Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 51 - 100 of 795 results

Title	Presenter Name	Presenter Surname	Conference year	Keywords
Effects of Urbanization and Agricultural activities on Aquifer storage and Groundwater quality	Athenkosi	Matshini	2015
Abstract POSTER Aquifer stress arising from urbanization and agricultural activities, these two factors affect aquifer properties when prolonged. Increase in urbanization especially those situated on top unconfined or semi-confined aquifer results in pressure on natural resources, this includes water resources, and changes of land use for agricultural purposes with high economic benefits has an effect on groundwater quality to due to application of Nitrogen- fertilizers during crop rotation and this is largely experienced in developing countries. The effects ranges from groundwater quality to aquifer storage as prolonged aquifer withdrawals due to irrigation, construction, manufacturing affects groundwater storage. Assessment of urbanization and agricultural effects on groundwater requires a complex analysis as integration approaches needs to be discovered for a better analysis of the two more specially when assessing groundwater pollution. The study was conducted to assess the impacts of urbanization and agricultural activities on aquifer storage and groundwater quality: by (a) determining the relationship between the occurrence of contamination due to urbanization by assessing contaminants present in the study area (b) develop groundwater protection, and if any offer recommendation for groundwater management. Multiple-well tests were conducted observing the behavior of drawdown and recovery for assessing groundwater storage. Two aquifer properties were observed to yield information about any changes in aquifer storage (transmissivity and storage coefficient) and groundwater quality lab test focusing on TDS, nitrate and pH were conducted. Historical results reflect that before industrial and urban revolution the groundwater contained small amounts of TDS compared with the present results. Increase in nitrate and pH concentrations observed in location closer to agricultural areas. Prolonged aquifer withdrawals increases expansion of cone of depression and therefore increases aquifer vulnerability and the risk of aquifer being polluted, and this increases storage coefficient. This study can be used to formulate protection zones for water resources and practice towards groundwater management.
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.
Variability In Kd And How It Relates To The New Guidelines For Contaminated Land	Michelle	Papenfus	2015
Abstract Globally, a growing concern have been that the heavy metal contents of soil are increasing as the result of industrial, mining, agricultural and domestic activities. While certain heavy metals are essential for plant growth as micronutrients, it may become toxic at higher concentrations. Additionally, as the toxic metals load of the soil increases, the risk of non-localized pollution due to the metals leaching into groundwater increases. The total soil metal content alone is not a good measure of risk, and thus not a very useful tool to determine potential risks to soil and water contamination. The tendency of a contaminant to seep into the groundwater is determined by its solubility and by the ratio between the concentration of the contaminant sorbed by the soil and the concentration remaining in solution. This ratio is commonly known as the soil partitioning or distribution coefficient (Kd). A higher Kd value indicate stronger attraction to the soil solids and lower susceptibility to leaching. Studies indicate that the Kd for a given constituent may vary widely depending on the nature of the soil in which the constituent occurs. The Kd of a soil represents the net effect of several soil sorption processes acting upon the contaminant under a certain set of conditions. Soil properties such as the pH, clay content, organic carbon content and the amount of Mn and Fe oxides, have an immense influence on the Kd value of a soil. Kds for Cu, Pb and V for various typical South African soil horizons were calculated from sorption graphs. In most cases there were contrasting Kd values especially when the cations, Cu and Pb, had high contamination levels, the value for V was low. There is large variation between the Kds stipulated in the Framework for the Management of Contaminated land (as drafted by the Department of Environmental Affairs) and the values obtained experimentally in this study. The results further indicate that a single Kd for an element/metal cannot be used for all soil types/horizons due to the effect of soil properties on the Kd. The results for Cu and Pb indicated that the Kds can range in the order of 10 to 10 000 L/kg for Cu and 10 to 100 000 L/kg for Pb. The variation in V Kd was not as extensive ranging from approximately 10 to 1 000 L/kg. {List only- not presented}
Application of GIS Mapping Techniques to Classify Karoo Aquifers	Mildred	Goes	2015
Abstract POSTER As the National Water Act has evolved to provide for more effective and sustainable management of our water resources, there has been a shift in focus to more strategic management practices. With this shift come new difficulties relating to the presentation of sensitivity issues within a spatial context. To this end it is necessary to integrate existing significant spatial layers into one map that retains the context, enables simple interpretation and interrogation and facilitates decision making. This project shows the steps taken to map and identify key groundwater characteristics in the Karoo using Geographic Information Systems (GIS) techniques. Two types of GIS-based groundwater maps have been produced to assist with interpretation of existing data on Karoo Aquifer Systems in turn informing the management of groundwater risks within Shell's applications for shale gas exploration. Aquifer Attribute and Vulnerability maps were produced to assist in the decision making process. The former is an aquifer classification methodology developed by the project team, while the latter uses the well-known DRASTIC methodology. The overlay analysis tool of ESRI's ArcGIS 10.1 software was used, enabling the assessment and spatial integration of extensive volumes of data, without losing the original detail, and combining them into a single output. This process allows for optimal site selection of suitable exploration target areas. Weightings were applied to differentiate the relative importance of the input criteria. For the Attributes maps ten key attributes were agreed by the project team to be the most significant in contributing to groundwater/aquifer characteristics in the Karoo. This work culminated in the production of a series of GIS-based groundwater attributes maps to form the Karoo Groundwater Atlas which can be used to guide groundwater risk management for a number of purposes. The DRASTIC model uses seven key hydrogeological parameters to characterise the hydrogeological setting and evaluate aquifer vulnerability, defined as the tendency or likelihood for general contaminants to reach the watertable after introduction at ground surface.
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".
Taking Capture Principle into Practice	Helen	Seyler	2015
Abstract The 'maintainable aquifer yield' can be defined as a yield that can be maintained indefinitely without mining an aquifer. It is a yield that can be met by a combination of reduced discharge, induced recharge and reduced storage, and results in a new dynamic equilibrium of an aquifer system. It does not directly or solely depend on natural recharge rates. Whether long-term abstraction of the 'maintainable aquifer yield' can be considered sustainable groundwater use should be based on a socio-economic-environmental decision, by relevant stakeholders and authorities, over the conditions at this new dynamic equilibrium. This description of aquifer yields is well established scientifically and referred to as the Capture Principle, and the link to groundwater use sustainability is also well established. However, implementation of the Capture Principle remains incomplete. Water balance type calculations persist, in which sustainability is linked directly to some portion of recharge, and aquifers with high use compared to recharge are considered stressed or over-allocated. Application of the water balance type approach to sustainability may lead to groundwater being underutilised. Implementation of the capture principle is hindered because the approach is intertwined with adaptive management: not all information can be known upfront, the future dynamic equilibrium must be estimated, and management decisions updated as more information is available. This is awkward to regulate. This paper presents a Decision Framework designed to support implementation of the capture principle in groundwater management. The Decision framework combines a collection of various measures. At its centre, it provides an accessible description of the theory underlying the capture principle, and describes the ideal approach for the development operating rules based on a capture principle groundwater assessment. Sustainability indicators are incorporated to guide a groundwater user through the necessary cycles of adaptive management in updating initial estimations of the future dynamic equilibrium. Furthermore, the capture principle approach to sustainable groundwater use requires a socio-economic-environmental decision to be taken by wide relevant stakeholders, and recommendations for a hydrogeologists' contribution to this decision are also provided. Applying the decision framework in several settings highlights that aquifer assessment often lags far behind infrastructure development, and that abstraction often proceeds without an estimation of future impacts, and without qualification of the source of abstracted water, confirming the need for enhanced implementation of the capture principle.
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.
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.
Development of United Nations Framework Classification for Resources (UNFC) for Groundwater Resources Management	Peter	van der Keur	2023	SDGs, UNFC, common pool resources, subsurface geo-resources, sustainable groundwater resources management
Abstract There is an urgent need to support the sustainable development of groundwater resources, which are under increasing pressure from competing uses of subsurface geo-resources, compounded by land use and climate change impacts. Management of groundwater resources is crucial for enabling the green transition and attaining the Sustainable Development Goals. The United Nations Framework Classification for Resources (UNFC) is a project-based classification system for defining the environmental-socio-economic viability and technical feasibility of projects to develop resources and recently extended for groundwater. UNFC provides a consistent framework to describe the level of confidence in groundwater resources by the project and is designed to meet the needs of applications pertaining to (i) Policy formulation based on geo-resource studies, (ii) Geo-resource management functions, (iii) Business processes; and (iv) Financial capital allocation. To extend use in groundwater resources management, supplemental specifications have been developed for the UNFC that provide technical guidance to the community of groundwater professionals to enhance sustainable resource management based on improved decision-making. This includes addressing barriers to sustainably exploiting groundwater resources, avoiding lack of access to water and also related to ‘common pool resources’ in which multiple allocations are competing with domestic water supply (e.g. geo-energy, minerals, agriculture and ecosystems, and transboundary allocation of natural resources). UNFC for groundwater resources is designed to enhance governance to protect the environment and traditional users while ensuring socio-economic benefits to society. Consequently, it is a valid and promising tool for assessing both the sustainability and feasibility of groundwater management at local, national and international levels.
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.
Dewatering Impacts of a South African Underground Coal Mine	Paul JH	Lourens	2017	coal mine, hydrocensus, dolerite contact zones, Monitoring, over-abstraction
Abstract The University of the Free State investigated the possible dewatering of boreholes situated on the farm properties in the vicinity of an underground coal mine. The investigation consisted of three phases. Phase one was a hydrocensus on the farm properties. Phase two consisted of borehole yield determination by conducting pumping tests on the boreholes (where possible) identified in the hydrocensus phase. Phase three included a visit to the underground mine workings, where water samples were collected at different groundwater inflow locations (especially water flowing in at the ventilation shaft). The monthly groundwater monitoring data of the underground coal mine was also incorporated for interpretation purposes. It appears that the water levels of the boreholes outside the mining boundaries are not affected. The water levels of the monthly monitored boreholes stabilized or even started recovering over the last few years. It also seems as though the larger streams in the area drains the groundwater as most of the deeper water level areas coincides with the presence of the streams. Most of the boreholes have typical borehole yields that is to be expected from Karoo formations i.e. between 0.5 and 1.5 L/s. An interesting observation is that a number of the boreholes with deep water levels are situated along dolerite contact zones at the western side of the mine. This may also be a geological structure resulting from the impact of a meteorite? From the available data it appears that the boreholes along this structure have the same chemical character as the water flowing down the ventilation shaft, strengthening the belief that the water from the shaft originates from this structure (or structures). To determine the origin of the water flowing down the ventilation shaft, a detailed study of the structure to the west of the shaft is recommended. The farmers in the area should carefully monitor their water use in the boreholes, as over-abstraction can result in total failure of some of the boreholes.
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.
Evaluating Groundwater Availability Based on Land Cover and Local Hydrogeology - A Groundwater Balance Approach	Hendrik	Botha	2019	land cover, water balance
Abstract The main purpose of this paper is to present a case study where a water balance concept was applied to describe the expected groundwater safe yield on a sub-catchment scale. The balance considers effective recharge based on local hydrogeology and land cover types, basic human needs, groundwater contribution to baseflow, existing abstraction and evaporation. Data is derived from public datasets, including the WRC 90 Water Resources of South Africa 2012 Study, 2013-2014 South African (SA) National Land Cover and Groundwater Resource Assessment Ver. 2 (GRAII) datasets. The result is an attempt to guide a new groundwater user regarding the volume of groundwater that can be abstracted sustainably over the long-term.
Estimating Hydraulic Parameters Through The Measurement Of Streaming Potentials	Jemias Clifford	Mazibuko	2019	hydraulic flow
Abstract The hydraulic parameters of heterogeneous aquifers are often estimated by conducting pumping (and recovery) tests during which the drawdown in a borehole intersecting the aquifer is measured over time, and by interpreting the data after making a number of assumptions about the aquifer conditions. The interpreted values of the hydraulic parameters are then considered to be average values that represent the properties of the bulk aquifer without taking into account local heterogeneities and anisotropies. An alternative and more economic approach is to measure streaming potentials in the vicinity of the borehole being tested. The streaming potential method is a non-invasive geophysical method that measures electrical signals generated by groundwater flow in the subsurface through a process known as electrokinetic coupling. This method allows data to be recorded at a high spatial density around the borehole. The interpretation of streaming potential data in terms of aquifer hydraulic parameters is facilitated by a coupled flow relationship which links the streaming potential gradient to the hydraulic gradient through a constant of proportionality called the electrokinetic coupling coefficient. In the current study, field measurements of streaming potentials were taken during the pumping and recovery phases of pumping tests conducted at two sites with dissimilar geological and geohydrological conditions. The recorded streaming potential data were interpreted by calculating the hydraulic head gradient from the streaming potential gradient, and by using the potential field analytical solution for the transient mode, which relates the streaming potential field directly to the average hydraulic conductivity. Hydraulic conductivity values estimated from the streaming potential method were of the same order as values determined from the analysis of drawdown data, with a relative error of 0.2. This study demonstrates that the streaming potential method is a viable tool to compliment pumping tests and provide a spatial representation of the hydraulic parameters.
GIS-PMWIN, A Preprocessor In ArcGIS For Groundwater Modeling With PMWIN	Haili	Jia	2015
Abstract PMWIN5.3 has been one of the most commonly used software for groundwater modeling because of its free source and the adoption of popular core program MODFLOW. However, the fixed formats required for data input and lack of GIS data support have posted big challenges for groundwater modelers who are dealing with large areas with complicated hydrogeological conditions. In South Africa, most geological and hydrogeological data have been captured and stored in GIS format during various national research projects such as WR2005, NGA and etc. Therefore, a proper linkage between PMWIN and ArcGIS is expected to do the preprocessing for modeling in PMWIN. Visual Basic for Application (VBA) embedded in ArcGIS 9.3 was used to develop the linkage. Based on the conceptualization of the study area, the model dimension, discretization and many value setting processes can be easily carried out in ArcGIS other than directly in PMWIN. Then the grid specification file and other input files can be exported as the PMWIN-compatible files. The functions of move, rotation, refinement, sub-model, deleting and inserting row(s) or column(s) of the model have also been developed to avoid the inconvenience aroused from model modification. The linkage can be used with a higher version of PMWIN or ArcGIS. It has been applied to several gold fields in the Witwatersrand gold basin to simulate the groundwater flow and mass transportation for various conditions and scenarios. One of the applications will be presented in this paper. It has been proved that the linkage is efficient and easy to use. {List only- not presented}
Temperature And Ec Stratification In The Gasification Zone And Surrounding Aquifers Of Underground Coal Gasification At The Majuba Pilot Plant	Lehlohonolo	Mokhahlane	2017	underground coal gasification, stratification
Abstract Underground coal gasification (UCG) is a chemical process that converts coal in-situ into a gaseous product at elevated pressures and temperatures. Underground coal gasification produces an underground cavity which may be partially filled with gas, ash, unburned coal and other hydrocarbons. In this study we assessed the stratification down the length of the boreholes. This was done by comparing the Electrical Conductivity (EC) profile of background boreholes to the verification borehole that were drilled after gasification was complete. Stratification was seen in all boreholes including the cavity borehole. The EC levels were lower in the cavity which may be due to the dilution factor induced by injecting surface water during quenching of the gasifier. The thermal gradient shows a steady increase in temperature with depth with higher temperatures measured in the verification boreholes. This increase in temperature may suggest that heat is still being retained in the cavity which is expected. This study serves as the preliminary investigation on the stratification of temperature and EC and will be proceeded with in depth surveys that covers all the groundwater monitoring wells that monitor different aquifers identified on site proceed.
Making groundwater a National Priority	Jay	Matta	2023	Unicef, Groundwater, Resilience, scaling up
Abstract Unicef is the WASH sector lead globally and is, present at the country level, the main counterpart of government, especially regarding the component of the water balance utilised for potable safe water supplies. This mandate means that Unicef then has a role in looking at water resources nationally and not just as individual projects, and in doing so, contributes to good water governance as an integral part of system strengthening. Ensure this is done in partnership with other ministries and stakeholders that support them through advocacy for humanitarian and developmental access and support in technical areas such as groundwater assessments and monitoring. The focus on groundwater is especially linked with the fact that groundwater plays a major role due to its buffering capacity to climate variations, easier access and global coverage. Since groundwater is the most significant component of accessible freshwater resources, it is in the interest of UNICEF to make this resource more visible to meet both development and humanitarian goals, strengthen national systems and ultimately build resilience in mitigating water scarcity to scale or at the National level. Therefore, examples will be presented where Unicef has engaged on this journey with nations such as Afghanistan, Yemen, Mozambique and Rwanda to understand their water resources better. The overall objective at the National level is to adapt the capacity to withstand and recover as quickly as possible from external stresses and shocks or build resilience.
The Role Of High Resolution Site Characterisation In Informing Remediation Decisions At A Petroleum Release Site Overlying A Fra	Steve	McKeown	2015
Abstract Inadequate characterization of petroleum release sites often leads to the design and implementation of inappropriate remedial systems, which do not achieve the required remedial objectives or are inefficient in addressing the identified risk drivers, running for lengthy periods of time with little benefit. It has been recognized that high resolution site characterization can provide the necessary level of information to allow for appropriate solutions to be implemented. Although the initial cost of characterization is higher, the long-term costs can be substantially reduced and the remedial benefits far greater. The authors will discuss a case study site in the Karoo, South Africa, where ERM has utilized our fractured rock toolbox approach to conduct high resolution characterization of a petroleum release incident to inform the most practical and appropriate remedial approach. The incident occurred when a leak from a subsurface petrol line caused the release of approximately 9 000 litres of fuel into the fractured sedimentary bedrock formation beneath the site. Methods of characterization included: - Surface geological mapping of regionally observed geological outcrops to determine the structural orientation of the underlying bedding planes and jointing systems; - A surface electrical resistivity geophysics assessment for interpretation of underlying geological and hydrogeological structures; - Installation of groundwater monitoring wells to delineate the extent of contamination; - Diamond core drilling to obtain rock cores from the formation for assessment of structural characteristics and the presence of hydrocarbons by means of black light fluorescence screening and hydrocarbon detection dyes; - Down-borehole geophysical profiling to determine fracture location, fracture density, fracture dip and joint orientation; and - Down-borehole deployment of Flexible Underground Technologies (FLUTe?) liners to determine the precise vertical location of light non-aqueous phase liquid (LNAPL) bearing joint systems and fracture zones, and to assist in determining the vertical extent of transmissive fractures zones. ERM used the information obtained from the characterization to compile a remedial action plan to identify suitable remedial strategies for mitigating the effects of the contamination and to target optimal areas of the site for pilot testing of the selected remedial methods. Following successful trials of a variety of methods for LNAPL removal, ERM selected the most appropriate and efficient technique for full-scale implementation. {List only- not presented}
Characterisation And Protection Of Deep Aquifers In South Africa: Consolidation Of Data Sources	Francois D	Fourie	2017	Deep aquifers, data sources
Abstract This paper describes the results of study aimed at consolidating the available data sources on deep aquifers and deep groundwater conditions in South Africa. The study formed part of the larger WRC Project K5/2434 (Characterisation and Protection of Potential Deep Aquifers in South Africa). Since very little is known about the aquifer conditions below depths of 300 m, all groundwater information from depths greater than 300 m was considered to represent the deep aquifer systems. Various confirmed and potential sources of data on deep aquifers and groundwater conditions were identified and interrogated during this study, namely: 1. Boreholes of the International Heat Flow Commission (IHFC). The IHFC database indicates the location of 39 deep boreholes ranging in depth from 300 to 800 m, with an average depth of 535 m. 2. The Pangea database of the International Council for Science (ICSU). The Pangea database has information on 119 boreholes in South Africa, of which 116 are deeper than 300 m. 3. A database on deep boreholes at the Council for Geoscience (CGS). This database contains information on 5 221 boreholes with depths exceeding 300 m. 4. Information on the deep SOEKOR boreholes drilled during the 1960s and 1970s (at least 38 boreholes). 5. Information on deep boreholes from the database of the Petroleum Agency SA. 6. The National Groundwater Archive (NGA) of the Department of Water and Sanitation (DWS). 7. Information derived from the thermal springs in South Africa. 8. Boreholes drilled as part of the Karoo Research Initiative (KARIN). 9. Information on the locations and depths of underground mines in South Africa. Information on the occurrence of deep groundwater could potentially be obtained from these mines. The study shows that, although information on a vast number of deep groundwater sites is listed in the various databases, the data relevant to the geohydrological conditions are scant at most sites. This paucity of geohydrological data implies that the deep aquifers of South Africa are currently poorly understood.
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.
High Resolution Site Characterisation (HRSC) In South Africa: Challenges, Successes And Lessons Learned	Samuel D	Mohr	2015
Abstract Inadequate characterization of contaminated sites often leads to the development of poorly constructed conceptual site models and consequently, the design and implementation of inappropriate risk management strategies. As a result, the required remedial objectives are not achieved or are inefficient in addressing the identified risks. Unfortunately, it is all too common to find remedial intervention strategies that run for lengthy periods of time at great cost while generating little environmental benefit due to inadequate characterization of site conditions. High resolution site characterization (HRSC) can provide the necessary level of information to allow for development of rigorous conceptual site models, which can be used to develop and implement appropriate risk management solutions for environmental problems. At the outset, the HRSC approach generally has comparatively higher costs than traditional state-of-the-practice assessment methods. However, the project lifecycle costs can be substantially reduced due to development of optimal risk management strategies. In developing countries where there is a lack of legislation relating to soil and groundwater contamination or, a lack of enforcement of legislation which is present, the long-term liabilities related to contaminated sites are often not immediately apparent to the parties responsible for the sites. This often creates a reticence to employ HRSC techniques due to their increased cost, especially when much of the technology must be imported on a project specific basis from either Europe or the United States. The Authors provide information from several case studies conducted in South Africa where HRSC techniques have been employed to gain a greater understanding of subsurface conditions. Techniques employed have included surface-based geophysical techniques such as electrical resistivity tomography (ERT) and multi-channel analysis of seismic waves (MASW), passive soil gas surveys, deployment of Flexible Underground Technologies (FLUTe?) liners, diamond core drilling, fluid electrical conductivity profiling, downhole geophysical logging tools, the Waterloo Advanced Profiling System (APS), and the use of field laboratories. Several of the techniques required importing equipment and personnel from Europe or the US, and in several case studies, were a first to be employed in South Africa, or the continent of Africa for that matter. The Authors present data obtained using the HRSC techniques from the case studies and elaborate on how the information obtained was used to drive effective decision making in terms of managing long term environmental risks at the various sites, which has been positively embraced by local clients. The authors also highlight key challenges in conducting HRSC investigations in an emerging market context.
Investigating the influence of fine ash leaching in a tailings dam on the underlying aquifers	Paul JH	Lourens	2015	primary aquifers
Abstract Groundwater in South Africa is the most important source of potable water for rural communities, farms and towns. Supplying sufficient water to communities in South Africa becomes a difficult task. This is especially true in the semi-arid and arid central regions of South Africa where surface water resources are limited or absent and the communities are only depended on groundwater resources. Due to a growing population, surface water resources are almost entirely being exploited to their limits. These factors, therefore, increases the demand for groundwater resources and a more efficient management plan for water usage. For these reasons, the relation between the geology and geohydrology of South Africa becomes an important tool in locating groundwater resources that can provide sustainable quantities of water for South Africans. It was therefore decided to compile a document that provides valuable geohydrological information on the geological formations of the whole of South Africa. The information was gathered by means of interviews with experienced South African geohydrologists and reviewing of reports and articles of geohydrological studies. After gathering the relevant information, each major geological unit of South Africa together with its geohydrological characteristics was discussed separately. These characteristics include rock/aquifer parameters and behaviour, aquifer types (primary of secondary), groundwater quality, borehole yields and expected striking depths, and geological target features and the geophysical method used to locate these targets. Due to the fact that 90 % of South Africa's aquifers are classified as secondary aquifer systems, groundwater occurrence within the rocks of South Africa is mainly controlled by secondary fractures systems; therefore, understanding the geology and geological processes (faulting, folding, intrusive dyke/sills & weathering) responsible for their development and how they relate is important. However, the primary aquifers of South Africa (Coastal Cenozoic Deposits) should not be neglected as these aquifers can produce significant amounts of groundwater, such as the aquifer units of the Sandveld Group, Western Cape Province. Drilling success rates and possibility of striking higher yielding boreholes can be improved dramatically when an evaluation of the structural geology and geohydrological conditions of an area together with a suitable geophysical method is applied. The ability to locate groundwater has been originally considered (even today) a heavenly gift and can be dated back to the Biblical story of Moses striking the rock to get water: "behold, I will stand there before thee there upon the rocks thou shalt smite the rock and there shall come water out of it" (Exodus 17:6).
Exploring The Potential Of The GRACE Derived Groundwater Drought Index (GGDI) To Forecast Groundwater Drought In South Africa	Kopano	Mokoena	2019	GRACE, Drought
Abstract Water has been recognized and acknowledged as a fundamental natural resource that sustains environmental diversity, social and economic development (Liu et al., 2017; Fisher et al., 2017). With increasing populations, climate change and limited monitoring networks for both ground and surface water, freshwater resources are becoming difficult to assess due to rapid changes in water supply and uses. Several efforts have been devoted towards the monitoring and management of water resources and discovery of alternative sources of freshwater. One of the more recent efforts is using gravity information to track changes in water storage on the earth's surface. The Gravity Recovery and Climate Experiment (GRACE) mission (https://www.nasa.gov/mission_pages/Grace/index.html) holds great potential for assessing our water resources in areas with little monitoring data. The increasing interest in the use of GRACE as a water resource information and monitoring tool, is due to its cost effectiveness and user-friendly system which affords a broad understanding of the world we live in and its processes, specifically in water resource management and hydrological modelling. South Africa's National Water Act (NWA) of 1998 highlights the importance of the sustainable development of water resources. However, it is difficult to sustainably manage South Africa's groundwater resources due to the difficultly in measuring and understanding our complex aquifers. The challenges in establishing sustainable monitoring of groundwater resources and its Reserve, are due to insufficient knowledge about the contribution that groundwater makes to surface water, and methods which reliably monitor groundwater resources. The GRACE is a joint satellite mission by the Deutschen Zentrum fur Luftund Raumfahrt (DLR) in Germany and the United States National Aeronautics and Space Administration (NASA). The satellite was launched on 17 March 2002 and provides monthly temporal differences of earth's gravity field and its mean gravity field (Schmidt et al., 2008). It can afford insights into the location of groundwater resources, and their changes. GRACE can however, only determine the change in total water storage and therefore information on other components of the water balance are required to isolate the groundwater component. Therefore, the integrated Pitman Model is ideal to be applied together with GRACE and the Model can isolate surface water, soil moisture and groundwater into various components. Many studies have evaluated GRACE-derived groundwater storage changes as a response to drought (Famiglietti et al. 2011; Scanlon et al., 2012), while Thomas et al. (2017b) evaluated a groundwater drought index based on GRACE observations in an effort to understand and identify groundwater drought. Typically, GRACE is applied at scales of 150 000 km2, however Thomas et al., (2017) has developed a recent method that allows for the application of his GRACE derived Groundwater Drought Index (GGDI) at smaller scales. This study applies Thomas et al. 2017 GGDI in South Africa to the Crocodile, Sedgefield and Doring catchments, in hopes to to evaluate drought characterisation using data from GRACE satellites, focusing on the total water storage deficits to characterise groundwater drought occurrence.
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}
Combined use of Environmental and Artificial Tracers to Characterise the Vadose Zone.	Yazeed	Van Wyk	2021	Poster, vadose zone, isotopic tracers, recharge mechanisms, Protection, aquifer protection
Abstract Approximately 982 km3 /annum of the world’s groundwater reserve is abstracted, providing almost half of all drinking water worldwide. Globally, 70% is used for agricultural purposes while 38% for irrigation. Most water resources of South Africa are threatened by contamination caused by industrial, agricultural, and commercial activities, and many parts of the country face ongoing drought with an urgent need to find alternative freshwater sources, such as groundwater. Groundwater constitutes approximately 15% of the total volume consumed, hence it is an important resource that supplements insufficient surface water supplies across South Africa. Very little attention has been afforded to understanding the anthropogenically altered vadose zone as a potential source or buffer to groundwater contamination. This is evident from few research studies that has applied multiple isotopic tracers to characterise this zone. Most subsurface systems in South Africa are characterised by fractures, whereby flow and transport are concentrated along preferential flow paths. This study aims to evaluate the performance of different tracer classes (environmental and artificial) with one another, and create a better understanding of the hydraulic properties, mean residence time and transport mechanisms of these tracers. The influence of unsaturated zone thickness on recharge mechanisms will also be evaluated. Site visits will be conducted for the proposed study areas, and the neighbouring sources of contamination will be assessed. The matric potential and unsaturated hydraulic conductivities will be measured using various techniques. Water samples will be collected and analysed for the various tracers from the vadose zone using gravity lysimeters including suction cups. Several tracers will also be injected into boreholes where samples will be collected to calculate tracer residence times (BTC’s) and further constrain the hydraulic properties of the vadose zone. All samples will be analysed, interpreted, and simulated using the numerical finite-element modelling code SPRING, developed by delta h. The software derives quantitative results for groundwater flow and transport problems in the saturated and unsaturated zones of an aquifer. The research is expected to provide more insight into the selection and use of environmental and artificial tracers as markers for detecting, understanding the transport processes and pathways of contaminants in typical altered South African subsurface environments. The impact derived improved characterisation of the pathways, transport, and migration processes of contaminants, leading to groundwater protection strategies and appropriate conceptual and numerical models. The output from this study will determine the vertical and horizontal flux for both saturated and unsaturated conditions.
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.
Reliability of laboratory testing of groundwater samples	Venetia	Mitchell	2015
Abstract Resources required for groundwater sampling includes but not limited to pumping equipment, trained manpower and technical resources specific to the sampling function. Bearing these expenses in mind, choosing a laboratory for testing the water samples collected should be a carefully considered purchase. Choosing a testing facility that cannot deliver an efficient, reliable and technically sound service could render the sampling futile. Water samples submitted to a laboratory for testing are received from third party sources more than ninety percent (90%) of the time and sampling techniques and sample integrity cannot be verified by the laboratory. However, the validity, reliability and integrity of the laboratory testing are within the control of the testing facility. These aspects of a laboratory are usually controlled within a quality management system where established policies and procedures form the basis of such a system. This system maintains a foundation for technical competence and customer service at the laboratory. There are numerous testing facilities available to Consultants requiring chemical and microbiological groundwater testing, each with varying levels of integrity and technical ability. It is imperative to maintain confidence in the validity of results of analyses from a laboratory and this assurance can be understood through an examination of a facility's management system. An established quality management system would comprise a policy statement, associated technical methods and technical and administrative procedures. This system would be formally documented and audited as part of the on-going laboratory's management system. In some instances, laboratories formalise this into an accreditation of the laboratory to an international standard, such as ISO 17025:2005. The assurance that the results of analyses from any laboratory are of sound technical integrity would depend on factors such as - personnel training, - accommodation and environmental conditions under which the tests are carried out, - validation of the methodology applied (including the uncertainty of measurement), - the calibration and maintenance of the equipment used, - understanding the traceability of and measurement undertaken, - handling and preservation of the sample on receipt and while in the laboratory. Each of these factors plays a critical role in the integrity of results of analyses and should be interrogated when trying to understand the reliability and competence of the laboratory of choice.{List only- not presented}
Ensuring the provision of sustainable water services in water-scarce humanitarian environments	F	Ward	2023	Water scarcity, Groundwater, Climate change, assessments, Monitoring, system strengthening, Resilience
Abstract Annually, UNICEF spends approximately US$1B in water, sanitation and hygiene programming (WASH), approximately half of which is spent in humanitarian contexts. In emergencies, UNICEF supports the delivery of water, sanitation and hygiene programming under very difficult programming contexts – interruptions to access, power supply and a lack of reliable data. Many of these humanitarian situations are in contexts where water scarcity is prevalent and where the demand and competition for water are increasing, contributing to tension between and within communities. While water scarcity is not new to many of these water-scarce areas, climate change is compounding the already grave challenges related to ensuring access to safe and sustainable water services, changing recharge patterns, destroying water systems and increasing water demand. Incorrectly designed and implemented water systems can contribute to conflict, tension, and migration. Ensuring a comprehensive approach to water security and resilient WASH services can reduce the potential for conflict and use water as a channel for peace and community resilience. This presents an enormous opportunity for both humanitarian and development stakeholders to design water service programmes to ensure community resilience through a four-part approach: 1. Groundwater resource assessments 2. Sustainable yield assessments (taking into consideration future conditions) 3. Climate risk assessments 4. Groundwater monitoring/early warning systems UNICEF promotes this approach across its WASH programming and the sector through technical briefs, support and capacity building.
Comparative use of groundwater by invasive alien PROSOPIS SPP and co-occurring indigenous V. Karoo in a semi-arid catchment	Sebinasi	Dzikiti	2015
Abstract Groundwater is a vital source of water for many communities in South Africa and elsewhere. Besides the changing climate, rapidly spreading invasive alien plants with deep roots e.g. Prosopis spp, pose a serious threat to this water source. Dense impenetrable thickets of Prosopis occur in the drier parts of the country mainly along river channels in the Northern, Eastern and Western Cape Provinces. Few studies have quantified the actual water use by this species outside of the USA where it is native. Consequently the impacts of Prosopis invasions on groundwater resources are not well documented in South Africa. The aim of this study was to quantify the actual volumes of water used by Prosopis invasions and to establish the effects on groundwater. Because deep rooted indigenous trees that normally replace Prosopis once it has been cleared also use groundwater, we sought to quantify the incremental water use by Prosopis over and above that used by indigenous trees in order to determine the true impacts on groundwater. The study was conducted at a site densely invaded by Prosopis at Brandkop farm near the groundwater dependent town of Nieuwoudtville in the Northern Cape. One in seven trees at the site is the Vachellia karroo (formerly A. karroo) which is the dominant deep rooted indigenous tree species. Actual transpiration rates by five Prosopis and five V. karroo are being measured using the heat pulse velocity (HPV) sap flow technique. Additional HPV sensors were installed on the tap and lateral roots to study the water uptake dynamics of the trees. Groundwater levels are being monitored in four boreholes drilled across the site while sources of water used by the trees (i.e. whether soil or groundwater) is being determined using O/H stable isotopes. For similar size trees, V. karroo had higher transpiration rates than Prosopis because of the larger sapwood to heartwood ratio in V. karroo than in Prosopis. However, at the stand level Prosopis consumed significantly larger amounts of water than V. karroo. This is because Prosopis invasions had a much higher tree density than V. karroo. From August 2013 to July 2014, annual stand transpiration for Prosopis (~ 372 mm) was more than 4 times higher than that of V. karroo (~ 84 mm). Tree water uptake was correlated to changes in groundwater levels (R2 ~ 0.42) with groundwater abstractions of ~ 2600 m3/ha/y by Prosopis compared to ~ 610 m3/ha/y for V. karroo. In addition, Prosopis showed evidence of hydraulic redistribution of groundwater wherein groundwater was deposited in the shallow soil layers while V. karroo did not. Results of this study suggest that clearing of Prosopis to salvage groundwater should target dense stands while less dense stands should be prevented from getting dense. {List only- not presented}
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.
Observations on seepage from platinum tailings	Terry	Harck	2015	platinum tailings
Abstract Tailings storage facilities are significant contributors of dissolved solids to underlying aquifers and adjacent watercourses. Salt balances indicate estimated seepage loads of the order of 1 500 tonnes of chloride per year. Actual seepage loads will be determined by the hydraulic conductivity of the tailings and mechanisms of flow within the tailings. Field observations and sample analytical results from several platinum tailings facilities are presented. These indicate the development of lenses of clay sized material within coarser silty material and suggest a tortuous seepage flow path, perhaps characterised by zones of preferential flow. The implications of seepage modelling and geochemical data on the salt loads mobilised from tailings are discussed. Results suggest that tailings facilities are effective at retaining salts and that release of accumulated salts after closure may take place at long time scales. {List only- not presented}
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.
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.
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}
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.
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.
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.
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.
Groundwater Sampling: Measurement Uncertainties And Their Implications For Decision Making	Modreck	Gomo	2019	sampling
Abstract The uncertainties associated with both the sampling process and laboratory analysis can contribute to the variability of the results. In most cases, it does appear that if the water samples have been analysed by an accredited laboratory, the results are acceptable. While the accreditation of analytical laboratory and therefore its credibility is very important to uphold quality and integrity, the same should be said about the sampling process. The quality and credibility of a sampling process is typically left to the responsibility of the appointed groundwater practitioner without any criteria to evaluate the quality and integrity of the sampling process. Perhaps the quality and integrity of the sampling process is evaluated based on trust or experience of the practitioner. However without any form of scientific criteria to evaluate the quality and integrity of the sampling process, it is difficult for the sampling process to be scrutinized. The quality and integrity of both the sampling process and laboratory analysis must be scientifically evaluated based on the uncertainty of measurements in line with the monitoring goals/requirements. This presentation discusses the aspects of evaluation of measurement uncertainties associated with groundwater sampling as an important component of quality assessment of groundwater sampling processes. The potential implications of the uncertainties on the final results and their use in decision making is also discussed. The credibility of the decisions made also depends on the knowledge about the uncertainties of the final results
The Utilisation Of Hydro-Geophysical Methods For Soil Moisture Measurements To Optimise Irrigation Management	Christian	Steyn	2019	soil moisture, Irrigation, flow
Abstract Precision agriculture continuously seeks improved methods to enhance productivity whether it is for greater crop yields or economic viability regarding labour inputs and satisfying the demand in a shorter time span. Soil moisture is one important factor that drives the agricultural industry and is therefore of utmost importance to manage it correctly. A shortage of water may result in reductions in yield, while excess irrigation water is a waste of water resources and can also have a negative impact on plant growth. Knowledge of the spatial distribution of soil moisture is important for determining soil moisture storage and soil hydraulic transport properties. Capturing field heterogeneity without exhaustive sampling and costly sample analysis is difficult. Electromagnetic induction, Frequency Domain Reflectometry, Neutron Scattering and conventional soil sampling have been utilised to determine the spatial variability of soil moisture within a field. Emphasis has been placed on practicality and accuracy of all the methods. Electromagnetics have proven itself to be the primary method to determine soil moisture within the field by comparing the results of the volumetric soil water content present in the field together with a combination of various soil properties such as clay and silt content, sand fraction, concretions, density and soil depth that contribute towards the accumulation of soil water. Electromagnetic induction has the highest resolution of data collected for a specific time period of all considered methods making it economically the best option for soil moisture management within a variable rate irrigation system. Electromagnetic induction has proven to be successful in delineating a field into management zones consisting of different classes based on observed conductivity values. Higher conductive zones are considered with small water demand. Lower conductive zones are considered with a greater water demand through a variable rate irrigation system. These water management zone maps could be informative for modelling, experimental design, sensor placement and targeted zone management strategies in soil science, hydrogeology, hydrology, and agricultural applications.
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.
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 fresh look at the National Water Balance	Andries	Wilke	2015
Abstract The national water balance is primarily based on the availability of surface water and the historic allocation thereof. The changes that are required the next 20 years to ensure sustainable development of the nation will be painful, but is unfortunately at present not part of the public discussion, it is essentially ignored in favour of more "popular water topics".This paper intends to look at a few core aspects, they include the current water allocation in the national water balance, the relative value of the utilisation, the position of groundwater resources in changing the current relative allocation and the current groundwater utilisation. The paper further intends to be a less formal presentation of these aspects with the required data, references and conclusions available for distribution afterwards.
Groundwater Assessment using Borehole Magnetic Resonance	Benjamin	Birt	2019	magnetic resonance
Abstract Hydraulic behaviour of an aquifer is defined in terms of the volumes of water present, both producible and not (specific yield and specific retention), and the productivity of the water (hydraulic conductivity). These parameters are typically evaluated using pumping tests, which provide zonal average properties, or more rarely on core samples, which provide discrete point measurements. Both methods can be costly and time-consuming, potentially limiting the amount of characterisation that can be conducted on a given project, and a significant measurement scale difference exists between the two. Borehole magnetic resonance has been applied in the oil and gas industry for the evaluation of bound and free fluid volumes, analogous to specific retention and specific yield, and permeability, analogous to hydraulic conductivity, for over twenty years. These quantities are evaluated continuously, allowing for cost-effective characterisation, and at a measurement scale that is intermediate between that of core and pumping tests, providing a convenient framework for the integration of all measurements. The role of borehole magnetic resonance measurements in hydrogeological characterisation is illustrated as part of a larger hydrogeological study of aquifer modeling. Borehole magnetic resonance has been used for aquifer and aquitard identification, and to provide continuous estimates of hydraulic properties. These results have been compared and reconciled with pumping test and core data, considering the scale differences between measurements. Finally, an integrated hydrogeological description of the target rock units has been developed.
Stampriet Transboundary Aquifer System	Kwazikwakhe	Majola	2015

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.
Developing A Transboundary Aquifer Analytic Framework To Support Localised Groundwater Decision-Making Using Big Data	Zaheed	Gaffoor	2019	transboundary, big data
Abstract Big data analytics (BDA) is a modern and innovative platform of applications that include advanced analytical techniques such as data mining, statistical analysis, artificial intelligence, machine learning, and natural language processing. Regional data are generated through groundwater monitoring, remote sensing applications or global circulation models (GCM), however this is often too course for a local understanding. Groundwater managers rely on locally relevant information for effective operational decision making, however this is often missing. A Transboundary Aquifer (TBA) Analytic Framework was developed to match, integrate and model local hydrogeological data with regional earth-observation data using BDA. Drawing on the literature on BDA, a reference architecture for the TBA analytical framework was identified for application to various groundwater management scenarios in the Ramotswa Dolomitic Aquifer (Botswana - South Africa) and Shire Valley Alluvial Aquifer (Malawi - Mozambique). The TBA analytical framework allows for local clouds to store the local and regional structured and unstructured datasets and interconnecting these local clouds through a federated cloud infrastructure. In this regard, tools that are incorporated in the TBA analytical framework include data ingestion operators, data transformation operators, and feature extractors. Various machine learning algorithms and statistical techniques are incorporated in the TBA analytical framework to downscale the regional datasets. The downscaling involves selection of potential predictors and predictants variables based on data needs to address local groundwater management scenarios such as regulating groundwater abstraction to prevent groundwater depletion. Using the downscaled data the TBA analytical framework can be utilised to uncover patterns and statistical relationships in the datasets in order to model local groundwater processes such as cone of depression, groundwater levels forecasting, well protection zoning, amongst others.
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.
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