Conference Abstracts

Abstract

A groundwater study at Middelburg Colliery was completed with the emphasis on the investigations into water balances on a rehabilitated coal mining environment. Water balance calculations and water scheduling for collieries in Mpumalanga have become important facets of mine planning over the past years. Opencast mining involves the blasting and removal of rocks overlying the coal layer, which is removed completely. The overburden is then replaced (backfilled) and covered with soil and the terrain is rehabilitated. Rainwater penetrating through the soil into the backfill may become acidic by pyrite and sulphides in the backfill material and ultimately decants on the surface. Decanting generally commences a decade or more after mining ceases. Opencast mining impacts the natural groundwater regime and radically alters the nature of groundwater-surface water interactions. The Department of Water Affairs and Forestry in South Africa requires that mines minimise the release of their polluted water. A groundwater balance is the numerical accounting of the annual recharge to a groundwater resource. It can further be described as a quantitative assessment of the total water resources of a basin over a specific period of time. In a groundwater development program, such a budget is necessary to efficiently manage and utilize the resource. Many of the parameters that determine recharge to an aquifer are measured directly and some are computed from hydraulic characteristics and measured field data. The Middelburg Mine Services has been experiencing excess water problems in past years. Because of the lack of space and the concerns of decanting of mine water out of the rehabilitated pit, it was suggested that mine water treatment should be considered. Geohydrological models were created to determine the decant positions and water volumes for the rehabilitated area. The size of the water treatment plant can then be determined using the calculated decant volumes and positions.

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.

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

Abstract

Accurate parameter estimation for fractured-rock aquifer is very challenging, due to the complexity of fracture connectivity, particular when it comes to artesian flow systems where the potentiometric is above the ground level, such as semi-confined, partially confined and weak confined aquifers in Table Mountain Group (TMG) Aquifer. The parameter estimates of these types of aquifers are largely made through constant-head and recovery test method. However, such a test is seldom carried out in Table Mountain Group Aquifer in South Africa due to a lack of proper testing unit made available for data capturing and appropriate method for data interpretation. An artesian borehole of BH 1 drilled in TMG Peninsula Formation on the Gevonden farm in Western Cape Province was chosen as a case study. The potentiometric surface is above the ground level in rainy season, while it drops to/below ground level during the dry season. A special testing unit was designed and implemented in BH 1 to measure and record the flow rate during the free-flowing period, and the pressure changes during the recovery period. All the data were captured at a function of time for data interpretation at later stage. Curve-fitting software developed with VBA was adopted for parameter estimation based on the constant-head and recovery tests theories. The results indicate that a negative skin zone exists in the immediate vicinity of the artesian borehole, and the hydraulic parameters estimates of transmissivity (T) ranging from 6.9 to 14.7 m2/d and storativity (S) ranging from 2.1*10-5 to 2.1*10-4 appear to be reasonable with measured data collected from early times. However, due to formation losses, the analytical method failed to interpret the data collected at later times. Consequently the analysed results by analytical solution with later stage data are less reliable for this case. The MODFLOW-2000 (Parameter Estimation) package developed by USGS was also adopted to determine these parameters for the same aquifer. It approves that there exist formation losses, which leads to the aquifer response distinctly different at later stage of overflow and recovery tests. The aquifer parameter estimates with early time data of tests by analytical and numerical methods show that there is generally good agreement. However, significant errors could be generated by analytical method applied where there is occurrence of well or formation losses, while these restrictions could be overcome by applying a numerical method.

Abstract

Underground coal gasification (UCG) is technology that aspires to exploit coal reserves using in-situ gasification. This mining method gasifies coal seams while extracting a syngas that can be used for electricity generation. Since the bulk of this process occurs in the subsurface, there is a possibility of impacting on regional groundwater quality. This paper seeks to assess this impact on groundwater across different aquifers while taking into account the chemical evolution of these aquifers. Three aquifer systems were identified namely the shallow, intermediate and the deep aquifer which comprises of the coal seam. The water chemistry was reviewed over a two year period during which the gasifier was still active. Alkaline conditions were prevalent across the three aquifers with minor seasonal changes. High levels of dissolved solids were observed especially in the deep aquifer but the quality of water was poor even in background samples. The impact of gasification does have small variation in already unusable water in the deep aquifer which was also characterized by low hydraulic conductivity. Higher hydraulic conductivity values were established in the shallow aquifer. No significant groundwater chemistry change was detected in this aquifer as a result of gasification process.

Abstract

In order to meet the increasing national and international demand for coal, substantial expansion plans for existing as well as new coal mines were put forward in recent years. The mine developments are often proposed in environmentally sensitive areas and require an appropriate assessment of potential environmental impacts, including impacts on groundwater dependent ecosystems. This paper describes the development of a conceptual and numerical groundwater model as part of a wetland reserve determination in the Witbank coalfields. The model was used to assess potential mining related impacts on the shallow groundwater flow, including surface seepages and spring discharges feeding hill slope and valley bottom wetlands as well as pans. A number of shallow monitoring boreholes were sited, drilled and tested in the focus area around a pan to characterise the shallow perched and weathered aquifers. While these aquifers were generally found to be very low to low yielding, higher yields were encountered in a coarser grit layer intersected by two of the eight boreholes. The grit layer represents a potential preferential groundwater flow path towards the pan and was subsequently further delineated based on the exploration drilling logs from the mine. The different aquifers, the target coal seam, and over 60 mapped hill slope and valley bottom wetlands as well as pans, were incorporated into a numerical groundwater flow model. A free seepage boundary was assigned to the entire surface area to evaluate if the model is able to represent the observed seepages and spring discharges. The simulation of unsaturated flow processes (Richard's equation) was found to be crucial for the representation of discharges from perched aquifers. Following a satisfactory calibration of the model, different open cast mine layouts were then incorporated into the model to assess their impacts on the groundwater contribution to wetlands. The presented quantitative simulation of groundwater contributions towards wetlands and pans based on site specific groundwater investigations and data is considered a best practice example in assessing the groundwater component for a wetland reserve determination.

Abstract

Industrial Management Facilities represent a hazard to the down gradient surface water and groundwater environment. The assessment of the risks such facilities pose to the water environment is an important issue and certain compliance standards are set by regulators, particularly when the potential for an impact on the water environment has been identified. This paper will aim to describe how the contamination was conceptualized, estimated, limitations and how it is technically not feasible to establish one limit or compliance value of known contamination in different aquifers.

Abstract

In recent years there has been renewed interested in identifying and understanding groundwater resources. Airborne electromagnetic (AEM) surveys can provide useful, cost effective information about the geometry of aquifers and their host rocks. TEMPEST is a fixed wing AEM system which has been used extensively for groundwater applications. The system possesses many attributes which aid in groundwater exploration including: broad operational bandwidth; multifaceted software approach; and, a distinctive calibration technique. These features allow both shallow and deep subsurface features to be imaged which aid in mapping groundwater aquifers along with the broader groundwater subsystem. This paper will review TEMPEST surveys flown for the Western Australian Department of Water (DoW) for the purpose of groundwater characterisation. The surveys were focussed on the identification of geological contacts, subsurface aquifers and seawater intrusion extents. The survey data was interpreted using an integrated approach which involved reviewing the newly acquired geophysical data, identifying contacts and anomalous features in the acquired data, reviewing existing geological and geophysical data in the area and correlating features identified in acquired data to known geology. The first case study was flown over the North Gnangara area of the Perth Basin with the primary aim of defining the spatial distribution of clay and silty layers that impede recharge to the groundwater table. The survey succeeded in achieving its primary aim of identifying the distribution of clay layer targets. Through the integrated interpretation approach it was also successful in achieving its secondary aims by clearly defining the contact between superficial units and the underlying stratigraphy, identifying key structures within the basin, outlining the top of the seawater intrusion, and mapping confining strata within the deeper aquifer systems in the Perth Basin. The second case study was flown over the lower reaches of four river systems in the North Pilbara coast with the aim of understanding the aquifer geometries and groundwater salinity distribution within the region. The primary aims of the survey were achieved and provided a basement geology map, relative porosity maps, approximate weathered and unweathered bedrock surfaces as well as the approximate geometry of the seawater intrusion within all survey areas. It was also possible to map the interpreted extents of alluvial aquifers within two of the river systems as well as the contact between two sandstone aquifers present in one of the river systems. These case studies show that the TEMPEST AEM system can provide valuable information about the geometry of aquifers and their host geology. AEM surveys should be used as an initial method for determining broad aquifer geometry and the identification of priority areas prior to further less cost effective water bore drilling.

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.

Abstract

POSTER High iron (Fe) content in the waters of the aquifers around Lake Sibayi is derived from the geological units in which the aquifers are situated. When drawn to the surface the water precipitates solid iron hydroxide [Fe (OH)3] causing a cloudy reddish colour, a condition which is partly caused by the exposure of the high Fe water to the atmosphere. Fe is an essential ion necessary for the growth of people, animals and plants

Abstract

It is estimated that the three coal layers in the Springbok Flats contain about 5 TCF of coal bed methane (CBM). Two sedimentary basins, namely the southern Tuinplaas basin and the northern Roedtan basin, exist with coal layers with a total thickness of 7m which occurs mainly in three mayor seams. The coal layers are located between 20 m to more than 600m.
Farmers in the Flats are concerned about the environmental impact of fracking the coal beds. They are mostly worried about the risk of groundwater pollution; the drawdown of the water table and the producing of a bad quality water during the mining process. They set up an EPA for the Springbok Flats in 2010 and until now, they have stopped more than 6 companies to conducted exploration (stopped strictly on account of the different laws in SA that were not adhered too).
On average, 1000 liters of water is produced for every 2000 cubic feet coal bed methane mined in the USA. The quality of the produced water is not good (with typical Na values of more than 5 000 mg/l) and cannot be used for irrigation purposes.
It is thus expected that about 500 million m3 of bad quality water will be produced for every 1 TCF mined in the Flats. This groundwater will be removed from the system and it is expected that a drawdown of up to 30m will be evident at places in the Springbok Flats. There are also a large number of dykes and faults in the Flats which imply that the upward movement of methane and water will be very probable after abandonment of each coal methane well.

Abstract

This article present field evidence on the effect of artefacts other than the horizontal groundwater flux on the single-borehole tracer dilution test. The artefacts on the tracer dilution were observed during two single-borehole tracer dilution tests conducted in an alluvial channel aquifer in the main Karoo Basin of Southern Africa. Field evidence shows that early time of the tracer dilution plot can be affected by artefacts other than the horizontal groundwater flux. These artefacts have great potential to increase the early time gradient of tracer dilution curve leading to overestimation of the horizontal groundwater flux. A qualitative approach that can be used to isolate and remove portion of the dilution plot that has resulted from artefacts other than the groundwater flow prior to calculating the horizontal groundwater flux is proposed.

Abstract

Coastal wetlands are complex hydrogeological systems in which groundwater have a significant influence on both its water balance and hydrochemistry. Differences in groundwater flow and groundwater chemistry associated with complex hydrogeologic settings have been shown to affect the diversity and composition of plant communities in wetland systems. A number of wetlands can be found across the flat terrain of the Agulhas Plain, of which the most notable is the Soetendalsvlei and the Vo?lvlei. Despite the ecological and social importance of the Vo?lvlei, the extent to which local, intermediate and regional groundwater flow systems influences the Vo?lvlei is poorly understood. The aim of this work is to characterize the spatial and temporal variations in surface water and groundwater interactions in order to demonstrate the influence of groundwater flow systems on the hydrology of the Vo?lvlei. The specific objectives of the study are; 1) to establish a geological framework of the lake sub-surface, 2) to determine the physical hydrological characteristics of the Vo?lvlei and 3) to determine the physical-chemical and isotopic characteristics of groundwater and surface water. Data collection will be done over the period of a year. Methods to be used will include the use of geophysical (electrical resistivity) to determine high water bearing areas surrounding the wetland, a drilling investigation (the installation of piezometers at 5-10m depths and boreholes at 30m depth, sediment analysis (grain size analysis, colour and texture), hydraulic (slug testing to determine hydraulic properties; hydraulic conductivity and transmissivity), hydrological (to estimate groundwater discharge; Darcy flux and hydraulic head difference between groundwater level and lake level), physical-chemical (electrical conductivity, temperature and pH) and stable environmental isotopic (oxygen and hydrogen) analysis of surface water and groundwater, to determine flow paths and identify processes. Thus far, results obtained for the geophysical survey has revealed that the sub-surface of this wetland system is highly variable. Three traverses were done on the South-Western, South-Eastern and Northern side of the wetland (See Figure 1). In VOEL1 (South west), the upper couple of meters show areas of very low resistivity, which is associated with clays, poor water quality and water which has high dissolved salts. The changing of medium to high resistivity values on the North-eastern side is usually indicative of weathered sandstone (Table Mountain Group). VOEL2 (South eastern), indicates that the subsurface is of low resistivity. These low values are the result of noticeable salt grains in the sand. VOEL3 (Northern), indicated upper layers of low resistivity, while the lower depth indicate areas of high resistivity. It is expected that the results of this study will provide a conceptual understanding of surface water-groundwater interactions and the processes which control these interactions, in order to facilitate the effective management and conservation of this unique lacustrine wetland.

Abstract

The manner in which municipal and industrial wastes generated are disposed in the urban areas in Nigeria is worrisome. The practice of dumping solid wastes in abandoned burrow-pits or valley and the discharge of liquid wastes directly on soils or surface water without any form of treatment has resulted in soil and water pollution. The continuous release of dangerous gases into the atmosphere by industries unabated has contributed to air pollution. These inadequate waste disposal techniques have created serious environmental and health challenges. Due to increasing population growth rate, urbanization, industrialization and economic growth, there has been a phenomenal increase in the volume of wastes generated daily and handling of these wastes have constituted an environmental problem. The need to manage these wastes in an environmentally-friendly manner that will guarantee safety of the soil and water resources lead to the present study. The newly designed waste management landfill incorporates advanced features such as complex multiple liner construction to facilitate organic decomposition and maintain structural integrity. The multiple protective layers and regular monitoring ensure that the waste management landfills exist in harmony with their surrounding environments and communities. These features that enhances maximum protection of soil and water from contamination by plume by decaying waste is lacking in the un-lined open waste dumps been practiced in the country. Pollution abatement, waste reduction, energy saving, health and economic benefits are some of the advantages of the newly designed sanitary landfill system.

Abstract

Decades of monitoring, characterising, and assessing nitrate concentration distribution and behaviour in the soil profile and it's pathway into groundwater have resulted in a good understanding of its distribution in the country. While the national distribution is of great importance, site specific conditions determine fate, transport, and ultimately concentration in a specific area. Field experimental work included installation of a barrier containing a cheaply available carbon source to treat groundwater. The "reactor"/ tank with dimensions- 1,37m height, 2.15m diameter used for the experiment was slotted for its entire circumference by marking and grinding through the 5mm thick plastic material. The top section was left open to allow for filling and occasional checking of filled material during the experiment. The tank was packed with Eucalyptus globulus woodchips which was freely available at the site. Concentrations of groundwater nitrate at the site were well over what could be expected in any naturally occurring groundwater systems, and would result only by major anthropogenic activities in unconfined aquifer areas of South Africa. The changes in parameter concentrations with time were measured in order to determine the efficiency and life span of the carbon source used for the experiment. This paper considers 35 months of monitoring at a site where a low technology method was implemented. Field implementation was tested at a site which previously experienced some NH4NO3 spills. Main results from the field work showed that nitrate was totally removed at the treatment zone and surrounding boreholes, and even sulphate and NH4+ were removed during the experiment. This shows that the woodchips were successful in affecting denitrification for 35 months. Data also shows that boreholes further downstream from the tank had reduced NO3-, SO42- and NH4+ levels. Using the available biodegradable carbon for the woodchips based on its composition, a barrier lifespan could be determined. The results of calculations showed that the barrier would be effective for at least another 6.9 years from the period of the last sampling date. A total lifespan of about 10 years can thus be estimated.

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}

Abstract

Water management is a difficult and complex business requiring appropriate institutional arrangements as well as guidance and support from government, which is often unable to act effectively to address day-to-day water resource management (WRM) issues. Theoretically, water as a 'common pool resource' is best managed by users self-organised at a local level and within a basin framework. Water users and other stakeholders have detailed and up-to-date local knowledge as well as an interest in ensuring effective management to share water equitably between different users and to control pollution. This approach is supported by South Africa's National Water Act (NWA), which provides for the establishment of Catchment Management Agencies (CMAs) to perform a range of WRM activities within the framework of a National Water Resource Strategy (NWRS).
Hence, water resource management in general and conjunctive use in particular requires cross sector and cross level cooperative governance. Relevant institutions include the DWA at national and regional level, the CMA, if established, provincial departments that might impact on the water resources, water user associations, water services authorities, water services providers, water boards, and individual water users. These institutions are responsible for various activities and often require some level of inter- and intra-institutional cooperation. Ideally, multiple organisations, policies, legislation, plans, strategies and perspectives should be involved in water-related decision-making, which in turns creates complex leadership challenges. Globally, the lack of sustainable groundwater management can be ascribed to poor governance provisions. These include, but are not limited to, institutional arrangements and political will, including fragmented and overlapping jurisdictions and responsibilities, competing priorities, traditional approaches, rights and water pricing systems, diverging opinions, incomplete knowledge, data as well as uncoordinated information systems. Adding the poor operational and maintenance issues, decision-makers often view groundwater as an unreliable resource and are hesitant to make significant investments in groundwater infrastructure and capacity.
The recent Worldbank and WRC report on groundwater governance in South Africa revealed that the technical, legal, institutional and operational governance provisions were found to be reasonable at the national level but weak concerning cross-sector policy coordination. At the local level, basic technical provisions such as hydrogeological maps and aquifer delineation with classified typology are in place but other governance provisions such as institutional capacity, provisions to control groundwater abstraction and pollution, cross-sector policy coordination and the existence and implementation of groundwater management action plans are weak or non-existent.
It appears from this review that the major hindrances for sustainable groundwater governance and more so for integrated water resource management and conjunctive use scenarios are the discrepancy between groundwater and surface water provisions in the relevant legislation, associated guidelines and their implementation at regional and local, and the lack of skills and clear responsibilities for implementing water resource management actions at municipal level. This is demonstrated with several case studies.

Abstract

Understanding the hydrogeochemical processes that govern groundwater quality is important for sustainable management of the water resource. A study with the objective of identifying the hydrogeochemical processes and their relation with existing quality of groundwater was carried processes in the shallow aquifer of the Lubumbashi river basin. The study approach includes conventional graphical plots and multivariate analysis of the hydrochemical data to define the geochemical evaluation of aquifer system based on the ionic constituents, water types, hydrochemical facies and groundwater factors quality control. Water presents a spatial variability of chemical facies (HCO3- - Ca2+ - Mg2+, Cl- - Na+ + K+, Cl- - Ca2+ - Mg2+ , HCO3- - Na+ + K+ ) which is in relation to their interaction with the geological formation of the basin. The results suggest that different natural hydrogeochemical processes like simple dissolution, mixing, and ion exchange are the key factors. Limited reverse ion exchange has been noticed at few locations of the study. At most, factor analyses substantiate the findings of conventional graphical plots and provide greater confidence in data-interpretation. {List only- not presented}

Abstract

For a long time, professionals regarded social media as a superficial, unprofessional platform where internet users would submerge themselves in a virtual world, detached from real-life issues. Slowly, the myths and stigmas surrounding the use of social media has faded as more and more professionals and scientists have realized that these social platforms could be positively exploited in a professional manner which could be beneficial. In a digital age where information at our fingertips is the norm, professionals should co-evolve and ensure that their work is just as accessible and appealing, without the unnecessary jargon. Currently, science is mostly restricted to a very particular audience and conveyed in one direction only. Using a social media platform such as Twitter-which limits messages to only 140 characters-challenges scientists to convey their work in a very concise manner using simpler terminology. Furthermore, it dismisses the usual one-way form of communication by opening dialogue with fellow Twitter users. At conferences, Twitter can serve as a useful tool for active engagement which will not only "break the ice" between delegates but also ensure that important information is communicated to a much wider audience than only those in attendance. This idea was tested at the 2014 Savanna Science Network Meeting held in Skukuza, Kruger National Park, where the hashtag #SSNM was used. More than 63% of the Twitter users who participated in the #SSNM hashtag were actually not present at the conference. These external "delegates" were interested individuals from five different continents and in different professions besides Science. This highlights how social media can be exploited at conferences to ensure that key messages are conveyed beyond the immediate audience at the event.

Abstract

Despite majority of the terrestrial fresh water resources being groundwater, there still exists a public perception that the only source of potable water is from surface water bodies. Due to this misperception, the general public is often ignorant about the importance of groundwater as a resource. This is evident in the lack of appreciation for the Upper and Lower Fountains in Pretoria as the main reason for various historical events in and around Pretoria, leading to it eventually becoming the capital of South Africa. This project, which introduces a broader Hydrological Heritage Overview programme, is intended to create awareness regarding the history and importance in the development of South Africa, and to improve public understanding of the important role that hydrology and hydrogeology is playing in our day to day lives. Additionally, scientific appraisal of historical data will aid the relevant managements to better manage these valuable resources, while making interesting and important archived data available to the scientific community in the form of trend analyses and conceptual models. The paper will showcase a 10-minute narrated video on the importance of groundwater in the history of Pretoria. As part of a water awareness programme to inform the general public about Pretoria's water supply from springs since its founding in 1855, the video depicts the development of the capital city around these springs from its founding to present.

Abstract

South Africa relies on coal and imported crude oil for most of its energy demands. However, the current high demand for the coal and oil and other sources of energy threat the sustainability of such energy sources, hence, the need to diversity the energy sources. However, these energy sources (coal and oil) are non-renewable sources of energy and the production of energy from renewable sources is almost non-existent. Therefore, the production of shale gas in the main Karoo Basin of South Africa provides a potential and opportunity to diversify South Africa energy mix. In pursuing such an opportunity, one has to be mindful that shale gas is neither sustainable nor a green energy system. This study aims to improve knowledge on groundwater governance arrangements regarding shale gas exploration and production in order to inform the appropriate regulatory regime and best practices to protect groundwater resources. Although there has been much effort to understand the technical implications of shale gas exploration and production on groundwater, not much attention has been given to understanding the broader groundwater governance issues. Addressing groundwater governance issues is critical to effective regulation of unconventional gas exploration and production. This is because; failure of groundwater management often results from inadequate governance arrangements, rather than lack of knowledge about sustainable yield or pollution vulnerability of aquifers. It has been argued that, there exists a perpetual tension between viewing groundwater as a common-resource and the rights of private appropriation of groundwater for use. Thus, groundwater is inherently vulnerable to the "tragedy of the commons" in which actual users and potential polluters act solely in their individual short-term interest rather than taking into account long-term communal considerations. The study provides significant insights regarding appropriate and effective institutional arrangements for groundwater governance.

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.

Abstract

South Africa is classified as a semi-arid region where the evapotranspiration sometimes exceeds the annual recharge through rainfall which leads to more drought periods. Combine the before mentioned issue with the water shortages and the impact of mining on water in South Africa, the focus therefore then needs to be placed on the proper estimation of recharge from rainfall and subsequent water management of these water sources. The Ermelo region in Mpumalanga was chosen for the investigation into calculating recharge from rainfall, using water balance methods as the basis on which recharge is calculated. The Ground Water Balance, Saturated Volume Fluctuation, Ground water level fluctuation and Cumulative Rainfall Departure methods was used to calculated recharge and then compare the different methods and their values with each other to compile an accurate estimation of recharge in the area. The data was analysed for each of the methods and then plotted and compared on a simple x-y chart. A new equation was formulated whereby any recharge from the previously mentioned methods can be normalized against the new formula for a more accurate recharge value. As a secondary objective a recharge intensity map was compiled for the area showing the areas of potentially high recharge.

Keywords: South Africa, Ermelo, Recharge Estimation, Water balance methods, Ground Water Balance, Saturated Volume Fluctuation, Ground water level fluctuation, Cumulative Rainfall Departure, Intensity maps.

Abstract

A multi seam open pit coal mine is planned to be developed in the Moatize Basin of Mozambique. The proposed project includes a new coal mine and coal handling facility to produce up to six million tons per annum of coking and thermal coal for the export market, which will have a life of mine of approximately 30 years. The mine will require 65 l/s for the first five years to supplement their process water make-up. Geo Pollution Technologies Ltd was appointed to investigate the feasibility of supplying groundwater to the mine. Due to the complexity of the Revuboe River during flooding and other difficulties abstracting water directly from the river, abstraction of groundwater from the alluvial aquifer next to the Revuboe River was selected as bulk water supply to the mine as it proved to be a sustainable source of water at other mining operations in the area. The benefits of the alluvial aquifer is the potential volume of water in storage and the zero losses to evaporation and seepage.

Taking into consideration the information gathered from previous groundwater and geophysical studies done in the area, a number of boreholes were sited based on geophysical results, alluvial material thickness and the energy of the river. Four of the six initial borehole positions had to be changed due to unforeseen access restrictions and concerns from the community. After the borehole positions were cleared and finalised, six boreholes were drilled up to a depth of roughly two meters below the bottom of the alluvial aquifer, which is on average 20 meters thick. The boreholes were logged in terms of geology and hydrogeology and cased to allow maximum water inflow from the aquifer. Due to one of the six boreholes being dry, five of the boreholes were subjected to 24 hour pump testing. The discharge rates varied between 4 and 20 l/s. The pump test results were interpreted using the Flow Characteristic method and final yields of between 5 and 30 l/s were achieved. The bulk water supply target of 65 l/s were exceeded by 9 l/s, with a final supply from the five holes combined of 74 l/s sustainably for the next five years.

Abstract

Characterization of Groundwater Potential in the northern parts of the Limpopo Province, South Africa: Results from Integrated Geophysical Studies across the Sagole and Tshipise Hot Springs.
The Sagole and Tshipise hot springs are located in the northern Limpopo Province of South Africa. The geology of the area consists of dykes, dolerite sills, quartzite and undifferentiated meta-sediments. Regional-scale airborne magnetic data and satellite images were used for mapping structures and lithological boundaries in order to identify permeable zones that are associated with thermal groundwater aquifers. Various filtering techniques were used to enhance the magnetic signatures that correspond to structural features. Modeling of airborne magnetic data indicated that the heat source depth was an anticlinal structure at a depth range of 3 km to 5 km. Based on results of interpretation of the magnetic and satellite images, ground follow-up targets were identified. Detailed ground geophysical surveys were carried out across the identified targets using the frequency-domain electromagnetic (EM), electrical resistivity tomography (ERT) and magnetic methods.
{List only- not presented}

The result of interpretation of magnetic data was combined with two-dimensional modeling EM and (ERT). Modeling of the electrical conductivity of the subsurface layers was constrained using existing borehole data. Interpretation of the airborne magnetic data revealed the presence of number of NE-SW striking lineaments that transect the metasedimentary rocks of the Soutpansberg Supergroup. In addition, these structures are manifested by a number of hotsprings that are aligned along major lineaments. The interpretation of 2D modeling of ERT data revealed a highly conductive layer with a depth ranging from surface to 40 m that may be attributed to elevated moisture content. Two-Dimensional modeling of frequency-domain electromagnetic data was carried out to delineate lateral and vertical variation of electrical conductivity. Electrical conductivity values in the range 50 mS/m to 100 mS/m were obtained, indicating the presence of water bearing zones or fractures. Results of the study have shown that hot water rises to the surface along near vertical faults or fractures.

Keywords: Aquifer, geophysics, groundwater, thermal spring

Abstract

The National Water Act (NWA) 36 of 1998 is regarded as providing a platform for an innovative way of managing the country's water resources. However, demands on the nation's water resources are intensifying as more and more catchments are coming under increasing stress. This may be attributed to significant changes in land-use and poor water resource governance which negatively affects the Environmental Water Requirement (EWR) flows of rivers in many catchments in South Africa. EWR refers to the flow needed by a river to sustain a healthy ecosystem. It is vital that the determined EWR flows are met and to ensure that all water-users receive their allocated water supplies. To ensure effective water management and water provision, it is critical to understand transmission losses considering that it is a key component of the water balance or hydrological budget. Quantitative investigations of transmission losses are necessary in order to calculate flows in a river and appropriately allocate water for different users. The Groot Letaba River situated in the north-eastern region of South Africa is a prime example of a river system where uncertainties in channel losses and gains are complicating effective water management. The Groot Letaba River is a model river where Strategic Adaptive Management (SAM) is currently being implemented to ensure adaptive and sustainable water resource management. This unique approach is facilitated by the institutional interaction between dam operators (from the upstream Tzaneen Dam) and stakeholders including Kruger National Park. However, there are huge uncertainties surrounding natural water losses (e.g. evapotranspiration) or gains (e.g. groundwater discharge) in the real-time model currently being used by dam operators. This study aims at attempting to narrow down the uncertainty by understanding and quantifying the natural hydrological processes between the two dominant land-uses along this river, i.e. agriculture and protected areas. In particular, the project will investigate the hydrological connectivity between groundwater and surface water along the Letaba River. This project will contribute significantly to management strategies by using a precise hydrological approach which will aid in improving estimates of water supply in the Groot Letaba River. Furthermore, this project could contribute to the development of appropriate water management strategies not only in the Letaba catchment but other similar Lowveld catchments as well.

Abstract

The colliery is situated in the Mpumalanga Coalfield, north of Trichardt in the Republic of South Africa. The opencast is already rehabilitated but still acts as an entrance to the underground sections of the mine. The Life of Mine indicates active mining until 2035. We were tasked to develop a mine closure plan. Two surface drainage systems are present, namely the Trichardt Spruit and the Steenkool Spruit. Both these systems have been diverted locally around the opencast with the necessary permission, to maximize coal extraction and protect the environment. Several passive treatment options were tabled to minimise the post closure environmental contamination. After careful consideration it was decided to develop a mine flooding plan to exclude oxygen from the mine thereby minimising the sulphate generation inside the opencast and underground sections. To start flooding as early as possible, sections of the underground mine were identified as natural or artificial compartments to store water. The rehabilitated opencast is flooded using recharge water from rainfall. The capacity of the rehabilitated open pit is enlarged to evaporate all the excess water in the pit making the need for a treatment plant unnecessary.

Abstract

The question about the natural recharge areas for two of the Lower Berg river aquifers units, Elandsfontein Aquifer unit and Langebaan Road aquifer unit, has been keeping geohydrologists working in the area without a definite answer. Tredoux and Engelbrecht have postulated that it must be from the higher grounds around Hopefield, while Woodford hinted that an offshoot fault from the Coleso fault system could also cause the systems to be recharged from the Darling hills. Isotope studies had been done for the proposed Hopefield recharge area, but none has so far been done for the possible Darling recharge system. This paper will look at the studies done up to date and evaluate the data available for the boreholes drilled in the area in an attempt to get a clearer understanding of the two possibilities. It will also identify possible gaps in our knowledge of the area and the steps that would make it possible to fill in the gaps.

Abstract

POSTER The improvement in horizontal drilling and hydraulic fracturing techniques has resulted in the exploitation of gas associated with low-permeability organic-rich shale formations in the United States of America (USA) to become one of the most important energy resources. The USA experience has resulted in renewed exploration interest in the shale formations in the main Karoo Basin. The basins consist of sediments of the Karoo Supergroup, which were deposited during the Late Palaeozoic-Early Mesozoic. Typically, South Africa has been heavily reliant on coal for its primary energy supply, but currently, the country is seeking to develop alternative sources in order to diversify its energy sources. In the Karoo basin, the Whitehill Formation is the most prospective shale gas target. The neighbouring shales such as the Prince Albert Formation are of commercial interest, particularly if the Prince Albert Formation is exploited as an extension of the Whitehill play. Water management has emerged as being crucial for the sustainable development of unconventional gas resources in particular the risks to groundwater resources. This study attempts to develop a conceptual model of deep basin groundwater flow systems in the main Karoo Basin. The conceptual model aims to inform possible solution to protect groundwater resources. This will be done by investigating possible scenarios for interaction between deep and shallow aquifers as to establish possible migration pathways of flowback and produced water that would lead to possible pollution to shallow Karoo aquifers during and/or after the hydraulic fracturing process or activities in the main Karoo Basin.

Abstract

Introduction: Verlorenvlei catchment in the renowned potato Sandveld area is shared by three main towns where agriculture is a primary economic activity. This semi-arid catchment, receives low winter rainfall, but has a dynamic groundwater system providing almost all water services in the catchment and sustaining the acclaimed Verlorenvlei RAMSAR site. There have been recurring concerns of land use as a potential threat to water resources and the sustainability of Verlorenvlei RAMSAR site. The Minister of Water and Sanitation as custodian of water resources requires that surface water use less than 18 250 m3 and ground water use less than 3 650 m3/a to be granted under general authorization. All water use above such general authorization volumes is to be registered (Government Gazette No. 20526 of 1999). Water use registration, is identified as a tool used to achieve the effective management and governance of water resources. Water use above general authorization, is associated with larger scale land use activity, which may have an impact on water resources and the environmental at large. The following study, seeks to examine and compare catchment water use for land uses, to catchment water availability using water use registration data. Comparing water allocation and catchment capacity, this study further seeks to explore the effectiveness of water use registration in achieving good governance of water resources. Purpose: The purpose of this study was to determine effectiveness of water use registration in promoting good governance in the Verlorenvlei catchment Results: Of 124 registered water users identified in the Verlorenvlei catchment, only two of these water users are within the legislative limit outlined by Government Gazette No. 20526 of 1999. Overall, permissible water use is 447 547 259.5 m3/a, over 10 times the catchment capacity of 40 000 000 m3/a. Conclusion: Overall, excessive water use for land use activity is observed within the catchment, despite provision of legislature guiding against excessive water use. Increased water use registration, does however correlate with improved land use practices for agricultural production (Potato SA, 2014) suggesting probability of good governance. Lastly, there is a need for monitoring; improved water and land use efficiency, Integrated Water Resources Management and good governance in the catchment.

Abstract

The Table Mountain Group (TMG) Formation in the Uitenhage region, in the Eastern Province of South Africa, has many groundwater users, which could result in the over-exploitation of the underlying aquifer. Consequently, several investigations have been conducted to help in the planning and management of groundwater resources within the region. Traditionally, these investigations have considered groundwater and surface water as separate entities, and have been investigated separately. Environmental isotopes, hydrochemistry and feacal colifom bacteria techniques have proved to be useful in the formulation of interrelationships and for the understanding of groundwater and surface water interaction. The field survey and sampling of the springs, Swartkops River and the surrounding boreholes in the Uitenhage area have been conducted. After full analysis of the study, it is anticipated that the data from the spring, Swartkops River and the surrounding boreholes show interannual variation in the isotope values, indicating large variation in the degree of mixing, as well as to determine the origin and circulation time of different water bodies. ?D and ?18O value for the spring ranges from ?18.9? to ?7.4?, and 5.25? to 4.82?, respectively, while ?D values for borehole samples range from ?23.5? to ?20.0? and ?18O values range from ?5.67? to ?5.06?. In the river sample, ?D values ranges from ?12.1? to ?4.2?, ?18O from ?3.7? to ?1.13?, respectively. The entrobacter aerogen and E.Coli bacteria were detected in the samples. E. coli population for spring and the artesian boreholes indicated low value while the shallow boreholes had higher values are relatively closer to those of the middle ridges of the Swartkops River. The EC values for the spring samples averages at 14 mS/m, borehole samples ranges from 21 mS/m to 1402 mS/m, and surface water ranges from 19 mS/m to 195 mS/m. Swartkops River is an ephemeral, therefore it is expected that diffuse recharge occurs into the shallow aquifer.

Abstract

Based on a modified DRASTIC model and GIS techniques, shallow groundwater vulnerability assessment was carried out in the Federal Capital City of Abuja, Nigeria. The results indicate that the studied area can be divided into three zones, namely: low groundwater vulnerability zone (vulnerability index <100) which covers about 60% of the City; moderate vulnerability zone (vulnerability indexes 100-140) which covers 35% of the City and high vulnerability zone (vulnerability index >140) which covers only 5% of the City. The highest groundwater vulnerability zone mainly locates in the central solid waste disposal site area in the outskirt of the City. The findings correlate well with the results of the physicochemical and microbiological investigation. The general low contamination vulnerability signature of the City may be attributed to absence of industries, limited agricultural activities, and preponderance of clayey top soil which effectively forms the first defence against contamination of the underlying aquifers as well as the presence of central sewage collection facility that covers about 25% of the City.

Abstract

Underground coal gasification (UCG) is considered a cleaner energy source as its known effect on the environment is minimal; it is cheaper and a lesser contributor to greenhouse gas emissions when compared to conventional coal mining. It has various potential impacts but the subsidence of the surface as well as the potential groundwater contamination is the biggest concerns. Subsidence caused by UCG processes will impact on the groundwater flow and levels due to potential artificial groundwater recharge. The geochemistry of the gasifier is strongly depended upon site specific conditions such as coal composition/type and groundwater chemistry. Independent of the coal rank, the most characteristic organic components of the condensates is phenols, naphthalene and benzene. In the selection of inorganic constituents, ammonia, sulphates and selected metals and metalloids such as mercury, arsenic, and selenium, are identified as the dominant environmental phases. The constituents of concern are generated during the pyrolysis and after gasification as dispersion and penetration of the pyrolysis take place, emission and dispersion of gas products, migration by leaching and penetration of groundwater. A laboratory-based predictive study was conducted using a high pressure thermimetric gasification analyser (HPTGA) to simulate UCG processes where syngas is produced. The HPTGA allows for simulation of the actual operational gasifier pressure on the coal seam and the use of the groundwater sample consumed during gasification. A gasification residue was produced by gasifying the coal sample at 800 °C temperature and by using air as the input gas. The gasification residue was leached using the high temperature experimental leaching procedure to identify the soluble phases of the gasified sample. The leachate analysis is used to determine the proportion of constituents present after gasification which will be removed by leaching as it is exposed to external forces and how it will affect the environment. The loading to groundwater for the whole gasifier is then determined by applying the leachate chemistry and rock-water ratio to the gasifier mine plan and volumes of coal consumed. 

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".

Abstract

Worldwide many aquifer systems are subject to hydrochemical and biogeochemical reactions involving iron which limit the sustainability of groundwater schemes. This mainly manifests itself in clogging of the screen and immediate aquifer with iron oxyhydroxides resulting in loss of production capacity of the borehole. Clogging is caused by chemical precipitation and biofouling processes which also manifests in South African wellfields such as the Atlantis and the Klein Karoo Rural Water Supply Scheme. Both wellfields have the potential to provide a sufficient, good quality water supply to rural communities, however clogging of the production boreholes has threatened the sustainability of the scheme as quality and quantity of water is affected. Repeated rehabilitation of the affected boreholes using techniques such as the Blended Chemical Heat Treatment (BCHT) method does not provide a long term solution. Such treatments are costly with varying restoration of original yields achieved and clogging recurs with time. Currently, the research, management and treatment options in South Africa have focused on the clogging processes which are complex and site specific making it extremely difficult to treat and rectify. This project attempts to eliminate the cause of the clogging which is elevated concentrations of dissolved iron. High iron concentrations in groundwater are associated with reducing conditions in the aquifer allowing for dissolution of iron from the aquifer matrix. These conditions can be natural- and/or human-induced. Attempts to circumvent iron clogging of boreholes have focussed on increasing the redox potential in the aquifer to prevent dissolution and facilitate fixation of the iron in the aquifer matrix. Various in situ treatment systems have been implemented successfully overseas for some time. However, in South African in situ treatment of iron has only been a theoretical approach. Based on experience from abroad the most viable option to research and apply elimination of ferrous iron in South African aquifer systems would be through the in situ iron removal treatment The objective of this paper is to set out the experience from abroad and to outline the initial results of this treatment. A pilot plant for testing the local applicability of this method was constructed at the Witzand wellfield of the Atlantis primary aquifer on the West coast of South Africa.

Abstract

In this study, petroleum hydrocarbon contamination assessment was conducted at a cluster of petroleum products storage and handling facilities located on the Southern African Indian ocean coastal zone. The Port Development Company identified the need for the assessment of the soil and groundwater pollution status at the tank farms in order to develop a remediation and management plan to address hydrocarbon related soil and groundwater contamination. Previous work conducted at the site before consisted out of the drilling and sampling of a limited number of boreholes. The current investigation was triggered by the presence of free phase product in the coal grading tippler pit located ~350 m down gradient and south-east and east of the tank farms, rendering the operation thereof unsafe. The assessment intended identifying the source of product, distribution and mobility, the extent of the contamination, and the human health risks associated with the contamination. To achieve these, the investigation comprised site walkover and interviews, drilling of 76 hand auger and 101 direct push holes to facilitate vertical soil profile VOC screening and sampling (soil and groundwater) as well as granulomeric analysis to understand grain size distribution within the soil profile. The highest concentrations were associated with the coarse sand layers with the highest permeability. Free phase hydrocarbons product was found in holes adjacent to the pipeline responsible for the distribution of the product form the jetty to the different tanks farms. Of the 57 soil samples, 21 had high values of GRO and DRO, with 22 below Detection Limit and 14 can be described having traces of hydrocarbon. Both TAME and MTBE were detected in most of the water samples taken, including from wells located far down gradient. The groundwater sink, adjacent to the pipeline running from west to east, resulted in the limited lateral spread of MBTE in this area, with limited movement towards the sea. The depth of the soil contamination varies over the sites. Based on the site assessment results it was concluded that most of the groundwater contamination, which is a mixture of different product types, is associated with the pipeline responsible for transporting product from the jetty to the different petroleum companies. {List only- not presented}

Abstract

Acid mine drainage (AMD) has lately received considerable media coverage in South Africa. This has caused considerable increase in researchers most of them with emphasis on decantation of contaminated water from the old gold mines in Witwatersrand basins and fewer on mine residue contamination from Coal and Gold mines in Mpumalanga and Limpopo provinces. The paper outlines results of ground geophysical surveys that were carried out along the perimeter of two mine dumps in the Barberton Greenstone belt in the Mpumalanga Province, South Africa. The aim of the study was to generate a 3D geo-electric model of the subsurface showing possible acid mine drainage contaminant pathways. Two geophysical methods namely Frequency Domain Electromagnetic profiling (FDEM) and electrical resistivity tomography (ERT) were applied in order to investigate the variation of electrical conductivity in the subsurface. ERT method was done over frequency domain electromagnetics anomalies to further investigate depth extent of the anomalies.
{List only- not presented}

On the resistivity section ERT1 of Dump 1, a discontinuity in the bedrock was identified. The FDEM survey identified an area with high conductivity values to the north of Dump 1. The ERT results show a shallow plume at 20m depth, which is consistent on two parallel sections on Dump 1. The area could be a possible pathway of mine dump residue (AMD) to a stream in the north. The bedrock is generally characterized by high resistivity values; a break in the bedrock exists on this high resistivity zone on ERT 6. The identified breaks in the bedrock in terms of resistivity could be a fault zone which can act as possible pathway of mine dump residue (AMD) to a shallow aquifer.

Potential contaminant recharge pathways were delineated using geophysical electrical and electromagnetic methods. Potential groundwater recharge pathways and sub-vertical low resistivity zones with values <100 Ohm.m were delineated using the ERT method. Investigation of contaminant plume migration is recommended over the anomalies that were generated from geophysics data in the Barberton areas.

KEYWORDS
Acid mine drainage, Frequency Domain Electromagnetic profiling and electrical resistivity tomography

Abstract

This study explores some of the principle issues associated with quantifying surface and groundwater interactions and the practical application of models in a data scarce region such as South Africa. The linkages between the various interdependent components of the water cycle are not well understood, especially in those regions that suffer problems of data scarcity and there remain urgent requirements for regional water resource assessments. Hydrology (both surface and groundwater hydrology) is a difficult science; it aims to represent highly variable and non-stationary processes which occur in catchment systems, many of which are unable to be measured at the scales of interest (Beven, 2012). The conceptual representations of these processes are translated into mathematical form in a model. Different process interpretations together with different mathematical representations results in the development of diverse model structures. These structural uncertainties are difficult to resolve due to the lack of relevant data. Further uncertainty is introduced when parameterising a model, as the more complex the model, the greater the possibility that many different parameter sets within the model structure might give equally acceptable results when compared with observations. Incomplete and often flawed input data are then used to drive the models and generate quantitative information. Approximate implementations (model structures and parameter sets), driven by approximate input data will necessarily produce approximate results. Most model developers aim to represent reality as far as possible, and as our understanding of hydrological processes has improved, models have tended to become more complex. Beven (2002) highlighted the need for a better philosophy toward modelling than just a more explicit representation of reality and argues that the true level of uncertainty in model predictions is not widely appreciated. Model testing has limited power as it is difficult to differentiate between the uncertainties within different model structures, different sets of alternative parameter values and in the input data used to run a model. A number of South African case studies are used to examine the types of data typically available and explore the extent to which a model is able to be validated considering the difficulty in differentiating between the various sources of uncertainty. While it is difficult to separate input data, parameter and structural uncertainty, the study found that it should be possible to at least partly identify the uncertainty by a careful examination of the evidence for specific processes compared with the conceptual structure of a specific model. While the lack of appropriate data means there will always be considerable uncertainty surrounding model validation, it can be argued that improved process understanding in an environment can be used to validate model outcomes to a degree, by assessing whether a model is getting the right results for the right reasons.

Abstract

Conjunctive use of surface water and groundwater resources offers huge advantages to municipalities. It can significantly increase the resilience of the municipal water supply to drought situations. Optimal use and integration of different sources would result in a yield of the total system that is higher than the combined yield of each source separately. However, integrated water resource management (IWRM) in general and planned conjunctive use of both groundwater and surface water resources in particular have not been successfully implemented yet in South Africa. Six selected case studies of municipalities across South Africa, which utilize both surface water and groundwater for the water supply to specific towns, have undergone a review of their current water governance provisions wrt groundwater, surface water and conjunctive use. The review has been based on a questionnaire for direct interaction with the local government officials, supported by other readily available documents such as municipal Integrated Development Plan (IDP) and Water Services Development Plan (WSDP), municipal websites, Blue Drop and Green Drop Assessment Reports, Municipal Strategic Self-Assessment (MuSSA) and the All Towns Reconciliation Strategy reports. These case studies reveal the different institutional arrangements for water resource management and water supply services that exist in municipalities. The advantages and disadvantages of the institutional arrangements for each case study have been determined. Problem areas identified include split of responsibilities for surface water and groundwater resources between different institutions, lack of financial and HR support within the government spheres, lack of formal and structured stakeholder engagement, insufficient monitoring for both sources, inter alia. Based on this comparative study of different municipalities, a draft framework of optimal institutional arrangements and governance provisions at local government level is developed to support the integration and optimisation of surface water and groundwater supply. The proposed framework is based on three pillars; viz. leadership and clear structures within the responsible local government institution, formal engagement with all relevant internal and external stakeholders and a sufficient monitoring network that supports the stakeholder engagement and decision making.

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}

Abstract

POSTER The study aims at using hydrogeochemical model to establish groundwater quality in shallow and deep aquifers in Heuningnes Catchment which is located within Bredasdorp in the Western Cape Province. The catchment is positioned at latitude of 34o42'50"S and longitude 20o07'13"E. The area is about 1400km2 has vleis, lakes and pans and its predominant formation is sedimentary rocks of Table Mountain and Bokkeveld Groups sitting on a crystalline basement of the Malmesbury granites. Comprehensive characterisation of the hydrogeochemical evolution is lacking and the current study argues that the use of hydrogeochemical Analysis Model (HAM) has potential to establish water-type, water source, water mixing/rock-water interactions, salinity, saturated adsorption ratio and hardness-softness of that predominant hydrochemical facies in the study area in addition to assessing the compliance of such water to WHO and South Africa water quality guidelines for drinking and agricultural use. Groundwater samples will be collected in 45 different locations (wellpoints/shallow wells, boreholes and wetland as end member) using in-situ sampling techniques to measure pH, electrical conductivity, total dissolved solids and temperature. Turbidity, total hardness, calcium, chloride and bicarbonate will be analysed using analytical chemistry methods including titrimetric method. Magnesium, potassium, sodium, nitrate and phosphate analysed by Atomic Absorption Spectrophotometer whilst sulfate will be analysed using spectrophotometer. Graphical methods such as piper diagram will be used to present the results to determine water-type, water freshness/hardness, water source, water mixing/rock-water interactions, salinity, saturated adsorption ratio and hydrogeochemical processes. The results from the present study are envisaged to inform formulation of science-based interventions strategies that will lead to sustainable utilization and management of the water resources in the area to improve the livelihoods of people and environmental integrity.

Key words: Groundwater quality, Heuningnes Catchment, hydrogeochemical Analysis Model, Piper diagrams, Hydrogeochemistry

Abstract

When planning an experimental setup in the laboratory, it is very important and possible to control all the variables so that one can manipulate particular variables at a given time. Experimental setups under natural conditions could be a challenging task. The success of an experiment depends to a large extent on the correct understanding of the functioning of a natural system. If the conceptual understanding of the natural system is erroneous, it is likely that unexpected results could be achieved. This was the case with the artificial recharge pilot project that was done in 2008 and 2009 at the Langebaan Road wellfield just outside Hopefield in the Western Cape. Years of research gave scientists a fairly good idea of the way in which the aquifer system functioned, especially since the establishment of the well field. This provided information of the response of the aquifer unit to large scale abstraction. The Langebaan Road aquifer unit is a multilayered system with a lower aquifer composed of Elandsfontyn gravel overlaying a bedrock layer of either granite of the Vredenburg or Darling plutons of the Cape Granite Suite or Malmesbury shale. The bedrock was considered impermeable. The upper aquifer layer was composed of mostly the Varswater Formation with peat and clay of the Elandsfontyn Formation forming the confining layer between the two aquifer layers. The extent of the different layers of the aquifer unit was plotted with a fair amount of accuracy and the clay layer was considered to be continuous between the two aquifer layers. Monitoring data for the area was done since 1974 with a gap in data-set between 1991 and 2001. Despite all the data from geophysical work, boreholes drilled, and the monitoring record, the research done prior and during the artificial recharge pilot project in 2008 and 2009 the aquifer units did not respond quite as anticipated. The Artificial Recharge (AR) pilot project team concluded that the aquifer units responded in a particular manner as opposed to the expected response according to the data and conceptual model at hand. It was thus clear that there are gaps in the conceptual model of the aquifer systems in the bigger Lower Berg River Valley that include the Langebaan Road, Elandsfontein and other aquifers that needed to bridge before another pilot test is attempted. Although the artificial recharge pilot project did not yield the expected results, valuable lessons were learned. This article will look at the conclusions and recommendations of the research done on the pilot project and attempt to evaluate the monitoring data (water levels, chemistry and rainfall) from the period just before the beginning of the AR pilot project. The monitoring data would be manipulated using the following techniques

Abstract

In recent years acid mine drainage (AMD) has become the focus on many mine sites throughout the world. The Witwatersrand gold mines have been the main focus of AMD in South Africa due to their extensive impact on especially groundwater resources. The Witwatersrand Basin is a regional geological feature containing the world-famous auriferous conglomerate horizons. It is divided into sub-basins and the East Rand Basin is one of them. Due to the regional scale of the East Rand Basin AMD issues, a systems approach is required to provide a useful tool to understand the pollution source term and fate and transport dynamics and to aid in environmental decision making and to evaluate the geochemical impact of mitigation measures and evaluate future scenarios.
The numeric geochemical models, using a systems perspective, show that the mine waste facilities, specifically the tailings dams are significant contamination point sources in the East Rand Basin, specifically for acidity (low pH), SO4, Fe, Mn, U, Ni, Co, Al and Zn. When the AMD solution enters the soil beneath the tailings, ferrous and SO4 concentrations remain elevated, while Mn, U, Ni and Co and perhaps other metals are adsorbed. After ~50 years the pollution plume starts to break through the base of the soil profile and the concentration of the adsorbed metals increase in the discharging solution as the adsorption capacity of the soil becomes saturated. The pollution pulse then starts to migrate to the shallow groundwater where contamination of this resource occurs.
Toe seepage from the tailings either first reacts with carbonate, where acidity is neutralised to a degree and some metals precipitated from solution, where after it reaches the surface water drainage, such as the Blesbokspruit, where it is diluted. Some evaporation can occur, but evaporation only leads to concentration of acidity and dissolved constituents, thereby effectively worsening the AMD solution quality. The mixing models have shown that the dilution factor is sufficient to mitigate much of the AMD, although seasonal variability in precipitation and evapotranspiration is expected to have some influence on the mixing ratio and some variability in the initial solution will also be reflected in variation in surface water and groundwater quality.
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Abstract

The subsurface has been likened to a maze due to the intricate and often disconnected pathways contained even in unconsolidated and relatively homogeneous aquifer systems. The weathered fractured aquifers in the Karoo offer unique challenges to those planning monitoring campaigns and provide opportunities for the research community to identify innovative solutions. Careful thought needs to be given to the objectives of monitoring as these can change the requirements of the work. Other important considerations are the location and design of monitoring wells which often needs to be tailored to site specific conditions while the selection of determinands to be analysed introduces yet another layer of complexity. These include questions around the relevant detection limits, representative sampling methods and a host of other aspects. Following prescribed approaches designed for managing traditional industrial processes may not be relevant even though these approaches are based on decades of research and learning from past experience, both good and bad. Careful consideration of the technical detail in advance of beginning any monitoring in the field is essential and even then, as in any hydrogeological assessment, a level of uncertainty will always remain. This presentation will cover the status of planning work on Karoo aquifer characterisation and geochemical assessment of the ambient or baseline conditions. Significant effort continues to be made to tailor fieldwork to site specific conditions and be ready to collect a representative data set when conditions allow. {List only- not presented}

Abstract

Fine ash is a by-product generated during coal combustion and gasification. It is often disposed of as slurry and stored on tailings dams over long periods of time, where it is exposed to weathering. Weathering causes soluble ions to go into solution and to be transported along preferred pathways through the tailings dam. This study was conducted to assess the leaching behaviour of fresh and weathered fine ash and to evaluate the impact on the underlying aquifers. A kinetic test was conducted over 21 weeks to analyse the leachate composition of progressively-aged fine ash and to calculate the release rates for major ions and trace metals of environmental concern. The leachate composition was compared to the groundwater composition of the underlying aquifers to assess the environmental impact of long term ash leaching. The study showed that the release rate of Ca decreased with increasing depth and age of the fine ash. The release rate of Mg, Na, K, Mo, V, Ba, Cr and Mo increased slightly between 22 m and 28 m in the tailings dam. Aluminium had a decreasing release rate from 28 m depth onwards. It was concluded that fine ash leaching influenced the water composition of the underlying aquifers because similarities were observed in the water type trend. The shallow aquifer south of the tailings dam contained Ca/Mg/SO4/Cl/NO3 water with a significant increase in Ca, Mg, Na, Cl and SO4 over time. These ions were expected to be found in the pollution plume due to their high release rate observed in the fine ash. The deeper aquifer northeast and south of the tailings dam showed a reverse trend of decreasing Ca, Mg and NO3 with time. This is possibly due to decreasing release rates in the aging fine ash and due to the cation exchange capacity (CEC) of the aquifer retarding the movement of Ca and Mg in the pollution plume. The shallower aquifer northwest of the tailings dam showed a decrease in Ca and Mg but an increase in K, while the water composition of the deeper aquifer increased in Ca, Mg, Na, K and Cl. This indicates that the pollution plume moved from the shallower to the deeper aquifer and that most of the Ca and Mg content in the fine ash has been leached from the tailings dam after more than 30 years of storage. The study confirmed that leaching of elements from the fine ash tailings dam had a negative influence on the underlying aquifers and that the clay lining was not sufficient in retaining the leachate.

Abstract

The town of Loeriesfontein, situated in the northern Cape, is entirely groundwater dependent, and is currently facing a serious water shortage. Low rainfall and the lack of storm events have resulted in groundwater levels dropping drastically. The current supply boreholes have been over abstracted and cannot meet the required demand. Water levels are close to pump depth for some of the municipal boreholes, and yields are decreasing. The town at one stage was trucking in water in order to supply its residents. Additional supplies are therefore urgently required.

A number of measures were implemented to monitor and manage the current demand and the limited supply. Thereafter GEOSS investigated the occurrence of groundwater within a 20 km radius of Loeriesfontein, and found that dolerite represents the primary target formation for groundwater exploration. Groundwater occurrence is found at the lower dolerite contact with the host rock, or in fractures in the dolerite itself. Based on an extensive hydrocensus, geophysical surveys, drilling and yield testing, the Rheeboksfontein area was identified as a suitable water source. Initially water was being trucked into Loeriesfontein from Rheeboksfontein and later an innovative arrangement of solar driven borehole pumps and reservoir pumps resulted in water being transported much closer to Loeriesfontein, reducing the transportation distances and costs.

During this first Phase of exploration the projected supply still did not meet the water demand and water quality targets. A number of high yielding boreholes were drilled, however the water quality was such that it would have required treatment and disposal of brine in that area is problematic. The extent of the exploration was then increased to a distance of 40 km from Loeriesfontein. A detailed hydrocensus was completed, followed up with further geophysical surveys, drilling and yield testing. Successful boreholes were drilled and the required demand and water quality standards could just be met. This finding is being verified with numerical modelling.

A process is underway to develop a mini-wellfield and then the environmental processes are being followed so that a pipeline can be built delivering water directly into the reservoirs at Loeriesfontein. On-going monitoring and maintenance is crucial to the long-term success of the groundwater supply.

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.

Abstract

A Waste Water Treatment Works (WWTW) is being constructed at Pearly Beach. A geohydrological assessment was conducted to assess the potential discharge of treated effluent above and below the subsurface calcrete layers. A hydrocensus has been completed of the area to confirm there is no use of groundwater down-gradient of the WWTW and there is no likely impact on ecosystem functioning. Based on existing boreholes, infiltration above the calcrete layer in the vadose zone was found to be more efficient. A geophysical study was conducted to determine the optimal locations of boreholes for disposal of the treated effluent. The geophysics included an extensive electromagnetic (EM) survey. Resistivity data were acquired along a single resistivity profile to use as calibration for the EM data. This information has been correlated with borehole information from the monitoring boreholes that were drilled at the proposed WWTW site. From this information it would seem that the areas with higher conductivity (lower resistivity) can be targeted for drilling boreholes to dispose of the treated effluent. Also, the higher conductivity areas are interpreted as the areas with increased porosity. However, the change in conductivity could result from an increase in salinity or changes in calcrete content in the subsurface. The expected depth of the unconsolidated sand formations is generally less than 10 m based on the interpreted depth of the saturated formation from the resistivity data. Drilling will target the unconsolidated sands, as well as potential higher porosity zones beneath the calcrete. The geophysics data should then be calibrated with the information obtained from drilling the first borehole. The other sites can then be confirmed or reviewed based on the information. The boreholes are to be drilled soon and pump tested. The obvious concern is that the boreholes may clog, however measures will be put in place to minimise this risk. A detailed monitoring network will also be established. On-going monitoring is crucial to ensure the success of the scheme. The full conference paper will include the drilling and pump testing results and infiltration tests. This method of disposal needs to be taken into consideration especially if such schemes can be run successfully so that another option is available for the disposal of treated effluent. {List only- not presented}

Abstract

The proposed underground copper mine is one of the first Greenfield developments in the Kalahari Copper Belt. Groundwater resources in the region are scare and saline mainly due to minimal recharge. Management and simulations of groundwater inflows formed an integral part of the new mine design to reduce production losses caused by the inflows and to ensure a safe mining environment. The mine is located is a complex hydrogeological setting characterised by folding and deep water levels. Multiple fractured aquifers are associated with the mining area. Groundwater numerical modelling was performed in Groundwater Modelling System (GMS) using MODFLOW-NWT. Results of the scenarios were used as a management tool to aid in the potential inflow predictive simulations and dewatering management. The numerical model was calibrated by using field measured aquifer parameters and piezometric heads. Numerical simulations assisted in estimating average groundwater inflows at certain stages of the proposed mine development. The simulated mine groundwater inflow volumes were used as input into the design of the dewatering measures to ensure a safe mining environment.

Abstract

The development of groundwater supply schemes is on the increase in South Africa. However, the sustainability of many of these wellfields is threatened due to the presence of iron (Fe2+) and manganese (Mn2+) ions in the groundwater. Their occurrence can manifest in problems with water quality and supply to consumers. The World Health Organisation recommends the removal of iron and manganese to below 0.3 mg/? and 0.1 mg/? respectively, to circumvent water quality risks. However, production borehole clogging is of greatest concern in the operation of wellfields due to the severe cost implications associated with reduced production. Clogging is caused by the precipitation of iron- and manganese-oxides at the borehole screen initiated by biogeochemical processes. Since Fe2+ and Mn2+ ions and the bacterial populations are naturally present in anoxic/anaerobic aquifer systems and the ingress of oxygen through pumping cannot be entirely prevented. The only approach to controlling borehole clogging is through management and rehabilitation procedures. Locally, these procedures have been implemented and in severe clogging cases the Blended Chemical Heat Treatment method has been applied. However, the effectiveness of rehabilitation has been limited. This can be ascribed to factors such as the incorrect production borehole design