Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 51 - 100 of 795 results

Title	Presenter Name	Presenter Surname	Conference year	Keywords
An investigation into the effectiveness of underground water pollution mitigation policies	Sibanda	Kin	2015
Abstract Pollution of underground water is fast becoming a global problem and South Africa is not immune to this problem. The principal objective of this paper is to investigate the effectiveness of laws and policies put in place to mitigate underground water pollution. The paper also seeks to examine the causes and types of underground water pollution followed by a closer look into the laws and policies in place to mitigate the pollution levels. Finally, the paper seeks to ascertain whether the current policies are properly implemented. The paper follows content analysis (desk research) to achieve the objectives. Policy recommendations are given based on the findings. {List only- not presented}
Characterising The Hydrological Regime Of The Rietvlei Wetland: Implications For Ecohydrology	Nathasha R	Gariremo	2019	Poster, ecohydrology
Abstract In the following study, the soil and groundwater regime of the Rietvlei wetland near Cape Town are characterised. This has been done by means of logging the subsurface material during the construction of 8 shallow wells, complimented with field observations, and surveying the dug wells. The water stemming from these wells was sampled and analysed for Oxygen 18 and Deterium. Downhole salinity logs of the wells were also undertaken and rainfall samples were analysed for the aforementioned stable isotopes. Results indicate a distinct relationship between elevation and soil structure. Through the use of the water table method, it was found that the relationship between elevation and soil moisture had a direct impact on spatially distributed groundwater recharge on an event basis. Furthermore, higher salinities were found with depth in groundwater in the same wells which had higher recharge values. Isotopic results indicate that groundwater all stems from rainfall, with the exception of Well 8 is influenced by the river due to its proximity to the surface water body. The various water chemistries and soil profiles have a direct impact on the type of flora and its distribution throughout the study area. This study managed to conceptualize the relationship between groundwater, soil profiles and the various plant types surviving in the Rietvlei wetland. Future studies can focus on computer based approaches in order to predict how changes in groundwater characteristics caused by natural or anthropogenic factors would affect other ecohydrological processes within the wetland. These findings can be incorporated in decision making processes concerning groundwater management.
Groundwater Protection Zoning- A case study of the Rawsonville research site.	Shuaib	Dustay	2015	groundwater protection zones
Abstract Currently limited progress is made in South Africa (and Africa) on the protection of groundwater used for drinking water. To achieve the objective of water for growth and development and to provide socio-economic and environmental benefits of communities using groundwater, significant aquifers and well fields must be adequately protected. Groundwater protection zoning is seen as an important step in this regard. Till today, limited case studies of groundwater protection zoning exists in Africa. A case study at the Rawsonville research site is conducted in this research project. Generic protection zones can be delineated at the site using published reports and database data. However, due to the complexity of the fractured rock at the research site, these would be of limited value and would not provide adequate protection for the well field Baseline data was collected by conducting a hydro census and through aquifer tests. An inventory of the activities that can potentially impact water quality was done and aquifer characteristics such as transmissivity and hydraulic conductivity were determined through various types of aquifer testing. Fracture positions were identified using fluid logging and fracture flow rates were also measured using fluid logging data. A conceptual model and preliminary 3D numerical model were created to try to understand groundwater movement at the research site. The knowledge gained will be used to guide information gathering and monitoring that can be used to build a more detailed numerical model and implement a trustworthy groundwater protection plan at a later stage. The expected results will have applicability to groundwater management in general. The protection plan developed during this project can be used as a case study to update and improve policy implementation. {List only- not presented}
Study on the Relationship between Water Quality and Wetland Plant Community in Huixian Karst Wetland	L	Shen	2023	Huixian Karst Wetland, Water quality, Wetland Plant Community
Abstract Huixian Karst National Wetland Park is the most typical karst wetland in the middle and low latitudes of the world and has become an internationally important wetland. The relationship between water quality and aquatic organisms in Huixian Wetland is a hot research topic in wetland ecology. This article focuses on the relationship between the current water quality situation in Guilin Huixian Karst Wetland and the growth of wetland plants. Sixteen sampling points are set up in the wetland to monitor and analyze water quality in wet, normal, and dry seasons. The Kriging index interpolation method is used to obtain a comprehensive water quality interpolation map in the survey area during normal water periods and in combination with the wetland plant survey sample data and the landscape status. A comprehensive analysis of the relationship between wetland plant growth and water quality. The results show that the centre of Huixian Wetland receives recharge from surrounding groundwater, which is greatly affected by the surrounding water quality. The comprehensive water quality is relatively good in the dry season, relatively poor in the normal season, and the worst in the wet season. Agricultural production, non-point source pollution, rural domestic sewage, and human interference affect wetland water quality, which directly affects the structure and function of plant communities and the ecological service function of wetlands.
Determination Of Water Retention For Ash Dumps And Implications On Groundwater Contamination	Gundo	Mathoho	2019	contamination
Abstract Burning of coal for electricity production has resulted in vast amounts of ash being deposited in ash dumps. Rain water and ash water conditioning results in the wetting of ash dumps and if the water retention capacity is exceeded there is a possibility of leaching to soil and underlying aquifers. In this study two different coal ash are used to determine the water retention as excess amount of process water at power stations ash dumps can lead to impeding the desired water balance, which can be critical for maintain various plant processes. The nonlinear relationship between soil water content and matrix suction of a porous material under unsaturated conditions is described by the soil water characteristic curve (SWCC). The SWCC for a given material represents the water storage capability enabling the determination of varying matric suction such as prediction of important unsaturated hydraulic processes including soil permeability, shear strength, volume change with respect to the water content changes. This paper presents an alternative, cost effective and rapid method for measuring and subsequent estimating of the soil-water characteristics of any soil type. Several methods are available to obtain the measurements required for defining soil-water characteristics. However, obtaining the required measurements for a SWCC is generally difficult since there is no laboratory or field instrument, capable of measuring a typical complete plant available water suction range accurately. Due to high methodological effort and associated costs of other methods, a simplified evaporation method which was implemented in the HYPROP (Hydraulic Property analyzer, UMS, 2012) becomes a possible alternative. It relies on the evaporation method initially proposed Schindler (1980). A typical work range for a HYPROP system is 0 to 100 KPa as read out from the two high capacity tensiometers installed at different heights within a saturated sample column. For a dry coal ash dump to be optimally used as sinks, input water applications should be matched with evaporation rates and capillary storage. This will ensure the moisture storage of the ash dump is not exceeded and consequently avert leachate generation at the base of the ash dump. The field capacity of waste materials is of critical importance in determining the formation of leachate in landfills which in this case is the coal ash dump facility. It is the field capacity limit when exceeded which give rise to leachate generation consequently promoting a downward movement of generated leachate.he study found that it is possible to use the Hyprop together with an empirical based fitting model to define a complete SWCC along a dewatering path. The study found the Brooks-Corey model as the suitable representative of the Hyprop measured data, confirmed by AICc and RMSE analysis. The Brooks-Corey estimated retention function parameters within +/- 1% error. A mean value of 35.3% was determined as the water retention or field capacity value for Matimba Coal ash. If the ash dump is operated in excess of this value, chances of groundwater pollution are high.
Management of water-related risks in drinking water supplies	Barbara	Cencur Curk	2023	risk analysis, water-related hazards, water safety plan, water supply system
Abstract With the revision of the European Drinking Water Directive (Directive on the quality of water intended for human consumption 2020/2184) in December 2020, the preparation of Water Safety Plans (WSP) is foreseen according to the guidelines of WHO. Within the EU Interreg Adrion MUHA project, a decision support tool (DST) has been developed to provide a holistic approach to drinking water infrastructure risk analysis. The project mainly addresses four water-related risks: accidental pollution, floods, droughts and earthquakes. The core of the DST is the inventory of hazardous events (causes, their consequences and impacts) for each component of the drinking water supply chain: (1) drinking water source - catchment area, (2) water supply system, and (3) domestic distribution system. For each identified potential hazard, the type of hazard was determined (e.g., biological, chemical, radiological, or physical hazard (including turbidity), inadequate availability of water supplied to customers, safety to personnel, external harm to third parties, including liability). The DST was tested in the partner countries (Italy, Slovenia, Croatia, Serbia, Montenegro and Greece) to verify the resilience of the measures and elaborate the WSP. In the end, the REWAS-ADRION strategy was elaborated, aiming to increase the resilience of drinking water supplies to floods, droughts, accidental pollution, and earthquake-related failures by improving the water safety planning mechanism based on the concept of inter-agency cooperation to support water utilities, civil protection organizations, and water authorities.
The National Integrated Water Information System (NIWIS) for geohydrology in South Africa	N	Nungu		Data, Decision Making, Groundwater, Information, Information System, Integration, South Africa
Abstract For the Department of Water and Sanitation (DWS) to better leverage the wealth of information being collected by various “silo” operational source water information systems, a high-priority initiative was launched to establish a National Integrated Water Information System (NIWIS), which currently consists of over 40 web-accessible dashboards including groundwater related dashboards mostly accessible to the public. Dispersed and disintegrated data and information stored in different sources and formats would hinder decision support in the water sector and deter improvement in service delivery by the DWS. The DWS undertook an extensive and rigorous business requirements analysis exercise within the DWS to ensure that the proposed system does not become a white elephant and facilitate the prioritization of system deliverables. A prototype (waterfall) approach was adopted to develop the NIWIS to ensure the development was still within the suggested business requirements. NIWIS has enabled mostly DWS managers to establish one trusted source of decision-making information for timeous, effective and efficient responses to service delivery. The number of NIWIS dashboards continues to grow as improved data-related business processes are adopted. The unavailability of reliable data from DWS data sources and the exclusion of business requirements from organizations external to DWS were identified as the main challenges to NIWIS disseminating comprehensive, credible information. Therefore, this paper aims to provide some details of the geohydrological information that NIWIS provides and seek feedback from this International Hydrogeologists community for further development of NIWIS.
Numerical Modelling Of a Coal Mine to Improve the Understanding of Mine Water Decant: A 1000-Piece Puzzle	Amy	Allwright	2017	coal ash, dolomites, Mining , numerical modelling
Abstract A coal mine in South Africa had reached decant levels after mine flooding, where suspected mine water was discharging on the ground surface. Initial investigations had indicted a low-risk of decant, but when ash-backfilling was performed in the defunct underground mine, decant occurred. Ash-backfilling was immediately suspended as it was thought to have over-pressurised the system and caused decant. Contrariwise, a number of years later decant was still occurring even though ash-backfilling had been terminated. An investigation was launched to determine whether it was the ash-backfilling which had solely caused decant, or if additional contributing factors existed. Understanding the mine water decant is further complicated by the presence of underlying dolomites which when intersected during mining produced significant inflows into the underground mine workings. Furthermore, substantial subsidence has taken place over the underground mine area. These factors combined with the inherent difficulty of understanding unseen groundwater, produced a proverbial 1000-piece puzzle. Numerical groundwater modelling was a natural choice for evaluating the complex system of inter-related processes. A pre-mining model simulated the water table at the ground surface near the currently decanting area, suggesting this area was naturally susceptible for seepage conditions. The formation of a pathway from the mine to the ground surface combined with the natural susceptibility of the system may have resulted in the mine water decant. This hypothesis advocates that mine water was going to decant in this area, regardless of ash backfilling. The numerical groundwater flow model builds a case for this hypothesis from 1) the simulated upward flow in the pre-mining model and 2) the groundwater level is simulated above the surface near the currently decanting area. A mining model was then utilised to run four scenarios, investigating the flux from the dolomites, subsidence, ash-backfilling and a fault within the opencast mine. The ash-backfilling scenario model results led to the formation of the hypothesis that completing the ash-backfilling could potentially reduce the current decant volumes, which is seemingly counterintuitive. The numerical model suggested that the current ash-backfill areas reduce the groundwater velocity and could potentially reduce the decant volumes; in spite of its initial contribution to the mine water decant which is attributed to incorrect water abstraction methods. In conclusion, the application of numerical models to improve the understanding of complex systems is essential, because the result of interactions within a complex system are not intuitive and in many cases require mathematical simulation to be fully understood.
Stampriet Transboundary Aquifer System	Kwazikwakhe	Majola	2015

Automation Of Interpretation Of Geoelectrical Resistivity Using Artificial Intelligence	Emmanuel	Sakala	2019	Resistivity, AI
Abstract Artificial Intelligence (AI) has been used in a variety of problems in the fields of science and engineering in particular automation of many processes due to their self-learning capabilities as well as their noise-immunity. In this paper, we describe a study of the applicability of one of the popular branch of AI (Artificial Neural Network (ANN)) as an alternative approach to automate modelling of one-dimensional geoelectrical resistivity sounding data. The methodology involves two ANNs; first one for curve type identification and the other one for model parameter estimation. A three-layer feedforward neural network that was trained from geoelectrical resistivity data taken at boreholes with geology logs was used to predict earth models from measured data without the need to guess the initial model parameters or use synthetic data as is done with most conventional inversion approaches. The motivation for using the ANN for geophysical inversion is that they are adaptive systems that perform a non-linear mapping between two sets of data from a given domain. For network training, we use the back-propagation algorithm. An example using data from southern Malawi shows that the ANN results outperforms the conventional approaches as the results after adequate training, produce reasonably accurate earth models which are in agreement with borehole log data.
Building a Groundwater Educational Pipeline from Elementary to Continuing Education	Todd	Halihan	2023	K-12, PSM, Drilling, online education, professional master’s programs
Abstract Water resources worldwide are stressed, and the number of groundwater professionals required to manage those resources is not being generated in sufficient numbers. Groundwater educational resources must be placed in schools to generate excitement and raise awareness. Additionally, people entering the workforce need training throughout their professional careers. Oklahoma State University partnered with the U.S. National Ground Water Association to develop a framework for providing education and training programs in groundwater that allow for interactive online education at all levels. The Awesome Aquifer 360 program targets grades 5-8, allowing students to conceptually explore aquifers and the people who manage them. The Drilling Basics Online program provides a 40-hour basic safety and drilling training to recruit professionals into the groundwater industry and reinforce safe operations. These programs and future plans for the technique will be discussed.
Post Mining Aquifer Testing At A South African Coal Mine	Marnus	du Toit	2017	coal mine, dewatering, geochemistry, pumping test, analytical mocels
Abstract Mining site remnants are everlasting and impact the groundwater regime on a long term scale. An integrated approach to geoscience is necessary due to the complexity of nature and the unknown relationships that must be discovered to further the understanding of impacts on the natural environment. Furthermore, groundwater resources are negatively impacted by mining activities affecting the groundwater quality and quantity. Underground coal mining can be accompanied by roof failure events. This may change the matrix which subsequently alters the flow regime; leads to variations within the water chemistry, provided there is inter- aquifer connectivity; and alters the recharge rate. Dewatered mine voids are in direct contact with oxygen initiating oxidation reactions, depending on the geology of the specific site. A change in water chemistry was analyzed, and this coincides with a roof failure event as interpreted from water level measurements. Concentrations of Mg, Ca, and alkalinity indicate anomalous changes that are still in effect, five to six years after the majority of water levels had stabilized. The changes in the system coincides with and correlates to events of roof failure and different parameters. The latter changes are applied as extra tools when interpreting different site specific anthropogenic induced impacts on the system. Also within this study, constant rate pumping tests were conducted for the interest of the hydraulic properties, using three farming boreholes. The results put forward a range of 0.21 – 0.44L/s and 6.5 – 11.5m2 /d, for sustainable yield and transmissivity, respectively. Furthermore, it is recommended that a better understanding can be gained on system behaviors if chemistry correlations can be gathered through certain events causing specific systems to be in disequilibrium. It is also recommended that additional pumping tests will allow more insightful interpretation and delineation between the abovementioned chemical and water level changes. Finally, the combination of parameters during events can aid in deciding the most appropriate analytical models used for further analysis.
Performance Monitoring Of The Monitored Natural Attenuation Of Petroleum Hydrocarbons In Groundwater Using Geochemical Parameters	AR	Gemmell	2017	MNA, geochemical indicators, geochemical parameters, monitoring network
Abstract Monitored Natural Attenuation (MNA) refers to the monitoring of naturally occurring physical, chemical and biological processes. Three lines of evidence are commonly used to evaluate if MNA is occurring, and this paper focusses on the second line of evidence: The geochemical indicators of naturally occurring degradation processes and the site-specific estimation of attenuation rates. The MNA geochemical indicators include the microbial electron acceptors (e.g. dissolved oxygen, nitrate and sulphate) and the metabolic by-products (manganese (II), iron (II) and methane). In addition, redox and alkalinity are important groundwater indicators. So as to properly assess the geochemical trends a groundwater monitoring well network tailored to assessing and defining the contaminant plume is required. The expressed assimilative capacity (EAC) is used to estimate the capacity of the aquifer to degrade benzene, toluene, ethylbenzene and xylene (BTEX compounds) using the concentrations of geochemical indicators. Using the EAC, the groundwater flow through a perpendicular cross-section of the source area, and the source mass, the life of the contaminant source can be made. A practical example of the performance monitoring of MNA using geochemical parameters is described for a retail service station in KwaZulu-Natal, which has groundwater impacted by a petroleum hydrocarbon plume. This includes a description of the monitoring well network, the geochemical measurements, the calculation of the EAC, and the estimated life of the contaminant source.
A Decision Support System to Assess Climate Change Impacts on Rural Communities	Musiiwa	Luruli	2015
Abstract Climate change contributes to the way in which people live. Natural resources such as groundwater, wood and surface water form a great part of livelihood in rural communities and are used extensively in rural areas where basic services have not yet been provided. The effect of climate change to all these natural resource may impact the lives of those in rural communities. Climate change is already starting to affect some of the poor and most vulnerable communities around the world. The aim of the dissertation is to develop a framework to assess the vulnerability of rural communities to climate change, with a specific focus groundwater and issues relating to gender. A questionnaire and interviews were used to collect data about rural communities' level of awareness climate change, their attitudes toward coping with climate change impact, level of education, income scale and how does this affect their security. Hyrodocensus was taken around the village to determine the rivers, dams, boreholes, abandoned boreholes and wells. Water samples were collected and analysed. The response rate was higher in females than in male's stakeholders (54% vs 46%).the results show that woman were mostly doing the hard work to complete daily basic activities. Education was found to be of high school level and incomes were low. The framework was developed with basic need showed that the area was at risk of poverty .Boreholes was found and water quality was analysed to be adequate for drinking water purpose. More information will be discussed on presentation.
Integrated System Approach To Evaluate Natural Processes And Hydrodynamics Linked To Groundwater-Surface Water Interaction	Teboho	Shakhane	2015
Abstract This study was aimed at developing an integrated groundwater-surface water interaction (GSI) model for a selected stretch of the Modder River by considering the following five different aspects of the GSI: 1) the distribution of different aquifer systems (structural connectivity) along the river 2) the hydraulic connectivity between the aquifer systems, 3) the volumes of water abstracted from the aquifers by streamside vegetation, 4) the volumes of water replenished to the groundwater system through rainfall recharge, and 5) the exchange fluxes between the various components of the groundwater-surface water system. The distribution of the aquifer systems was investigated by means of a) geo-electrical surveys, and b) in situ slug tests while their hydraulic connectivity was investigated by hydrogeochemical routing. The volumes of water abstracted by streamside vegetation were estimated by the quantification of the transpiration from individual plants and the groundwater recharge was estimated by a root zone water balance. The water exchange fluxes between the groundwater and surface water were determined from a simple riparian zone groundwater budget. The results of the geo-electrical surveys and slug tests allowed the delineation of the riparian area aquifers (RAA) and the terrestrial area aquifers (TAA) on both the south-eastern and north-western sides of the river. Based on the results of hydrochemical analyses, saturation indices and inverse mass balance modelling, the GSI involves flow of water from the TAA to the RAA, and finally to the river on the south-eastern side while it involves flow from the river into the RAA with a limited exchange with the TAA on the south-eastern side. The dominant vegetation on the study area was found to be the Acacia karroo and Diospyros lycioides. The close similarities in isotope compositions of the xylem sap and the borehole water samples suggested that the Acacia karroo sourced its water from the groundwater storage while differences in isotope compositions suggested that the Diospyros lycioides did not source water from the groundwater storage at the time of measurement. The results of groundwater recharge estimation in the study area highlighted the fact that both the antecedent moisture and the rainfall amounts determine whether recharge to the groundwater system will take place. Finally, the results of baseflow estimation indicated that the river is a gaining stream along the south-eastern reach while acting as a losing stream along the north-western reach.
Complexity versus Simplicity: A comparative analysis of complex geology in hydrogeological modelling	Anton	Lukas	2012	modelling, FEFLOW
Abstract This paper was presented at the GWD Central Branch Symposium, Potchefstroom in 2012 Numerical modelling of hydrogeological systems has progressed significantly with the evolution of technology and the development of a greater understanding of hydrogeology and the underlying mathematical principles. Hydrogeological modelling software can now include complex geological layers and models as well as allow the pinching out of geological features and layers. The effects of a complex geology on the hydraulic parameters determined by numerical modelling is investigated by means of the DHI-WASY FEFLOW and Aranz Geo Leapfrog modelling software packages. The Campus Test Site (CTS) at the University of the Free State in Bloemfontein, South Africa was selected as the locale to be modelled. Being one of the most studied aquifers in the world, the CTS has had multiple research projects performed on it and as a result ample information is available to construct a hydrogeological model with a high complexity. The CTS consists primarily of stacked fluvial channel deposits of the Lower Beaufort Group, with the main waterstrike located on a bedding-plane fracture in the main sandstone aquifer. The investigation was performed by creating three distinct hydrogeological models of the CTS, the first consists entirely of simplified geological strata modelled in FEFLOW by means of average layer thicknessand does not include the pinching out of any geological layers. The second model was created to be acopy of the first, however the bedding-plane fracture can pinch out where it is known to not occur. The third and final model consisted of a complex geological model created in Leapfrog Geo which was subsequently exported to FEFLOW for hydrogeological modelling.
Estimating groundwater availability at catchment scale using streamflow recession and instream flow requirements of rivers	Girma Yimer	Ebrahim	2015	streamflow, RDM
Abstract Groundwater is an important resource for multiple uses in South Africa. Hence, setting limits to its sustainable abstraction while assuring basic human needs is required. Due to prevalent data scarcity related to groundwater replenishment, which is the traditional basis for estimating groundwater availability, the present article presents a novel method for determining allocatable groundwater in quaternary catchments through information on streamflow. Using established methodologies for assessing baseflow, recession flow, and instream ecological flow requirement, the methodology develops a combined stepwise methodology to determine annual groundwater storage volume using linear reservoir theory, essentially linking low flows proportionally to upstream groundwater storages. The approach was trialled for twenty-one perennial and relatively undisturbed quaternary catchments with longterm and reliable streamflow records. Using the Desktop Reserve Model, maintenance low instream flow requirements necessary to meet present ecological state of the streams were determined, and baseflows in excess of these flows were converted into allocatable groundwater storages on an annual basis. Results show that groundwater development potential exists in nineteen of the catchments, with upper limits to allocatable groundwater volumes (including present uses) ranging from 0.02 to 2.60 Mm3/a over the catchments. With a secured availability of these volumes 75% of the years, variability between years is assumed to be manageable. A significant (R2 = 0.86) correlation between baseflow index and the drainage time scale for the catchments underscores the physical basis of the methodology and also enables the reduction of the procedure by one step, omitting recession flow analysis. The method serves as an important complementary tool for the assessment of the groundwater part of the Reserve and the Groundwater Resource Directed Measures in South Africa.
A predictive study to better protect groundwater at Underground Coal Gasification site	Venessa	Aphane	2015	underground coal gasification
Abstract Underground coal gasification (UCG) is considered a cleaner energy source as its known effect on the environment is minimal; it is cheaper and a lesser contributor to greenhouse gas emissions when compared to conventional coal mining. It has various potential impacts but the subsidence of the surface as well as the potential groundwater contamination is the biggest concerns. Subsidence caused by UCG processes will impact on the groundwater flow and levels due to potential artificial groundwater recharge. The geochemistry of the gasifier is strongly depended upon site specific conditions such as coal composition/type and groundwater chemistry. Independent of the coal rank, the most characteristic organic components of the condensates is phenols, naphthalene and benzene. In the selection of inorganic constituents, ammonia, sulphates and selected metals and metalloids such as mercury, arsenic, and selenium, are identified as the dominant environmental phases. The constituents of concern are generated during the pyrolysis and after gasification as dispersion and penetration of the pyrolysis take place, emission and dispersion of gas products, migration by leaching and penetration of groundwater. A laboratory-based predictive study was conducted using a high pressure thermimetric gasification analyser (HPTGA) to simulate UCG processes where syngas is produced. The HPTGA allows for simulation of the actual operational gasifier pressure on the coal seam and the use of the groundwater sample consumed during gasification. A gasification residue was produced by gasifying the coal sample at 800 °C temperature and by using air as the input gas. The gasification residue was leached using the high temperature experimental leaching procedure to identify the soluble phases of the gasified sample. The leachate analysis is used to determine the proportion of constituents present after gasification which will be removed by leaching as it is exposed to external forces and how it will affect the environment. The loading to groundwater for the whole gasifier is then determined by applying the leachate chemistry and rock-water ratio to the gasifier mine plan and volumes of coal consumed.
A numerical simulation of solute transport in dry coal ash dumps with a case study in South Africa	Innocent	Muchingami	2015
Abstract An understanding of the movement of moisture fluxes in the unsaturated zone of waste disposal sites play a critical role in terms of potential groundwater contamination. Increasing attention is being given to the unsaturated or vadose zone where much of the subsurface contamination originates, passes through, or can be eliminated before it contaminates surface and subsurface water resources. As the transport of contaminants is closely linked with the water ?ux in through the unsaturated zone, any quantitative analysis of contaminant transport must ?rst evaluate water ?uxes into and through the this region. Mathematical models have often been used as critical tools for the optimal quantification of site-speci?c subsurface water ?ow and solute transport processes so as to enable the implementation of management practices that minimize both surface and groundwater pollution. For instance, numerical models have been used in the simulation of water and solute movement in the subsurface for a variety of applications, including the characterization of unsaturated zone solute transport in waste disposal sites and landfills. In this study, HYDRUS 2D numerical simulation was used to simulate water and salt movement in the unsaturated zone at a dry coal ash disposal site in Mpumalanga, South Africa. The main objective of this work was to determine the flux dynamics within the unsaturated zone of the coal ash medium, so as to develop a conceptual model that explains solute transport through the unsaturated zone of the coal ash medium for a period of approximately 10 year intervals. Field experiments were carried out to determine the model input parameters and the initial conditions, through the determination of average moisture content, average bulk density and the saturated hydraulic conductivity of the medium. A two dimensional finite-element mesh of 100m x 45m model was used to represent cross section of the ash dump. Two dimensional time lapse models showing the migration of moisture fluxes and salt plumes were produced for the coal ash medium. An explanation on the variation of moisture content and cumulative fluxes in the ash dump was done with reference to preexisting ash dump data as well as the soil physical characteristics of the ash medium. {List only- not presented}
The Management of Groundwater resources using GIS/Cartography splay)	Freda	Jonck	2015
Abstract The Department of Water Affairs and Sanitation is the custodian of the Water Resource in South Africa. The Western Cape Regional Office, Geotechnical Service Sub Directorate, is responsible for management of groundwater resources in two Water Management Areas (WMA), Olifants Doorn-Berg and Breede-Gouritz. Twenty-nine monitoring routes comprising 800 sites in total are monitored across the Western Cape Region. The purpose of this paper is to create awareness of groundwater related databases and the type of information products used in assessing the status of data bases and groundwater resources. This is to assist and support the scientists, technicians, managers, external stakeholders and/or general public. The main question that needs to be answer is: "What is the current groundwater data management situation in the Regional office?" With the GIS as platform, geographical information was generated from existing data bases to answer questions such as, what is being monitored, where is it being monitored, who is monitoring it, why is it being monitored and when is it being monitored? These questions are applicable to the Region, Water Management Areas, the monitoring route and geosites. Graphical time-series information generated from available data, in combination with the generated geographical information, showed the gaps, hot spots and what is still needed for all the facets of groundwater management (from data acquisition to information dissemination) processes. The result showed the status of data bases, need for data in areas of possible neglect, training gaps, inadequate structure and capacity, instrumentation challenges, need for improvement of commitment and discipline, as well as many other issues. The information generated proves to be an easy tool for Scientists, Technicians and Data Administrators to assist them to be on top of the groundwater resource management in their area of responsibility. The expansion of the use of GIS as a groundwater management tool is highly recommended. This will ensure better understanding of the resource: "The Hidden Treasure".
Variability In Borehole Responses During Yield Testing: Case Studies Deviating From Ideal Drawdown Curves.	Reuben	Lazarus	2019	yield-testing, theory vs practice, realistic aquifers
Abstract The expectation that during yield tests, a borehole will react within the expected framework of the existing numerical models, is often not met within real-world scenarios. This is mainly due to the observation that the Theis solution for confined aquifers, Neuman solution for unconfined aquifer and Barker Generalised Radial Flow Model for hydraulic tests in fractured rocks all include idealised assumptions regarding the physical aspects of a hypothetical. In order to interpret the data from a yield test these methods, along with the Flow Characteristic method for sustainable yield estimates, are commonly used. However, as these assumptions are not always met, the analysis is usually focused on time periods within the test that approximate these solutions. In some cases, the extent to which these assumptions are not met can produce drawdown data that is not well described by the usual analytical models used to analyse this data. This study addresses some of the shortcomings experienced during testing in non-ideal aquifers, as well as briefly describing some tests where small budgets, short deadlines, a lack of information and/or unforeseen circumstances resulted in similar challenges to analyses. This study does not present new solutions to drawdown data analyses, but rather discusses how the mentioned solutions were used during testing to accommodate for the shortcomings experienced.
#GWD: The use of social media for science communication	Tercia	Strydom	2015
Abstract For a long time, professionals regarded social media as a superficial, unprofessional platform where internet users would submerge themselves in a virtual world, detached from real-life issues. Slowly, the myths and stigmas surrounding the use of social media has faded as more and more professionals and scientists have realized that these social platforms could be positively exploited in a professional manner which could be beneficial. In a digital age where information at our fingertips is the norm, professionals should co-evolve and ensure that their work is just as accessible and appealing, without the unnecessary jargon. Currently, science is mostly restricted to a very particular audience and conveyed in one direction only. Using a social media platform such as Twitter-which limits messages to only 140 characters-challenges scientists to convey their work in a very concise manner using simpler terminology. Furthermore, it dismisses the usual one-way form of communication by opening dialogue with fellow Twitter users. At conferences, Twitter can serve as a useful tool for active engagement which will not only "break the ice" between delegates but also ensure that important information is communicated to a much wider audience than only those in attendance. This idea was tested at the 2014 Savanna Science Network Meeting held in Skukuza, Kruger National Park, where the hashtag #SSNM was used. More than 63% of the Twitter users who participated in the #SSNM hashtag were actually not present at the conference. These external "delegates" were interested individuals from five different continents and in different professions besides Science. This highlights how social media can be exploited at conferences to ensure that key messages are conveyed beyond the immediate audience at the event.
Geochemical Behaviour Of Arsenic In Contact With Dolomite	Johan	Fourie	2017	Arsenic, geochemical, dolomites
Abstract Arsenic is a common contaminant typically found in effluent from gold mine operations and copper smelters throughout the world. The geochemical behaviour of arsenic in contact with dolomite underlying an arsenic containing waste rock pile was investigated. The interaction between the arsenic and the dolomite is an important control in the subsequent transport of the arsenic in the dolomitic aquifer. Rocks with varying dolomite content were tested to investigate the interaction between the arsenic and dolomite. From the modelling and test results it was estimated that in the aquifer, between 60 - 90% of arsenic is present in the solid phase under oxidation conditions at >50 mV. At 50 to -25 mV about 40 - 60% of the arsenic is estimated to be present in the solid phase and below -25 mV about 0 - 10% of arsenic will be present in the solid phase. Although some arsenic is removed by the dolomite in the aquifer the arsenic would still be present above acceptable guidelines for drinking water. The arsenic in the solid phase will be in equilibrium with the aquifer water and could be remobilised 1) under more reducing conditions or 2) with a decrease in arsenic in the aquifer.
Units for joint management of cross-border groundwater impacts in Transboundary Aquifers: An overview of concepts and methodologies	C	Morales	2023	cross-border groundwater impacts, hotspots identification, joint management units, time and space scales factor, transboundary aquifers, zoning
Abstract This study aims to contribute to the conceptual and methodological development of units of joint management in transboundary aquifers (TBAs) to prevent and mitigate cross-border groundwater impacts (GWIs) in quantity and/or quality. Joint management units are a relatively new but growing topic in the field of TBAs, and their conceptualisation and appropriate identification are still at an early stage. By reviewing the literature on the subject and elaborating on its terminology, main features, and current methodological progress, a comparison of the existing methodologies for identifying such units is analysed. On this basis, trends and recommendations for further research and application of such methodologies to the joint management of TBAs are presented. The literature on this issue is scarce and has been published mainly in the last five years. These publications lack consistency in the use of concepts and terminology. The above has led to miscommunication and semantic issues in the concept behind such units and in comprehending the particular challenges of identifying them. Still, some directions and methodologies for identifying or directly delineating these management units have been proposed in the literature. However, no analysis from these methodological attempts has been conducted; thus, there are no lessons to be learned about this progress. This research looks forward to closing these gaps and making headway toward dealing with cross-border GWIs in TBAs, thus helping countries meet international law responsibilities and maintaining stable relationships among them.
Modelling The Progression Of AMD Plume In Karst Aquifer Using Complex Resistivity Tomography Model	Sbonelo	Zulu	2019	modelling, AMD
Abstract The costs of acid mine drainage (AMD) monitoring result in the quest for alternative non-invasive method that can provide qualitative data on the progression of the pollution plume and ground geophysics was the ideal solution. However, the monitoring of AMD plume progression by ground geophysics (time-lapse electrical resistance) proves to be non-invasive but also time consuming. This gave way to a study that focuses on the modeling of different scenarios of the karstic aquifer. The models use the field parameters such as the electrical resistivity of the host rock and the target rock, depth to the target, noise level and electrode configuration in order to ensure that the model outcomes represent the field data as much as possible. This geoelectric modeling process uses Complex Resistivity Model (CRMod) and Complex Resistivity Tomography (CRTomo) to generate geoelectric subsurface images. Different resistivity values are applied to targets in order to assess the difference against the baseline model for each target scenario. The model resistivity difference is reduced to the smallest difference possible between the reference and new models in order to gauge the lowest percentage change in the model at which the background noises start to have impact on the results. The study shows that the behavior of targets (aquifer) could be clearly detected through resistivity difference tomography rather than inversion tomography. The electrode array plays a significant part in the detection of target areas and their differences in resistance because of its sensitivity. This therefore indicates that the electrode array should be chosen according to study requirements. Furthermore, the model geometry also plays a role and this can be seen with the modelling of different target sizes, alignments and shapes. Future studies that can provide a correlation between the field quantitative data from sampling and the model outcomes have the ability to add to the knowledge field of geophysical modelling therefore reducing costs associated with field based plume AMD monitoring300-500 words without references; reach your conclusions rather than only delivering promises.
Hydraulic tests of strong artesian boreholes; wellhead construction and test design	Kornelius	Riemann	2015
Abstract Artesian boreholes are a common feature worldwide in confined aquifers, but the hydraulic testing of these boreholes, and estimation of aquifer properties from such tests, still poses a challenge for hydrogeologists. Common hydraulic tests, such as step-drawdown or constant-discharge rate tests require a static water level at the start of the test, and the measurement of drawdown (increasing over time) and abstraction rate (fixed for a period of time). Usually, when undertaking a pumping test in an artesian borehole, the drawdown is measured from ground level, and the drop in hydraulic head between static pressure and ground level is often ignored. This procedure also implies that the starting time of the test is not at the static water level. A constant-head test, set at ground level, is the other option. However, the decrease in flow rate is not only dependent on the hydraulic properties of the aquifer, but also masked by pipe hydraulic effects within the well. This kind of test would also limit the available drawdown to be utilized for the test. Hence, it was required to develop a method for undertaking hydraulic tests in strong artesian boreholes, allowing for the drawdown to fluctuate between levels both above and below ground and avoiding the pitfalls described above. The solution is a specially designed and constructed wellhead for the installation of the pump and monitoring equipment prior to the hydraulic test. The standard tests are slightly modified and are only undertaken after sealing the wellhead and reaching static hydraulic pressure. The recommended wellhead construction and subsequent hydraulic tests were implemented at a strong artesian borehole in the Blossoms Wellfield, south of Oudtshoorn in the Western Cape province of South Africa.
Physico-Chemical Assessment of Groundwater in the Orange Water Management Area	Olma Tsakani	Makonto	2015
Abstract The groundwater quality of the Orange Water Management Area (OWMA) was assessed to determine the current groundwater status. Groundwater is of major importance in the Orange Basin and constitutes the only source of water over large areas. Groundwater in the OWMA is mainly used for domestic supply, stock watering, irrigation, and mining activities. Increase in mining and agricultural activities place a demand for the assessment of groundwater quality. The groundwater quality was assessed by collecting groundwater samples from farm boreholes, household boreholes, and mine boreholes. Physical parameters such as pH, temperature and Electrical Conductivity (EC) were measured in-situ using an Aquameter instrument. The groundwater chemistry of samples were analysed using Inductively Coupled Plasma Mass Spectrometry, Ion Chromatography, and Spectrophotometer for cations, anions and alkalinity respectively. The analyses were done at Council for Geoscience laboratory. The results obtained indicated high concentration of Nitrate (NO3), EC, sulphate (SO4), Iron (Fe), and dissolved metals (Chromium, Nickel, Copper, Zinc, and Lead). The concentrations were higher than the South African National Standards (SANS) 241 (2006) drinking water required guideline. The OWMA is characterised by the rocks of the Karoo Supergroup, Ventersdorp Supergroup, Transvaal Supergroup, Namaqua and Natal Metamorphic Province, Gariep Supergroup, and Kalahari Group. Groundwater is found in the sandstones of the Beaufort Group. Salt Mining occurs in the Namaqua Group, hence the high concentration of EC observed. High EC was also found in the Dwyka Group. The salt obtained from the pans underlain by the Dwyka Group rocks has relatively high sodium sulphate content, this probably results from oxidation of iron sulphate to sulphate. Therefore, high concentration of SO4 is due to the geology of the area. High concentration of NO3 is due to agricultural activities, whereas high concentration of EC, Fe, SO4 and dissolved metals is due to mining activities.
Building Of A Gravity Lysimeter To Represent An Ash Backfilled Opencast Coal Mine.	Kamohelo	Mokoena	2019	Poster, Lysimeter, coal mine
Abstract Millions of tons of coal ash are produced across the globe, during coal combustion for power generation. South Africa relies largely on coal for electricity generation. The current disposal methods of coal ash are not sustainable, due to landfill space limitations and operational costs. One way/means of disposing of coal ash that could provide environmental and financial benefits; is to backfill opencast mines with the ash. However, a limited number of studies have been conducted to assess the feasibility of this method in South Africa. Thus the aim of the experiment is to monitor bulk ash disposal under field conditions to improve the understanding of the geochemical and hydrogeological processes occurring during the actual deposition of coal ash in opencast coal mines. To achieve the aim (1) a gravity lysimeter will be built containing both mine spoils and coal ash representing field conditions; (2) the factors (CO2, water level and moisture content) affecting acid mine drainage will be monitored in the lysimeter and (3) the change in the quantity and quality of the discharge released from the lysimeter.
Geochemical Simulation of Drain Water Quality in Gold Tailings	Terry R	Harck	2017	geochemistry, modelling
Abstract This paper presents data obtained from sampling and geochemical analysis of gold tailings and associated pool and drain water. Inverse geochemical modelling using PHREEQC indicated geochemical processes operating in the tailings between the pool and drains. These included pyrite oxidation and dissolution of various minerals identified in the tailings. The processes were incorporated into an ensemble geochemical model to calculate post-closure sulphate concentration in tailings seepage. The ensemble model included a spreadsheet model to calculate oxygen flux at various depths in the tailings column, and a one-dimensional transport model in PHREEQC. The calculated oxygen flux was applied to each cell in the tailings column to determine the amount of sulphide oxidation and the release of acidity into the tailings pore water. The rate of vertical transport of pore water in the column was determined from physical characterisation of the tailings particle size and saturated hydraulic conductivity. The model results indicate elevated sulphate concentrations and acidity moving as a front from the top of the column downwards. The modelled sulphate concentration of 1 500 to 1 900 mg/L 8-16 years after closure compared well with measurements of drain water quality at a tailings dam decommissioned approximately 16 years ago. This provided some credibility to the modelled result of 2 300 mg/L sulphate up to 50 years post-closure. However, the tailings moisture content, infiltration rate, and pyrite oxidation rate in the model were based on literature values, rather than site-specific measurements.
Comparitive analyses between LAK3 package and the high K techniques used for numerical simulation of lake-aquifer interactions	Jannie	Weitz	2015
Abstract Modelling of groundwater systems and groundwater-surface water interaction using advanced simulation software has become common practice. There are a number of approaches to simulate Lake-aquifer interactions, such as the LAK Package integrated into MODFLOW, the high conductivity and fixed stage approaches. LAK and the high conductivity approaches were applied and compared in simulating Lake- aquifer interaction in the Lake Sibayi Catchment, north-eastern, South Africa using the finite difference three-dimensional groundwater flow model, Visual MODFLOW Flex under steady state conditions. The steady state model consisted of two layers: an upper layer consisting of the Sibayi, KwaMbonambi, Kosi Bay and Port Durnford Formations which have similar characteristics, and a lower model layer representing the karst, weathered and calcareous Uloa Formation. The bottom model boundary is constrained by the impermeable Cretaceous bedrock. The model area covers the surface and groundwater catchments of Lake Sibayi which is constrained in the east by the Indian Ocean. A no-flow boundary condition is assigned to the northern, western and southern sides and a constant head boundary is assigned to the eastern side. The Mseleni River and neighbouring plantations were modelled using the River and Evapotranspiration boundary conditions respectively. Input parameters for the various boundary conditions were obtained from the previously developed high resolution conceptual model, including recharge
Groundwater Monitoring: Typical Methods To Improve The Understanding Of Aquifer Potential And The Associated Vulnerabilities	Donovan Craig	Samuels	2019	Monitoring
Abstract In the wake of the ongoing water restrictions in South Africa, the issue of groundwater potential for drought relief has been debated on many environmental and socio-economic platforms, nationally. Consequently, the development of groundwater and its related vulnerabilities has become a key topic to the decision makers and stakeholders. Currently, the recruitment of water professionals into government and private water sectors adds substantial value to understanding the importance of protecting this precious resource. This has allowed the monitoring of groundwater to gain ever increasing momentum. Groundwater monitoring has become an essential scientific tool for role-players to achieve robust and verifiable data used for modelling aquifer potential and vulnerability to pollution and over-abstraction. The data is generally sourced from various hydrogeological and environmental investigations which include groundwater development, vulnerability assessment and remediation projects. Groundwater and environmental consulting firms are tasked with imperative roles for implementing groundwater monitoring programmes to the ever growing industrial, commercial, agricultural and public sectors in South Africa. However, groundwater monitoring data, especially in the private sector, are reliable but remains mostly inaccessible due to confidentiality clauses. This does limit our accuracy and comprehensive understanding for determining aquifer potential and vulnerability risks at large. The conceptualisation and modelling of vast monitoring datasets has been recognised as an important contributing factor to enhance groundwater sustainability. This research emphasises the significance of groundwater monitoring for development, protection and remediation of aquifers. Comparing monitoring results from typical sites and methods, provides scientific validation to support good governance of water. Deterioration of groundwater potability in the sight of an existing drought can have irreversible environmental and economic implications for South Africa.
Groundwater fingerprinting for identifying potential project risks	Meris	Mills	2015
Abstract Implementation of a mining project in South Africa involved dewatering of a fractured rock aquifer at considerable depth below ground level. Groundwater quality within this aquifer is not suitable for domestic use due to high levels of salinity. Numerous geological investigations in the area indicate that the target aquifer is confined, with a different piezometric head to the shallower aquifers. However, regulators and other interested and affected parties expressed concern regarding the potential mixing of more saline groundwater from the deeper aquifer to be dewatered with groundwater from shallower aquifers, which are extensively used for farming and domestic purposes. A large database of groundwater quality monitoring data collected over 16 years was available to investigate the degree of mixing between the deeper more saline and shallower freshwater aquifers. The groundwater chemistry of selected boreholes with known geological profile, depth and construction was used to develop groundwater fingerprinting criteria for each of the aquifers in the area. These fingerprinting criteria were then applied to private and exploration boreholes in the area in order to identify the main aquifer from which groundwater was being sourced. Once the boreholes were classified in terms of groundwater origin, an attempt was made to identify indicators of mixing with deeper, more saline groundwater from the aquifer being dewatered. Groundwater fingerprinting allowed identification of impacts related to the mining operations. The data showed that there was no upward mixing of water related to dewatering operations, but rather that surface spillages and disposal schemes may have resulted in minor changes in shallow groundwater quality. {List only- not presented}
Optimizing borehole performance through dynamic flow and chemistry profiling	Steve	Kalule	2021	Drinking water standards, Groundwater Quality, supply boreholes, remediation system, optimised well design, well profiling
Abstract Stringent drinking water standards for constituents like chromium, arsenic, and nitrates, combined with continually higher demand for groundwater resources have led to the need for more efficient and accurate well characterization. Many boreholes are screened across multiple aquifers to maximize groundwater production, and since these aquifers can have different water qualities, the water produced at the wellhead is a blend of the various water qualities. Furthermore, the water entering a well may not be distributed equally across the screened intervals, but instead be highly variable based on the transmissivity of the aquifers, the depth of the pump intake, the pumping rate, and whether any perforations are sealed off due to physical, chemical, or biological plugging. By identifying zones of high and low flows and differing water qualities, well profiling is a proven technology that helps optimize operational groundwater production from water supply boreholes or remediation systems. This frequently results in increased efficiencies and reduced treatment costs. By accurately defining groundwater quantity and quality, dynamic profiling provides the data needed to optimize well designs. Conventional exploration methods frequently rely on selecting well screen intervals based on performing and analyzing drill stem tests for one zone at a time. Using dynamic flow and water quality profiling, the transmissivity and water quality can be determined for multiple production zones in a matter of one to two days. It also allows the location and size of the test intervals to be adjusted in the field, based on real-time measurements. In this paper we discuss dynamic well profiling techniques with project case examples of characterization different types groundwater boreholes for a variety of applications and industries resulting in significant cost saving and sustainable water abstraction.
Remediation of Groundwater at AngloGold Ashanti South Africa	Gawie	van Dyk	2015
Abstract Gold Mining activities the past 60 years at AngloGold Ashanti polluted the groundwater underlain by 4000 ha of land at the Vaal River and West Wits operations in South Africa. Sulphide material in Tailings Storage Facilities, Waste Rock Dumps and extraction plants produce Saline Mine Drainage with Sulphate, minor salts and metals that seep to the groundwater and ultimately into surface water resources. Water regulation requires mines to prevent, minimise/ reduce or eliminate pollution of water resources. The waste philosophy has matured from tolerate and transfer to treat and termination of pollution sources. The impact of the pollution was determined and possible technologies to treat the impact were evaluated. Source controls of proper water management by storm water management, clean dirty water separation, lined water conveyance structures and reduced deposition of water on waste facilities is crucial. The aquifer character determines the possible remediation technology. From the possible technologies phytoremediation, physical interception and re-use of this water was selected. In future possible treatment of the water would be considered. This paper explain the strategy and report on the phased implementation of these plans and the expected results. The establishment of 750 ha of woodlands as phytoremediation, interception trenches of 1250 m, 38 interception boreholes and infrastructure to re-use this water in 10 water management areas is planned. The total volume of 15 Ml/day would be abstracted for re-use from the boreholes and trenches. The woodlands can potentially attenuate and treat 5 ml/day. The established woodlands of 150 ha proof successful to intercept diffused seep over the area of establishment and reduce the water level and base flow. The 2 implemented trenches of 1000 m indicate a local decline in the water level with interception of shallow groundwater within 1-2 m from surface. The 2 production interception well fields abstracting 50 and 30 l/s respectively indicate a water level decline of between 2 to 14 m with regional cones of depression of a few hundred meters to intercept groundwater flow up to 20 meter. Predictions from groundwater modelling indicate that these schemes can minimise pollution during the operational phase and protect downstream water resources. Predictions from modelling indicate that the pollution sources need to be removed to ensure long term clean-up to return the land to save use. The gold and uranium prize is securing the removal of the sources through re-processing of the tailings and waste rock dumps. After removal of the sources of pollution the remediation schemes would have to be operated for 20 years to return the groundwater to an acceptable standard of stock watering and industrial water use. The water quality is observed by a monitoring network of approximately 100 observation boreholes.
Hydrocarbon plume delineation using a Hydrogeological and Geophysical approach	Albert	Kruger	2015
Abstract Simple and cost-effective techniques are needed for land managers to assess and quantify the environmental impacts of hydrocarbon contamination. During the case study, hydrocarbon plume delineation was carried out using hydrogeological and geophysical techniques at a retail filling station located in Gauteng. Laboratory and controlled spill experiments, using fresh hydrocarbon product, indicate that fresh hydrocarbons generally have a high electrical resistivity, whilst biodegraded hydrocarbons have a lower resistivity. This is attributed to the changes from electrically resistive to conductive behaviour with time due to biodegradation. As such, it should be possible to effectively delineate the subsurface hydrocarbon plume using two-dimensional (2D) Electrical Resistivity Tomography (ERT). As part of the case study, two traverses were conducted using an Electric Resistivity Tomography (ERT) survey with an ABEM SAS1000 Lund imaging system. The resultant 2D tomographs were interpreted based on the resistivity characteristics and subsurface material properties to delineate the plume. Localised resistivity highs were measured in both models and are representative of fresh hydrocarbons whereas areas of low resistivity represented areas of biodegraded hydrocarbons. More conventional plume delineation techniques in the form of intrusive soil vapour and groundwater vapour surveys as well as hydrochemical anlayses of the on-site monitoring wells were used to compare the results and to construct the detailed Conceptual Site Model. During the investigation, four existing monitoring wells located on the site and additional two wells were installed downgradient of the Underground Storage Tanks (USTs) in order to determine the extent of the plume. In conclusion, a comparison was found between the groundwater results and geophysical data obtained during the case study and it was concluded that ERT added a significant contribution to the Conceptual Site Model.
Water Monitoring in the Mining Industry: An Overview	Callie	Pickering	2015
Abstract Water monitoring is a key aspect in the mining industry, in terms of gathering baseline data during the pre-construction stage, identifying potential areas of concern and mitigating source pollutants during the operational stage. A proper water monitoring program assists in the monitoring of plume development and water level rebound during the closure phase. The data made available through consistent long term monitoring should not be underestimated. Monitoring the effect that coal mine operations have on the water quality and quantity of surface and groundwater resources is a complex and multidisciplinary task. Numerous methodologies exist for monitoring of this kind. This paper will supply an overview of the water- rock chemistry associated with coal mine environments and the key indicator elements that should be focused on for water monitoring as well a review of the Best Practice Guidelines requirements in terms of water monitoring. Two case studies of coal mines in KwaZulu Natal will be reviewed, the key challenges outlined and mitigation measures implemented. The impact of requirements such as those set out by the Department of Water and Sanitation in terms of strict water quality limits for water containment and waste facilities as specified by Water Use Licences has also created unrealistic non-compliance conditions. The initial approach to creating a water monitoring programme should involve first identifying gaps in previous datasets and delineating potential sources of contamination. The sampling frequency will depend primarily on the water resource being monitored and the water quality analysis will depend on the type of facility. The facilities required for a specific situation will depend on the type and amount of waste generated, potential for leachate formation, vulnerability of groundwater resources and potential for water usage or resource sensitivity.
Groundwater transport modelling: A fractional/fractal perspective	Amy	Allwright	2019	modelling
Abstract The complexity of real world systems inspire scientists to continually advance methods used to represent these systems as knowledge and technology advances. This fundamental principle has been applied to groundwater transport, a real world problem where the current understanding often cannot describe what is observed in nature. There are two main approaches to improve the simulation of groundwater transport in heterogeneous systems, namely 1) improve the physical characterisation of the heterogeneous system, or 2) improve the formulation of the governing equations used to simulate the system. The latter approach has been pursued by incorporating fractal and fractional derivatives into the governing equation formulation, as well as combining fractional and fractal derivatives. A fractal advection-dispersion equation, with numerical integration and approximation methods for solution, is explored to simulate anomalous transport in fractured aquifer systems. The fractal advection-dispersion equation has been proven to simulate superdiffusion and subdiffusion by varying the fractal dimension, without explicit characterisation of fractures or preferential pathways. A fractional-fractal advection-dispersion equation has also been developed to provide an efficient non-local modelling tool. The fractional-fractal model provides a flexible tool to model anomalous diffusion, where the fractional order controls the breakthrough curve peak, and the fractal dimension controls the position of the peak and tailing effect. These two controls potentially provide the tools to improve the representation of anomalous breakthrough curves that cannot be described by the classical-equation model. In conclusion, the use of fractional calculus and fractal geometry to achieve the collective mission of resolving the difference between modelled and observed is explored for the better understanding and management of fractured systems.
Investigation The Effect Of Excess Pumping On The Groundwater Salinity In Semi-Arid Aquifers Using Predicted Future Scenarios	Mohammed	Seyam	2019	Hydrological Modeling, Groundwater Quality, Salinity, Prediction scenario
Abstract The groundwater quality in semi-arid aquifers can be deteriorated very rabidly due to many factors. The most important factor affecting the quality of groundwater quality in Gaza Strip aquifer is the excess pumping that resulting from the high population density in the area. The goal of this study to investigate the future potential deterioration in groundwater salinity using scenario analysis modeling by artificial neural networks (ANN). The ANN model is utilized to predict the groundwater salinity based on three future scenarios of pumping quantities and rates from the Gaza strip aquifer. The results shows that in case the pumping rate remains as the present conditions, chloride concentration will increase rapidly in most areas of the Gaza Strip and the availability of fresh water will decrease in disquieting rates by year 2030. Results proved that groundwater salinity will be improved solely if the pumping rate is reduced by half and it also will be improved considerably if the pumping rate is completely stopped. Based on the results of this study, an urgent calling for developing other drinking water resources to secure the water demand is the most effective solution to decrease the groundwater salinity.
Practical Solutions for Academic Based Applications – Understanding the importance of correct aquifer test data interpretations	Jorette	Van Rooyen	2021	Gw-Sw interaction, test-pumping, FC, Monitoring
Abstract It has become increasingly apparent that understanding fractured rock mechanics as well as the interactions and exchanges between groundwater and surface water systems are crucial considering the increase in demand of each in recent years. Especially in a time where long term sustainability is of great importance for many water management agencies, groundwater professionals and the average water users. Previous callow experience has shown that there is a misunderstanding in the correct interpretation and analyses of pumping test data. The fracture characterisation (FC) method software provides a most useful tool in the overall understanding of a fractured rock aquifer, quantification of the aquifer’s hydraulic (flow regime and flow boundary conditions) and physical properties, only if the time-drawdown relationships are correctly interpreted and when the theoretical application principles are applied. Interpretation is not simply a copy and paste of the aquifer test data into the software to get a quick answer (especially when project time constraints are considered), however, recent experiences with numerous field examples, required intricate understanding of the geological environment, intended use and abstraction schedules coupled with the academic applications on which the software was based for correct interpretation. Through the application of correct interpretation principles, a plethora of flow information becomes available, of which examples will be provided in the presentation itself. By achieving this, flow can be conceptualised for inputs into a conservative scale three-dimensional numerical flow model and calibrated based on measurable data in a fraction of the time of a conventional regional model. Although higher confidence levels are achieved with these practical solutions, monitoring programmes are still required to provide better insight of the aquifer responses to long-term abstraction and recovery.
Groundwater In Sustainable Development Goal 6: The South African Case Study	Sivashni	Naicker	2019	Domesticate, South Africa, United Nations
Abstract South Africa has committed to achieving the United Nations Sustainable Development Goals (SDG's) by 2030. But what does this mean and how does groundwater fit in to this? SDG 6 in particular focuses on ensuring universal access to safe and affordable drinking water for all by 2030. SDG 6 requires that the country protects and restores water-related ecosystems such as forests, mountains, wetlands, aquifers and rivers which are essential if we are to mitigate water scarcity. To accomplish this, South Africa has proceeded to align various plans, strategies, and policies to encompass the targets of the SDG's. This paper will focus on SDG sub-goal 6.3 which incorporates improvement of water quality and sub-goal 6.6 which involves protection and restoration of ecosystems. The methodology given by the UN for the groundwater in indicator 6.3.2 stipulates that countries are required to report on "proportion of water with good ambient water quality", in South Africa however we had to domesticate the indicator i.e. render it suitable for South African conditions so we changed the methodology to "proportion of water the conforms to the Water Quality Objectives (WQO's)" but there are virtually no WQO's developed for groundwater. Four core groundwater quality parameters (Electrical Conductivity, pH, Nitrate and Sulphate) are available through ZQM stations categorized through 65 hydrogeological (Vegter) regions. Groundwater water quality baseline is calculated as a reference period/range per hydrogeological region. For SDG 6.6, the indicator required for groundwater is "Quantity of groundwater within aquifers" The methodology received by the UN for "Quantity of groundwater within aquifers" required a baseline (average reference period of five years) in meters per hydrogeological region. This indicator is again domesticated for South Africa and based on the 40-60 percentiles of groundwater levels per hydrogeological region. There are a number of future indicators that can be included for aquifers under SDG 6.6, but the groundwater sector needs to come together and decide what is important to report on. These SDG targets reporting has given the Water and Sanitation sector a new look at data. It has forced us to critically think of concepts such as baseline and performance monitoring. We now know where our data gaps and targets are, and we have to provide an action plan to address these.
Using gravity anomalies from GRACE to estimate changes in groundwater storage in the Vaal River Basin	Khuliso	Masindi	2015
Abstract The Gravity Recovery and Climate Experiment (GRACE) satellites detect minute temporal variation in the earth's gravitational field at an extraordinary accuracy, in order to make estimation of the total water storage (TWS). GRACE provides a unique opportunity to study and monitor real time water variation in the hydrologic stores (snow, groundwater, surface water and soil moisture) due to increases or decreases in storage. The GRACE monthly TWS data are being used to estimate changes in groundwater storage in the Vaal River Basin for a period (2002 to 2014). The Vaal River Basin has been selected, because it is one of the most water stressed catchments in South Africa; it is well-renowned for its high concentration of industrial activities and urbanized zones. Therefore, in order to meet future water demands, it is critical to monitor and calculate changes in groundwater storages as an important aspect of water management, where such a resource is a key to economic development and social development. Previous studies in the Vaal River Basin were mostly localised focusing mainly on groundwater quality and to a lesser extent groundwater assessment. Hydrological models have been generated for the whole of South Africa, but many of these models do not take into account the groundwater component. Thus, there is a significant gap in the understanding of surface and ground water dynamics in the Vaal River Basin. The paucity of data and monitoring networks are often the limitation in calculating changes in water storage over a large area, particularly in Africa. In this scenario GRACE is a good approach to estimate changes in hydrological storages as it covers large areas and generates real time data. It does not require information on soil moisture, which is often difficult to measure. The accuracy of calculating change in groundwater storage lies in the processing of GRACE data and smoothing radii. For this study, smoothing radii of 1500, 900, 500, 300, 150 and 1 km are used. Currently the associated error with different smoothing radii is unknown. The preliminary results indicate that the study area experienced a loss in TWS of -31.58 mm equivalent water height over a period of 144 months in TWS at 300 km smoothing radius. The change in groundwater storage is calculated by incorporating hydrologic components to the TWS (work in progress). The results obtained from this study will be compared to existing hydrological models and results generated from models applicable to the semi-arid region of South Africa. It is anticipated that this satellite observation technique, GRACE, will provide an accurate estimate of change in groundwater storage. Furthermore, it will show the usefulness of satellite based techniques for improving our understanding of groundwater dynamics, which will improve water management practices.
The value (or not) of measuring redox potential in groundwater: A case study	Meris	Mills	2015
Abstract The redox state of groundwater is an important variable for determining the solubility and mobility of elements which can occur in different redox states at earth surface conditions, such as Fe, Mn, Cr, As, U, N, S, V etc. Eh-pH diagrams are potentially invaluable for understanding and predicting the behaviour of these redox species yet, unlike pH, redox is seldom a routine field parameter due to the difficulties in measurement and interpretation. This paper discusses the potential use and limitations of field measurements of the redox state of groundwater with specific reference to the geochemical behaviour of dissolved iron in the Table Mountain Group (TMG) aquifer. As part of an investigation into iron cycling within the TMG aquifer, the redox state of groundwater was estimated through three different methods, namely direct in-situ measurement of Eh, direct measurement of DO and calculation from iron speciation in groundwater. Comparison of the results from the three methods highlights the potential value of collecting redox data, but also the complexity of controls on redox potential. The redox measurements allowed the determination of the controlling reactions on iron mobility within the TMG, but only by using the iron speciation method to calibrate the in-situ values and thereby identify which redox pair was controlling redox equilibrium. As this requires measurement of redox ion pairs in solution, it is unlikely to become a routine method for redox assessment, unless the specific redox state of an element is critical in understanding its mobility. For the majority of groundwater site investigations, measurement of the dissolved oxygen content of groundwater is probably sufficient as a first pass.
Using electrical resistivity method for subsurface mapping of shallow aquifers in Heuningnes Catchment, South Africa	Kinsley	Manyama	2015
Abstract The current study investigated the subsurface of aquifers in Heuningnes Catchment focusing on aquifer characteristics for groundwater resource assessments. Surface geophysical resistivity method was adapted for mapping the shallow subsurface layers and hydrogeologic units at selected sites within the catchment. The aim was to provide a preliminary overview of the subsurface nature of aquifers within the study area, by establishing features such as geological layers, position of weathered zones, faults and water bearing layers. The multi-electrode ABEM SAS 1000 resistivity meter system, using the Wenner array, was used to obtain 2D resistivity data of the subsurface. The acquired data was processed and interpreted using Res2DINV software to produce the 2D resistivity models. The analysis of the resistivity models of the subsurface reveals maximum of four layers; sandstone, shale, poor clayed and brackish water saturated layer. On comparing the model results with the surficial geological formation of the catchment geological map, the identified layers were found to correspond with the geology of the area. The findings i) provide insights on sites that can be drilled for groundwater exploration, ii) show possible water-type variations in the subsurface. Although the results are not conclusive but they provide basis for further research work on quality and flow dynamics of groundwater. {List only- not presented} Key words: aquifer properties, hydrogeologic units, geo-electric model, electrical-resistivity method
Regulating the regulations for managing groundwater use to improve water security in Southern Africa: Reflection on water use licence application process in South Africa	Mfundi	Biyela	2019	water entitlement, Regulations, WARMS, Southern Africa, South Africa
Abstract In the management of water resources especially groundwater resources, implementing existing regulations is one of the much needed aspects ensuring water security through the regulated use. However, such regulations are not regulated to ensure that they served the intended purpose in their original formulation. In South Africa, a study was carried out to assess the relevance and efficient of adhering to procedural requirements during water use licence application (WULA) process. Lived-experiences and observation methods were used to collect data. The department of water and sanitation was used as a case study. Interpretative analysis approach was used to provide the meaning on the analysed information. The WARMS database was accessed where the number of days that WULA process was extracted. The regulation No. 40713 about WULA process was analysed. The five-year-data prior and post the promulgation of regulation No. 40713 were extracted from WARMS database and evaluated in terms of the duration each application took to be processed for WULA. Data on water use for abstractions from all the regions were obtained from WARMS database and assessed. Dates when applications were submitted and when such applications were finalised were analysis per month and per years for temporal analysis. The number of entitlements received during the particular period and the number of applications recommended to be declined and issued were assessed using exploratory data analysis methods. Graphical method was adapted to increase results visualisation on water use entitlements. Key results showed that the process of WULA was generally slow and reasons were provided for such outcome. However, the temporal analysis revealed an increasing trend in the post promulgation of regulation No. 40713 suggesting that regulations when re-regulated serve its intended purpose. Although such findings are not conclusive but they inform a basis for re-regulating enforcement regulations in Southern African countries with issues similar to South Africa on water entitlement.
Ground Water Management in South Africa: Challenges and Constraints	Courage	Mlambo	2015
Abstract Water scarcity is a growing issue in South Africa. The consumption of water is rising and as such, water is becoming a scarce and valuable resource. Given the circumstances that South Africa is facing, improving the use of ground water could help tackle water scarcity in South Africa. Groundwater has been an important source of water and it can bring socio-economic benefits if properly used. Studies have proved that groundwater resources play a fundamental role in the security and sustainability of livelihoods and regional economies throughout the world. However, in South Africa, groundwater still remains a poorly managed resource and this hinders socio-economic development. This paper examines the current state of ground water management in South Africa. The paper also examines how ground water in South Africa is currently allocated and used, and explores some of the consequences of current water management arrangements. {List only- not presented}
A case study review of a high tech approach towards wellfield and aquifer management.	Paul	Lee	2015
Abstract Faced with a burgeoning population and property growth, and in preparation for a future drier climate regime; the coastal town of Hermanus in the Western Cape has set up two wellfields to abstract groundwater from the underlying aquifer in order to augment the constrained surface water supply from the De Bos Dam. Water Use Licences (WUL) were issued to the Overstrand Municipality in June 2011 and December 2013. The licences authorise a maximum annual abstraction of 1 600 Ml of water from the Gateway wellfield and 800 Ml of water from the Volmoed and Camphill wellfield via several boreholes. The water abstracted from the Gateway wellfield is pumped via a booster pump station to the Preekstoel Treatment Plant. The Volmoed and Camphill wellfield are situated at a higher altitude allowing for a gravity feed pipeline. Earth Science Company, Umvoto Africa, has the responsibility to ensure Resource Quality Objectives are met which include balancing the need to protect the resource on the one hand; and the to develop sustainable utilisation of the Hermanus groundwater resources and compliance with the WUL on the other. The consultancy provides hydrogeological support, wellfield management and technical advice in operating the boreholes, pumps, boosters and related infrastructures. Running the operations of the wellfield relies on a high-tech, semi-automated system, incorporating a remotely controlled, telemetry based structure. Vital parameters are monitored by electronic sensors, feeding data to processors which alters pump performance to maintain specified boundary levels. Data is simultaneously communicated via telemetry to a central control which uses data acquisition software to portray information to the operators. Warning alarms both alert operators via SMS and in certain instances auto-shut down the system. To ensure ecological sustainability of the ground water resource, the wellfield also requires hydrogeological monitoring at far field locations within the recharge areas. Some of these locations are in remote areas making data download costly. The high-tech telemetry approach is used with positive results. Any automated telemetry system is prone to malfunction and environmental hazards. The challenge lies in managing this and providing sufficient back up and duplication of systems. The paper gives an overview of the components and flow of data based on the experiences gained during the evolution and development over 12 years of operation. Automation produces vast data bases which are often not sufficiently analysed, the premise that "once collected, the task is done". However data is only as good as the people who drive the systems and this paper provides a critical analysis of human intervention in an automated system and the decisive role of quality-checks. Finally the paper seeks to provide a pragmatic guideline for water users to comply with the WUL and institutional regulations.
Estimation of Groundwater Recharge Response from Rainfall Events in a Semi-Arid Fractured Aquifer: Case study	Phathutshedzo	Nemaxwi	2015
Abstract Estimating groundwater recharge response from rainfall remains a major challenge especially in arid and semi-arid areas where recharge is difficult to quantify because of uncertainties of hydraulic parameters and lack of historical data. In this study, Chloride Mass Balance (CMB) method and Extended model for Aquifer Recharge and soil moisture Transport through unsaturated Hardrock (EARTH) model were used to estimate groundwater recharge rates. Groundwater chemistry data was acquired from the Department of Water and Sanitation (DWS) and Global Project Management consultants, while groundwater samples were collected to fill-in the identified gaps. These were sent to Council for Geoscience laboratory for geochemical analysis. Rainfall samples were also collected and sent for geochemical analysis. An average value of rainfall chloride concentration, average groundwater chloride concentration and mean annual precipitation (MAP) were used to estimate recharge rate at a regional scale. Local scale recharge was also calculated using chloride concentration at each borehole. The results were integrated in ArcGIS software to develop a recharge distribution map of the entire area. For EARTH model, long term rainfall and groundwater levels data were acquired from the South Africa Weather Services and DWS, respectively. Soil samples were collected at selected sites and analysed. These were used to determine representative values of specific yield to use on EARTH model. 60% of the groundwater levels data for 5 boreholes was used for model calibration while the remaining 40% was used for model validation. The model performance was evaluated using coefficient of determination (R2), correlation coefficient (R), Root Mean Square Error (RMSE) and Mean square error (MSE). Regional recharge rates of 12.1 mm/a (equivalent to 1.84% of 656 mm/a MAP) and 30.1 mm/a (equivalent to 4.6% MAP) were calculated using rainfall chloride concentrations of 0.36 and 0.9 mg/L, respectively. The estimated local recharge rates ranged from 0.9-30.2 mm/a (0.14 - 4.6%) and 2 - 75 mm/a (0.3 - 11.4%) using chloride concentration of 0.9 and 0.36 mg/L, respectively. The average recharge rate estimated using EARTH model is 6.12% of the MAP (40.1 mm/a). CMB results were found to fall within the same range with those obtained in other studies within the vicinity of the study area. The results of EARTH model and CMB method were comparable. The computed R2, R, RMSE and MSE ranged from 0.47-0.87, 0.68-0.94, 0.04-0.34, 0.16-3.16, and 0.50-0.79, 0.68-0.89, 0.07-0.68, 0.15-8.78 for calibration and validation, respectively. This showed reasonable and acceptable model performance. The study found that there is poor response of groundwater levels during rainy season which is likely to be due to lack of preferential flows between surface water and groundwater systems. This has resulted in poor relationship between estimated and observed groundwater levels during rainfall season. Key words: ArcGIS, CMB, EARTH, Groundwater recharge, rainfall
Decision making with web-based geo-spatial databases coupled to groundwater models	John	Wise	2015
Abstract Model calibration and scenario evaluations of 2D and 3D groundwater simulations are often computationally expensive due to dense meshes and the high number of iterations required before finding acceptable results. Furthermore, due to the diversity of modelling scenarios, a standardised presentation of modelling results to a general audience is complicated by different levels of technical expertise. Reducing computational time In this presentation we look briefly at the use of Reduced Order Models (ROM's), which is one of the recent developments in groundwater modelling. The method allows significant speed-up times in model calibration and scenario evaluation studies. In saturated flow for example, these approaches show speed-up times of >1000 when compared to full models created with Finite Element of Finite Difference methods. These methods are demonstrated to a case study in the Table Mountain Group, in which we show a simplified parameter calibration and scenario evaluation study. Standardising presentation In order to present the results to as wide an audience as possible, the use of a web-browser as a GUI is proposed, where the web-page is coupled to a geo-spatial database and data is presented in a spatial and numeric format. The use of the spatial database manager PostgreSQL with PostGIS is proposed. Through a browser interface, users can run modelling scenarios using the ROM, which is evaluated in near real-time. Following the evaluation of the model, we show how PostGIS can spatially present data on a base-map such as google maps. In keeping with the current trends in online map customisation, viewers can interactively choose to overlay the base-map with a data-type (such as pressure or hydraulic head contours or flow direction) that is most intuitive for their level of familiarity with the data. Conclusion In using advanced modelling techniques and a simplified browser based presentation of results, high-level decisions in water resource management can be significantly accelerated with the use of interactive scenario evaluations. Furthermore, by reaching a broader audience, public participation will be significantly enhanced.
Re-inventing the Wheel - The Iterative Development of Groundwater Sustainability in Southern Africa.	Jeffrey	Davies	2015
Abstract The SADC Grey Data archive http://www.bgs.ac.uk/sadc/ provides a chronology of groundwater development within the constituent countries of the SADC region. Early reports show how groundwater development progressed from obtaining water by well digging to the mechanical drilling of boreholes for provision of water for irrigation, township development, transport networks and rural settlement. During the 1930s steam driven drilling rigs were supplanted by petrol engine driven cable tool percussion drilling. Dixey (1931), in his manual on how to develop groundwater resources based on experiences in colonial geological surveys in eastern and southern Africa, describes aquifer properties, groundwater occurrence and resources as well as water quality and groundwater abstraction methods. Frommurze (1937) provides an initial assessment of aquifer properties in South Africa with Bond (1945) describing their groundwater chemistry. South African engineers transferred geophysical surveying skills to the desert campaign during World War II. Paver (1945) described the application of these methods to various geological environments in South Africa, Rhodesia and British colonial territories in eastern and central Africa. Test pumping methods using electric dippers were also developed for the assessment of groundwater resources. Enslin and others developed DC resistivity meters, replacing early Meggar systems, produced data that when analysed, using slide rules with graphs plotted by hand, identified water bearing fractures and deeply weathered zones. Tentative maps were drawn using interpretation of aerial photographs and heights generated using aneroid altimeters. The problems faced by hydrogeologists remain the same today as they were then, even though the technology has greatly improved in the computer era. Modern techniques range from a variety of geophysical surveying methods, automated rest level recorders with data loggers to GPS location systems and a whole host of remotely sensed data gathering methods. Worryingly, using such automated procedures reduces the ability of hydrogeologists to understand data limitations. The available collection of water level time series data are surprisingly small. Surrogate data need to be recognised and used to indicate effects of over abstraction as demand grows. As the numbers of boreholes drilled per year increases the number of detailed hydrogeological surveys undertaken still remains seriously small. Has our knowledge of hydrogeological systems advanced all that much from what was known in the 1980s? Case histories from Malawi, Zimbabwe and Tanzania illustrate a need for groundwater research with well-judged sustainability assessments to underpin safe long-term groundwater supply for the groundwater dependent communities in the region.
Modelling Mine Water Rebound With MODFLOW	Stephen	Fonkem	2015
Abstract A review from international literature discredits the capability of MODFLOW to simulate mine water rebound, due to the nonstandard hydrogeology of underground mine systems. The conceptual understanding is that, after cessation of dewatering, mine water inflow rates and hydraulic heads are related to the void-volume, the differences in head between the water in the mine void and head dependent source, plus natural recharge to the mine voids. The flooded mine voids in the study area are partially underlain by a dolomitic aquifer. The other head dependent source of inflow into the mine voids are the surrounding and overlying Karoo aquifers. Head independent inflow rates into the mine voids, using the long term decant rates, was estimated to be 0.2% of rainfall. During mining, dewatering occurred at approximately 3 to 6 Ml/d. The objective of the model was therefore to simulate the changes head-dependent inflow rates during the rebound period. Analysis of the water level recovery data depicted that once the mine filled up with water, the hydraulic head of the mine rose with the elastic storage coefficient value of the mine void and not the specific retention as conditions changed from unconfined to confined. A three layer model was setup, to represent the two seams mined, separated by a deep Karoo aquifer. The presence of the dolomite on the mine floor was incorporated using the general head boundary package. Head dependent influx from overlying shallow and intermediate Karoo aquifers were simulated using the river package. All model layers were simulated as confined, initially to avoid model convergence issues. The confined setup proved to be the core in simulating mine water rebound with MODFLOW. The modelling exercise showed that storage during rebound is a boundary condition. This simply means that the complexity of mine water rebound can only be achieved in MODFLOW by proper time stepping and dividing the model into different stress periods to represent the changes in storage. Rebound in the study area, modelled with 21 stress periods produced a perfect water level recovery data for the different mine compartments. This was achieved by applying storage capacities of between 0.3 to 0.006 to simulate rebound during unconfined conditions, and values of between 10-4 and 10-5 when the mine void is flooded. The results showed that the inflow from the dolomitic aquifer steadily decreased from 4121 m3/d to 0 m3/d as the mine hydraulic head increased and rose over the head in the dolomitic aquifer. During the same period, inflow from the surrounding Karoo aquifers decreased from 2422 m3/d to less than 10 m3/d. The results of the model were very important in determining the volumes of water to be abstracted from the mine voids for ash-backfilling. {List only- not presented}