Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 301 - 350 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort descending	Keywords
Effects of Urbanization and Agricultural activities on Aquifer storage and Groundwater quality	Athenkosi	Matshini		2015
Abstract POSTER Aquifer stress arising from urbanization and agricultural activities, these two factors affect aquifer properties when prolonged. Increase in urbanization especially those situated on top unconfined or semi-confined aquifer results in pressure on natural resources, this includes water resources, and changes of land use for agricultural purposes with high economic benefits has an effect on groundwater quality to due to application of Nitrogen- fertilizers during crop rotation and this is largely experienced in developing countries. The effects ranges from groundwater quality to aquifer storage as prolonged aquifer withdrawals due to irrigation, construction, manufacturing affects groundwater storage. Assessment of urbanization and agricultural effects on groundwater requires a complex analysis as integration approaches needs to be discovered for a better analysis of the two more specially when assessing groundwater pollution. The study was conducted to assess the impacts of urbanization and agricultural activities on aquifer storage and groundwater quality: by (a) determining the relationship between the occurrence of contamination due to urbanization by assessing contaminants present in the study area (b) develop groundwater protection, and if any offer recommendation for groundwater management. Multiple-well tests were conducted observing the behavior of drawdown and recovery for assessing groundwater storage. Two aquifer properties were observed to yield information about any changes in aquifer storage (transmissivity and storage coefficient) and groundwater quality lab test focusing on TDS, nitrate and pH were conducted. Historical results reflect that before industrial and urban revolution the groundwater contained small amounts of TDS compared with the present results. Increase in nitrate and pH concentrations observed in location closer to agricultural areas. Prolonged aquifer withdrawals increases expansion of cone of depression and therefore increases aquifer vulnerability and the risk of aquifer being polluted, and this increases storage coefficient. This study can be used to formulate protection zones for water resources and practice towards groundwater management.
The Groundwater Data Acquisition and Management Strategy for the Department of Water and Sanitation	Mxolisi	Mukhawana		2015
Abstract Data acquisition and Management (DAM) is a group of activities relating to the planning, development, implementation and administration of systems for the acquisition, storage, security, retrieval, dissemination, archiving and disposal of data. Data is the life blood of an organization and the Department of Water and Sanitation (DWS) is mandated by the National Water Act (No 36 of 1998) as well as the Water Services Act (No 108 of 1997), to provide useful water related information to decision makers in a timely and efficient manner. In 2009 the DWS National Water Monitoring Committee (NWMC) established the DAM as its subcommittee. The purpose was to ensure coordination and collaboration in the acquisition and management of water related data in support of water monitoring programs. The DAM subcommittee has relatively been inactive over the years and this has led to many unresolved data issues. The data extracted from the DWS Data Acquisition and Management Systems (DAMS) is usually not stored in the same formats. As a result, most of the data is fragmented, disintegrated and not easily accessible, making it inefficient for water managers to use the data to make water related decisions. The lack of standardization of data collection, storage, archiving and dissemination methods as well as insufficient collaboration with external institutions in terms of data sharing, negatively affects the management water resources. Therefore, there is an urgent need to establish and implement a DAM Strategy for the DWS and water sector, in order to maintain and improve data quality, accuracy, availability, accessibility and security. The proposed DAM Strategy is composed of the six main implementation phases, viz. (1) Identification of stakeholders and role players as well as their roles and responsibilities in the DWS DAM. (2) Definition of the role of DAM in the data and information management value chain for the DWS. (3) Development of a strategy for communication of data needs and issues. (4) Development of a DAM life Cycle (DAMLC). (5) Review of existing DAMS in the DWS. (6) Review of current data quality standards. The proposed DAM Strategy is currently being implemented on the DWS Groundwater DAM. The purpose of this paper is to share the interesting results obtained thus far, and to seek feedback from the water sector community.
Mapping irrigation potential from renewable groundwater in Africa - a quantitative hydrological approach	Karen	Villholth	Africa	2015
Abstract Groundwater provides an important buffer to climate variability in Africa. Yet, groundwater irrigation contributes only a relatively small share of cultivated land, approximately 1% (about 2 mill. ha) as compared to 14% in Asia. While groundwater is over-exploited for irrigation in many parts in Asia, previous assessments indicate an underutilized potential in parts of Africa. As opposed to previous country-based estimates, this paper derives a continent-wide, distributed (0.5 degrees spatial resolution) map of groundwater irrigation potential, indicated in terms of fractions of cropland potentially irrigable with renewable groundwater. The method builds on an annual groundwater balance approach using 41 years of hydrological data, allocating only that fraction of groundwater recharge that is in excess after satisfying other present human needs and environmental requirements, while disregarding socio-economic and physical constraints in access to the resource. Due to high uncertainty of groundwater environmental needs, three scenarios, leaving 30, 50 and 70% of recharge for the environment, were implemented. Current dominating crops and cropping rotations and associated irrigation requirements in a zonal approach were applied in order to convert recharge excess to potential irrigated cropland. Results show an inhomogeneously distributed groundwater irrigation potential across the continent, even within individual countries, mainly reflecting recharge patterns and presence or absence of cultivated cropland. Results further show that average annual renewable groundwater availability for irrigation ranges from 692 to 1644 km3 depending on scenario. The total area of cropland irrigable with renewable groundwater ranges from 44.6 to 105.3 mill. ha, corresponding to 20.5 to 48.6% of the cropland over the continent. In particular, significant potential exists in the semiarid Sahel and eastern African regions which could support poverty alleviation if developed sustainably and equitably. The map is a first assessment that needs to be complimented with assessment of other factors, e.g. hydrogeological conditions, groundwater accessibility, soils, and socio-economic factors as well as more local assessments.
TEMPEST for groundwater exploration	Odirile	Dingoko	Australia	2015	Airborne electromagnetic surveys
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.
Groundwater Exploration In The Anticlinorium Of The Jeffreys Arch In Jeffreys Bay	Vhuthu	Tshishonge	Eastern Cape	2015
Abstract POSTER The Jeffreys Bay Municipal borehole field is located in the coastal town of Jeffreys Bay, Eastern Cape Province, South Africa. It is underlain by the Jeffreys arch domain which features the Skurveberg and Baviaanskloof formations of the Table Mountain Group. The Jeffreys arch has been subject to groundwater exploration, targeting its characteristic faults and folds. The investigation was intended to establish five (5) high yielding boreholes with good water quality. Geophysical surveys, drilling and pump tests were conducted in succession. Ground surveys were carried out across the study area using the electromagnetic method to identify subsurface geological structures through anomalies in the earth's magnetic field. The interpretation of the data revealed significant anomalies within an anticlinorium. Drilling through quartz and quartzitic sandstone posed considerable difficulties mostly along zones of oxidation. The main water strikes with airlift yields of 9 - 35 L/s were intersected within quartzitic sandstone at depths of about 120m and greater. Chemical sampling results revealed adherence of iron and manganese concentrations to the drinking water recommended limits as per SANS 241-1 (2011). Two (2) of the five (5) boreholes revealed higher than recommended of iron and manganese concentrations. The aquifer test data was processed using the Flow Characteristic programme, the recommended abstraction rates range between 4-17 L/s/24 hrs. Results observed during different exploration phases revealed high yields and good water quality with greater depths as compared to the existing shallow boreholes with high iron, conductivity and manganese concentrations. Treatment of borehole water with high concentrations is necessary. It is recommended that drilling for groundwater resources within the anticlinorium of the Jeffreys arch be done at great depths.
Estimating Groundwater Recharge In Commercial Plantation Forests: A Case Study From George (Western Cape)	Richard DH	Bugan	George, Western Cape	2017	Forestry, afforestation, recharge mechanisms, Simulations, HYDRUS-2D
Abstract The benefits of the commercial plantation forestry sector (income generation, job provision, etc.) come at considerable environmental costs, particularly the impact of the industry on water resources. Plantation forests exhibit higher evapotranspiration rates when compared to that observed in indigenous forests/grasslands. A reduction of the water yield in a catchment is one of the most frequently reported impacts of afforestation. Afforestation also significantly impacts groundwater, which is becoming an increasingly important resource for water supply in South Africa. Very few studies have however quantified in detail the impact of different commercial forests grown in South Africa on groundwater and the interactions with surface water. This study seeks to contribute to addressing this important knowledge gap. The main objective was to comprehending groundwater recharge dynamics in commercial plantation forests, i.e. an environment where evapotranspiration losses is a major component of the water balance. The HYDRUS-2D model was used to simulate the hillslope hydrological dynamics in a commercial plantation forest (Pinus radiata) during the period 8 July 2016 to 12 June 2017. The model was used to simulate the interaction between the vegetation, unsaturated zone and the saturated zone in order to better understand the groundwater recharge dynamics evident in the area. As a precursor to model application a detailed conceptual model of the recharge processes occurring in the study areas was developed. The model considered the prevailing geomorphological and hydrogeological conditions. HYDRUS-2D was able to adequately simulate the soil hydraulic properties characterising the study area. The hydrological dynamics of the simulation results also conform to the conceptual understanding of groundwater recharge processes evident in the study area. Over the entire simulation period (340 days), the model quantified potential groundwater recharge to be 31.5 mm. This primarily occurred during a 60 day period (20 September 2016 - 19 November 2016) in response to significant rainfall events of 76.96 mm (DOS 56 – 58) and 45.98 mm (DOS 71 – 72). This groundwater recharge dynamic conforms to the notion that groundwater recharge is driven by single or multiple events and not by annual averages. The results of the investigation are promising and provide motivation for the application of HYDRUS-2D to estimate groundwater recharge in environments which are deemed to be suitable for model application. The model provides the ability to study the dynamics of groundwater recharge at short time scales, as opposed to annual average responses which are derived from commonly applied techniques.
Alluvial Wellfield Optimisation And Management Using Numerical Flow Modelling And Seasonal River Stages	Brendon	Bredenkamp		2017	Alluvial aquifer, wellfield management, numerical modelling, river stages
Abstract Three dimensional numerical flow modelling has become one of the best tools to optimise and management wellfields across the world. This paper presents a case study of simulating an existing wellfield in an alluvial aquifer directly recharged by a major perennial river with fluctuating head stages. The wellfield was originally commissioned in 2010 to provide a supply of water to a nearby Mine. Ten large diameter boreholes capable of abstracting ±2 000 m3 /hour were initially installed in the wellfield. The numerical groundwater flow model was used to evaluate if an additional 500 m3 /hour could be sustainably abstract from the alluvial aquifer system. A probabilistic river flow assessment and surface water balance model was used to quantify low and average flow volumes for the river and used to determine water availability in the alluvial aquifer over time. Output generated indicated that the wellfield demand only exceeded the lowest 2% (98th percentile) of measured monthly river flow over a 59 year period, thereby proving sufficient water availability. Conceptual characterisation of the alluvial aquifer was based on previous feasibility studies and monitoring data from the existing hydrogeological system. Aquifer parameters was translated into the model discretisation grid based on the conceptual site model while the MODFLOW River package was used to represent the river. Actual river stage data was used in the calibration process in addition to water levels of monitoring boreholes and pump tests results. The input of fluctuating river water levels proved essential in obtaining a low model error (RMSE of 0.3). Scenario modelling was used to assess the assurance of supply of the alluvial aquifer for average and drought conditions with a high confidence and provided input into further engineering designs. Wellfield performance and cumulative drawdown were also assessed for the scenario with the projected additional yield demand. Scenario modelling was furthermore used to optimise the placement of new boreholes in the available wellfield concession area.
Can Palaeochannels Be Used To Enhance Groundwater Recharge? A Case Study: Langebaan Road Aquifer	Awodwa	Magingi	Western Cape	2017	Palaeochannels, hydraulic parameters, Drought, artificial recharge
Abstract The assumed interconnection between palaeochannels and subsurface water resources is described. This paper (poster) discusses the different methods that can be used to indicate the significance of palaeochannels into groundwater recharge. Hydraulic parameters such as permeability and transmissivity of the layer underlying the palaeochannel act as the main dependents of groundwater recharge on palaeochannels. Considering the drastic drought from which South Africa is recovering or has recovered the importance of artificial recharge through palaeochannels is explained. The Langebaan Road Aquifer with its palaeochannel is used as a practical example and a detailed explanation on how palaeochannels can be used to enhance groundwater recharge is further demonstrated. Enhancement of recharge would ensure groundwater sustainability and augmentation to surface water especially during drought periods.
Stable Isotopes Reveal Pathways And Potential For Nitrate Mitigation In An Aquifer Used For Drinking Water Production	C	Kludt	Germany	2017	Biochemistry, Nitrate, Isotopes, agriculture, contamination
Abstract To control the impact of nitrate and its sustainable mitigation in groundwater systems used for drinking water production, it is crucial to understand and quantify sources as well as biochemical processes which (permanently) remove nitrate. In an alluvial aquifer in Germany (Hessian Ried) that serves as major drinking water recourse for the Frankfurt metropolitan area, water quality is challenged by nitrate contamination from intensive agricultural land use locally by far exceeding the drinking water limits of 50 mg/L. In order to evaluate the capability of the aquifer for natural mitigation of the nitrate contamination, we investigated the denitrification potential with respect to the availability of electron donors and the predominant reduction pathways in different sections of the aquifer. The content of sedimentary sulfide and organic carbon was quantified by solid-phase analyses of drill core samples from aquifer sediments. Water samples from vertical profiles gave access to information on the isotope-hydrochemical composition of the groundwater (multi-parameter profiles, major ions, nitrate isotope signature, sulfate isotope signature). Using this hydrochemical and isotope information in concert with the results of a groundwater flow model allowed determining the nitrate input and the average nitrate reduction kinetics along the flow path upstream of selected groundwater monitoring wells. Batch and column experiments provided detailed information on prevailing reaction pathways and the associated isotope fractionation pattern enabling the recognition and quantification of processes on field scale. Our results suggest that litho-autotrophic denitrification using sedimentary sulfide as an electron donor is preferably responsible for the nitrate degradation in the aquifer. However, due to the low sulfide content (max. 123 mg-S/kg), the potential for autotrophic denitrification is very limited. Consequently, if no active measures reducing the input of fertilizer-derived nitrate will be implemented in the near future, the limited potential for autotrophic denitrification will ultimately exhaust and a severe deterioration of the groundwater quality can be expected.
Geochemical Behaviour Of Arsenic In Contact With Dolomite	Johan	Fourie		2017	Arsenic, geochemical, dolomites
Abstract Arsenic is a common contaminant typically found in effluent from gold mine operations and copper smelters throughout the world. The geochemical behaviour of arsenic in contact with dolomite underlying an arsenic containing waste rock pile was investigated. The interaction between the arsenic and the dolomite is an important control in the subsequent transport of the arsenic in the dolomitic aquifer. Rocks with varying dolomite content were tested to investigate the interaction between the arsenic and dolomite. From the modelling and test results it was estimated that in the aquifer, between 60 - 90% of arsenic is present in the solid phase under oxidation conditions at >50 mV. At 50 to -25 mV about 40 - 60% of the arsenic is estimated to be present in the solid phase and below -25 mV about 0 - 10% of arsenic will be present in the solid phase. Although some arsenic is removed by the dolomite in the aquifer the arsenic would still be present above acceptable guidelines for drinking water. The arsenic in the solid phase will be in equilibrium with the aquifer water and could be remobilised 1) under more reducing conditions or 2) with a decrease in arsenic in the aquifer.
Hydrochemical Analysis Of Groundwater In The Danakil Depression, Northern Ethiopia	David C	McGibbon	Ethiopia	2017	hydrostratigraphy, hydrochemical, hydrothermal influx
Abstract An investigation of surface and groundwater chemistry was undertaken as part of a resource assessment of water-supply for potash solution-mining in the Danakil Depression of the Afar Rift, situated in northern Ethiopia on the N/S-trending Ethiopia-Eritrean arm of the East African Rift System. Four hydrostratigraphic units are recognised in the area: 1) Basement Tsaliet Group rocks, low yielding and with poor water quality; 2) Adigrat Formation and Antalo Group fractured sandstones and karstic limestones, high yielding with good water quality; 3) Danakil Group and Zariga Formation fine-grained sediments, forming a good regional aquifer; 4) Dogua Formation alluvial fans, forming a major, regional, primary aquifer with high yields and poor water quality (yields of >50 l/s but 3 times the salinity of sea water). In the mining concession area the only available target for groundwater exploration is the Dogua alluvial-fan system that extends off the Dogua Mountain range to the west. During 2015 and 2016, 5 production and 5 exploration/monitoring boreholes were drilled into the fans, thereafter test pumped and sampled for hydrochemical and isotope analysis. The aquifer stress test proved that there is sufficient groundwater available for the life of mining, but that the water quality is poor. The hydrochemical analysis found that in general, water quality is poor (brine with TDS values >100 000 mg/l and a density >1.05 g/cm3 ) and with temperatures of ~50°C. Water quality degrades from south to north, possibly due to recharge of fresh water from the Antalo limestones in the south and lesser quality water from the Tsaliet basement in the north. The high salinity and temperature found throughout the fans is due to hydrothermal influx along rift-boundary faults that extend downwards into the thermally active, volcanic rift zone. Prolonged pumping results in the degradation of the water quality in the southern boreholes and improvement of quality in the northern boreholes; this is likely as the groundwater heads towards equilibrium, with a similar hydrochemical signature to that of the dominant hydrothermal influx. Stable and radiogenic isotope sampling and analysis was undertaken to determine the source of the recharge, the results showing that it is likely a combination of evaporation from fresh water, lateral recharge of ancient sea water along faults from the Red Sea, and hydrothermal recharge from the sub-surface leaching of young Afar and Red Sea Basalts in the active rift zone.
Developing The South African National Groundwater Monitoring Network	Kevin C	Pietersen	National	2017	monitoring network
Abstract The Department of Water and Sanitation reviewed and re-designed (optimised) the national water resources monitoring networks. During the re-design, monitoring objectives were formulated and prioritised. The highest priority, i.e. to make available data and information related to quantity and quality of present and future water resources is through planned infrastructure development and other interventions. The data and information dissemination aims at providing strategic decision support for the equitable and sustainable allocation of resources to the population, environment and other economic sectors of society. In setting up the groundwater monitoring network, an approach was followed which allowed for the incorporation of local and international best-practice; hydrogeological information combined with expert knowledge. We used the following criteria to establish the baseline or background sites for the national groundwater monitoring network: borehole spatial densities; pristine areas (no land-use activities); aquifer yield; recharge; baseflow; sites for background monitoring related to groundwater reserve determinations and the setting of resource quality objectives; springs; and international obligations. Trend monitoring sites were selected around baseline sites and around towns who were groundwater dependent. The trend monitoring sites allow for trends to be determined in terms of: (i) over-exploitation/abstraction of groundwater; (ii) groundwater quality degradation from various land use practices; and (iii) groundwater water use. Regional Spatial Design Workshops were held to compare the existing water resources monitoring network with the newly designed network and the existing monitoring network were optimised accordingly. Google Earth was used to query the detail of the monitoring sites, consider land-use coverages and incorporated expert input to position sampling points in line with the monitoring objectives. The implementation of the updated groundwater monitoring network will rely predominantly on hydrogeological considerations and field- based investigations and observations. When the networks are optimised, statistical techniques will be useful to ascertain monitoring point location, redundancy and frequency.
Modelling Of The Steenkoppies Dolomite Compartment – Sustainable To ‘Unsustainable’ Groundwater Use	Martin	Holland	Gauteng	2017	Uncontrolled groundwater abstraction, Irrigation, numerical model
Abstract Seyler, H; Vahrmeijer, JT; Wiegmans FE The Steenkoppies dolomite aquifer/compartment is situated 15 km north-west of Krugersdorp and has received great attention in March 2007 when the naturally discharging spring (known as “Maloney’s Eye”) reached the lowest flow on record, which was an incident that has drawn much attention. This incident caused major concern to the downstream users as the spring forms part of the Magalies River’s flow. At the time of this incident the flow measured at a record low of 1.58 Mm3 /a compared to an average flow rate since 1908 of 13.8 Mm3 /a. Coincidently in March 2016 exactly nine years after this time the record low flow of 1.58 Mm3 /a was again measured at the Eye. Continued drought conditions in 2016 resulted in the lowest flow recorded for five consecutive months. The flow rate of less than 2.2 Mm3 /a is a mere 38 % of the average flows of (5.7 Mm3 /a) recorded for the last 10 years. While the interest in exploiting groundwater from the Steenkoppies compartment dates back to the late 1890s it is only since the 1980s to 1990s when abstraction for irrigation became substantial. The volume of groundwater abstracted for irrigation increased more than 7.5 times since 1980. The crop area increased 2.6 fold since 1997, while the volume of water abstracted increased 1.6 fold. Unfortunately, despite numerous conceptual reports, scientific papers, lawful water use verification studies and crop water use investigations, the Steenkoppies water users are still without a managing body and groundwater management/use plan. The lack of (adaptive) management has led to uncontrolled abstraction and issuing of new Water Use Licenses without the proper knowledge of the impact of additional water use on the system. The failed establishment of a water user association according to the National Water Act in 2013 dampened the hopes for any collaborated groundwater abstraction, -monitoring and -management plan. The groundwater model developed for the Steenkoppies compartment should be seen as a prospective evaluation tool to determine the potential behaviour of the system with time, given a set of changing parameters. Numerical groundwater models are considered the best tools available to quantify/estimate groundwater, and the results can be used in management decisions. Estimated groundwater abstraction per annum from the Steenkoppies compartment amount to between 25 Mm3 and 30 Mm3 , with a likely current rate of 28.5 Mm3 /a. Based on the modelled fluxes with average groundwater recharge (rainfall) conditions and induced recharge from irrigation return flows, it appears that 25 Mm3 is an optimal abstraction rate while maintaining a flow of around 5 Mm3 from the Maloney’s Eye. However, the Maloney’s Eye is sensitive to below average rainfall events leading to below average recharge conditions and resulting in lower volumes available for abstraction. Neglecting this fact for the past 30 years has resulted in the ‘unsustainable’ use of groundwater in the compartment
Quantifying Groundwater Resources In Alluvial Aquifers Of The Omaruru River; Simplifying Decision Making For Aquifer Management	W	Kabinda	Namibia	2017	Alluvial aquifer, IWRM, Bulk water supply, modelling, recharge potential
Abstract The Omaruru River Basin encompasses an area of approximately 19 625 km2 in central west Namibia. The headwaters extend to the area north of the Etjo Mountains, ephemeral surface runoff and groundwater flow is generally directed south-westward until they reach the Atlantic Ocean. Annual rainfall decreases steadily from 380 mm at the headwaters to <50 mm at the river mouth implying that majority of runoff is generated in the upper headwaters. The alluvial aquifer is recharged indirectly from seasonal floods whose runoff reduces significantly towards the coastal aquifers by transmission losses. Groundwater abstraction is controlled through a permitting system by the Department of Water Affairs, embracing the principles of Integrated Water Resource Management. The alluvial aquifer is a major contributor to bulk water supply in the basin. Four bulk water schemes were established along the aquifer for domestic and industrial use while the alluvial aquifers also sustain riparian and sensitive ecosystems established along the river. The current water demand of the Omaruru River Basin has been estimated at 12.7 Mm3 /a, of which 59 % is abstracted from the alluvial aquifer. An integrated geohydrological model was developed using dynamic system modelling software. Hydrological and geohydrological information was made available to highlight runoff and groundwater recharge as key indicators for integrated water resources management. River compartments were defined adopting the concept that the ephemeral rivers are characterised by pools and ridges formed by basement highs. Therefore, groundwater levels are regulated mostly by flood recharge, evapotranspiration and groundwater abstraction and to a lower extent by groundwater through-flow from the alluvium upstream. Sub-basin parameters such as rainfall, basin size, alluvial aquifer compartment length, width and depth were derived to estimate surface runoff produced per sub-basin, transmission losses and first estimate of groundwater recharge to the alluvial aquifer. Model results indicated total volume of saturated alluvium to approximately 377 Mm3, with recharge from transmission losses amounting to approximately 14.8M m3 for the entire basin. Groundwater recharge potential is highest in the upper part and decreases significantly towards the coast. Groundwater abstraction needs to be reconciled with the protection of sensitive ecosystems established along the ephemeral river. The model results have implications on management of the entire alluvial aquifer. The Geohydrological model provides fast assessment of the impact of groundwater abstraction on water levels and available water resources in downstream compartments. This can be a great benefit to the Department of Water Affairs and Forestry in processing abstraction permits as well controlling abstraction in times of prolonged drought. The resulting model shows that abstraction strategies downstream the river should be optimized to protect the aquifer against over-abstraction. In its simplicity the model can be adapted to other strategic alluvial aquifers.
Western Cape Coastal Groundwater Resources: Potential For Artificial Recharge And Conjunctive Use	Sumaya	Israel	Western Cape	2017	groundwater potential, artificial recharge, mixed use
Abstract Western Cape groundwater resources are often considered in isolation, per quaternary or aquifer depending on the level of management. This is an attempt to look at groundwater resources in its entirety for the major aquifer areas of the Western Cape. Atlantis in the Western Cape has been successfully operating for about 4 decades using artificial recharge, recycling of treated waste water and storm water. It is currently under used due to clogging of borehole screens and pumps with iron. However, there is no question of the potential for use and the volumes of water that the aquifer is able to supply. The Cape Flats Aquifer (CFA) has been identified in the past as a potential source to augment Cape Town’s municipal water supplies. Studies to assess the viability of the aquifer as a water supply to the Cape Metropolitan area all concluded that the CFA is a viable resource that can supply a projected sustainable yield of about 18 Mm3/a of bulk water. Artificial recharge was tested in the Cape Flats and showed great promise. The Langebaan area along the West Coast has an existing well field supply, which is able to supply the town. Artificial recharge was tested in Langebaan Road during 2009, and showed promise for the Langebaan area. In essence, the Western Cape has a large volume of untapped resources which could improve the water situation. Climatic data, groundwater levels, and chemistry for these areas are explored to consider the potential for artificial recharge, abstraction and use and the extent to which artificially recharged and existing resources can supply the coastal areas of the Western Cape.
Post Mining Aquifer Testing At A South African Coal Mine	Marnus	du Toit		2017	coal mine, dewatering, geochemistry, pumping test, analytical mocels
Abstract Mining site remnants are everlasting and impact the groundwater regime on a long term scale. An integrated approach to geoscience is necessary due to the complexity of nature and the unknown relationships that must be discovered to further the understanding of impacts on the natural environment. Furthermore, groundwater resources are negatively impacted by mining activities affecting the groundwater quality and quantity. Underground coal mining can be accompanied by roof failure events. This may change the matrix which subsequently alters the flow regime; leads to variations within the water chemistry, provided there is inter- aquifer connectivity; and alters the recharge rate. Dewatered mine voids are in direct contact with oxygen initiating oxidation reactions, depending on the geology of the specific site. A change in water chemistry was analyzed, and this coincides with a roof failure event as interpreted from water level measurements. Concentrations of Mg, Ca, and alkalinity indicate anomalous changes that are still in effect, five to six years after the majority of water levels had stabilized. The changes in the system coincides with and correlates to events of roof failure and different parameters. The latter changes are applied as extra tools when interpreting different site specific anthropogenic induced impacts on the system. Also within this study, constant rate pumping tests were conducted for the interest of the hydraulic properties, using three farming boreholes. The results put forward a range of 0.21 – 0.44L/s and 6.5 – 11.5m2 /d, for sustainable yield and transmissivity, respectively. Furthermore, it is recommended that a better understanding can be gained on system behaviors if chemistry correlations can be gathered through certain events causing specific systems to be in disequilibrium. It is also recommended that additional pumping tests will allow more insightful interpretation and delineation between the abovementioned chemical and water level changes. Finally, the combination of parameters during events can aid in deciding the most appropriate analytical models used for further analysis.
Testing Potential Reservoir Connectivity Using Isotopes	S	Dlakavu	Karoo	2017	Shale gas, hydraulic connectivity, geochemical, Isotopes, contamination
Abstract Anticipated Shale Gas Development could intensify possible natural hydraulic connectivity between deep groundwater reservoirs and shallow aquifers in the Karoo. This project attempts to test geochemical evidence of natural mixing between old groundwater from deep aquifers and young groundwater from shallow aquifers using selected isotopic signatures in conjunction with borehole yields. Borehole yields were determined using slug tests. All isotopes (δ18O, δ2H, δ13C, 3H and 14C) were analysed in the laboratory of Environmental Isotope Group of iThemba Laboratories in Gauteng. To date, results from four water samples collected in Jansenville reveal these average isotope signatures: δ18O = -3.02 ‰, δ 2H = -21.17 ‰, δ 13C = 12.46 ‰ 3H = 0.45 TU and 14C = 65.38 pMC. The δ18O-δ 2H relationship for the groundwater has a gradient of 4.48. This demonstrates that the groundwater has experienced evaporation before or during recharge. The unevaporated isotopic signature of the water is -5.86 ‰ and -33.89 ‰ for δ18O and δ2H, respectively. The enriched δ13CDIC signature suggests that methanogenesis has influenced the groundwater. The unstable isotopes (3H and 14C) suggest that there is groundwater mixing in Jansenville between younger water from shallow aquifers and older water likely from deeper aquifers. Borehole yields increase with decreasing radioactive isotope concentrations. This suggests that high yielding boreholes are areas of potential contamination because they are associated with mixed groundwater.
Applications of Satellite Based Techniques in Monitoring Water Storage in the Vaal River Basin, South Africa	Khuliso	Masindi	Gauteng	2017	GRACE
Abstract The demand for water continues to increase despite water shortages in the already over stressed Vaal River Basin. The Vaal River supplies water to the major metropolitan cities of Johannesburg and Tshwane. Water shortage threatens food security and the economic expansion of the country and it is unclear if there will be sufficient water to meet future water demands in the Vaal River Basin. In this study satellite observation techniques were used to quantify the available water resources and identify the underlying factors driving changes in water storage. Total Water Storage (TWS) values derived from the Gravity Recovery and Climate Experiment (GRACE) twin satellites were used to calculate changes in TWS anomaly in order to identify losses and gains in storage over 12 years. GRACE satellite data were compared with PERSIANN (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks) rainfall data and MODIS ET (Moderate-Resolution Imaging Spectroradiometer Evapotranspiration) time series data. It was observed that GRACE satellites are capable of recovering the geophysical signal caused by water storage changes at a coarser resolution. TWS anomaly indicates an increase in water storage over the study period of 0.0155 mm of EWH. Evapotranspiration from MODIS ET show a relatively steady trend with no significant changes. Based on visual comparison, seasonal effect was captured by all datasets. Linear trends fitted on the data shows that rainfall amount is decreasing and GRACE TWS is increasing, which indicates that there are other factors contributing to the TWS. A comparison of the GRACE TWS and surface water anomalies in the Vaal River Basin showed an increasing trend, which could imply that inter-basin transfers from adjacent basins play a significant role in TWS dynamics in the Vaal River Basin. It was found that a combination of satellite observation techniques allows for robust interpretation of the data. If water storage continues to decline at the current South Africa’s water crisis are likely to worsen and the impacts could be devastating, which necessitates the development of adaptation measures in order to survive in an ever changing climatic environment. This study proves that satellite techniques are useful tools for monitoring and water assessment studies in in large scale basins
Establishing A Groundwater Baseline For Unconventional Gas Projects In South Africa	M	Lourens		2017	Unconventional gas, hydraulic fracturing, Methodology, geological structures, baseline, Fracking
Abstract A standard methodology for establishing a groundwater baseline for unconventional gas projects in South Africa did not exist at the time the current study was undertaken. The study was therefore aimed at filling this gap, specifically focusing on hydraulic fracturing and underground coal gasification (UCG) operations. An extensive literature review was conducted to establish the baseline methodology. The latest literature on hydraulic fracturing and UCG was reviewed to determine how these activities may potentially impact on the groundwater environment. The literature review further examined the role that geological structures, such as dolerite intrusives, may be play in the migration of contaminants associated with unconventional gas projects. The literature review then focused on questions such as what size the study area should be, what geological and hydrogeological investigations need to be conducted before embarking on the sampling events, which chemical parameters need to be included in the groundwater analyses, whether the drilling of dedicated boreholes are required to collect representative groundwater samples, and how to collect representative samples for these different chemical parameters. In this paper, the proposed methodology is presented in the form of a flow diagram to be used to guide future groundwater baseline projects in South Africa.
Assessing the Endorheic Character of Groenvlei Using Four Independent Hydrogeological Tools	Roger	Parsons	Groenvlei, South Africa.	2017	Endorheic, Hydrogeological
Abstract It has been claimed that Groenvlei, a shallow lacustrine wetland on the southern Cape coast of South Africa, is endorheic. This characterisation was based solely on the inward sloping topography immediately surrounding the wetland and an absence of any surface water outflow. However, four independent hydrogeological tools were used to confirm that water discharges from the wetland into the aquifer along its southern banks, thus invalidating the endorheic characterisation. These tools included contouring of groundwater levels, interpretation of the hydrochemical character of groundwater, electrical conductivity depth profiling and a comparison of natural environmental isotopes in surface and groundwater. This case study supports the need for an integrated approach when characterising and assessing water bodies.
Numerical Modelling Of a Coal Mine to Improve the Understanding of Mine Water Decant: A 1000-Piece Puzzle	Amy	Allwright		2017	coal ash, dolomites, Mining , numerical modelling
Abstract A coal mine in South Africa had reached decant levels after mine flooding, where suspected mine water was discharging on the ground surface. Initial investigations had indicted a low-risk of decant, but when ash-backfilling was performed in the defunct underground mine, decant occurred. Ash-backfilling was immediately suspended as it was thought to have over-pressurised the system and caused decant. Contrariwise, a number of years later decant was still occurring even though ash-backfilling had been terminated. An investigation was launched to determine whether it was the ash-backfilling which had solely caused decant, or if additional contributing factors existed. Understanding the mine water decant is further complicated by the presence of underlying dolomites which when intersected during mining produced significant inflows into the underground mine workings. Furthermore, substantial subsidence has taken place over the underground mine area. These factors combined with the inherent difficulty of understanding unseen groundwater, produced a proverbial 1000-piece puzzle. Numerical groundwater modelling was a natural choice for evaluating the complex system of inter-related processes. A pre-mining model simulated the water table at the ground surface near the currently decanting area, suggesting this area was naturally susceptible for seepage conditions. The formation of a pathway from the mine to the ground surface combined with the natural susceptibility of the system may have resulted in the mine water decant. This hypothesis advocates that mine water was going to decant in this area, regardless of ash backfilling. The numerical groundwater flow model builds a case for this hypothesis from 1) the simulated upward flow in the pre-mining model and 2) the groundwater level is simulated above the surface near the currently decanting area. A mining model was then utilised to run four scenarios, investigating the flux from the dolomites, subsidence, ash-backfilling and a fault within the opencast mine. The ash-backfilling scenario model results led to the formation of the hypothesis that completing the ash-backfilling could potentially reduce the current decant volumes, which is seemingly counterintuitive. The numerical model suggested that the current ash-backfill areas reduce the groundwater velocity and could potentially reduce the decant volumes; in spite of its initial contribution to the mine water decant which is attributed to incorrect water abstraction methods. In conclusion, the application of numerical models to improve the understanding of complex systems is essential, because the result of interactions within a complex system are not intuitive and in many cases require mathematical simulation to be fully understood.
Application Of Environmental Isotope Tools To Improve Conceptual And Numerical Modeling Of Groundwater Flow In Kosh Goldfields, Witwatersrand Basin, South Africa	Haile A	Mengistu	North-West	2017	numerical modelling, dykes, mine shaft, stable isotopes, radiogenic isotopes, Tritium, tailing dams
Abstract Environmental isotope and hydrochemical analyses were employed to improve existing understanding of groundwater flow dynamics in the defunct mine for assessing the source of water at a pumping shaft located near Stilfontein Town, Northwest Province, South Africa. Currently pumping is done using the shaft at an average rate of 37,000 m3 /day to prevent flooding of downstream mines. The current findings point out that the source of water at the shaft comes from a much narrow area than previously reported and that the contribution of seepage water from a nearby return water dam is significant enough to compensate groundwater flow from the upper dolomite aquifer and limit northerly expansion of the cone-of-depression. Hydrochemical data reveals that shaft-water at deeper levels (950 m bgl) exhibit evidence of mine seepage originating from the nearby tailings dam. The isotope data also show that up to 45% of water is recycled between shaft water and the surface water. Tritium values of the shaft-water samples are above 4 TU suggesting recent recharge is taking place at deeper levels through open fractures and mine underground haulages. The information from the hydrochemical and environmental isotope data was used to improve an earlier understanding that the source of water as coming dominantly from dolomite aquifer. Finally, the results highlight the relevance of coupling various methods to check the result of numerical modelling, and indeed the centralized pumping is key to controlling subsurface water flooding in downstream mines, a successful implementation of regional mine water management.
Applied Geophysics To Investigate Groundwater Pollution Flow Paths Along A Fault System In An Industrial Environment	JSDR	Zielke-Olivier	South Africa	2017	preferential flowpaths, Geophysics, ERT, Electromagnetics, water management plans
Abstract A fault system may form preferential flow paths for groundwater along fault planes. In an industrial and mining environment, such geological structures pose a geohydrological challenge when delineating and managing groundwater pollution. A geophysical investigation, employing electric resistivity tomography (ERT) and electromagnetics (EM), was conducted along a section of a graben system to improve the geological understanding, define groundwater flow paths and pollution distribution in a mining and industrial setting. Additionally, the geophysical survey assisted in the siting of monitoring boreholes to gain an understanding of the geohydrological properties within the fault system. A total of 35 profiles were completed along a 12 km section of the graben including a refined grid around a water-filled quarry with elevated salinity. The geophysical results confirmed the presence of faults and indicated zones of lower apparent resistivity along the graben. Areas of elevated conductivity were modelled near industrial and mining operations, such as ash tailings, discard dumps and mine-water dams, suggesting that leachate could potentially seep into the underlying aquifers. A refined ERT model around the quarry indicated areas of high conductivity at dolerite contacts, fault planes and within a backfilled area which could form preferential groundwater flow paths from and to the quarry. This study showed that a fault system underlying industrial and mining activities with high conductivity zones could distribute seepage along secondary geological structures but could also aid as a barrier between different aquifer systems. An outstanding groundwater chemistry analysis is expected to provide further insight whether the detected groundwater flow paths along the fault planes contribute to the distribution of pollutants across the industrial site. Overall, the geophysical survey and consequent siting of monitoring boreholes were useful tools to identify groundwater flow paths for pollutants across a large scale structure to implement future water management plans.
Understanding Natural Groundwater Recharge Systems In The Lower Berg River Catchment, West Coast, Western Cape	Clinton W	Andries	West Coast, Western Cape	2017	MAR, geochemical, Lower Berg River Catchment, conceptual model
Abstract The CSIR has embarked on a study to investigate the potential for additional water in the West Coast, Western Cape through the application of Managed Aquifer Recharge (MAR). The benefits of MAR is that it may generate additional water supplies from sources that may otherwise be wasted with the recharged water stored in the aquifer to meet water supply in times of high demand. Determining recharge is the most important aspect of hydrological system. However, the accurate estimation of recharge remains one of the biggest challenges for groundwater investigators. Numerous studies have been conducted using geochemical methods to estimate and distinguish sources of recharge in different groundwater units of unconfined and confined aquifers internationally. The application of geochemical methods to produce accurate conceptual model describing natural recharge in aquifer units of Lower Berg River Region has not been widely published. The Lower Berg River catchment, consisting of 4 primary aquifer units (Adamboerskraal, Langebaan Road, Elandsfontein and Grootwater) will be used to demonstrate the applicability of such methods. The aim of the study is to estimate recharge in the lower berg river catchment, and develop a conceptual natural recharge model that will improve understanding of the aquifer system and be an indicator for water availability in the Lower Berg River Catchment. The objectives in developing the conceptual model includes establish groundwater recharge sources, groundwater flow paths, recharge mechanism and potential mixing of groundwater by using environmental isotopes; and obtain a reliable estimation of its recharge amount using the Chloride Mass Balance. As this study is still in progress, this publication will focus on reviewing literature and the outcomes envisioned from the project as to provide a complete understanding of the complex geology. This will lead to a better understanding of the functioning of natural recharge of the aquifer units in the Lower Berg River Catchment.
Temperature And Ec Stratification In The Gasification Zone And Surrounding Aquifers Of Underground Coal Gasification At The Majuba Pilot Plant	Lehlohonolo	Mokhahlane		2017	underground coal gasification, stratification
Abstract Underground coal gasification (UCG) is a chemical process that converts coal in-situ into a gaseous product at elevated pressures and temperatures. Underground coal gasification produces an underground cavity which may be partially filled with gas, ash, unburned coal and other hydrocarbons. In this study we assessed the stratification down the length of the boreholes. This was done by comparing the Electrical Conductivity (EC) profile of background boreholes to the verification borehole that were drilled after gasification was complete. Stratification was seen in all boreholes including the cavity borehole. The EC levels were lower in the cavity which may be due to the dilution factor induced by injecting surface water during quenching of the gasifier. The thermal gradient shows a steady increase in temperature with depth with higher temperatures measured in the verification boreholes. This increase in temperature may suggest that heat is still being retained in the cavity which is expected. This study serves as the preliminary investigation on the stratification of temperature and EC and will be proceeded with in depth surveys that covers all the groundwater monitoring wells that monitor different aquifers identified on site proceed.
Isotope Constraints On The Source And Residence Time Of Spring Water From The Table Mountain Group Aquifer, Paarl, South Africa	Jodie	Miller	Western Cape	2017	large-scale abstraction, urban water supply, fractured rock, springs, Tritium, residence time
Abstract Large scale groundwater abstraction is increasingly being used to support large urban centres particularly in areas of low rainfall but presents particular challenges in the management and sustainability of the groundwater system. The Table Mountain Group (TMG) Aquifer is one of the largest and most important aquifer systems in South Africa and is currently being considered as an alternative source of potable water for the City of Cape Town, a metropolis of over four million people. The TMG aquifer is a fractured rock aquifer hosted primarily in super mature sandstones, quartzites and quartz arenites. The groundwater naturally emanates from numerous springs throughout the cape region. One set of springs were examined to assess the source and residence time of the spring water. Oxygen and hydrogen isotopes indicate that the spring water has not been subject to evaporation and implies that recharge to the spring systems is via coastal precipitation. Although rainfall in the Cape is usually modelled on orographic rainfall, δ18O and δ2H values of some rainfall samples are strongly positive indicating a stratiform component as well. Comparing the spring water δ18O and δ2H values with that of local rainfall, indicates that the springs are likely derived from continuous bulk recharge over the immediate hinterland to the springs and not through large and/or heavy downpours. Noble gas concentrations, combined with tritium activities indicate that the residence time of the TMG groundwater in this area is decadal in age with a probable maximum upper limit of ~40 years. This residence time is probably a reflection of the slow flow rate through the fractured rock aquifer and hence indicates that the interconnectedness of the fractures is the most important factor controlling groundwater flow. The short residence time of the groundwater suggest that recharge to the springs and the Table Mountain Group Aquifer as a whole is vulnerable to climate change and reductions in regional precipitation. Any plans for large-scale abstraction to supplement the City of Cape Town water supply would need to factor this in to models of maximum sustainable yield.
Investigating the impact of Groundwater Impact around a leaking plugged Gas Exploration bore	Willem J	Van Biljon	Karoo	2017	case study, Shale gas, plugged bore
Abstract The exploration for shale gas is imminent in the Karoo basin of South Africa. There are concerns that the exploration and production of gas might lead to groundwater contamination in a sensitive area where many communities rely on groundwater. This case study presents data from an abandoned gas exploration bore that was plugged many years ago and from where both gas and water has been observed to be leaking recently. The study aimed to determine the source of the water flowing from the plugged bore using isotope analyses and to determine whether community water supply boreholes in the area have been impacted. The laboratory results indicated that none of the community boreholes were impacted by the compounds of concern. The geochemical signature of the groundwater in the community boreholes is also significantly different from the water that is flowing out from the gas exploration bore, because it has a signature typical of recently recharged shallow groundwater.
A Geostatistical-Hydrogeological Approach To Groundwater Monitoring Network Design In South Western Karoo, South Africa	Zaheed	Gaffoor	Karoo	2017	anthropogenic influence, Shale gas, Monitoring network design, kriging method, contaminant pathways, sampling grid
Abstract Groundwater in the South Western Karoo is of critical importance in the overall freshwater supply. However groundwater sustainability is vulnerable to natural as well as anthropogenic influence. Groundwater monitoring scheme are employed to provide the necessary information during decision making situations. Groundwater monitoring thus performs in important role in groundwater management and protection. Interest in exploiting potentially vast reserves of shale gas in the deep geological formations in the region, has been met with concerns that can negatively impact the groundwater system. The current monitoring network is not adequately designed to capture the necessary level of information. Hence in this paper a revised monitoring network is designed. A novel geostatistical hydrogeological approach is applied to a case study area in the South Western Karoo. Kriging methods are used to determine required density of the new network using the spatial autocorrelation of water levels in the case study area. Using the spatial autocorrelation range a hexagonal sampling grid is developed. Using key hydrogeological features, such as contaminant pathways and zones of favourable water resources monitoring points are systematically positioned within the sampling grid. Using thus approach the current monitoring network is expanded from 34 points to a total of 95 monitoring points. The new network shows an increase in optimization by lower overall kriging prediction standard error than the current network. This allows more efficient monitoring of baseline conditions and detection monitoring.
Characterisation and Protection of Deep Aquifers in South Africa: Potential Resources	Amy	Allwright	South Africa	2017	Deep aquifers, aquifer protection
Abstract The importance of groundwater in South Africa has become evident over the past decades, especially as pressure on surface water resources intensifies in response to increasing water supply demands. Research has significantly progressed on the shallow groundwater resources conventionally used for water supply, and leading on from this deeper groundwater resources have become a focus point as a future water source. This focus on deep aquifers is driven by new developments, such as shale gas development, injection of brines into deep aquifers, carbon sequestration and geothermal energy. The understanding of deep groundwater in South Africa is often limited due to insufficient data at these depths. To develop a body of knowledge on deep geohydrology in South Africa, an investigation on the currently available information was launched to assess potential deep groundwater resources. The investigation formed part of the larger WRC Project K5/2434 (Characterisation and Protection of Potential Deep Aquifers in South Africa). The geology of South Africa was reviewed from a deep groundwater perspective to provide an initial analysis of potential deep groundwater aquifers. The main potential deep aquifers were identified for further investigation using a ranking system, where Rank 1 shows a positive indication, Rank 2 shows some indication, Rank 3 shows a neutral indication, and Rank 4 shows a negative indication for deep groundwater systems. The Rank 1 geological groups include (in no particular order): the Limpopo Belt, Witwatersrand Supergroup, Transvaal Supergroup, Waterberg and Soutpansberg Groups, Natal Group, Cape Supergroup, Karoo Supergroup. In a number of the identified potential deep aquifers, the indicator for deep groundwater flow systems was the presence of thermal springs. Additionally, deep groundwater occurs below the traditionally exploited weathered zone, and the importance of fractured aquifers becomes paramount in the investigation of potential deep aquifers. In conclusion, three main components were considered for the investigation of potential deep aquifers systems, 1) geological groups; 2) thermal springs and 3) depth of fractures. These three components should be used holistically going forward to best characterise the potential deep aquifers of South Africa.
Effectiveness of Groundwater Governance in the Southern African Development Community (SADC) Countries	Kevin C	Pietersen	SADC	2017	Southern Africa Development Community
Abstract Water security is pivotal for economic growth, sustainable development and poverty reduction in SADC. Increasing aridity and dwindling surface water supplies are resulting in new opportunities for groundwater as a source for domestic, agricultural and industrial use. We carried out an assessment of groundwater governance in the SADC region to determine the effectiveness of provisions to regulate groundwater. Numerous sources of information were solicited, reviewed, and data was mined using framework analysis and qualitative context analysis approaches. This provided a systematic model for managing and mapping the data. There is a good understanding of aquifer systems at the regional level. Transboundary aquifers have been delineated and areas prone to groundwater drought have been identified. Information systems to manage groundwater data, however, are disparate throughout the region and institutions to manage groundwater are inadequate and are functioning within an environment of scarce financial and human resources. The hydrogeological capacity in public institutions such as government departments is a major concern and regulations to protect groundwater resources are often not in place. This includes instruments to control groundwater abstraction and potentially polluting activities. Where regulatory instruments are in place, often no enforcement or sanctions of unlawful activities are taking place. There is also limited coordination with other sectors such as energy and mining. Furthermore, the implementation of groundwater management action plans, where developed, is weak. Overall, groundwater management in the SADC region was found to be poor. Whilst the groundwater governance challenges are great, there are opportunities to support diagnostic analysis of transboundary aquifer systems, competency development, establishing regional groundwater monitoring networks, strengthening institutional frameworks, and development of groundwater resources, e.g. to clear the backlog in access to improved water supply.
Investigating The Potential Impacts Of Bentonite Mining At Matsopa Mine On The Groundwater System	Lerato	Mokitlane	Free State	2017	bentonite, community supply, hydrocensus, geophysical methods, geochemical investigation, Monitoring
Abstract This paper describes the results of geohydrological studies conducted at Matsopa Mine, where a shallow bentonite body is mined, to investigate the potential impacts of mining on the groundwater environment. An understanding of such potential impacts is crucial since the communitiesin the area are dependent solely on groundwater for their domestic water supply. The studies consisted of a) a hydrocensus to investigate the current groundwater quality and use in the vicinity of the mine, b) geophysical surveys to investigate the presence of geological structures that may influence groundwater migration, c) geochemical investigations of the ore body and host rock to predict the character of potential contaminant impacts, and d) groundwater monitoring to determine whether mining has impacted on the groundwater quality. The hydrocensus found that the groundwater is used for domestic water supply, as well as livestock watering and irrigation, on a number of farms surrounding the mine. The geophysical surveys conducted with the magnetic and electrical resistivity tomography (ERT) methods revealed the presence of dolerite structures adjacent to and in the vicinity of the opencast pits. These structures are likely to be associated with fractures, joints, fissure and cracks which could form preferential pathways for groundwater migration. The results of geochemical analyses using the XRD and XRF methods showed that both the ore and host rock are dominated by SiO2 and contain very low concentrations of trace elements that could pose a threat to the environment and human health. Groundwater monitoring was done on a bimestrial basis. The groundwater quality was found to be good with little or no evidence of contaminant impacts from mining. Elevated nitrate concentrations at a single monitoring site are likely to be due to agricultural activities on the different farms surrounding the mine. During the time spanned by the monitoring events, increasing water level elevations were recorded in the boreholes surrounding the mine. This observation shows that groundwater recharge to the aquifer system was taking place as a result of the higher rainfall experienced as compared to the preceding years. Activities at Matsopa Mine do therefore not appear to have a significant impact on the groundwater levels in the vicinity of the mine. The results of the geohydrological studies therefore indicate that bentonite mining at Matsopa Mine has not had significant detrimental impacts on the groundwater quality and quantity.
Chemical Processes Governing Siloam And Tshipise Geothermal Springs, Limpopo Province, South Africa	Olatunde	Durowoju	Limpopo	2017	geothermal, hydrochemical, Water quality
Abstract Geothermal springs occur throughout the world and South Africa (SA) is endowed with several springs of this nature. Siloam and Tshipise are among the known scalding geothermal springs found in Limpopo Province. The optimal use of a geothermal spring is largely dependent upon its physical and chemical characteristics. Hence, there is need to understand the chemical processes controlling the springs. Hydrochemical characteristics of Siloam and Tshipise geothermal springs were undertaken for a period of six months May – December 2014. Water samples were collected from the springs and stored at low temperatures (+/- 4 °C) for analysis of hydrochemical characteristics. The results show that Siloam and Tshipise geothermal spring water is not suitable for drinking and irrigation due to high pH, high fluoride concentrations, high sodium absorption ratio (SAR), Residual sodium carbonate (RSC) and permeability index (PI) values. The water type found in Siloam and Tshipise were Na-Cl and Na-HCO3, respectively. The variations were probably due to the differences in fundamental changes in water chemistry and the geology. Plot (Ca+Mg) vs (HCO3+SO4) shows the distribution of geothermal water between silicate and carbonate weathering processes. The chloro-alkaline indices (CAI) 1, 2 calculated from the waters of the study area give negative values and this implies the presence of base-exchange reaction. Hence, sources of the geothermal springs were deep and could not significantly be affected by rainfall recharge. Therefore, major processes controlling the water quality are silicate weathering, mineral dissolution, cation exchange and inverse cation exchange.
Modelling Of Cumulative Mine Dewatering And Flooding Impacts	Kai T	Witthueser	South Africa	2017	mine life cycle, regional flow model, water balances, post-closure liabilities
Abstract Many of South Africa’s coal fields are characterised by a complex lateral and vertical pattern of mine voids, targeting different lease areas and coal seams, and applying different mining methods such as open cast (strip) and underground (board and pillar) mining. Many are at different stages in their life of mine from exploration to closure stage. Despite the general recognition that the water management or absence thereof at neighbouring mines influences each other (evident for example in the recognition of inter-mine flow in the overall water balance for a site), and the requirement of cumulative impact assessments, very few studies actually attempt to tackle and quantify cumulative impacts of numerous mines on the ambient groundwater environment. While the parameterisation and calibration of a groundwater model for a single mine is often hampered by environmental data scarcity, the absence of cumulative impact assessments is mostly related to the unwillingness of neighbouring and competing mines to share these data. Soft- and hardware as well as budget limitations pose additional challenges for the development of regional groundwater models taking cognisance of complex mining environments. This paper describes a regional groundwater flow model that takes into account five surface and underground mining areas. The different start and closure dates for the opencast and underground mining areas result in a complex mining schedule, with groundwater abstractions and inflows for the different areas potentially influencing each other during life of mine and post-closure and requiring therefore a simultaneous simulation thereof. A further complication in the model development was the explicit consideration of cut-and-fill operations, necessitating alterations of the model topography to reflect annual cuts as free seepage boundaries, and to reflect rehabilitated backfilled areas with topography different from the pre-mining environment. The case study has led to numerical model software developments to enable transient changes in layer elevations over a simulation period. While the model attempted to simulate the cumulative impact of the mines, it was also used to predict the impact of a new mining development on the life of mine and post-closure water balances for the remainder of the neighbouring mines. The model outcomes could therefore theoretically inform apportionment of post-closure liabilities.
Investigating Risks To Groundwater Systems In The Main Karoo Basin Of South Africa	Thandokazi	Maceba	Karoo	2017	hydraulic fracturing, Shale gas, contamination, conceptual risk assessment, over-abstraction
Abstract The improvement in hydraulic fracturing techniques resulted in the exploitation of natural gas associated with low-permeability organic-rich shale formations in the United States. South Africa has prospective shale gas resources linked with the marine black shales of the Whitehill Formation found in the Karoo Basin. Plans exist to develop the Karoo shale gas resources to diversify the primary energy mix. However, concerns among stakeholders about groundwater contamination and source of water for hydraulic fracturing remain unresolved. Such concerns include the potential of spills, fugitive gases, mechanical well integrity, and water management practices individually and collectively to introduce methane, hydrocarbons, metals, radionuclides, or other chemicals in groundwater posing human and environmental health-related risks. However, such concerns have not been assessed to provide evidence-based results that can be used to develop either an early warning or mitigation or adaptive monitoring system for shale gas development activities. The study was designed to develop a conceptual risk assessment model of potential shale gas operations to provide insights for groundwater protection. The western part of Greater Karoo Basin was used as a case study area. Applying this model suggests that hydraulic fracturing itself will have low risks in contaminating groundwater resources. However, the risks for over-abstracting groundwater remain high. These results suggest that it is crucial to learn from countries which have practised hydraulic activities for long periods of time, especially countries where the environmental setting are similar to South Africa. These findings form the basis of designing field-based studies that will influence policy making for action planning.
Understanding Groundwater Geochemsitry Of A Plunging Syncline South Of Robertson, Western Cape, South Africa	Neville	Paxton	Robertson, Western Cape, South Africa	2017	Groundwater Geochemistry, Plunging Syncline
Abstract The use of groundwater in the Robertson area, Western Cape, specifically to the south of the town is underdeveloped. The Breede River is the primary source for irrigation of vineyards and livestock watering through various channels and waterways. In an attempt to secure an additional water supply, small scale groundwater exploration was conducted which has culminated into an extensive network of boreholes with varying yields and geochemical signatures. As demand for usable water increases, a better understanding of the quality of the groundwater is as significant as the quantity of groundwater available for informed decision-making. This study area overlies a plunging asymmetrical syncline which comprises of the Rietvlei sandstones of the Table Mountain Group (TMG) and the younger Bokkeveld Group. The TMG forms mountain ranges on the southern and northern limbs of the syncline. Boreholes of higher blow yields were selected to undergo yield tests to determine sustainable yields. Higher yielding boreholes with an average yield of 7.4 L/s were drilled into the highly fractured and quartz-rich sandstones, while lower yielding boreholes with an average yield of 2.2 L/s were drilled into the Bokkeveld Group. The only existing borehole in use, situated on the northern limb of the syncline along the Sewefontein Fault, had a higher yield than neighbouring boreholes and a significantly better groundwater quality, somewhat of an anomaly in this section of the study area. In an attempt to access groundwater from the same formation, additional geophysical exploration, drilling and testing was conducted. The results however indicated low blow yields and poor quality groundwater. AQTESOLV software was used to further characterise and classify aquifer parameters. Descriptive statistics together with graphical hydrological methods were used to characterise the geochemical composition of the groundwater. The lithology of the study area indicates that the syncline has been extensively fractured as a result of post depositional folding and faulting. Fractures with a primary strike direction of 120° to 140° provide flow paths across the different formations, indicated by geological logs and borehole connectivity. Mean transmissivity values for the TMG are almost double that of the Bokkeveld Group, and salinity of the latter is significantly higher than that of the TMG. Transmissivity provides an indication of residence time (with an inverse relation) and thus leads to the assumption that groundwater flow rate is slower in the Bokkeveld Group. Elevation also plays a role, with a negative correlation to salinity. Recharge is delayed in lower lying areas which are predominantly underlain by Bokkeveld Group rocks, and clay rich derivative soils. Water readily ponds here and undergoes increased evapouration. The resultantsalt precipitation gets flushed into the saturated zone during future rainfall events. Recharge that does reach the saturated zone increases in salinity along its flow path due to ion absorption and cation exchange with clay minerals. Higher lying areas have little to no soil cover, with the thin soils comprising almost solely of quartz grains - considered chemically inert. As groundwater flows from the TMG into the Bokkeveld Group, residence time increases and salinity levels increase significantly.
Dewatering Impacts of a South African Underground Coal Mine	Paul JH	Lourens		2017	coal mine, hydrocensus, dolerite contact zones, Monitoring, over-abstraction
Abstract The University of the Free State investigated the possible dewatering of boreholes situated on the farm properties in the vicinity of an underground coal mine. The investigation consisted of three phases. Phase one was a hydrocensus on the farm properties. Phase two consisted of borehole yield determination by conducting pumping tests on the boreholes (where possible) identified in the hydrocensus phase. Phase three included a visit to the underground mine workings, where water samples were collected at different groundwater inflow locations (especially water flowing in at the ventilation shaft). The monthly groundwater monitoring data of the underground coal mine was also incorporated for interpretation purposes. It appears that the water levels of the boreholes outside the mining boundaries are not affected. The water levels of the monthly monitored boreholes stabilized or even started recovering over the last few years. It also seems as though the larger streams in the area drains the groundwater as most of the deeper water level areas coincides with the presence of the streams. Most of the boreholes have typical borehole yields that is to be expected from Karoo formations i.e. between 0.5 and 1.5 L/s. An interesting observation is that a number of the boreholes with deep water levels are situated along dolerite contact zones at the western side of the mine. This may also be a geological structure resulting from the impact of a meteorite? From the available data it appears that the boreholes along this structure have the same chemical character as the water flowing down the ventilation shaft, strengthening the belief that the water from the shaft originates from this structure (or structures). To determine the origin of the water flowing down the ventilation shaft, a detailed study of the structure to the west of the shaft is recommended. The farmers in the area should carefully monitor their water use in the boreholes, as over-abstraction can result in total failure of some of the boreholes.
Assessment of Groundwater Pollution Risk using Geophysical Methods: A Case Study Lagos Coastal Area, Southwestern Nigeria	MA	Yusuf	Nigeria	2017	Aquifer vulnerability to pollution
Abstract This study was carried out in Lagos State, southwestern Nigeria. It is a coastal city that lies approximately between longitude 30 13’30”E and 30 17’15”E and between latitude 60 28’N to 6 0 42’N. The study assessed the groundwater pollution risk using geophysical methods and the concepts of Dar Zarrouk parameters as veritable tools. Resistivity measurement was taken at twelve (12) vertical electrical sounding (VES) stations and along eight (8) 2D resistivity profiles using the Schlumberger array and dipole-dipole array respectively. The VES data were processed using IP2Win computer iteration software. The geoelectric model from the interpretation revealed four/five geo-electric layers. These include: Top sandy layer with resistivity and thicknesses ranging from 2.29-1915 Ωm and from 0.46-4.55 m respectively. The second layer is mostly clay soil of varying degree of saturation which is obvious from its resistivity behavior. This layer has a minimum resistivity of 3.52 Ωm at VES1 and maximum resistivity of 20 Ωm at VES6. Also, the thickness of this layer varies from 1.85 m at VES9 to 7.32 m at VES6. The third/fouth layers delineated are clay and clayey sand/sandy clay. However, the highest thickness value of 43.1m for clay occurred at the third layer at VES10. The apparent resistivity of this layer varies from 1.61 Ωm to 265 Ωm and varies inversely with the clay content from 16.3 m to 33.3 m. Also the thickness of this layer varies from 4.8 m to 45.3 m. The 2D resistivity data (dipole-dipole) acquired along Oniru, Elegushi, and Adeniji were processed using RES2D. Along Oniru traverse 1, low resistivity zones diagnostic of contaminant plume was observe at distances between 12 m to 30 m and also, an isolated plume of contaminants deducible from low resistivity occur along traverse 3 at depth below 30 m. At Elegushi , vertically migrating plumes of contaminant indicated by low resistivity zones equally occur at distance between 320 m along traverse 1 and spread towards the centre from the western and eastern parts of the traverse respectively. Furthermore, pockets of contaminants are also observed all along the distance between traverse 2. However, at Adeniji, a plume was only observed at 384 m along the same traverse. The longitudinal conductance and the corresponding vulnerability of the lithologies delineated in the study area shows that the longitudinal conductance and protective capacity of clay is maximum at VES10 with a value of 26.7702 Ω-1 at a depth of 65.6 m. Therefore, the sand aquifer confined by clay is the least vulnerable in the study area. This is because the highly impervious clayey overburden, characterized by relatively high longitudinal conductance, offers protective shield to the underling aquifer. However, sand being the most vulnerable,has the least values of longitudinal conductance ranging from 0.6884 Ω-1 at VES11 to 0.0006 Ω-1 at VES2. The vulnerability sandy clay/clayed sand are of intermediate value and the risk improves/reduces with increasing clay content.
Baseflow as a Proxy for Groundwater Recharge Variation Following Environmental Disturbances, Jonkershoek Valley, Western Cape, South Africa	Raven J	Pietersen	Jonkershoek Valley, Western Cape, South Africa	2017	Environmental Disturbances, groundwater recharge
Abstract Groundwater recharge is of strategic importance in groundwater research both globally and locally in South Africa as it ensures that the development of groundwater does not exceed the systems rate of renewal, protecting the integrity of these resources. The Table Mountain Group (TMG) system is considered to a potential source of future bulk water supply with a recharge potential ranging from 7 to 23% of Mean Annual Precipitation (MAP). However, estimation of true groundwater recharge is challenging as groundwater recharge is affected by many factors which influence the ability of water to reach the water table. Various studies have been carried out within the Jonkershoek Nature Reserve which investigated the response of a catchment’s hydrological functioning and biodiversity to land use management and disturbance regimes such as fires. Previous studies assessed the effect of fire on the hydrology of the catchment, highlighting the associated increase in streamflow components and hydrological response of catchments due to the development of soil water repellency which generated rapid runoff but do not discuss the possible effects on the recharge potential to the groundwater system. The present study investigated the possible effects of wildfire disturbances on local groundwater recharge system of the TMG aquifer system in Jonkershoek Valley, Western Cape Province of South Africa using baseflow as a proxy for groundwater recharge. The possible effects of wildfire disturbance on groundwater recharge processes were determined through review of literature, lithological logs and geological maps. Baseflow separation of hydrographs was conducted using the Recursive Digital Filter Method. It was found that the baseflow response to rainfall events following the March 2015 fire remained unchanged for the Tierkloof sub-catchment of Jonkershoek whereas Langrivier experienced a decline in baseflow response following the winter rainfall period later that 2015. The findings suggest that wildfire to some extent influences groundwater recharge but not all times thereby providing insight on the extent of influence of a vegetation cover on groundwater recharge and confirming findings from previous studies. The present study recommends long term studies on the influence of wildfire on groundwater recharge and the use of both direct and indirect methods for investigating groundwater response to fires.
Development Of The Training Manual For Groundwater Resource Management And Groundwater Governance For Municipalities In South Africa	George G	Molaolwa	South Africa	2017	Municipalities, Training manual, Training needs assessment
Abstract In order to establish sound groundwater resource management within towns and Municipal areas the development of a training manual on groundwater resource management and groundwater governance for Municipalities is of utmost importance. A Training Manual can be extensively used for capacitating municipal official, technicians, managers, and decision-makers, as well as communities where villages and towns are partially or solely reliant on groundwater resources. Increased knowledge and skills will not only lead to more effective groundwater resource management, but also to more sustainable groundwater use and protection of groundwater resources. This also forms part of provisions made by the National Water Act 1998 (Act 36 of 1998). Before a training manual can be compiled, training needs assessments of all reachable training institutions in South Africa and Free State Municipalities and Northern Cape Municipalities as identified as pilot areas in the proposal of the Training Manual for Groundwater Resource Management and Groundwater Governance for Municipalities in South Africa needed to be performed. Training needs assessment determines if a gap exist regarding available training and training needs on Groundwater Resource Management and Groundwater Governance. If a gap exists then it proofs that the development of a Training Manual on Groundwater Resource Management and Groundwater Governance for Municipalities in South Africa is required, as well as the accessibility to such a training course is of utmost importance.
Danish Groundwater Management Approaches In A South African Context	P.G.	Pedersen	Denmark	2017	Denmark, South Africa
Abstract The North-European country Denmark is in many ways different from the Republic of South Africa. Similarities also exist, for example the common ownership of underground resources. In Denmark, like in South Africa, groundwater forms a strategic resource for water utilization, and a coherent management approach is needed in both countries in order to secure a sustainable and balanced use, in which the wishes of different stakeholders are optimized. Denmark is solely depending on the use of groundwater for domestic, industrial and agricultural use. Therefore, an effective management scheme and new technologies have been developed in order to make groundwater assessments, delineating groundwater protection zones, water preservation, leakage detection, well field monitoring systems etc. This expertise forms the basis of the bilateral Strategic Water Sector Cooperation Programme (SSC), initiated in 2015. The programme consists of three main tracks, respectively focusing on urban water services and NRW, groundwater management, and water efficiency in industries. In addition to these, two cross-cutting tracks focus on water sector financing and the potential for research and innovation cooperation. The preliminary findings of the programme indicate that some of the Danish management approaches and technologies can be used in South Africa, either adapted or directly. In exchange, the South African experiences, amongst others, in how to handle drought, may be relevant in a future Danish context, where extreme weather situations, induced by climate change, is to be expected.
Rigorous Methodology For Sustainable Yield Estimation Using Groundwater Numerical Modelling Validation To Detailed Long Term Pumping Test Data	Shuaib	Dustay	Port Alfred	2017	numerical modelling, WUL, large-scale abstraction, Monitoring
Abstract Groundwater numerical models are commonly used to determine the impact that groundwater abstraction has on the ability of surrounding areas to supply water, and thus to inform Water Use Licence (WUL) Applications. However, data available is often limited to that generated by relatively short-term geohydrological studies and pumping tests. In most cases this data and the degree of defined uncertainty in the model results are sufficient. However, for large scale abstractions (such as municipal abstraction) and in sensitive or complex geological areas, a more rigorous approach to calculating the impact from pumping is recommendable. The study area is located on a syncline consisting of two sandstone aquifers. However, there was a lack of data to quantify the connectivity between the two aquifers. SRK Consulting (South Africa) (Pty) Ltd undertook a rigorous, long-term approach, which included a 3- year monitoring plan of the area, input from stakeholders, extending the hydrocensus to the entire catchment and monitoring of pumping in the area. Using this comprehensive data set, the existing numerical groundwater model was updated, re-calibrated and validated such that predictive scenarios could be run to assess the long-term potential impact of the municipal wellfield. These results were submitted for the final allocation of the WUL. Along with mitigation measures, recommendations could also be made on where to focus monitoring and future testing. This rigorous methodology and the use of long- term comprehensive monitoring data is recommended for future use in similarly complex environments to decrease uncertainty on the expected impacted area from large-scale abstractions.
Possible Wastewater Volumes Associated With Unconventional Oil And Gas Extraction In South Africa And The Management Thereof	RD	Williamson	Karoo	2017	Unconventional gas, Wastewater, Fracking
Abstract Several oil and gas companies have applied for licenses to extract unconventional oil and gas (UOG) resources in South Africa (SA) through a process known as hydraulic fracturing or fracking. The South African government is in the process of drafting regulations and procedures to allow the extraction of these resources. It is surmised, based on evidence from fracking examples around the world, that large volumes of wastewater may, however, potentially be generated during the extraction of these UOG resources. The issues arise when it comes to determining the actual volumes of wastewater that may be generated from this process, should it be used in SA, as well as the management of the wastewater. The volume of wastewater generated is dependent on a number of factors, with well properties, rock formation, basin properties and the number of fracturing stages within the well, being some of the dominant factors. In this project an extensive review of existing literature, reports and fracking databases was used to identify the methods used for determining wastewater volumes, which databases were used as well as the assumptions and challenges each data source faced. The data was analysed and interpreted in order to come up with various ranges and averages of wastewater generated through UOG extraction. The potential volumes of wastewater generated through fracking were then modelled into the hypothetical scenarios outlined in the Strategic Environmental Assessment (SEA) on Shale Gas Development in the Central Karoo. This allowed for the determination of potential volumes of wastewater associated with UOG extraction in SA from which management implications for wastewater in South Africa can be determined.
Spatial Variability of Physicochemical Parameters and Suitability of Groundwater for Drinking in Three Administrative Zones of the Chókwè District, Mozambique	Paulo SL	Saveca	Mozambique	2017	Groundwater Quality, Water chemistry, Physicochemical parameters, Gaza Province, Chókwè district
Abstract The analysis of water chemistry data is widely used to assess groundwater quality and to understand its variability in an area. This study was carried out in the Chókwè district in the Gaza Province located in the south-western part of Mozambique, a downstream area of the Limpopo River basin. A total of twenty[1]seven groundwater samples collected from handpumps, boreholes and wells were analysed with the aim to investigate the groundwater quality and its spatial variability in Lionde, Macarretane and Chókwè city. The physicochemical parameters such as pH, total dissolved solids, and electrical conductivity, as well as major and minor ions were analysed from the groundwater samples. The data analysis and interpretation of water chemistry were done with the help of the Windows Interpretation System for Hydrogeologists (WISH), version 3.02.188, the Quantum GIS 2.0.1 and Microsoft Excel. The results showed the cation dominance order of Na⁺>Mg²+>Ca²⁺>K⁺ , while for anions it was Cl−>HCO₃ −>SO₄²⁻ . The groundwater quality in the Macarretane area was classified as unacceptable, and in the Lionde area it was classified as poor for drinking. The average value of the major physicochemical ions in these areas was not within the permissible limits, except for potassium (K⁺), sulphate (SO₄²⁻) and bicarbonate (HCO₃⁻ ). The electrical conductivity values in the district ranged from 241 µS/cm to 12 000 µS/cm, while total dissolved solids ranged from 162.8 mg/L to 7 652.6 mg/L. The spatial analysis of water quality revealed that the groundwater quality is influenced by the local geology, through halite, calcite and dolomite dissolution processes or chemical reactions. The groundwater is highly mineralised in quaternary deposits dominated by alluvium, sand, silt, gravel and eluvial floodplain clayey sand with an average value of 1 621 mg/L and 1 498 mg/L, respectively. The quality of the groundwater is classified as very hard with more than 180 mg/L of CaCO₃ of total hardness.
Open Source Software for Hydrogeologists	Robel	Gebrekristos		2017	Open Software, project management, conceptual model, GIS, database management, numerical modelling, geochemical modelling
Abstract There are various software packages used by hydrogeologists for a variety of purposes ranging from project management, database management, data interpretation, conceptual and numerical modelling and decision making. Software is either commercial (produced for sale) or open source (freely available to anyone and for any purpose). The objective of this paper is to promote open source software that can be used by the hydrogeological community to reduce expenses, enhance productivity and maximise efficiency. Free software was previously associated as being inferior in quality in the corporate world. Companies often use commercial software at a hefty price, but little do they know that open source is often equal to, or superior to their commercial counterparts. The source code of open source software can freely be modified and enhanced by anybody. Open source software is a prominent example of open collaboration as it is developed by users for the user community. Companies using open source software do not need to worry about licensing and do not require anti-piracy measures such as product activation or a serial number. However, the decision of adopting open source software should not just be taken just on the basis of the low-cost involved. It should entail a detailed analysis and understanding of the requirements at stake, before switching to open source to achieve the full benefits it offers and to understand what the down side is. There are plenty of open source products that can be used by hydrogeologists. The packages considered in this article are those that are frequently used by the author and do not necessarily mean that they are the best available. Software gets updated or abandoned with time and what is considered powerful today may be obsolete in a few years. Some of the well-known open source packages recommended for hydrogeologists include: OpenLibre for project management, Blender 3D or Sketchup for 3D conceptual modelling, QGIS for GIS mapping and database management, SAGA GIS for interpolation and ModelMuse for numerical modelling (comprising of Modflow for finite difference, Sutra for finite element and Phast for geochemical modelling). In addition, there are a number of free software packages developed by the USGS, various universities and consultants across the globe that can be used for aquifer test interpretation, borehole logging and time-series data analysis. A saving of more than R250,000 can be made per hydrogeologist by utilising such open source packages, while maintaining high quality work that is traditionally completed using commercial software.
Investigation of Sustainable Groundwater Resource Supply in the Crystalline Basement Aquifer at Matoks (Mokomene) ,in Molemole Municipality, Limpopo Province, South Africa.	Ronald	Ramathieledza	Molemole Municipality, Limpopo, South Africa	2017	Groundwater resource supply, crystalline basement aquifers, geophysical techniques, magnetic anomalies, borehole yield, water quality.
Abstract Water is an essential resource for livelihood (humans, animals and plants) and without water there is no life on earth. Worldwide over 1.1 billion people do not have access to safe water and more than 1 billion people are living in water stressed areas. The scarcity of water is more intense in developing countries where statistics show that 67% of the rural population have no access to safe water supply. Detailed geohydrological investigation and chemical analysis were conducted in crystalline basement rocks at Matoks in Capricorn District, Limpopo province of South Africa to determine the groundwater availability and its quality for human consumption. Groundwater potential was identified by the use of geophysical techniques (electromagnetic profiling, magnetic profiling). Traverse lines were set based on the information acquired from the desktop studies (DWS-mapped structures such as faults, joins or lineaments, Topographical map, Google Earth and geological mapping). Drilling positions were configured based on the magnetic anomalies, followed by the drilling of selected targets. Water strikes ranges were at 20 – 36 mbgl, these showed that the area has shallow aquifers. The aquifer response under applied pressure produced a blow yield ranging from 3-20 l/s. The recommended borehole yields ranges from 1 – 6 l/s which makes about 2 747.52 m³/day and the average transmissivity was 41.04 m²/day. Water samples were analysed through the use of various techniques, namely: AAS, IC, IC-PMS, water quality from the study area ranges from class I to class IV, which is good to poor water quality according to South African National Standards. The aquifers at Matoks can meet the present water abstraction demand and the aquifers are having good to poor water quality.
Multivariate Statistical Analysis Of Hydrochemical And Environmental Isotope Data To Characterise The Hydrogeological And Hydrogeochemical System Of The Lake Sibayi Catchment, North-Eastern South Africa	Jannie	Weitz	KwaZulu-Natal	2017	Environmental Isotopes, multivariate statistics, Hydrochemistry, coastal aquifers, Lake Sibayi
Abstract An integrated approach involving multivariate statistical analysis combined with graphical methods (Piper trilinear diagram and δ18O-δ 2H plots), and environmental isotope analyses were successfully applied to characterise the spatial distribution of hydrogeochemical parameters and their controlling factors within the Lake Sibayi catchment located in north-eastern South Africa. Bivariate and Multivariate statistical analyses (Factor and Hierarchical Cluster Analyses) were performed on 12 physiochemical parameters (variables) including pH, EC, TDS and major ions of 46 samples collected from various water sources (streams, Lake, shallow and deep boreholes). Bivariate Pearson’s correlation matrix of the measured variables revealed a strong positive correlation between EC and several major elements, which included Na+ , K+ , Mg2+, Ca2+ , Cland HCO3 - indicating their contribution to the salinity. These major ions were also found to be strongly correlated to one another with all correlations found to be significant. Factor analyses in the form of Principal components analyses were performed with the main aim of identifying the underlying factors or processes responsible for the observed hydrochemistry in the study area. The results revealed three principle factors explained about 95% of the hydrochemical variation in the study area. Most of the variance is contained within Factor-1 (69.5%), which has a high positive loading factor associated with EC, TDS, Na+ , Mg+ and Clconcentrations, interpreted in terms of the contribution of these major ions to the salinity of the water (EC and TDS). Factor-2 represents 17.7% of the total variation in the hydrochemistry and has high positive loadings for pH, HCO3 - , K+ , Ca+ and Fe concentrations. The HCO3 - , K+ and Ca+ could be the result of weathering and dissolution of carbonate minerals in calciferous Uloa and Umkwelane Formations and redox processes. The Fe concentrations could be related to leaching of ferricrete layers known to exist in the area and a result of anoxic condition within the aquifer. The variables NO3 - and SO4 - contribute most strongly to Factor-3, which explains 8.01% of the total variance. The loading for NO3 - was positive and could result from anthropogenic pollution of the shallow aquifer and streams, while that of SO4 - being negative and could result from historical marine influences. Hierarchical cluster analysis of hydrochemical data performed using the Ward method with squared Euclidean distance, grouped the water samples into two clusters, representing unique hydrochemical systems, i.e. surface water and groundwater. Each of these two clusters was in turn divided into two sub-clusters, representing stream and lake samples, and shallow and deep aquifers, respectively. These groupings were further supported by characteristic water types; namely, a Na-Cl-HCO3 facies for the river, lake and surrounding boreholes; a Na-Cl hydrochemical facies for shallow boreholes, while deep borehole samples were Na-Ca-Cl to Na-Cl-HCO3 in composition. These clustering were supported by isotopic signals that show a clear distinction between groundwater and lake water samples.
Lessons From Implementing Groundwater Schemes For Drought Relief	Roger	Parsons	Cape Town	2017	Groundwater levels, Drought Relief
Abstract A review of groundwater levels in the greater Cape Town area toward the end of the 2017 summer revealed that groundwater levels had not yet been impacted by the below average rainfall over the past two to three years. This is in contrast to the dam levels which reached record lows, necessitating the implementation of strict water restrictions in the city. This buffer between drought and impact to aquifers is well known, and is a characteristic of many groundwater systems. Consequently groundwater can play an important role in managing the effects of drought on urban water supplies. From experiences in implementing groundwater-based drought relief schemes in the southern Cape in 2009 / 2010 and bolstering the water supply to Ladismith in 2013, lessons were learnt in implementing such schemes. This paper identifies ten key issues that require consideration, including the selection of drilling sites, the time it takes to implement emergency groundwater schemes and the need to avoid over-promising at a time when those responsible for water supplies are under increasing pressure from all around them. It is worrying that current planning around managing the drought appears to include little hydrogeological expertise at a decision-making level.
Performance Monitoring Of The Monitored Natural Attenuation Of Petroleum Hydrocarbons In Groundwater Using Geochemical Parameters	AR	Gemmell		2017	MNA, geochemical indicators, geochemical parameters, monitoring network
Abstract Monitored Natural Attenuation (MNA) refers to the monitoring of naturally occurring physical, chemical and biological processes. Three lines of evidence are commonly used to evaluate if MNA is occurring, and this paper focusses on the second line of evidence: The geochemical indicators of naturally occurring degradation processes and the site-specific estimation of attenuation rates. The MNA geochemical indicators include the microbial electron acceptors (e.g. dissolved oxygen, nitrate and sulphate) and the metabolic by-products (manganese (II), iron (II) and methane). In addition, redox and alkalinity are important groundwater indicators. So as to properly assess the geochemical trends a groundwater monitoring well network tailored to assessing and defining the contaminant plume is required. The expressed assimilative capacity (EAC) is used to estimate the capacity of the aquifer to degrade benzene, toluene, ethylbenzene and xylene (BTEX compounds) using the concentrations of geochemical indicators. Using the EAC, the groundwater flow through a perpendicular cross-section of the source area, and the source mass, the life of the contaminant source can be made. A practical example of the performance monitoring of MNA using geochemical parameters is described for a retail service station in KwaZulu-Natal, which has groundwater impacted by a petroleum hydrocarbon plume. This includes a description of the monitoring well network, the geochemical measurements, the calculation of the EAC, and the estimated life of the contaminant source.
Assessing The Influence Of Groundwater Recharge Mechanism In Non-Perennial River Systems, Tankwa Karoo, South Africa	Phumlani	Mqondeki	Karoo	2017	Ephemeral rivers, localized recharge, baseflow, Hydrochemistry, stable isotopes
Abstract In South Africa and neighboring countries such as southern Zimbabwe, Botswana, southern Angola and Namibia, most river systems are non-perennial due to semi-arid/arid climatic characteristics. In such river systems, the interaction between groundwater and surface water is of significance in terms of developing appropriate methods for determining ecological water requirements among others. However, the interaction is not well understood in terms of the influence on the volume and quality of water on the gaining and losing water bodies. In past years, research on non-perennial rivers (NPRs) has not been widely published for various reasons. In certain cases, NPRs experience extended periods of water ponding within their channels. This could possibly be caused by groundwater seepage that is sufficient to maintain pools but insufficient to generate channel flow (gaining stream) and overcome evaporation losses. The opposite can also occur, whereby some reaches of the river channel are recharging the underlying aquifer (losing stream). Abstraction of either groundwater or surface water thus impacts on both water resources. The objectives of the study are to investigate the role of the Tankwa River in recharging the underlying aquifer and the role of the aquifer in recharging the Tankwa River. Preliminary findings through literature review and field observations seem to suggest that the groundwater flow in terms of the regional perspective is driven by recharge in the far upland TMG Mountains. However, on a local scale, field observations seem to suggest that there is some aquifer-river interaction, whereby the aquifer is maintaining the pools in some parts of the channel whereas some parts of the river are dry. These findings suggest that the river contains both losing and gaining reaches thereby providing indication of an exchange of water between the water resources. This has implication on the quantity and quality of water in gaining and losing water bodies in aquifers and rivers. Future work will involve installing piezometers at points where permanent pools are located and along the river riparian zone. Monitoring of groundwater levels and the river will be carried through the different seasons. Samples will be collected from the aquifer, surface water bodies and rain gauges to integrate with the groundwater chemistry. The overall purpose of the present study is to develop a regional hydrogeological conceptual model of recharge for the Karoo in order to improve understanding of the recharge mechanism in non-perennial river systems especially in the semi-arid environment, using the Tankwa River as a case study.
Conceptualization Of Groundwater Flow System In Heuningnes Catchment	Vincent	Banda	Western Cape	2017	hydrochemical, groundwater flow
Abstract Records review and field based methods were used to collect and interpret groundwater level and hydro- chemical data to characterise groundwater occurrence and flow system in the Heuningnes catchment, Western Cape Province of South Africa. Our research outcome indicates that the study area has alluvial and fractured rock aquifers. The groundwater system has a rainfall driven recharge mechanisms resulting in freshwater in higher altitudes situated in the northern and western parts of the catchment. Highly saline waters are found in low-lying areas. Few samples showing high salinity water exhibit a signature of seawater although in many instances the groundwater chemistry is by and large governed by the geological formation. Groundwater potentiometric surface map shows that the general groundwater flow direction is southwards. In relation to the surface water bodies, groundwater mainly flows towards the Nuwejaars River especially in the northern and north-west part of the study area resulting in fresh water in this part of the river. As this is an ongoing study, these preliminary findings provide the required insight for further analysis and investigation. Future work will involve carrying out aquifer hydraulic tests and collection of water samples for analysis of major ions and stable isotopes. Further discussion will wait for the validation of these results to inform a meaningful implication of such findings.