstract

The City of Cape Town is a favourite tourist destination. With Table Mountain being one of the new seven natural wonders of the world, Cape Town is also uniquely positioned where the Benguela and Atlantic ocean currents meet. Proximate environs play home to some of the most unique biodiversity found in the world with the fynbos biome protected in numerous reserves such as the Cape Peninsula, Table Mountain and Kogelberg Nature Reserves. Cape Town is also South Africa’s cultural heartbeat where artists, film makers, designers and wine connoisseurs contribute to the tourism of the country.

The recent drought and increasing demands through urbanisation are raising concerns regarding water scarcity and supply. Will the city be able to supply this growing demand, notably with additional stress due to climate change?

The Hydrological Heritage Overview aims to address the important power water has over Mankind and how we can harness that to our benefit without compromising the environment. The selection of Cape Town (following completion of Pretoria and Johannesburg) supplies the opportunity to address the mechanical impacts of water: Table Mountain formed through the action of water, and was shaped into its characteristic landform due to subsequent erosion by water action. Additional emphasis on the power of water relates to aspects of hydropower, the impacts of floods and droughts, and additionally of the power of water as it is harnessed as a vital life supporting resource and as a means of recreation.

As the final deliverable of this project, a short 12-minute documentary film has been made for the information of the general public and interested parties. The film showcases the water history of the City of Cape Town, emphasising supply from springs, dams and, more recently, artificial groundwater recharge. Although not a technical presentation, showcasing of the film will advance citizen science and public appreciation for the value of water.

Abstract

Historically groundwater exploration consisted of reconnaissance geophysical surveys followed by detail ground surveys. Where no potentially water-bearing geological structures are shown on geological maps and aerial photos, the project area would be divided into a grid on which the ground geophysical survey would be done. This type of exploration is time-consuming and expensive. In some cases the terrain or cultural noise prohibits the use of conventional geophysical methods, with only more expensive and time-consuming methods being left as an option. This is where the high resolution airborne magnetic survey excels. The results obtained from this type of survey are of such a nature that ground geophysical surveys are only performed where potential drilling targets were identified  from  the  aerial  survey.  Not  only  can  there  be  cost-  and  time-savings  on  ground geophysical surveys, but drilling of dry boreholes can be limited, which makes up the largest cost component of a groundwater exploration project. This paper will discuss successes achieved using high resolution aeromagnetic surveys as the basis for groundwater exploration in traditionally low- yielding igneous geology.

Abstract

Aurecon was appointed to conduct groundwater exploration for production well fields in the towns of Setlagole and Madibogo. These towns are located in an arid part of the North West province on the edge of the Kalahari. The landscape is flat and covered by aeolian sand underlain by basement granite of the Kraaipan Group Geology.
Historically groundwater exploration consisted of reconnaissance geophysical surveys followed by detail ground surveys. Where no potentially water bearing geological structures are shown on geological maps & aerial photos, the project area would be divided into a grid on which the ground geophysical survey would be done. This type of exploration is time consuming and expensive. In some cases the terrain or cultural noise prohibits the use of conventional geophysical methods, with only more expensive and time consuming methods being left as an option. This is where the high resolution airborne magnetic survey excels. The results obtained from this type of survey are of such nature that only a small amount of ground geophysics is necessary to locate drilling targets. This survey method is also cost effective allowing a larger area to be covered in a short amount of time as compared to conventional ground techniques.
This paper will discuss successes achieved using high resolution aeromagnetic surveys as the basis for groundwater exploration in traditionally low-yielding igneous geology.

Abstract

POSTER Since June 2010 and still ongoing today, the Lower Orange River Valley has experienced over a 1168 tremors(a) and earthquakes in the vicinity of Augrabies. Of these 1168 tremors, 71 quakes registered above 3 on the Richter scale and on 18 December 2011, the area was struck with an earthquake that registered 5 on the Richter scale. Four thermal springs are also located near this earthquake zone and the temperature of the water have a range of between 38?C -46.6?C, according to Kent LE. (1949/1969). 25?C is the division between thermal and non-thermal waters and the thermal gradient for the Riemvasmaak area(b) is 24?C, clearly indicating that the four springs are thermal when looking at the temperature difference. The Department of Water Affairs has been monitoring these springs monthly since 2011 and has been taking field measurements and chemical analyses. The aim of this study is a) to see if the tremors and earthquakes have an effect on the chemistry of the thermal springs, b) to create a data set for the thermal springs, as these springs was recorded and mentioned in Kent LE. reports of 1949 and 1969 but no samples were collected and analysed, c) to see if the water source for the groundwater in the area and the thermal springs are connected and d) to see if the recent floods may have had an influence on the earthquake zone seeing as the Orange River runs through the zone. The following sources are used to describe the earthquakes and water quality: (a) Earthquake data from the Council of Geosciene (b) ZQM data on NGA temp range between 21-28?C depending on the season with 24?C being the mean.

Abstract

Hydrogeology and hydrology are commonly overlooked aspects of geoheritage, despite strong geological links. Water in all its forms has played a critical role in the development of Earth, and the shaping of its landforms (in addition to sustaining all life on the planet), and access to water has been the core reason for the establishment of numerous human settlements. The evolution of a settlement’s water supply tracks its development history across the Holocene, providing an excellent tool for teaching the public about human interactions with the Earth and our shared future going forward in a changing climate. To this extent, two self-guided trails (with associated guidebooks and mobile apps) have been developed in areas of the Western Cape province of South Africa with rich water supply histories and hydro-geoheritage – the Table Mountain Dams Trail in Cape Town and the Hermanus Water Walk in the Overberg region. The surface and groundwater supply systems that both trails cover have an inherently unique link with the Ordovician-Devonian Table Mountain Group fractured aquifer systems (including the complex tectonic and geomorphic evolutionary history that has led to the present landscapes), which most residents and international visitors are generally unaware of (despite being major tourist regions in South Africa). It is envisioned that through these guides/trails, the reader/walker will gain a better understanding of/appreciation for the value of water, a greater feeling of ownership for the natural history of the city/region they reside in, and will strive to preserve associated hydro-geoheritage for future generations.

Abstract

This keynote paper addresses several issues central to the conference theme of “Change, Challenge and Opportunity”. For hydrogeologists to exert greater influence on groundwater management globally, proper education and training is essential. Universities play a key role in educating hydrogeologists in the fundamental principles of groundwater science through taught Masters and other degree programmes. Scientific associations such as the International Association of Hydrogeologists (IAH) also have an important part to play in education and training through short courses, conferences and mentoring schemes, and in enhancing groundwater science through journal and book publications and scientific commissions. IAH’s mission is to promote the wise use and protection of groundwater and, in this respect, a series of Strategic Overview papers have been prepared to inform professionals in other sectors of the interactions between groundwater and these sectors. Two of the Strategic Overview papers focus on the SDGs and global change, and some of the groundwater challenges in these areas are described. Whilst these challenges will provide hydrogeologists with opportunities to influence global water issues in the 21st century, hydrogeologists will need to be able to communicate effectively with all of the stakeholders, using traditional and more modern forms of communication, including social media.

Abstract

Limestones  and  dolomites  form  an  important  aquifer  system  in  Zambia.  The  municipal  water supplies for Lusaka and several population centres on the Copperbelt all depend on the carbonates for a substantial proportion of their water supply. Currently 155,912 ha of land are irrigated in Zambia, which is about 30 percent of the economical irrigation potential. Development of large scale irrigation schemes from carbonate rock aquifers proves to be a viable groundwater resource in Zambia.

The Katanga carbonate rock aquifers are considered to have good groundwater potential, with high yielding anomalies of up to 60l/s common in certain areas of the country. A phased approach was adopted  to   characterise   the   Katanga   Carbonates   by  means  of  quantifying   the  volume  of groundwater available for abstraction within the geological boundaries. The first phases included geophysical surveys (mainly electrical resistivity and magnetic methods), exploration drilling and aquifer   testing.   Later   phases   included   the   drilling   of   production   boreholes   and   wellfield development. 

Lessons learned during the exploration included the identification of high yielding drilling targets and the role of anomaly frequency in target selection. Further development of the Katanga aquifers for production provided challenges regarding production borehole construction and design. The feasibility of the optimum  design of  production  boreholes versus  the  initial capital  cost of the development of these carbonates proved to be an important consideration in this regard.

Abstract

This paper describes the characteristics of the deep aquifer systems in South Africa as derived from the available data. The study formed part of the larger WRC project K5/2434 (Characterisation and Protection of Potential Deep Aquifers in South Africa). A review of the available literature relevant to potential deep aquifers in South Africa was done to allow characterisation of these aquifer systems. In addition, data obtained from the geological logs of the SOEKOR and KARIN boreholes were considered.

This paper focuses on deep aquifers in 1) the Karoo Supergroup, 2) the basement and crystalline bedrock aquifers, 3) the Table Mountain Group, 4) the Bushveld Igneous Complex and 5) the dolomites of the Transvaal Supergroup. From the available data the deep aquifer systems are described in terms of the following characteristics: lithology, occurrence, physical dimensions, aquifer type, saturation level, heterogeneity and degree of isotropy, formation properties, hydraulic parameters, pressurisation, yield, groundwater quality, and aquifer vulnerability.

The results of the study show that the deep aquifer systems of South Africa are generally fractured hard-rock aquifers in which secondary porosity was developed through processes such as fracturing and dissolution. The primary porosity of most of the rocks forming the aquifers is very low. Apart from the dolomite aquifers, most of the water storage occurs in the rock matrices. Groundwater flow predominantly takes place along the fractures and dissolution cavities which act as preferential pathways for groundwater migration. The aquifers are generally highly heterogeneous and anisotropic.

The deep aquifers are generally confined and associated with positive hydraulic pressures. The groundwater quality generally decreases with depth as the salinity increases. However, deep dolomite aquifers may contain groundwater of good quality. Due to the large depths of occurrence, the deep aquifer systems are generally not vulnerable to contamination from activities at surface or in the shallow subsurface. The deep dolomite aquifers are a notable exception since they may be hydraulically linked to the shallower systems through complex networks of dissolution cavities. The deep aquifers are, however, very vulnerable to over-exploitation since low recharge rates are expected.

Abstract

This paper describes the results of study aimed at consolidating the available data sources on deep aquifers and deep groundwater conditions in South Africa. The study formed part of the larger WRC Project K5/2434 (Characterisation and Protection of Potential Deep Aquifers in South Africa). Since very little is known about the aquifer conditions below depths of 300 m, all groundwater information from depths greater than 300 m was considered to represent the deep aquifer systems. Various confirmed and potential sources of data on deep aquifers and groundwater conditions were identified and interrogated during this study, namely:

1. Boreholes of the International Heat Flow Commission (IHFC). The IHFC database indicates the location of 39 deep boreholes ranging in depth from 300 to 800 m, with an average depth of 535 m.
2. The Pangea database of the International Council for Science (ICSU). The Pangea database has information on 119 boreholes in South Africa, of which 116 are deeper than 300 m.
3. A database on deep boreholes at the Council for Geoscience (CGS). This database contains information on 5 221 boreholes with depths exceeding 300 m.
4. Information on the deep SOEKOR boreholes drilled during the 1960s and 1970s (at least 38 boreholes).
5. Information on deep boreholes from the database of the Petroleum Agency SA.
6. The National Groundwater Archive (NGA) of the Department of Water and Sanitation (DWS).
7. Information derived from the thermal springs in South Africa.
8. Boreholes drilled as part of the Karoo Research Initiative (KARIN).
9. Information on the locations and depths of underground mines in South Africa. Information on the occurrence of deep groundwater could potentially be obtained from these mines.

The study shows that, although information on a vast number of deep groundwater sites is listed in the various databases, the data relevant to the geohydrological conditions are scant at most sites. This paucity of geohydrological data implies that the deep aquifers of South Africa are currently poorly understood.

Abstract

Work is being conducted in Limpopo province following a large volume release of petroleum hydrocarbons that took place from a leaking underground pipeline, resulting in significant groundwater contamination. This is considered to be the largest petroleum hydrocarbon release recorded to date in South Africa. The leak took place for 15 years before it was discovered 13 years ago in 2000. From the pressure tests that were performed, 10-15 ML of A-1 Jet fuel is considered to have  been  released  to  the  subsurface.  Product  bailing was  the  first method  employed  for  the recovery of the free product, and was later replaced with a P&T system which was considered to be more effective.

The village located about 6 km to the north of the spillage depends mostly on groundwater. This paper presents a progress update of works that have been conducted in support of developing a conceptual model which aims to determine the areal extent of the plume.

Abstract

Work is being conducted in Limpopo province following a large volume release of petroleum hydrocarbons that took place from a leaking underground pipeline, resulting in significant groundwater contamination. This is considered to be the largest petroleum hydrocarbon release recorded to date in South Africa. The leak took place for 15 years before it was discovered 13 years ago in 2000. From the pressure tests that were performed, 10-15 ML of A-1 Jet fuel is considered to havbeen  released  to  the  subsurface.  Product  bailing was  the  first method  employed  for  the recovery of the free product, and was later replaced with a P&T system which was considered to be more effective.

The village located about 6 km to the north of the spillage depends mostly on groundwater. This paper presents a progress update of works that have been conducted in support of developing a conceptual model which aims to determine the areal extent of the plume.

Abstract

The Sagole hot spring is located in the northern Limpopo Province of South Africa. Investigations were carried out in order to investigate the groundwater aquifer and water chemistry. Results were envisaged to the understanding of the geothermal potential of the area. Regional scale airborne magnetic data and geology were used for identifying structures and lithological boundaries that are associated with thermal groundwater aquifers. Detailed ground follow-up and verification surveys were  carried  out  across  the  target,  using  magnetic,  electrical  resistivity  tomography  (ERT), frequency-domain electromagnetic (FDEM) and radiometric methods. Water samples were collected from the spring eye and archival groundwater data was analysed. The interpretation of the airborne magnetic data revealed the presence of west to east, northwest and intersecting lineaments at the hot spring. From magnetic data, the groundwater aquifer was found to be capped by basalt with heat rising to the surface along possible geological contacts, faults or fractures. The FDEM profile data across the aquifer zone had peak values above 100 mS/m. The inversion of ERT data defined a highly electrical conductive, low resistivity with thickness of about 60 m. Chemical analysis of the ground water revealed that the water does not have any indication of pollution. The thermal water was found to be of meteoric origin. The drilling of artesian thermal boreholes through the capping basalt should be explored. The hot-water boreholes will be utilised by the community for domestic, irrigation and possible development of micro-geothermal systems.

Abstract

Soil and water pollution are major environmental problem facing many coastal regions of the world due to high population, urbanisation and industrialisation. The hydrofacies and water quality of the coastal plain-sand of part of Eastern Niger-Delta, Nigeria, was investigated in this study. Hydrogeological investigations show that the aquifers in the area are largely unconfined sands with intercalations of gravels, clay and shale which are discontinuous and, however, form semi-confined aquifers  in  some  locations.  Pumping  test  results  show  that  the  transmissivity  ranged  between 152.0 m2/day  and  2 835.0 m2/day  with  an  average  value  of  1 026.0 m2/day,  while  the  specific capacity varied between 828.0 m3/day and 15 314.0 m3/day with a mean value of 6 258.0 m3/day. Well-discharge  ranged  between  1 624.0 m3/day  and  7 216.0 m3/day  with  an  average  value  of 3 218.0 m3/day, while hydraulic conductivity varied between 3.2 m/day and 478.4 m/d with a mean value of 98.6 m/day. These findings indicate that the aquifer in the area is porous, permeable and prolific.

The observed wide ranges and high standard deviations and mean in the geochemical data are evidence that there are substantial differences in the quality/composition of the groundwater within the study area. The plot of the major cations and anions on Piper, Durov, and Scholler diagrams indicated six hydrochemical facies in the area: Na-Cl, Ca-Mg-HCO3, Na-Ca-SO4, Ca-Mg-Cl, Na-Fe-Cl and Na-Fe-Cl-NO3. Heavy metal enrichment index revealed 12 elements in the decreasing order of: Fe > Ni > Cu > Zn > Mn > Cd > V > Co > Pb > Cr > As > Hg. The study identified salt intrusion, high iron content, acid-rain, hydrocarbon pollution, use of agrochemicals, industrial effluents and poor sanitation as contributors to the soil and water deterioration in the area. Saltwater–freshwater interface occurs between 5 m to 185 m, while iron-rich water is found between 20 m to 175 m. The first two factors are natural phenomenon due to the proximity of the aquifer to the ocean and probably downward leaching of marcasite contained in the overlying lithology into the shallow water table, while the last four factors are results of various anthropogenic activities domiciled in the area.

The DRASTICA model, a modification of the DRASTIC model, was developed and used in the construction of the aquifer vulnerability map of the area. Modern sanitary landfill that ensures adequate protection for the soil and groundwater was designed and recommended to replace the existing  open-dumpsites.  Owing  to  the  monumental  and  devastating  effects  of  hydrocarbon pollution in the area, the need to eradicate gas-flaring and minimise oil spills in the area was advocated. Bioremediation and phytoremediation techniques were recommended to be applied in the clean-up of soils and water contaminated with hydrocarbon in the area.

 

Abstract

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

Abstract

The importance of groundwater in South Africa has become evident over the past decades, especially as pressure on surface water resources intensifies in response to increasing water supply demands. Research has significantly progressed on the shallow groundwater resources conventionally used for water supply, and leading on from this deeper groundwater resources have become a focus point as a future water source. This focus on deep aquifers is driven by new developments, such as shale gas development, injection of brines into deep aquifers, carbon sequestration and geothermal energy. The understanding of deep groundwater in South Africa is often limited due to insufficient data at these depths. To develop a body of knowledge on deep geohydrology in South Africa, an investigation on the currently available information was launched to assess potential deep groundwater resources. The investigation formed part of the larger WRC Project K5/2434 (Characterisation and Protection of Potential Deep Aquifers in South Africa). The geology of South Africa was reviewed from a deep groundwater perspective to provide an initial analysis of potential deep groundwater aquifers. The main potential deep aquifers were identified for further investigation using a ranking system, where Rank 1 shows a positive indication, Rank 2 shows some indication, Rank 3 shows a neutral indication, and Rank 4 shows a negative indication for deep groundwater systems. The Rank 1 geological groups include (in no particular order): the Limpopo Belt, Witwatersrand Supergroup, Transvaal Supergroup, Waterberg and Soutpansberg Groups, Natal Group, Cape Supergroup, Karoo Supergroup. In a number of the identified potential deep aquifers, the indicator for deep groundwater flow systems was the presence of thermal springs. Additionally, deep groundwater occurs below the traditionally exploited weathered zone, and the importance of fractured aquifers becomes paramount in the investigation of potential deep aquifers. In conclusion, three main components were considered for the investigation of potential deep aquifers systems, 1) geological groups; 2) thermal springs and 3) depth of fractures. These three components should be used holistically going forward to best characterise the potential deep aquifers of South Africa.