Conference Abstracts
Title | Presenter Name | Presenter Surname | Area Sort descending | Conference year | Keywords | ||||||
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Defining the Goldilocks Zone for Aquifer Thermal Energy Storage versus Unidirectional Ground Source Heat Pumps using Groundwater Flow and Heat Transport Modelling | H | Williams | Spain | 2023 | Aquifer Thermal Energy Storage, Ground Source Heat Pump, Urban Groundwater | ||||||
AbstractAquifer Thermal Energy Storage (ATES) is increasingly utilised to optimise the efficiency of Ground Source Heat Pump (GSHP) systems. However, the criteria for selecting ATES over Unidirectional GSHP is not well-defined. Inappropriate selection of AETS can adversely impact the long-term viability and the GSHP system itself, as well as regional hydraulic and thermal sustainability due to adverse groundwater levels and temperature change. This is a concern in urban aquifers, where GSHP systems are increasingly common. There is a perception that ATES is always the most efficient; however, there is no clear definition of efficiency and how it can be readily assessed at the GSHP design stage. It is proposed and demonstrated herein that GSHP efficiency can be assessed by modelling borehole pumping in lieu of complex Coefficient of Performance calculations for the whole GSHP system. Borehole pumping is a more readily definable modelling outcome for comparing options at an individual site but is also a suitable proxy for comparing efficiency at different sites when given as a flow per unit rate of pumping. Operational efficiencies for ATES versus Unidirectional systems are presented using the pumping rate criteria for modelled scenarios. Here, three model inputs are varied: 1) the balance of heating and cooling, 2) the configuration of a single borehole pair across a hydraulic gradient and 3) the hydraulic gradient itself. These were assessed using coupled groundwater flow and heat transport modelling in Feflow to refine the Goldilocks Zone, the perfect balance, for these variables. |
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Peculiarities of the chemical composition of the Ordovician aquifer as a source of potable water supply (St. Petersburg, Russia) | E | Kayukova | St. Petersburg, Russia | 2023 | aquifer properties, ground water contamination, radon, saturation index | ||||||
AbstractThe Ordovician aquifer of the Izhora deposit is widely used for drinking by the population of St. Petersburg and its suburbs. Carbonate Ordovician rocks are intensively karstified. The water is fresh (0,5-0,8 g/l), bicarbonate-calcium on the predominant ions, pH 7.6; calcium content is 50-80 mg/l, magnesium content is 30-60 mg/l and the total hardness is 7,6-8,0 mg-equ./l. Western, northern and northeastern boundaries of the Izhora deposit go along the Baltic Klint, which is evident on the relief. Its southern boundary is along the zone of the dip of Ordovician limestone beneath the Devonian sandstone. The territory of the Izhora plateau belongs to the areas of intensive economic activity. Often, objects of human economic activity are located near drinking water intakes. Almost all sites are marked by excess sanitary norms of chemical elements. Pollution of groundwater in the Ordovician aquifer has been identified in some areas. Priority substances have been identified for assessing the quality of groundwater: total hardness, Fe, Mn, Ba, and B. According to hydrochemical modelling data, Ordovician groundwater is saturated with calcite over most territory. There are many springs of underground water along the Baltic Klint, for example, near the village of Lopukhinka, Duderhof springs and others. The springs waters have natural radioactivity (due to the contact of groundwater with dictyonema shales), which makes their use hazardous to human health. |
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Test pumping derivative analysis to improve conceptual understanding in a complex aquifer: Steenbras Wellfield. | Kevin | De Bruin | Steenbras Wellfield, Cape Town | 2021 | flow regime analysis, flow models, test-pumping, drawdown derivative curve, hydraulic conductivity, Derivative data | ||||||
AbstractTest-pumping drawdown curves are not always sufficiently indicative of aquifer characteristics and geometry. In fact, drawdown curves should never be analysed and interpreted alone. The derivative analysis (Bourdet et al., 1983) and flow dimension theory (Barker, 1988) make it possible to infer the regional geometries and flow characteristics of fractured aquifers which are otherwise often unknown or inconclusive when interpreting point-source borehole logs. The propagation of the drawdown and/or pressure front through the aquifer reaches distal hydrogeological objects which influence the flow regime and imprints signatures in the drawdown derivative curves. The conjunctive interpretation of these flow regime sequences and geological data results in a robust, well-informed conceptual model which is vital for resource management. A methodology similar to that of A. Ferroud, S. Rafini and R. Chesnaux (2018) was applied to the test-pumping data of 14 confined and unconfined Nardouw Aquifer boreholes in the Steenbras area, Cape Town, which has been under exploratory investigation since the early 2000’s. The Steenbras wellfield was developed following the major 2017-2018 Western Cape drought. The NE-SW trending open folds and dextral strike-slip Steenbras-Brandvlei Megafault Zone (with crosscutting faults and dykes) make the aquifer hydrogeologically complex. It is due to these complexities that the sequential flow regime analysis was undertaken to enhance the current conceptual understanding. The analyses reveal domains of flow models which include open vertical fracture, T-shaped channel, double(triple) porosity model, and leaky/recharge boundary amongst others. Poor data quality and noise issues are also highlighted. The outcomes of the sequential flow regime analysis allow for identification of applicable flow models for type curve fitting to avoid erroneous aquifer parameter estimations; improvement of the hydrogeological understanding of the aquifer; enhancements of the current conceptual model in order to inform on subsequent numerical modelling, groundwater resource management and ecological protection. |
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Stable Isotope Techniques for the Evaluation of Water Sources for Domestic Supply in Stellenbosch, South Africa | Jared | Van Rooyen | Stellenbosch | 2021 | Poster, stable water isotopes, Monitoring, Monitoring, urban water supply | ||||||
AbstractDuring 2017-2018, the City of Cape Town, South Africa faced an unprecedented drought crisis with the six main water storages supplying Cape Town falling to a combined capacity of just under 20%. With the threat of severe water shortages looming, various additional water sources were examined to supplement the municipal water supply network. These were focussed on groundwater, desalination and treated effluent. However, private citizens and businesses also made plans to avoid shortages, resulting in numerous uncontrolled water sources competing with the municipal supply network. Throughout the crisis, groundwater was considered the most important alternative urban water supply source but also the most vulnerable to contamination through accidental and uncontrolled return flows from the municipal network, private residences and agricultural industries. This project aims to constrain the water supply network in the Stellenbosch municipality and monitor the augmentation of groundwater into the network using stable isotopes. Long term monitoring points have been established at 35 tap water sites, 20 private wells as well as at the supply reservoirs that feed the municipal network. Preliminary data show’s distinct isotopic signals associated with each supply reservoir as well as in the local groundwater. The data also shows significant return flow into the alluvial aquifer system during warmer months when private stakeholder’s water consumption is at its highest. Groundwater is expected to supplement this urban supply network in the latter part of 2021 and will likely disrupt the current distribution of stable isotopes in the network, providing further insight into the potential return flow into the local groundwater system. |
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Understanding and Affecting Water Consumer Behavior Using Technological Interventions at a Primary School in Stellenbosch | C. | Ripunda | Stellenbosch | 2017 | Water Consumption, Interventions | ||||||
AbstractThis paper studies and reports the water usage behavior of a primary school. Three interventions were implemented to change this behavior to support water conservation. The aim of the study was to quantify the effects of the technological interventions on behavioral change. The school’s water usage pattern was found to be predictive and regular except for daily losses, which were measured and extrapolated from midnight to early morning volumes. The water usage distribution was Gaussian with the mean being centered around break time. The interventions were able to reduce water consumption of the school by 44% when compared to the use of a school across the road where the interventions were not implemented. |
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A Case Study That Demonstrates The Importance Of Scientific Borehole Yield Testing. | C | Brand | Stellenbosch | 2017 | yield-testing, farmer method | ||||||
AbstractAmongst groundwater users, the importance of a scientific borehole yield test is often highly underrated. From experience, a vast number of groundwater users make use of a method of yield testing known as the ‘farmer test’ or even just the air lift yield obtained when the borehole is drilled. In many cases, a scientific yield test is only conducted so that the borehole can be licensed with the Department of Water and Sanitation. A recent yield test undertaken near Stellenbosch demonstrated the importance of a scientific yield test, and the short comings associated with the “farmer method”. The case study pertains to a borehole where the air lift yield was much higher than expected for the area. The borehole was drilled into a high transmissivity aquifer of limited extent. As such, the yield testing was able to quite quickly detect and demonstrate impacts from aquifer boundary conditions. The case study demonstrates the need for hydrogeological conceptualization of the aquifer and flexibility in designing and modifying the yield test. The safe yield potential of this borehole was reduced from an expected 15 L/second to 0.5 L/second. Aquifer boundary conditions occur at most boreholes to some degree, and this case provides a demonstration of the effect on yield testing. |
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Groundwater monitoring of South Africa through numerical model | Akhona | Maqhubela | Sutherland | 2021 | Monitoring, numerical modelling, GRACE, SG measurements, MODFLOW, SAGOS | ||||||
AbstractMonitoring groundwater storage is conducted in the study. World Health Organisation estimates, about 55 million people affected by drought yearly. However, Surface water holds 0.3 percent of the freshwater, and groundwater holds 30.1 percent of the freshwater. Hence, monitoring groundwater storage is vital. Though the GRACE (Gravity Recovery And Climate Experiment) satellite provides global-scale groundwater data, but does not provide any information about changes in groundwater flow systems and has uncertainties, due to large noise produced. A correlation has to be established between gravity changes and groundwater storage variations through a program that simulates the flow of groundwater. The relationship between developed numerical models and data derived from superconducting gravity is imperative. This study is conducted in South African Geodynamic Observatory Sutherland (SAGOS) area at Sutherland, South Africa. The study aims to develop a numerical geohydrological model to monitor subsurface variations in water distribution through superconducting gravimeters (SG) records. The interpretation of the SG measurements to directly compare to one another at a higher resolution is considered in the study, through the correlation of the developed model and installed superconducting gravimetric residual data. A numerical groundwater flow model is developed using model muse on MODFLOW. Assigned boundary conditions, fractured rocks were activated by the model. Hydraulic conductivities were simulated for any layer, including storage coefficient. Hence, hydraulic conductivity is an important aspect of the study. In conclusion, gravity is an excellent tool for measuring groundwater recharge within the immediate vicinity of the SAGOS. This implies that gravity can aid in monitoring groundwater recharge and discharge in semi-arid areas. The application of the hydrological model at various scales comparing the Superconducting Gravimeter and GRACE satellite data is paramount to improve modelling groundwater dynamics. The consideration of developing numerical hydrological to monitor groundwater storage will add much value to missing information. |
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Groundwater Development For The Swartland Municipal Area In Response To The 2017/2018 Drought. | Charl | Muller | Swartland Municipal Area | 2019 | groundwater exploration, wellfield testing, FRA | ||||||
AbstractThe Western Cape has experienced a drought since 2015 and one of the regions most adversely affected by this drought was the Swartland. Towns in this region make use of water supplied by the Vo?lvlei Dam, which is the Swartland Municipality's bulk and only source of water. Groundwater exploration was undertaken to find alternative sources of water which would be used to relieve some of the pressure on surface water resources. A total of seven towns and communities were identified as high risk and most vulnerable. These include Abbotsdale, Koringberg, Malmesbury, Moorreesburg, Riebeek Kasteel, Riebeek West and Riverlands. This project posed several challenges, namely: available land, proximity to infrastructure and unfavourable geology (in terms of groundwater potential). The project had mixed results in terms of quality and yield. This paper presents the approach and results of the groundwater development. |
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The Thermal Springs Of Swaziland – A Review | Nicholas | Robins | Swaziland | 2013 | thermal springs, hydrochemical | ||||||
AbstractThe thermal springs of Swaziland and adjacent KwaZulu-Natal have, over the years, attracted attention from hydrogeologists, hydrochemists and structural geologists. While some of the springs in Swaziland are well known amenities, others are less well-visited and some difficult to access. There are eleven warm springs in Swaziland, discharging between 1 and 10 l/s from Precambrian age rocks; all are situated at or near valley bottoms. The springs have surface discharge temperatures of between 25 and 52 oC and total dissolved solids concentrations of less than 400 mg/l. In all cases the water is meteoric in origin. Geothermometry indicates that maximum temperatures up to 100 oC are achieved during circulation. If the average geothermal gradient is about 20 oC/km as recorded in a deep mine at Barberton, then this would require circulation up to a depth of several kilometres. However, it is likely that circulation bottoms at about 1 km, as pressure of overburden inhibits dilation of fractures at such depths, and the excess temperature may derive from a locally enhanced geothermal gradient. The discharge water is young, with 14C ages of between 4 000 and 5 000 years. |
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A stochastic data integration approach to generate geologically consistent hydrogeological models from geophysical and hydrogeological data | A | Neven | Switzerland | 2023 | Hydrogeophysics; Inversion; Data-Integration; Groundwater | ||||||
AbstractThis study presents a novel approach for developing geologically and hydrogeologically consistent groundwater models at large valley scales. Integrating geological, geophysical, and hydrogeological data into a single model is often challenging, but our methodology overcomes this challenge by combining the Ensemble Smoother with Multiple Data Assimilation algorithm (ESMDA) with a hierarchical geological modelling approach (ArchPy). The ESMDA framework assimilates geophysical and hydrogeological field data jointly. To diminish the computational cost, the forward geophysical and groundwater responses are computed in lower-dimensional spaces relevant to each physical problem, alleviating the computational burden and accelerating the inversion process. Combining multiple data sources and regional conceptual geological knowledge in a stochastic framework makes the resulting model accurate and incorporates robust uncertainty estimation. We demonstrate the applicability of our approach using actual data from the upper Aare Valley in Switzerland. Our results show that integrating different data types, each sensitive to different spatial dimensions enhances the global quality of the model within a reasonable computing time. This automatic generation of groundwater models with a robust uncertainty estimation has potential applications in a wide variety of hydrogeological issues. Our methodology provides a framework for efficiently integrating multiple data sources in geologically consistent models, facilitating the development of hydrogeological models that can inform sustainable water resource management. |
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Radical evolution of the Geneva transboundary aquifer agreement: an example for the sustainability of TBA governance? | Gabriel | de los Cobos | Switzerland | 2023 | Geneva aquifer, MAR, Climate change, Governance, transboundary aquifer agreement | ||||||
AbstractThe Geneva aquifer is internationally recognized for its transboundary resource management agreement between Switzerland and France, described as the first groundwater management agreement in the world. Signed in 1978 and renewed in 2008, this agreement on managing a shared underground resource has long been an example for establishing other agreements worldwide, particularly by UNESCO and its hydrological program via the TBA commission of the IAH. Like many countries worldwide, Switzerland and France experienced a critical summer of 2022 concerning the use of water resources, both surface and underground. The system applied in the cross-border agreement for using the aquifer involves French participation in the costs of managing aquifer recharge (MAR), depending on the total pumping. It shows that the French part, having consumed more water to compensate for the extreme drought of 2022, has seen its bills increase considerably. Development plans show that the population of Greater Geneva will increase considerably by 2030-2040, requiring significant medium-term water availability (30% additional water). Therefore, the French institutions’ political leaders have formally asked the authorities of the canton of Geneva to review the conditions linked to the quotas and calculation methods included in the 2008 agreement. A new agreement could be a real example of positive cross-border coordination for decision-makers finding themselves in a blocked or even conflicting situation due to differences in managing a shared resource revived by the effects of climate change. |
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Multiple-tool approach of combining microbial markers with artificial and natural tracers to specify the origin of faecal contamination on karst groundwater catchment scale | M | Sinreich | Switzerland | 2023 | Karst spring, MST, Catchment, faecal indicators, toolbox, tracers | ||||||
AbstractDiverse tools exist to study the transfer of contamination from its source to groundwater and related springs. A backward approach, i.e. sampling spring water to determine the origin of contamination, is more complex and requires multiple information. Microbial source tracking (MST) using host-specific markers is one of the tools, which, however, has shown to be insufficient as a stand-alone method, particularly in karst groundwater catchments. A karst spring in the Swiss Jura Mountains was studied concerning the occurrence and correlation of a set of faecal indicators, including classical parameters and bacteroidal markers. Sporadic monitoring proved the impact on spring water quality, mainly during high water stages. Additional event-focused sampling evidenced a more detailed and divergent pattern of individual indicators. A multiple-tool approach, complementing faecal indicator monitoring with artificial tracer experiments and measuring natural tracers, could specify the origin of ruminant and human faecal contaminations. Natural tracers allowed for distinguishing between water components from the saturated zone, the soil/epikarst storage, or freshly infiltrated rainwater. Additionally, the breakthrough of injected dye tracers and their remobilization during subsequent recharge events were correlated with the occurrence of faecal markers. The findings hypothesize that human faecal contamination is related to septic tanks overflowing at moderate rainfall intensities. Linkage with vulnerability assessment and land-use information can finally better locate the potential point sources. Such a toolbox provides useful basics for groundwater protection and catchment management and insight into general processes governing the fate and transport of faecal contaminants in karst environments. |
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Spatiotemporal Water Budget Calculation At The Regional-Catchment Scale Using Remotely Sensed Data: A Case Study From The Thur Catchment, Switzerland | Nicole | Burri | Switzerland | 2019 | Spatiotemporal water budget, ultiparameter, data-assimilation, Groundwater, surface water | ||||||
AbstractFor sustainable water resource management it is crucial to assess the water budget. However, estimating a region's spatiotemporal water budget is fraught with difficulties. The heterogeneous nature of every hydrological system poses major obstacles, particularly at the regional scale where monitoring data are scare. This is further complicated by rapidly changing climatic and land use trends. When estimating water availability and its distribution, the presence and sustainability of groundwater is a vital factor to consider: adequate recharge, whether natural or artificial, can ensure both the productivity of an aquifer as well as the health of its associated aquatic habitats. In order to ameliorate water budget estimates at the regional scale (>1000 km2) we investigate the capability of a multiparameter data-assimilation approach for the Thur catchment in Switzerland, with a focus on the exchange of surface water and groundwater in unconfined aquifers. With a catchment size of ~1700 km2, a dynamic topography (elevation ranging from 356 - 2505 m.a.s.l.), underlain by both consolidated and unconsolidated lithologies, no major barriers along the length of its course (~130 km), naturally variable discharge rates (3 - 1129 m3s-1), an annual average rainfall of 2,701 mm, and 10 operational gauging stations, the Thur River is well suited to this study. We aim to determine 1) the usefulness of multiparameter techniques, particularly when used in conjunction with remotely sensed data, 2) the catchment-wide spatiotemporal water distribution and budget, and 3) the groundwater storage potential within the catchment. Historic and current precipitation data, along with evapotranspiration estimates, a product derived from the MODIS sensor on board the Terra satellite, was used in conjunction with measured long-term hydrological discharge data, groundwater levels, and hydrogeochemical parameters. A remotely sensed water balance was determined for the years 2001 - 2017 and compared to spatiotemporal and statistical geochemical water characteristics from long-term surface water and groundwater monitoring sites. The results are used to determine the primary physical processes involved in regulating the catchment's water distribution. Our working hypothesis suggests that, when coupled with available hydrogeochemical water quality data and geological information, the remotely sensed water budget can be used as a tool to determine the physical processes governing the distribution of a catchment's available water. We aim to determine 1) the usefulness of multiparameter techniques, particularly when used in conjunction with remotely sensed data, 2) the catchment-wide spatiotemporal water distribution and budget, and 3) the groundwater storage potential within the catchment. Historic and current precipitation data, along with evapotranspiration estimates, a product derived from the MODIS sensor on board the Terra satellite, was used in conjunction with measured long-term hydrological discharge data, groundwater levels, and hydrogeochemical parameters. A remotely sensed water balance was determined for the years 2001 - 2017 and compared to spatiotemporal and statistical geochemical water characteristics from long-term surface water and groundwater monitoring sites. The results are used to determine the primary physical processes involved in regulating the catchment's water distribution. Our working hypothesis suggests that, when coupled with available hydrogeochemical water quality data and geological information, the remotely sensed water budget can be used as a tool to determine the physical processes governing the distribution of a catchment's available water. Understanding a catchment's spatiotemporal water distribution will help determine where water bodies could be suitably buffered, either through the rehabilitation and protection of wetlands and river reaches or via managed aquifer recharge, in order to abate the effects of increasing water demand, and climate and land use change on the water budget. |
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Tracer applications in an urban MAR (Rhine) scheme: Identifying the presence of regional groundwater in a complex geological setting | Jared | van Rooyen | Switzerland | 2023 | Isotopes, MAR, Online monitoring, Urban Groundwater | ||||||
AbstractManaged aquifer recharge (MAR) has become increasingly popular in Central Europe as a sustainable, clean, and efficient method for managing domestic water supply. In these schemes, river water is artificially infiltrated into shallow aquifers for storage and natural purification of domestic water supply, while the resulting groundwater mound can simultaneously be designed to suppress the inflow of regional groundwater from contaminated areas. MAR schemes are typically not managed based on automated optimization algorithms, especially in complex urban and geological settings. However, such automated managing procedures are critical to guarantee safe drinking water. With (seasonal) water scarcity predicted to increase in Central Europe, improving the efficiency of MAR schemes will contribute to achieving several of the UN SDGs and EU agendas. Physico-chemical and isotope data has been collected over the last 3-4 decades around Switzerland’s largest MAR scheme in Basel, Switzerland, where 100 km3 /d of Rhine river water is infiltrated, and 40 km3 /d is extracted for drinking water. The other 60 km3 /d is used to maintain the groundwater mound that keeps locally contaminated groundwater from industrial heritage sites out of the drinking water. The hydrochemical/isotope data from past and ongoing studies were consolidated to contextualize all the contributing water sources of the scheme before online noble gas and regular tritium monitoring commenced in the region. The historical and the new continuous tracer monitoring data is now used to inform new sampling protocols and create tracer-enabled/assimilated groundwater-surface water flow models, vastly helping algorithm-supported MAR optimization |
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Assessing aquifer vulnerability using tritium and machine learning in Africa’s western Sahel | Joel | Podgorski | Switzerland | 2023 | Groundwater, groundwater mapping, groundwater recharge, Groundwater Vulnerability, Isotopes, Machine learning, Tritium | ||||||
AbstractUnderstanding 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. |
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Hydrodynamic and Hydrochemical characterization of groundwater resources of a municipality in Switzerland | Cedric | Meier | Switzerland | 2015 | |||||||
AbstractThe study characterized the hydrodynamic and hydrochemical properties of the quaternary porous aquifer which supplies the municipality of Pont-en-Ogoz (Department of Fribourg in Switzerland) with drinking water. The hydrostratigraphic series is composed of a thin overburden material, a porous aquifer composed of gravel and sand, a thin silt-clay layer and sandstone that forms the deeper aquifer. Pumping tests of a borehole nearby the well PSG1 and well PSG1 itself was used to calculate a mean hydraulic conductivity of the aquifer. The hydraulic conductivity from the test varies between 7.4?10-7 m/s and 2.4?10-5 m/s. The values of hydraulic conductivities are typical for sedimentary rocks as silt, fine sandstone and fine sand. The main physical and chemical parameters like concentration in cations and anions, as well the pH, the dissolved oxygen, the electrical conductivity and the alkalinity were measured and saturation indices were calculated. The analysis of the physical and chemical parameters shows that the type of water is Ca-HCO3 and that it contain mixture of old water coming from a regional groundwater flow system, probably from the deeper aquifer, and from recently infiltrated water as local groundwater flow system. The quality of water is generally good, but the effect of the purification of it through the thin overburden layer is limited. An initial one dimension steady state models based on the hypothesis of Dupuits for an unconfined and confined aquifer was used to calculate the mean recharge. This model gives us a recharge values from 24.8 cm/year and 12.1 cm/year, respectively. A second, two dimensional, confined, homogeneous and isotropic model has been calibrated in order to represent the spatial distribution of the piezometric surface. All the models have been calibrated as a steady state. Two groups of predictive scenarios were done to evaluate the drawdown in the well PSG1 using the 2D model. The maximum drawdown calculated was 40 m for the first group of scenarios and 3-4 m for the second group. The second group of scenarios considered from the deeper sandstone aquifer contributing to the well PSG1. The results of the second group of scenarios fit the field results better and the capture zone is much smaller than the one from the first model. The reality is probably between those two models. In order to lower the uncertainty, spatial variation should be added |
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Observation and monitoring of field parameters for springs and rivers of a Swiss alpine valley in relation to seasonality. | Cedric | Meier | Switzerland, France | 2021 | Monitoring, data management, data science libraries, Water security, Groundwater Sampling, training, municipal water supply | ||||||
AbstractThe study area is located in a Swiss alpine valley at the border between Switzerland and France and is situated in Valais. It is delimited by the hydrologic catchment of the river “La Vièze de Morgins”. The catchment area is situated in the Municipality of Troistorrents and of Monthey. Its population is approximately 4500 inhabitants. From the geological point of view, the valley “Val de Morgins” is mostly comprised of sedimentary rocks, amongst others breccia, schist, flysch, limestone, and quaternary sediments. The valley is affected by several natural hazards, such as landslides, rockfalls, and avalanches. Hydrogeologically, the valley contains few main springs that are outlets of porous and fissured aquifers. For this study, an inventory and monitoring of springs and rivers has been carried out since 2018 until April 2021. Particularly, more than 110 springs and rivers have been registered and observed during this time. The data includes GPS coordinates, photos, measurements of physical-chemical parameters and flowrates. Complementary to measurements, specific geological and topographical maps, and site information have been gathered. The analysis and interpretation of this huge set of hydrogeological data will be concluded with a new and innovative approach using different data science libraries that are implemented for the Python programming language. In this case study, groundwater sampling training is used to increase the understanding of the water quality. Four years of field measurements enable a better understanding of the parameter variability in relation to seasonality. Furthermore, new data analysis can aid the integrated resource management for the municipal water supply. The sampling and monitoring are key aspects to ensure water security, in terms of quality and volume. Additionally, it can also unlock prospective groundwater resources for municipal water supply. Case study data will also be compared with South African and other Swiss dataset of similar aquifer type. |
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Experiments of the artificial-recharge rate of sand and gravel aquifer through shallow recharge wells in the Chao Phraya River basin region | Kwankwai | Daranond | Thailand | 2023 | MAR, Managed aquifer recharge, clogging, recharge rate | ||||||
AbstractThe aquifers in the Chao Phraya River basin region were abundant in groundwater. Lately, the groundwater level has been declining due to agricultural activities. While in the wet season, these areas frequently suffered from flooding due to lower elevation than their surroundings. The Managed Aquifer Recharge (MAR) methods were applied to ease problems by constructing artificial recharge wells which can detain stormwater runoff and let it gradually infiltrate into the aquifer directly. For decades, the Department of Groundwater Resources started the MAR project to alleviate groundwater depletion and flooding over specific areas. However, most of the projects in the past lacked follow-up results and evaluation. Thus, later projects attempted to study recharge processes to evaluate the volume of recharged water through structures and calculate the infiltration rate through filter layers within the structures. Recently, the field experiments of artificial groundwater recharge were conducted as 8-hour and 20-day experiments with shallow recharge wells in the Chao Phraya River basin regions. These two types of experiments provided similar results. The average recharge rates of 8-hour and 20-day experiments are 2.22 m3/hr and 2.57 m3/hr, respectively. Recharge rates of each well were independently distinct depending on sedimentation characteristics, aquifer thickness, and volume of dry voids. During the test, the recharge well continuously encountered the problem of sediment clogging due to using untreated water from neighbouring streams and ponds. This clogging issue needed to be treated regularly to maintain the efficiency of the recharge well. |
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Water allocation and economic analysis for developing groundwater resources | P | Tungkidwanichakul | Thailand | 2023 | Epanet, WUSMO, groundwater management | ||||||
AbstractThailand has been grappling with a water scarcity problem every year, leading to insufficient water supply for consumption in many areas. To tackle this issue, groundwater is developed from large sources, making water allocation and economic analysis essential for measuring investments in water supply projects. This research study analyzes the water allocation for consumption and irrigation, including the water sent to hospitals, in two areas, Si Somdet & Roi Et Province and Nong Fai. The study uses the WUSMO program to analyze irrigation water and the EPANET program to analyze the entire water allocation system. The expected results include the appropriate allocation of water for maximum benefit, considering both delivery time and the amount of water to ensure adequate delivery. The study provides a guideline for effective and sustainable water allocation and management, including appropriate and sufficient water costs for managing the water distribution system in both areas. The results show that a water rate of 19 baht per cubic meter in Si Somdet & Roi Et Province results in a B/C value of 1.04 and an EIRR of 6.48%, while a water tariff of 15 baht per cubic meter in Nong Fai results in a B/C of 1.01 and an EIRR of 6.16%. The study highlights the importance of regular analysis of water allocation and cost-effectiveness of projects to ensure sustainable and efficient water management for the people. |
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Integrated assessment of groundwater potential zones for deep groundwater exploration in hard rock aquifers using GIS and geophysical techniques: A case study of Huai Krachao, Kanchanaburi, western Thailand | Vanachawan | Hunyek | Thailand | 2023 | Deep groundwater exploration; Hard rock aquifer; groundwater potential zones; Analytical Hierarchy Process; weighted overlay analysis; spring | ||||||
AbstractGroundwater is an important freshwater supply that has a significant role in the economy. However, water is increasingly becoming scarce in several regions. Huai Krachao Subdistrict in Kanchanaburi Province is an example of an area that has been experiencing a severe drought for decades due to the impacts of climate change. This study was conducted to delineate the groundwater potential zones in hard-rock terrains using geographic information system (GIS) techniques. The study aims to explore deep groundwater resources in challenging areas and propose alternative methods supporting traditional groundwater exploration. This finding revealed that the groundwater potential zones were classified into high, moderate, and low potential zones based on the groundwater potential index (GWPI), integrated using the Weighted Index Overlay Analysis. The computed weights from the Analytical Hierarchy Process were acceptable and consistent. The high potential zones mainly occur in the Silurian-Devonian metamorphic rocks. The GIS-based analytical results were later prepared for detailed field investigation, including collecting well information and conducting the 2-dimensional geophysical survey. To prove the GWPI map, 9 groundwater wells were drilled in the high potential zones. Consequently, well yields obtained from the pumping-test analysis ranged from 24-40 m3 / hr, some of which are springs rich in dissolved minerals. Accordingly, a significant amount of water could meet the water demand, supplying about 1 million m3 /year. Under these circumstances, discovering new groundwater resources can support roughly 5,000 people and agricultural lands no less than 480 hectares (4.8 km2 ). |
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Petroleum Hydrocarbon Contamination In Soil And Groundwater: Case Study On The Coastal Tank Farm, Southern Africa | Pieter | Badenhorst | The Coastal Tank Farm, Southern Africa | 2013 | petroleum, Hydrocarbon, contamination, Groundwater, case study | ||||||
AbstractIn this study, a petroleum hydrocarbon contamination assessment was conducted at a cluster of petroleum products storage and handling facilities located on the Southern African Indian Ocean coastal zone. The Port Development Company identified the need for the assessment of the soil and groundwater pollution status at the tank farms in order to develop a remediation and management plan to address hydrocarbon related soil and groundwater contamination. Previous work conducted at the site consisted of the drilling and sampling of a limited number of boreholes. The current investigation was triggered by the presence of a free-phase product in the coal-grading tippler pit located ~350 m down gradient and south-east and east of the tank farms, rendering the operation thereof unsafe. The assessment intended identifying the source of product, distribution and mobility, the extent of the contamination, and the human health risks associated with the contamination. To achieve these, the investigation comprised site walkover and interviews, drilling of 76 hand auger and 101 direct push holes to facilitate vertical soil profile VOC screening and sampling (soil and groundwater), as well as granulomeric analysis to understand grain size distribution within the soil profile. The highest concentrations were associated with the coarse sand layers with the highest permeability. Free-phase hydrocarbons product was found in holes adjacent to the pipeline responsible for the distribution of the product from the jetty to the different tanks farms. Of the 57 soil samples, 21 had high values of GRO and DRO, with 22 below Detection Limit and 14 can be described having traces of hydrocarbon. Both TAME and MTBE were detected in most of the water samples, including from wells located far down gradient. The groundwater sink, adjacent to the pipeline running from west to east, resulted in the limited lateral spread of MBTE in this area, with limited movement towards the sea. The depth of the soil contamination varies over the sites. Based on the site assessment results it was concluded that most of the groundwater contamination, which is a mixture of different product types, is associated with the pipeline responsible for transporting product from the jetty to the different petroleum companies. |
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Effects Of Dolerite Intrusions On The Geohydrology Of Upper Karoo Sediments In The Elundini Area, South Africa | Jakobus | Prinsloo | The Elundini Area, South Africa | 2013 | Geohydrology | ||||||
AbstractThe Karoo Supergroup has a hydrogeological regime which is largely controlled by Jurassic dolerite dyke and sill complexes. The study area is located in the north-eastern interior of the Eastern Cape Province, close to the Lesotho border. The sedimentary rocks of the upper Karoo constitute fractured and intergranular aquifers, due to relatively hydro-conductive lithologies. The main groundwater production targets within the upper-Karoo are related to dolerite intrusions that have a number of characteristics that influence groundwater storage and dynamics. Magnetic, electromagnetic and electrical resistivity geophysical techniques are used to determine the different physical characteristics of the dolerite intrusions, such as size, orientation and the level of weathering. Trends in the data collected from a large-scale development programme can provide evidence that intrusion characteristics also play a role in determining the hydrogeological characteristics of the area. Interpreted geophysical borehole drilling, aquifer testing and water chemistry data can be used to indicate hydrogeological differences between dolerite intrusion types. Observed trends could be used for more accurate future well-field target areas and development. |
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Effects Of Dolerite Intrusions On The Geohydrology Of Upper Karoo Sediments In The Elundini Area, South Africa | J | Prinsloo | The Elundini Area, South Africa | 2013 | Dolerite Intrusions, Geohydrology, Groundwater | ||||||
AbstractThe Karoo Supergroup has a hydrogeological regime which is largely controlled by Jurassic dolerite dyke and sill complexes. The study area is located in the north-eastern interior of the Eastern Cape Province, close to the Lesotho border. The sedimentary rocks of the upper Karoo constitute fractured and intergranular aquifers, due to relatively hydro-conductive lithologies. The main groundwater production targets within the upper-Karoo are related to dolerite intrusions that have a number of characteristics that influence groundwater storage and dynamics. Magnetic, electromagnetic and electrical resistivity geophysical techniques are used to determine the different physical characteristics of the dolerite intrusions, such as size, orientation and the level of weathering. Trends in the data collected from a large-scale development programme can provide evidence that intrusion characteristics also play a role in determining the hydrogeological characteristics of the area. Interpreted geophysical borehole drilling, aquifer testing and water chemistry data can be used to indicate hydrogeological differences between dolerite intrusion types. Observed trends could be used for more accurate future well-field target areas and development. |
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Development Of The Evander Goldfields 3-D Mine Void Model | Martin | Holland | The Evander Goldfield, Mpumalanga | 2013 | development, gold mining | ||||||
AbstractPOSTER The Evander Goldfield basin has been mined since the early 1950s at depths between 400 and 2 000 m below ground and is detached from the larger Witwatersrand basin. The assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in the Witwatersrand basin as more mine shafts mothballs and dewatering ceases. The development of a 3-D mine void model is crucial in predicting the rate of flooding as the prediction of the groundwater rebound is primarily driven by the volumes of mine voids along with the amount of recharge. All available mine plan data for the Evander Gold Mine (EGM) were obtained digitally from Harmony Gold. However, the majority of the old mine workings (e.g. Leslie and Winkelhaak) were available as 2-D data and elevations of the mine developments (stopes and drives) had to be captured from hardcopy plans. Data from the more recent mining operations (e.g. Shaft 6), including updated survey and mine plan data, were directly used for the development of the 3-D void model. The calculated mine void volume, based on the EGM operations mine plan data, is approximately 80 518 045 m3. The mine void calculations were checked against the total tons of rock milled by the EGM operations since the late 1950s and was considered valid estimations of the EGM mine void volume. The validated EGM 3-D mine workings plan was subsequently used to determine the stage- volume relationships. The 3-D mine void model established, will then be incorporated into a regional numerical groundwater flow model to be calibrated against observed abstractions and water levels and utilised to predict future dewatering rates. |
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Linking Geology And Wildlife Water Supply In The Hwange National Park, Kalahari Basin | David | Love | The Hwange National Park, Kalahari Basin, Zimbabwe | 2013 | Water supply, Geology | ||||||
AbstractMost of the 14 651 km2 Hwange National Park in Zimbabwe is on monotonous Aeolian sands of the Kalahari Basin, with endorheic drainage. The large game populations of the park are sustained by seasonal accumulations of water in grassy pan depressions and year-round supply of groundwater to pans (except in the northwest where there are rivers and dams). Some of this is from natural seeps, such as at the Shakwanki, Nehimba and Ngweshla Pans, but most are supplied from boreholes. Game animals show clear preferences for some pans over others and it has long been speculated by wildlife managers that there is a nutritional or taste basis for this discrimination. In this preliminary study, the location, host geology and sub-Kalahari lithologies of the pans are compared with the frequency of use by game animals. Results show that the pans that are most frequented by game are hosted in fossil drainage channels, with limestone horizons (calcrete) developed within the Kalahari Sands. Many popular pans are also found on Kalahari Sand overlying the granitic rocks and the meta- sedimentary Malaputese Formation of the Kamativi–Dete Inlier. This can be related to sodium and potassium enrichment. |
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Modelling Of Impacts Of Fracking On The Karoo Groundwater Systems | Jennifer-lee | Pretorius | The Karoo | 2013 | Fracking | ||||||
AbstractPOSTER Hydraulic fracturing, also known as hydrofracking or fracking, is being engaged in the Karoo region of South Africa in order to enhance energy supplies and improve the economic sector. It will also lead to independence in terms of reduced amount of imports for fuel due to an estimated 13.7 trillion cubic metres of technically recoverable shale-gas reserves in South Africa. Fracking is an extraction technique used with the purpose of having access to alternative natural methane gas, which is interbedded in shale deposits deep under the surface of the earth. In this process boreholes are drilled horizontally into shale formations to cover a larger area in the shale and subsequently attain more natural gas. After these horizontal boreholes are drilled, large volumes of water, mixed with chemicals and sand, are pumped into these boreholes under a very high pressure, forcing the natural gas out. This water mixture is referred to as the fracking fluid. Water is the main component in the fracking fluid and the water used for the fluid reaches volumes up to 30 million litres per borehole. The aim of this study is to present a baseline study of the area and its water resources to ultimately facilitate in resolving the actual impact hydraulic fracturing will have in the area, using a simulation model which will predict the migration of the fracking fluid in the subsurface. In this model, the chemistry of the fracking fluid will be included to determine the impact it might have on the groundwater quality in the area |
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Hydrogeology Of The Kosi Bay Lakes System, South Africa | Mbali | Ndlovu | The Kosi Bay Lakes, KwaZulu-Natal, South Africa | 2013 | Hydrogeology, Groundwater | ||||||
AbstractPOSTER Lake Kosi Bay is an estuary-linked lake system composed of four interconnected lakes, namely Makhawulani , Mpungwini , Nhlange , Amanzamnyama and interconnecting channels, which drains via a sandy opening to the Indian ocean and three extensive areas of swamps (Wright 2002 ). The Kosi Bay lake system is considered as the most pristine lake system on the South African coast and has been used as a recreational fishing destination since 1950 (James et al. 2001). The lakes are separated from the ocean by a strip of forested sand dunes (South African Wetlands Conservation Programme 1999; Wright 2002). Groundwater utilisation in the area ranges from extraction of seasonal groundwater from shallow, hand-dug wells to drilling of boreholes for family or communal use and development of groundwater well-fields for agricultural projects (Botha et al. 2012). The exact amount of abstraction of the groundwater is unknown. The Kosi Bay system is situated on the northern KwaZulu-Natal coast, 2.9 km south of the Mozambique international boarder. According to a Statistics South Africa survey (2007), the approximate population is 163 694. The Kosi system falls under the UMkhanyakude District Municipality, which covers more than 128 818 km2. The travelling distance from north of Durban is 470 km and coordinates of the Kosi Bay system are 2650S-2711S, 3238E- 3253 (Write et al. 1997). The catchment has an area of about 304 km2. The Kosi Bay system is principally clean, white sands, particularly in the northern most reaches where tidal influences are most marked and the system experiences a seasonal inflow of fresh water into its heard (Andeas Holbach 2012). |
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An Updated Hydrogeology Concept Within The Kruger National Park Southern Supersite | Ashton | van Niekerk | The Kruger National Park, Limpopo, Mpumalanga | 2013 | Hydrogeological, ERT | ||||||
AbstractPOSTER Electrical Resistivity Tomography (ERT) surveys were conducted in the Kruger National park (KNP) as part of a recent Water Research Commission project (titled: Surface water, groundwater and vadose zone interactions in selected pristine catchments in the Kruger National Park). The surveys were carried out in a pristine ephemeral third-order supersite catchment, namely the southern granite (Stevenson Hamilton). This supersite is representative of the southern granite region of KNP as it covers part of the dominant geology, rainfall gradient and dominant land system. Electrical resistivity profiling provided valuable data on the subsurface geological material distribution and results depended on soil/rock properties, water content and salinity. The purpose of electrical surveys was to characterise the hydrogeological components of weathering and depth to water level using the subsurface resistivity distribution. The ground resistivity is related to various geological parameters such as the mineral and fluid content, porosity and degree of water saturation in the rock. Based on the initial ERT survey interpretations, boreholes were drilled providing actual subsurface results in the form of borehole drilling logs, water levels, hydraulic data and in situ groundwater quality parameters. Integrating the ERT survey data with the results from the intrusive survey enabled an updated conceptualisation of groundwater flow characteristics and distribution across the southern granite supersite. |
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Showcasing a global-scale, 3D coastal groundwater salinity model | J | King | The Netherlands | 2023 | coastal aquifers, global modelling, groundwater salinity, paleo-reconstruction, parallel. SEAWAT, sea level rise | ||||||
AbstractBeing extensively available and of high quality, groundwater is the primary source of freshwater in coastal regions globally. However, due to anthropogenic and natural drivers, groundwater salinisation is a growing threat to this resource’s long- and short-term viability. The causes and timescales of aquifer salinisation are complex and difficult to quantify, information essential for suitably timed mitigation strategies. One way to inform these strategies and develop storylines of future freshwater (un)availability is through 3D groundwater salinity modelling. These models can predict current groundwater distributions and quantitatively assess the impacts of a projected increase in groundwater extraction rates and sea-level rise. Until recently, detailed 3D models on this scale have been largely unattainable due to computational burdens and a shortage of in-situ data. Fortunately, recent developments in code parallelization, reproducible modelling techniques, and access to high-performance computing (e.g., via parallel SEAWAT) have made this feasible. Machine learning and data mining developments have also allowed an unprecedented opportunity to constrain and calibrate those models. With this in mind, we present our progress towards global 3D salinity modelling by showcasing a regional-scale model in the Mediterranean Sea area. This test case uses newly developed, automated geological and salinity interpolation methods to create initial conditions while implemented in a parallelized version of SEAWAT. The modelling outcomes highlight the potential of supra-regional scale modelling in the context of global (planetary) processes and localised anthropogenic effects. |
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onitoring a deep fresh-saline water interface using repeatVertical Electrical Soundings measurements | S | Meekes | The Netherlands | 2023 | Fresh-saline interface, Geo-electrical, Monitoring, Vertical Electrical Sounding | ||||||
AbstractMonitoring deep (~100 – 200 m) fresh-saline water interface is a challenge because of the low spatial density of deep boreholes. In this project, Vertical Electrical Soundings measurements were used to evaluate changes in the depth of the interface over various decades. Water quality monitoring is a well-known application of geo-electrical measurements but generally applies to the relatively shallow subsurface. In this case study, the saline groundwater interface is around 120 -200 m deep, and the time interval between the measurements is several tens of years. Several locations showing good-quality existing VES-measurements acquired in the last century were selected to see whether repeat measurements could be performed. The number of locations where a repeat measurement could be performed was limited due to the construction of new neighbourhoods and greenhouse complexes. When interpreting the measurements for the change in the depth of the fresh-salt interface, it is assumed that the transition from fresh to saline groundwater occurs over a small depth range and that the electrical conductivity of the fresh water above this interface has not changed. However, it turned out that the ion concentration of the groundwater in the layers above the fresh-saline interface had increased sharply at almost all locations. This complicated the approach, but still, useful results could be obtained. Based on the measurements, it can be said that the fresh-saline water interface has shifted downwards at 3 locations, and hardly any change has occurred at 5 locations. |
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Evaluation of the conditions that impact the spreading, impact and groundwater monitoring for the risk of brine leakage from wells into fresh groundwater aquifers | Niels | Hartog | The Netherlands | 2023 | Groundwater Contamination, brines, density-driven flow, groundwater monitoring, leakage risk | ||||||
AbstractContamination of fresh groundwater aquifers by leakage of saline water (brine) from wells may result from various activities, such as salt mining, wastewater or concentrate injection and geothermal heat production. Here, the brine transport and consequences for groundwater monitoring have been explored for a wide range of brine compositions, leakage and hydrogeological conditions using numerical simulations that considered buoyancy impacts from both temperature and density differences. Results show that at close distances to the leak (up to 3-5 meters away), breakthroughs of the salt ( at 1,000 mg/L) occurred within one month of leakage in all modelled scenarios. At a radial distance of 10 meters, with a leak rate of 2 m3 /d, it took three to six months in most cases. For the leakage of relatively warm brines, the heat transport is separated from the salinity due to thermal retardation resulting in monitoring the breakthrough of heat more closely to the depth of the leakage point than the salinity breakthrough. In summary, this study indicates that the mode of dispersion of leaking geothermal brine strongly depends on the brine properties and the leakage and hydrogeological conditions. At the same time, vertical monitoring of temperature and conductivity at a limited distance from brine injection wells (<5m) appears to be a robust method for detecting a possible leak relatively quickly (within a month) and after limited contamination. The monitoring signal in the event of leakage is also sufficiently distinctive to prevent false positives. |
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Planning for increased water security and preventing salinisation in coastal areas of the Netherlands: A study on the suitability for managed aquifer recharge and extraction of brackish water, including quantification of potential extractable volumes | I | de Groot-Wallast | The Netherlands | 2023 | Aquifer Storage and Recovery, Managed aquifer recharge, aquifer salinisation, brackish water extraction, suitability maps, Water supply | ||||||
AbstractYear-round water security is at risk as socio-economic developments lead to increasing water demands, while climate change affects water availability through higher-intensity rainfall and prolonged periods of drought. Coastal zones and deltas with often high population densities experience additional risks of salinisation and land subsidence. These developments ask for creative solutions to secure sustainable and year-round access to fresh water. The subsurface provides storage capacity to actively infiltrate freshwater, bridging the time-gap between demand and supply. Combining infiltration with extraction and desalination of brackish water prevents the salinisation of aquifers whilst providing an additional water source. We call this COASTAR. A Dutch research consortium with partners like water companies and water boards develops COASTAR. Among COASTAR results are suitability maps for Aquifer Storage and Recovery (ASR) and Brackish Water Extraction (BWE) in the coastal zone of the Netherlands. The maps are based on geohydrological factors. A quick-scan analysis was also performed to quantify the nation-wide potential extractable ASR and BWE volumes. COASTAR develops case study models and local scale pilots on ASR and BWE. For two water supply regions, an analysis has been made to geographically match development in water demand with suitability for ASR and BWE as a step in the search for strategic locations to develop ASR and BWE. The suitability maps provide guidance for initiatives’ development and practical experiences from pilot projects; this provides important information for further upscaling of COASTAR approaches. |
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Netherlands National Groundwater reserves: 3D mapping and development of management policies as part of a multilevel strategy to secure water supply for disasters and the far future. | G | Nijsten | The Netherlands | 2023 | 3-D mapping, Multi-layer governance, National fresh-salt groundwater model, Water supply strategies | ||||||
AbstractThe Netherlands produces about 2/3 of drinking water from groundwater. Although there is seemingly abundant groundwater, the resource needs to be carefully managed and used wisely to safeguard the resource for future generations and in case of disasters whilst also preventing negative impacts from groundwater extraction on other sectors such as nature. Provincial governments are responsible for the protection of existing groundwater abstractions for water supply against pollution. To secure groundwater resources for the future, two additional policy levels have been introduced: Provincial governments have been made responsible for mapping and protecting Additional Strategic Reserves. These allow for additional groundwater abstractions to meet growing demands in coming decades (horizon 2040/2050). The National Government is responsible for mapping and protecting the National Groundwater Reserves (NGRs) as a third level of resource protection. NGRs serve multiple goals: to protect natural groundwater capital for future generations, to provide reserves for large-scale disasters affecting water supply and to provide reserves for possible use as structural water supply in the far future (horizon 2100 and beyond). NGRs are being delineated in 3D using detailed existing geological models and the Netherlands’ national (fresh-saline) hydrological model. The dynamics of the groundwater system are analysed through scenario analyses. Reserves for potential structural use are selected such that negative impacts on nature are prevented if future abstractions are to be realised. The policies being developed must balance interests of water supply against other sectoral interests such as the green-energy transition with increased use of geothermal energy and aquifer-thermal-energy-storage. |
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A Rapid Analysis Of Spring Water Quality In Some Neighbouring Villages Of Thohoyandou Town In Thulamela Local Municipality | Vusumzi | Mema | Thulamela Local Municipality, Limpopo | 2013 | springs, Water quality | ||||||
AbstractPOSTER A quick analysis of spring water quality was conducted in four neighbouring villages, namely Vondo, Matondoni, Maranzhe and Murangoni in Thohoyandou town under the Thulamela Local Municipality (TLM) of the Vhembe District Municipality (VDM). For the purposes of this study these villages will be termed VMMM villages. A study on the spring water quality of VMMM villages was conducted by the CSIR to determine whether the natural quality state of the spring water used by the surrounding communities was suitable for drinking purposes without pre-treatment. From the four springs that were identified in the VMMM villages, namely Tshali (S1), Ramufhufhi (S2), Tshinwela (S3) and Tshivhase (S4), water samples were taken for the quality analyses in the laboratory. The results indicated that S2 and S4 had a high coliform count of 35 and 600 per 100 ml, respectively), that is above 10 counts per 100 ml. In springs S2 and S4 the total coliform count also displayed the presence of E.coli (6 and 310 per millilitre, respectively) – E.coli should not be detected at all according to SANS standard limits (2011). While all other parameters were within standard limits (SANS 241, 2011), it was also interesting to note that both S3 and S4 had a problem of high turbidity (1, 6 and 105 NTU, respectively) compared to 1 NTU which is the standard limit (SANS 241, 2011). These results showed that although these communities relied on groundwater in the form of springs for drinking purposes, unmonitored use of these resources may be a health hazard that has a potential to result in disease outbreak and unprecedented deaths. While groundwater through springs is considered natural, increased activity around the source due to human activity and interference by domestic animals, these sources may be rendered unsafe for drinking purposes without prior treatment. Therefore, there is need for local authorities to put measures in place to monitor water resources considered indigenous and traditional to the communities, especially in areas where these resources have become the main source of water supply for drinking purposes. |
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Hydrogeochemical And Environmental Isotope Characteristics Of The Thyspunt Area, Eastern Cape, South Africa. | Seeke | Mohuba | Thyspunt, Eastern Cape | 2019 | Environmental Isotopes, Hydrogeochemistry, Seawater Intrusion, Hydrochemical Evolution, Regional Recharge And Hydraulic Link | ||||||
AbstractHydrogeochemical and environmental isotope investigation of the Thyspunt area, located in Eastern Cape South Africa, has been undertaken to understand the hydrogeological conditions in the area. Fifty-nine water samples from springs, wells, streams and ocean were collected for major ions, metals, and environmental isotope analyses. The hydrogeochemical and environmental isotope signatures were used to identify the interaction between various waters bodies, major hydrogeochemical processes, and possible sources of moisture in the Thyspunt area. The groundwater is characterised by electrical conductivity (EC) that varies between 286 and 7040 ?S/cm, dominant alkaline pH conditions and calcium-magnesium-bicarbonate hydrochemical water type. Hydrochemical evolution of groundwater is observed along the groundwater flow direction (west to east), from fresh calcium-magnesium-bicarbonate water type to saline sodium-chloride water type. Furthermore, mixing of calcium-magnesium-bicarbonate and sodium-chloride type groundwater is apparent in the analysed spring samples, indicating deep circulation. Gibbs plot of major ion hydrochemical data indicates that the groundwater hydrochemistry is primarily controlled by water-rock interactions (mineral dissolution) and evaporation processes. Isotopically, water samples from springs and wells have depleted isotope signatures indicative of rainfall recharge from either high attitude moisture source or recharge during colder seasons or both. None of the groundwater samples have isotope signatures similar to ocean water, signifying that there is no seawater intrusion in any of the sampled aquifers. Deuterium excess values range between -0.71 ? and 22.64 ?, suggesting the presence of numerous moisture sources. Tritium activity in groundwater varies between 0.2 T.U and 3.2 T.U, showing submodern to modern (5 - 10 years) recharge. Hydrochemical and environmental isotope similarities between spring and borehole samples confirm the fact that springs are a surface manifestation of the local groundwater flow conditions. |
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Conceptual Hydrogeological Modelling Of The Thyspunt Area, Eastern Cape, South Africa. | Moneri Joel | Modiba | Thyspunt, Eastern Cape | 2019 | modelling | ||||||
AbstractA conceptual hydrogeological and numerical groundwater flow modelling study is being undertaken around and within the proposed ESKOM Thyspunt Nuclear Site, located 120 km west of Port Elizabeth. The study aims to improve the understanding of the prevailing hydrogeological condition around the Thyspunt area. The area is characterized by folded and jointed geological conditions. The local geology comprises the Table Mountain Group (TMG) and the Bokkeveld Group rocks of the Cape Supergroup, and Quaternary to recent sand deposits of the Algoa Group. The study area receives mean annual precipitation (MAP) of 922.6 mm. The mean annual estimated evapotranspiration is 821 mm and the average annual recharge rate estimated using the Water Table Fluctuation method is about 71 mm. A robust conceptual hydrogeological model is developed through detailed aquifer characterisation including pumping test analyses, determination of groundwater occurrence, storage, and flow, hydrogeochemical and environmental isotope analyses. Groundwater occurs within intergranular of the Algoa Group and fractured quartzitic aquifers of the TMG. The depth to groundwater ranges from 4.5 to 28.9 m below ground level (b.g.l.) and though the local groundwater flow is complex, the general groundwater flow direction is from west to east, towards the Indian Ocean. The upper unconfined intergranular Algoa aquifer and the deeper semi-confined fractured TMG aquifer are characterised by wide range of hydraulic properties, including aquifer thickness (2.2 - 22.0 m and 18.0 - 138 m), hydraulic conductivity ( 4.5 - 19.1 m/d and 8.9x10-3 -1.58 m/d), transmissivity (108.3 - 275 m2/d and 0.4 - 44.0 m2/d), specific yield (1.5x10-2 - 0.1) and storativity (5.0x10-5 - 5.9x10-3), respectively. The main hydrochemical facies of groundwater in the shallow Algoa is Ca-Mg-HCO3 type and groundwater circulating in the deep TMG aquifers are Na-Cl type. Environmental isotope signatures (?2H, ?18O) results indicate groundwater - surface water interactions |
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Turning The Tide - Curbing Groundwater. Over-Abstraction In The Tosca-Molopo Area, South Africa. | Gawie | Van Dyk | Tosca-Molopo Area | 2019 | over-abstraction | ||||||
AbstractNote: This case study was submitted and reported in the Publication Advances in Groundwater governance. The demand on fresh water has increased to such an extend that supply cannot keep up with demand, especially in areas where desalination of seawater is not an option. There is a large gap between the water user, the water supplier and the capacity of the resource/s. The water user sees it as his/her right to be provided with clean water in sufficient volumes to sustain their most basic needs.At the same time people want higher levels of service, especially where sanitation is concerned. The recent droughts in Cape Town and in Port Elizabeth have put significant focus on groundwater and we've seen uncontrolled drilling for groundwater reaching new heights, which is a problem on its own. We can no longer afford not to bring the groundwater user into the water planning cycle, so that the users, on all levels of society, can be educated to understand that the quantity and quality of fresh water (ground -and surface water) is limited and dependent on recharge from rainfall, size of the catchment, topography and all that takes place on the surface. This education must be specific to a target audience and must take into account the existing knowledge and understanding of the user profile. As an example, a case study will be discussed where there are large groundwater users operating within the upper parts of a catchment, followed by municipal abstractions and private abstractions within the central parts of the same catchment. Four profiles of users are therefore present: (1) large-scale irrigation by farmers, (2) large-scale municipal abstractions, (3) private residents and (4) formal / informal settlements, with the latter probably competing for top pot in terms of water use, with the irrigation. They key deliverable of the presentation / paper will be to (1) make people aware of the problem/challenge, and (2) suggest ways to bridge gaps and get all users and service providers to work together to save water and to understand that there are limits to the quantities available. |
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Hydrological processes and evolution in the critical zone of a small island: the case of Pianosa Island in the Tuscan Archipelago | Matia | Menichini | Tuscan Archipelago | 2023 | unsaturated zone, high-precision lysimeter, effective infiltration, shallow aquifer | ||||||
AbstractUnderstanding and quantifying hydrology processes represent a mandatory step in semi-arid/arid regions for defining the vulnerability of these environments to climate change and human pressure and providing useful data to steer mitigation and resilience strategies. This generally valid concept becomes even more stringent for highly sensitive ecosystems, such as small islands like Pianosa. The project intends to deploy a multi-disciplinary approach for better understanding and quantifying the hydrological processes affecting water availability and their evolution, possibly suggesting best practices for water sustainability. First results pointed out as over the last decade the precipitation regime has led to a major rate of evapotranspiration and minor effective infiltration that caused a decreasing of piezometric level over several years. Quantity and chemical-isotopic features of rainfall and effective infiltration water measured/collected by a raingauge and a high precision lysimeter describe the hydrological processes at soil level and characterize the rate and seasonality of groundwater recharge. Hydrogeological and geochemical data of groundwater are highlighting the distribution and relationship among different groundwater components, including the seawater intrusion. Furthermore, the comparative analyses of continuative data monitoring in wells and weather station showed the presence of possible concentrated water infiltration processes during rainfall extreme events that induce a quick response of shallow groundwater system in terms of water level rise and decrease of electrical conductivity. Thus, elements of vulnerability of the aquifer to pollution are pointed out, as well as the possibility to provide technical solutions for enhancing water infiltration and groundwater availability. |
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An Investigation Of The Impacts Of Acacia Mearnsii Plantations On Secondary Aquifer Systems Within The Two-Streams Catchment, Kwazulu-Natal, South Africa. | Caiphus Zimise | Ngubo | Two-Streams Catchment, Kwazulu-Natal | 2019 | plantations, impact | ||||||
AbstractThe Two-Streams catchment located in the KwaZulu-Natal Midlands, South Africa has been used as an experimental catchment over the past decade to investigate the impacts of Acacia mearnsii stands on hydrological processes. As part of the ongoing study, the hydrogeology of the catchment was investigated and characterized to understand the impacts of Acacia Mearnsii plantations on groundwater. The hydrological, hydrogeological, hydrochemical and environmental isotope methods were employed in characterizing the hydrogeology of the catchment. The study area is underlain by three geological units: top weathering profile, mainly of clay, which is underlain by weathered shale. Shale is in turn underlain by granite rock. Two hydrostratigraphic units were identified: an unconfined aquifer occurring along the weathered shale and the underlying regional semi-confined aquifer. The regional aquifer is characterised by transmissivity range of 0.15 to 0.48 m2/day, hydraulic conductivity of 0.04 m/day and annual recharge of 31.9 mm. The catchment receives a mean annual rainfall of 778 mm, mean annual evapotranspiration of 802 mm and mean annual stream discharge of 20387 m3. The groundwater and stream samples are characterised by mean specific electrical conductivity of 28.5 mS/m and Ca-HCO3 and Ca-Cl dominant hydrochemical facies. Isotopic values indicate recharge from rainfall with insignificant evaporation during or prior to recharge. Seasonal stream isotope data analysis indicates groundwater as the main contributor of streamflow during dry season. Furthermore, the impacts of Acacia mearnsii trees on groundwater were investigated. Results show that direct groundwater uptake by tree roots from the saturated zone at Two-Streams would not be possible due to limiting root depth. Thus, in instances where the regional groundwater table is not available for direct abstraction by tree roots, trees can have large impact on groundwater by extracting water from the unsaturated zone, reducing recharge to aquifers and baseflow, without having direct access to groundwater |
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Hydrogeological assessment for sourcing regionally significant freshwater supplies in southern Malawi | Jonas | Bernasconi | USA | 2023 | Brackish Groundwater, development, Lower Shire River Valley, Malawi, Satellite Imagery/Field Survey, Water Quality Data Clustering | ||||||
AbstractCommunities in the Lower Shire River Valley in the Chikwawa District of southern Malawi face extreme development challenges due to highly variable climate, including floods and droughts, that trap them in poverty and food insecurity. The area has been the focus of numerous studies and data collection campaigns to understand better the causes and processes associated with brackish groundwater (in alluvial aquifers) and dry boreholes. An applied groundwater assessment was performed to evaluate water supply alternatives and solutions to deliver potable water to approximately 15% of the district without water access after a multi-year campaign to reach 100%. The assessment synthesized a significant volume of water quality data collected by researchers and nongovernment organizations, larger scale geological interpretations published in segmented literature, multi-spectral satellite imagery datasets, and combined field reconnaissance to investigate areas of interest further and address pertinent data gaps. Improved understanding of geologic structure and lithology, complex aquifer recharge, and evapotranspiration processes supported identifying areas unsuitable for groundwater development and yielded recommendations for groundwater exploration and other solutions. A high permeability zone and strong surface-groundwater connection was identified along the Gungu River. Data collected throughout the area of interest corroborated that significant freshwater recharge occurs in the alluvial aquifer, promoting an aquifer zone where freshwater and higher yields are likely. Exploratory drilling resulted in a very high-yielding freshwater well that supported the development of a piped water system serving several villages. |
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Electrical Hydrogeology of Managed Aquifer Recharge from Meter to Kilometer Scales | Todd | Halihan | USA | 2023 | Byrds Mill Spring, carbonate, electrical resistivity imaging, enhanced aquifer recharge, Karst spring | ||||||
AbstractWhile traditional well and spring sampling are limited to the integration of point data and the interpolation of the data across large scales. Electrical measurements of aquifers can be extended across a range of scales and integrated to provide an improved quantitative understanding of groundwater systems. At a site in Oklahoma, USA, a karst-managed aquifer recharge research site is being used to test electrical techniques for aquifer characterization on the kilometer scale and monitoring the aquifer on the meter scale. At the kilometer scale, the data illustrate fault locations, siphons in flow paths, and previously uncharacterized conduits. At the metre scale, the monitoring data illustrate porosity structure, flow paths, and potential biological changes in the subsurface. The results indicate that electrical approaches can significantly change aquifer conceptual models and provide targeted sampling locations in karstic bedrock aquifers. |
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Investigating Deep Basin Groundwater Flow Systems In The Main Karoo Basin Of South Africa | Thandokazi | Maceba | USA | 2015 | |||||||
AbstractPOSTER The improvement in horizontal drilling and hydraulic fracturing techniques has resulted in the exploitation of gas associated with low-permeability organic-rich shale formations in the United States of America (USA) to become one of the most important energy resources. The USA experience has resulted in renewed exploration interest in the shale formations in the main Karoo Basin. The basins consist of sediments of the Karoo Supergroup, which were deposited during the Late Palaeozoic-Early Mesozoic. Typically, South Africa has been heavily reliant on coal for its primary energy supply, but currently, the country is seeking to develop alternative sources in order to diversify its energy sources. In the Karoo basin, the Whitehill Formation is the most prospective shale gas target. The neighbouring shales such as the Prince Albert Formation are of commercial interest, particularly if the Prince Albert Formation is exploited as an extension of the Whitehill play. Water management has emerged as being crucial for the sustainable development of unconventional gas resources in particular the risks to groundwater resources. This study attempts to develop a conceptual model of deep basin groundwater flow systems in the main Karoo Basin. The conceptual model aims to inform possible solution to protect groundwater resources. This will be done by investigating possible scenarios for interaction between deep and shallow aquifers as to establish possible migration pathways of flowback and produced water that would lead to possible pollution to shallow Karoo aquifers during and/or after the hydraulic fracturing process or activities in the main Karoo Basin. |
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Groundwater resources of the Danakil Depression – hydrogeology in the hottest place on Earth | L | Towers | Umvoto | 2023 | Danakil Depression, Alluvial aquifer, potash, rift basin, solution mining | ||||||
Abstracthe Danakil Depression of the Afar Rift forms part of the north/south-trending Ethiopia-Eritrean arm of the East African Rift System, whereas the western margin of the depression forms part of an active plate boundary between the western Nubian and eastern Danakil tectonic blocks. Dallol (within the Danakil Depression) currently holds the record for the highest average temperature for an inhabited place on Earth, with annual average temperatures of ~35-36°C. The isolated area was initially explored geologically in the late 1960s, with recent geological and hydrogeological interest in its northeast Ethiopian portion due to easier access, geo-tourism and potash-ore exploration. Potash mining is proposed via solution-extraction techniques, requiring large volumes of water in one of the driest hyper-arid regions. Various hydrogeological investigations were therefore conducted between 2014 and 2016 as part of a feasibility and water resource study towards developing a water resource estimate for the region and proposed mining operations. Alluvial fans on the west side of the rift basin form a major, regional primary aquifer – fan boreholes have yields of 50 litres per second, although groundwater is highly saline (up to 3-5 times the salinity of seawater) and can reach temperatures of 50°C. Groundwater yields of hundreds of millions of cubic metres per annum are potentially available from the saline alluvial fan primary aquifers for potash solution mining. In contrast, groundwater from karstic limestone aquifers could provide a freshwater resource to settlements within the Lelegheddi River basin and the Danakil. |
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An Investigation Of Groundwater Recharge And Residence Time Using Noble Gases, Tritium, And Terrigenic Helium | Hugh | Klein | Utah, USA | 2015 | |||||||
AbstractNoble gases are used in this study to investigate the recharge thermometry and apparent groundwater residence time of the aquifers on the eastern slope of the Wasatch Mountains in the Snyderville Basin of Summit County, Utah. Recharge to and residence time for the basin aquifer in the Salt Lake Valley, Utah, from the western slope of the Wasatch Mountain range by 'mountain-block recharge' (MBR), is a significant source of subsurface flow based on noble gas and tritium (3H) data. The Snyderville Basin recharge thermometry from 15 wells and 2 springs indicates recharge temperatures fall within the temperature "lapse space" defined by the recharge thermometry determined in the study of MBR for the Salt Lake Valley and the mean annual lapse rate for the area. Groundwater residence times for the Snyderville Basin were obtained using tritium and helium-3 (3He). The initial 3H concentrations calculated for the samples were evaluated relative to the 3H levels in the early 1950s (pre-bomb) to categorize the waters as: (1) dominantly pre-bomb; (2) dominantly modern; or (3) a mixture of pre-bomb and modern. Apparent ages range from almost 6 years to more than 50 years. Terrigenic helium-4 (4He) is also used as a groundwater dating tool with the relationship between terrigenic 4He in Snyderville Basin aquifers and age based on the apparent 3H/3He ages of samples containing water from only one distinct time period. The 4He is then used to calculate groundwater residence times for samples that are too old to be dated using the 3H/3He method. The mean groundwater residence times calculated with both methods indicate the water yielded by wells and springs in the Snyderville Basin generally ranges from 6 to more than 50 years. In addition, the calculated terrigenic 4He age for the pre-bomb component of many samples was found to exceed 100 years. While terrigenic 4He residence times are not as definitive as those calculated with the 3H/3He method, or chlorofluorocarbons (CFCs), age dating with terrigenic 4He allows initial estimates to be made for groundwater residence times in the Snyderville Basin, and is an important tool for establishing groundwater residence times greater than 50 years. Historic water levels from production wells indicate a declining water table. This trend in conjunction with precipitation data for the area illustrates the decline in the water levels to be a function of pumping from the aquifers. Groundwater residence times in the Snyderville Basin and declining water levels support the need for a groundwater management program in the Snyderville Basin to effectively sustain the use of groundwater resources based on groundwater age. {List only- not presented} |
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The Geohydrological Status Of The Vanrhynsdorp Karst Aquifer | Jana | Brits | Vanrhynsdorp | 2013 | Geohydrological, Aquafer | ||||||
AbstractThe aim of this study was to determine the geohydrological status of the aquifer within the boundaries of the Vanrhynsdorp Water User Association with emphasis on the central catchment, E33F. This will assist the Department of Water Affairs with the introduction of compulsory groundwater-use licensing and empowerment of the Vanrhynsdorp Water User Association to manage the resource. In this study emphasis was given to the determination of the water balance and groundwater reserve of the central catchment and the designing of a representative groundwater monitoring network. A literature study of five projects conducted since 1978 was done. Comparisons were made between the data and results of these studies. All the historical data from these studies, as well as the data from the current monitoring programme up until December 2012, were put together and analysed. A conceptual model and groundwater reserve determination, as well as a representative monitoring network, were produced. The study showed a general decline in groundwater levels over a 34-year period. It also showed an increase in rainfall over the last 20 years. Based on the reserve determination and the declining groundwater level in spite of increased rainfall and thus recharge, it was concluded that over-abstraction of groundwater in the study area is taking place. It is recommended that compulsory licensing should be put in place as soon as possible and that no additional groundwater-use licences should be granted in the study area. The installation of flow meters on all production boreholes should be stipulated in the licensing condition. This will assist the monitoring and regulation of groundwater abstraction volumes. |
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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 | ||||||
AbstractThe 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. |
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Vanwyksvlei: Water provisioning and the Blue Drop system - how effective is this? | Danita | Hohne | Vanwyksvlei | 2015 | Blue drop standards, water supply challenges | ||||||
AbstractPOSTER 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. |
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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 | ||||||
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3-D electrical conductivity image as a decision-aiding tool in the post-closure management of a South African colliery | Lize | Wessels | Vereniging | 2015 | |||||||
AbstractThe 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. |
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Water Quality Assessment And Water Use Practices Of Groundwater In Vhembe District, South Africa. | Joshua | Edokpayi | Vhembe District | 2019 | quality | ||||||
AbstractGroundwater 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. |