Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 251 - 300 of 795 results

Title	Presenter Name	Presenter Surname Sort descending	Area	Conference year	Keywords
Hydrocarbon groundwater analyses: a Karoo case study	Danita	Hohne	Karoo	2021	Hydrocarbon, Water level, contamination, Artisan borehole, Methane concentration, Natural gas, Dolrites, quality, Fracturing
Abstract The South African government is considering shale gas extraction in the Karoo basin, South Africa. To protect groundwater resources, there is an urgent need to do a groundwater baseline in possible gas extraction areas. Various groundwater samples have therefore been taken at a borehole and 2 soekor wells in the Northern Cape, from 2016 to 2021. The groundwater samples were analysed for dissolved gasses, specifically focussing on methane. As laboratories became more efficient ethane was also included in later analyses. From the analyses we found that drought might influence the dissolved gas concentrations in the groundwater via pressure influences on the groundwater flow and the dissolved gas flow towards the shallow aquifers. Artesian conditions at this site are helping with the flow of dissolved gasses from deep to shallow aquifers via preferential pathways. The possibility of shallow-deep groundwater interconnections and the migration of deep methane to shallow aquifers make it important to establish a groundwater baseline in the Karoo. By focusing on boreholes and wells that are emitting methane, a better understanding of groundwater flow and interaction with geological layers can be determined. If other gasses like propane and butane can be analysed in addition to methane, more information can be gathered to determine the origins of the methane and whether it is thermogenic or biogenic.
Assuring supply during a changing environment focussing on drought	Danita	Hohne	National	2021	Drought, community supply, operating rules
Abstract Fourie, F Communities reacted differently to the drought. In some cases, you would notice a proactive approach and good management of the wellfields. In other cases, communities have been under a misconception that they received good rainfall for a recharge which did not reflect in monitoring data, and lastly, you get the communities that are mismanaging the groundwater. Various lessons were learned from the change in the climate and environment. But a lot can be done to minimise the impact of these changes on the water supply to communities. This paper addresses the changes that we can apply to deal with the changing environment around us to provide a sustainable water supply. The changes can include relooking at operating rules to ensure better management on the aquifer and borehole level. Recharge determined during pump test must be considered periods low to no recharge. Methods to enhance the recharge to the aquifer will ensure recharge occur during low rainfall events By implementing these rules, groundwater can be sustainably managed for future use.
Drought in the Northern Cape Karoo: Lessons Learned and Options for Future Use	Danita	Hohne	Karoo	2017	Drought
Abstract Most of the Northern Cape has been hit with a drought for the past 4-7years. The western part of the Northern Cape have been dry for at least 7 years now with no rainfall or very little rainfall, while the more central part have been dry for the past 4 years with very little rainfall. It is only the past 2 years that this has been seen as a problem, but for the past 7years the Department with local municipalities have tried their utmost to manage the problem of water scarcity. During the past 7years the DWS has learned many lessons on how to manage the groundwater in these areas to ensure sustainable future use but must also look at new initiatives to deal with this problem as drought is going to be the new norm in the western parts of South Africa.
A Geochemical Investigation On Two Soekor Wells Located In The Northern Cape, South Africa	Danita	Hohne	Northern Cape	2017	hydraulic fracturing, geochemical investigation, Isotopes
Abstract The past few years hydraulic fracturing has been a hotly researched topic. Currently, most published documents are just speculation of what can happen if hydraulic fracturing is to take place in South Africa. There is very little work done to firstly establish a baseline on the current groundwater quality and secondly look at the current state of the groundwater around the Soekor wells. For these reasons a geochemical investigation was launched looking at the Soekor wells and the surrounding boreholes to determine a valid baseline. Looking at the two Soekor wells; geochemical analyses was conducted on water, soil and rocks. The drill core of the wells; soils from the waste ponds and water at or nearby the wells were sampled and analysed. By making use of XRF; XRD, Stable Isotopes and water chemistry analyses, a better picture of these wells and groundwater can be developed to give better guidelines to what should happen during the monitoring of hydraulic fracturing wells.
Mitigating climate change with managed aquifer recharge: 5 Case Studies	D	Hohne	South Africa	2023	Climate change; drought; MAR; nature-based solution; case studies
Abstract In the past decade, Southern Africa has experienced periods of extreme drought. This was especially true in the western Karoo in South Africa. Continuous drought and limited rainfall led to declining aquifer water levels that curtailed sustainable water supply for towns and livestock. The western Karoo is almost completely dependent on groundwater. Managed aquifer recharge (MAR) is being used to reduce the effects of droughts and mitigate climate change impacts. A good understanding of the geology and the behaviour of the aquifers is needed for implementing various MAR designs, including nature-based solutions, which are used to recharge aquifers with limited rainfall. This paper discusses 5 active MAR case studies in the Western Karoo. Here, site-specific MAR methods that use small rainfall events deliver reasonable results, whereas the implemented MAR options keep most aquifers functional. Observations at the MAR sites also showed improved water quality and less bacterial clogging. This improves the environment around the managed aquifer recharge sites. The MAR methods and designs discussed in this paper can be used on a larger scale for a town or a smaller scale for a farm. Maintenance costs are low, which makes these options cost-effective for less wealthy areas.
Numerical groundwater flow model for the Palla Road wellfield, Botswana	Martin	Holland	Botswana	2013	numerical groundwater flow model
Abstract The Palla Road well-field is located in the Central District of Botswana approximately 160 km from Gaborone and 50 km from Mahalapye. The aim of this project was to review and update the existing groundwater model developed in the late 1990s of the Palla Road well-field in order to assess the viability of long-term groundwater abstraction due to the increasing water demands in the region. The main hydrogeological units recognised in the project area comprise of aquifer systems developed in the Ntane Sandstone Formation and formations of the Middle Ecca Group with minor aquifers developed in Mosolotsane Formation and the Stormberg Basalt. The finite-difference model boundary covers an area of 3 702 km2 and was set-up as a three-dimensional semi-uniform grid comprising of four layers. Eight recharge and 14 hydraulic conductivity zones in accordance with the geological model were distinguished. Steady state calibration was accomplished by varying the hydraulic conductivity values, while keeping the recharge rates constant in order to achieve a unique solution. Transient calibration of the model covered three larger stress periods namely: (1) initial condition (pre-1988), (2) abstraction period (1988 to 2012) and (3) predicted model simulations (2013 to 2036). The calibrated groundwater flow model was used to assess the impacts associated with the proposed abstraction scenarios for the Palla Road and Chepete well-fields with consideration of potential cumulative impacts due to the Kudumatse well-field. Three basic scenarios comprising certain sub-scenarios based on the future water demand for the Palla Road and Kudumatse region were considered. The model simulations show that the abstraction scenario 2a, namely simultaneous abstractions from the Chepete/Palla Road and Kudumatse well-fields, poses a risk to the sustainability of downstream water resources. The maximum simulated drawdown in the central and southern parts of the Palla Road well-field reach 14 m after six years of pumping. Although outflow diminishes after a six-year period, it is restored to approximately 80-90% after the simulated recovery period. The presented 3-D multi-layer model can be used as a tool to determine the optimal abstraction rates while giving cognisance to the sustainability of the resource.
Development Of The Evander Goldfields 3-D Mine Void Model	Martin	Holland	The Evander Goldfield, Mpumalanga	2013	development, gold mining
Abstract POSTER The Evander Goldfield basin has been mined since the early 1950s at depths between 400 and 2 000 m below ground and is detached from the larger Witwatersrand basin. The assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in the Witwatersrand basin as more mine shafts mothballs and dewatering ceases. The development of a 3-D mine void model is crucial in predicting the rate of flooding as the prediction of the groundwater rebound is primarily driven by the volumes of mine voids along with the amount of recharge. All available mine plan data for the Evander Gold Mine (EGM) were obtained digitally from Harmony Gold. However, the majority of the old mine workings (e.g. Leslie and Winkelhaak) were available as 2-D data and elevations of the mine developments (stopes and drives) had to be captured from hardcopy plans. Data from the more recent mining operations (e.g. Shaft 6), including updated survey and mine plan data, were directly used for the development of the 3-D void model. The calculated mine void volume, based on the EGM operations mine plan data, is approximately 80 518 045 m3. The mine void calculations were checked against the total tons of rock milled by the EGM operations since the late 1950s and was considered valid estimations of the EGM mine void volume. The validated EGM 3-D mine workings plan was subsequently used to determine the stage- volume relationships. The 3-D mine void model established, will then be incorporated into a regional numerical groundwater flow model to be calibrated against observed abstractions and water levels and utilised to predict future dewatering rates.
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
Update of regional groundwater flow models for the Vaal Gamagara SD1 and SD2 wellfields	Martin	Holland	Northern Cape	2021	Demand, exploitation potential, Simulations, CRD, Production rates, Prediction scenario, adaptive management
Abstract Wiegmans, FE The increasing water demand for the Northern Cape Province resulted in the detailed assessment of the exploitation potential of three groundwater development target areas namely SD1, SD2 and SD4, largely underlain by karst aquifers. Since 2014 the implementation of the wellfields was delayed pending authorisation. The potential impact on the groundwater resources was raised by several stakeholders as part of the process, resulting in the re-assessment of the SD1 and SD2 wellfields. The model update considered crucial data retrieved from several groundwater level loggers from April 2014 to December 2019. As a precursor to the model update the Cumulative Rainfall Departure (CRD) curves for the relevant rainfall stations for the study areas was updated. While for most sites a good relationship between rainfall and groundwater fluctuations was observed. A poor response of groundwater levels in comparison to the observed CRD curve suggests abstractions more than the recharge of the aquifer. Metered groundwater use is for most parts not available but was estimated based on the hydrocensus data. Once the models demonstrated to reproduce past behaviour, they were used to forecast the future behaviour. More importantly was to assess whether the 2014 proposed abstraction rates still held true after the re-calibration of the model. Several simulations were carried out iteratively to identify the optimal pumping rates and the temporal variability of the withdrawal period considering the impact on the groundwater resource. Based on the results the 2014 proposed production rates were reduced from 751,608 m3/month to 597,432 m3/month representing a 2019 mitigated (optimised) proposed abstraction scenario. The case study is an excellent example of adaptive groundwater management informed by crucial datasets and scenario modelling.
Development of regional groundwater flow models for the Vaal Gamagara well fields	Martin	Holland	Northern Cape	2015	flow models
Abstract The increasing water demand for the Northern Cape Province initiated the feasibility study to augment and/or upgrade the Vaal Gamagara Water Supply (VGWS) scheme. The study completed in 2011, recommended the upgrade of the total VGWS scheme to supply the water demand of users for the planning horizon to 2030. However, short term water demand and to augment the water from the Vaal River could also be sourced from groundwater and/or mine dewatering. This resulted in the detailed assessment of the exploitation potential of three groundwater development target areas namely SD1, SD2 and SD4, largely underlain by karst aquifers. The intrusive work done on the Vaal Gamagara target areas is arguably one of the largest groundwater investigations of modern time for South Africa. This paper describes the development of the 3-dimensional groundwater flow models for the three target areas as part of this investigation. The software code chosen for the modelling work was the program SPRING which uses the finite-element approximation to solve the groundwater flow equation. Each conceptual groundwater model developed was converted into a multi-layer numerical flow model for each groundwater development area and calibrated against observed heads, spring flows and long term water level monitoring data. Once the models demonstrated to reasonably reproduce past behaviour, they were used to forecast the outcome of future groundwater behaviour (i.e. abstraction from the well fields). Three large scale transient groundwater models have been built to analyse regional flow systems, to simulate water budget component changes, and to optimize groundwater development on a ‘sustainable’ basis. Different scenarios were developed for each target area to study the impact of different recharge scenarios and variable abstraction rates on the groundwater development of the area. Several simulations were carried out iteratively to identify the necessary number, optimal pumping rates and the temporal variability of the withdrawal period. While the proposed abstraction rates for all three groundwater regions (SD1, SD2 and SD4) of 13 million m3 / annum are considered as ‘sustainable’, by definition ‘sustainability’ has so determine the balance between economic, social and environmental interest. Perhaps a more applicable term for the long-term abstractions rates for the SD well fields is the maintainable aquifer yield which simply refers to a yield (volume/ time) that can be maintained by reduced discharge or enhanced recharge, without continually mining the aquifer or depleting aquifer storage.
Managed Aquifer Recharge within the Greater Kruger National Park and Implementation of Recharge Scheme	Michael	Holloway	South Africa	2023	aquifer, Dolerite, Feasibility, Gneiss, Increased, Managed, recharge
Abstract West of the world-renowned conservation site, Kruger National Park, lies the larger extent of the Greater Kruger National Park within the Limpopo province. Boreholes have been drilled for decades to provide water to game lodges, large resorts, and watering holes for game viewing and livestock. The area contains both primary and secondary aquifers classified as having yields between 0.5 and 5.0 l/s, based on the geological setting, which consists of gneiss intruded by dolerite dyke swarms. A geohydrological assessment revealed that groundwater quality within the project area has an EC of 100 - 350 mS/m, linked to borehole proximity to surface water systems. The Makhutswi Gneiss and Doleritic Dyke swarms are the major controlling geology of the area, with higher-yielding boreholes close to dykes and major structural lineaments (faulted / weathered zones). A concern identified through geohydrological assessment observations is that boreholes frequently dry up after a few years, requiring deeper drilling/redrilling or drilling a new borehole. Aggressive calcium hardness in the water frequently damages equipment and increases maintenance costs. This project investigated the feasibility of increasing recharge to the aquifer with seasonal flooding/rainfall events by constructing artificially enhanced recharge locations overlaying doleritic dykes. This is expected to decrease the groundwater’s salinity and hardness, reducing operational costs. This pre-feasibility assessment has been completed, and the project has continued through a gradual implementation phase.
Prefeasibility Study for Managed Aquifer Recharge within the Greater Kruger National Park, Limpopo Province, South Africa.	Michael	Holloway	Limpopo, KNP	2021	MAR, Doleritic Dyke Swarms, Prefeasability Study
Abstract Lourens, PJ West of the world-renowned conservation site, Kruger National Park, lies the larger extent of the Greater Kruger National Park within the Limpopo province. Boreholes have been drilled here in the last few decades to century for the provision of water supply to game lodges, large resorts, watering holes for game viewing and also historically for agriculture and livestock. The area contains both primary and secondary aquifers classified as having yields between 0.5 and 5.0 l/s, based on the geological setting which consist of gneiss intruded by dolerite dyke swarms. A geohydrological assessment of the area revealed that groundwater quality within the project area is characterised as having an EC of 100 - 450 mS/m, which seems to link to borehole proximity to surface water systems. The Makhutswi Gneiss and Doleritic Dyke swarms are the major controlling geology of the area, with higher yielding boreholes located in close proximity to dykes and major structural lineaments (faulted / weathered zones) of the Gneiss. A major concern identified through geohydrological assessment and hydrocensus observations is that boreholes frequently dry up after a few years and require either deeper drilling / redrilling or drilling a new borehole and that the very aggressive calcium hardness in the water frequently damages equipment and leads to overall higher maintenance costs. This project investigates the feasibility of increasing recharge to the aquifer with seasonal flooding / rainfall events by constructing artificially enhanced recharge locations overlaying several doleritic dykes. This is expected to decrease the salinity and hardness of the groundwater, which will reduce operational costs. Water security will also be increased through enhanced long-term sustainability of the groundwater by balancing some of the current annual abstraction.
Teaching Machines Hydrogeology: Demonstrating The Use Of Machine Learning In Groundwater Science And Management	Rui	Hugman		2019	Machine learning, AI
Abstract The advent of the 'Big Data' age has fast tracked advances in automated data analytics, with significant breakthroughs in the application of artificial intelligence (AI). Machine learning (ML), a branch of AI, brings together statistics and computer science, enabling computers to learn how to complete given tasks without the need for explicit programming. ML algorithms learn to recognize and describe complex patterns and relationships in data - making them useful tools for prediction and data-driven discovery. The fields of environmental sciences, water resources and geosciences have seen a proliferation of the use of AI and ML techniques. Yet, despite practical and commercial successes, ML remains a niche field with many under-explored research opportunities in the hydrogeological sciences. Currently physical-process based models are widely applied for groundwater research and management, being the dominant tool for describing and understanding processes governing groundwater flow and transport. However, they are limited in terms of the high data requirements, costly development and run time. By comparison, ML algorithms are data-driven models that establish relationships between an input (e.g. climate data) and an output (e.g. groundwater level) without the need to understand the underlying physical process, making them most suitable for cases in which data is plentiful but the underlying processes are poorly understood. Combining data-driven and process-based models can provide opportunities to compensate for the limitations of each of these methodologies. We present applications of ML algorithms as knowledge discovery tools and explore the potential and limitations of ML to fill in data gaps and forecast groundwater levels based on climate data and predictions. Results represent the first step in on-going work applying ML as an additional tool in the study and management of groundwater resources, alongside and enhancing conventional techniques such as numerical modelling.
Numerical Modelling of Groundwater Flow Between a Complex Underground Mine and an Operational Opencast Mine	Altus	Huisamen	Mpumalanga	2015
Abstract The management of groundwater inflows into an opencast colliery in Mpumalanga is normally fairly easily achievable due to low inflow volumes and high evaporation rates. But, when flooded underground mine workings are encountered, groundwater inflow complexity increases dramatically. Understanding, predicting and managing groundwater inflow under these conditions can be challenging and highly complex. While normal opencast inflows are easily modelled these connected mines are pushing numerical models to their limits. This case study aims to illustrate an approach based on a finite difference model that has been used successfully in a South African coal mine. Based on a study at a colliery near Ermelo, Mpumalanga, the understanding and conceptualisation of the aquifer geometry, geological structures, hydrogeology, defunct underground mine geometry and interconnection between opencasts and the underground, proved to be vital, not only in calibration of the model, but also in the construction of the various layers and calculation of flow volumes between the various sources and sinks. This also aided greatly in constant source contaminant transport modelling to trace which mining areas may have a contamination effect on each other or the surrounding aquifer. In constructing the numerical flow model, the underground mine geometry was found to intersect various layers in the MODFLOW based model and pinching out in some areas. Due to the requirement of MODFLOW that layers should be continuous with no pinchouts to the model boundaries, this presented a notable challenge in the model construction. Therefore, mine geometry was divided into various slices, fitting within the hydrogeological layers, but still retaining the original geometry. The layers were then further divided laterally using different materials to represent the mine hydraulic properties and aquifer properties respectively, ensuring that the lateral distribution of materials also represents the underground mine geometry accurately. Using this model construction, the calculated mean residual head for the simulation of the current situation was found to be less than 3m while the simulation of the current mining situation with no underground mine present, yielded a mean residual head of approximately 10m. Additionally, inflows measured in the opencast penetrating the underground were measured at approximately 1000m3/d while the calibrated model calculated inflows of 1160m3/d, while simulating the current mining situation including the defunct underground. The current decant from the defunct underground, to the southeast of the site, was calculated as 1.9 L/s by the model while the measured rate was just over 1 L/s. Also, as expected, the dewatering of the opencast penetrating the flooded, defunct underground mine, was calculated to predominantly impact an underground mine compartment, isolated by underground seals, as opposed to the aquifer, which has a much lower hydraulic conductivity. {List only- not presented}
Hydrogeochemical Evolution of an Opencast Colliery After Decommissioning - Static vs. Dynamic Prediction	Altus	Huisamen	Mpumalanga	2015
Abstract Static indicator tests, such as acid-base accounting, are commonly used to provide an indication of ARD potential of backfill material in opencast coal mines. This potential for acidity is then commonly incorporated into numerical models, wrongfully, as a constant contamination source with the maximum possible sulphate being released from the pit, ad infinitum, which is, obviously, not the case. Dynamic tests on the other hand, are considered superior, but are expensive and time consuming. The proposed alternative approach is geochemical modelling, illustrated by a case study in the Mpumalanga coal fields. A decommissioned colliery near Carolina, Mpumalanga, was recently confronted with the prediction of the impacts that its backfilled opencasts might have on groundwater in the long term with regards to acid and contaminant generation, demanding a more realistic and well-defined conceptual and numerical approach than the simple minimum screening method. This study utilised the integration of a well-defined conceptual model, mineralogical data, acid-base accounting data, leaching test data, literature and groundwater monitoring data to address the long term hydrogeochemical evolution of groundwater at the colliery, using transiently calibrated geochemical and numerical flow models. Using the mineralogical data available from samples collected, as well as the sulphur content identified by ABA, a standard error was calculated for the abundances of all mineral phases present along with mean weight percentages, defining the likely boundaries of mineral abundances. Using these values along with reactive surface areas calculated from average grain sizes, using a collapsing core model, as well as rate constants from literature, the fluid rock interaction in the leaching tests was simulated and calibrated against leaching test results in the geochemical model, by varying mineral abundances, reactive surface areas and rate constants within the statistically acceptable boundaries. Once a calibrated mineral assemblage was identified using this method, the assemblage was geochemically modelled in the natural environment, after calculation of fluid to rock ratios, which in this case was purely potential backfill porosity vs. recharge due to the natural groundwater level being below the pit base, as well as potential oxygen fugacity. The calculated concentrations of constituents were then introduced into a transiently calibrated numerical flow and transport model via recharge concentrations, to also chemically calibrate this model. The chemical calibration was successful within a 20 mg/L range, illustrating the reliability of the conceptual and geochemical models, but also the reliability of predicted numerical modelling results. Based on the available data and modelling results, the colliery would not have a future impact on groundwater with regards to ARD and metals. However, elevated major cation and anion concentrations are expected, calculated within order of magnitude accuracy, and can be managed according to dynamic and realistic models, instead of a static worst case scenario.
Delineating wellhead protection areas and aquifer vulnerability in the Cape Flats, South Africa	Brynn	Hunink	South Africa	2023	Aquifer vulnerability mapping, groundwater sustainability, Resource protection, Source protection, Wellhead protection areas
Abstract Prevention of threats to the quality and quantity of groundwater supply is critical to ensure its sustainability. Several African studies have shown that contamination of aquifers is primarily caused by improper placement of land-based human activities. Therefore, adequate preventative measures are required to safeguard the water quality of African aquifers to avoid long-term deterioration. Spatially explicit, 3D numerical groundwater modelling is a common methodology to assess contaminant transport. However, model development is time-consuming and complex. Contrastingly, DRASTIC-L is a 2D, GIS-based aquifer vulnerability mapping technique. The method is simple to apply, but analyses are qualitative and subjective. The study aims to compare both methods and to combine their strengths using GIS overlay. Overall, aquifer vulnerability was determined using the DRASTIC-L method, while wellhead protection areas were delineated using steady-state numerical modelling. This study focuses on the Cape Flats area due to its rapid development and growing municipal water supply supplementation needs. DRASTIC-L mapping revealed that aquifers in the Cape Flats are highly vulnerable to contamination due to the region’s unconfined hydrogeological properties, shallow water table and high-risk land use types. Moreover, groundwater vulnerability mapping combined with the delineation of wellhead protection areas allows for reduced uncertainty in the contamination potential of delineated groundwater protection zones. As a result, this study highlights the need for overall resource protection of the Cape Flats aquifers and provides insights into mapping out potential source protection areas of existing water supply wells.
Basin Water Balance modelling with the aim to make transboundary groundwater flow visible	M	Hunt	Estonia	2023	EUWaterres, Modflow6, transboundary aquifers, surface water groundwater interactions, water balance modelling
Abstract A conceptual water budget model is required to “make groundwater visible” in the shared transboundary area of Estonia and Latvia, which doesn’t face any significant water management issues. Despite having a water management agreement since 2003, it wasn’t until 2018 that cooperation on groundwater began. In the EU-WATERRES project, the water balance modelling of the ~9,500 km2 transboundary (TB) area with MODFLOW 6 was performed. Based on budget calculations, the area’s average precipitation is 203 m3 /s, with ~50% (102 m3 /s) of it discharging to the sea as surface water. The infiltration share (7%, 14.4 m3/s) is a small fraction of overall precipitation, but as an average, it forms ~14% of surface water flow, with 98% of infiltrated groundwater forming the baseflow. Modelling produced two main conclusions: surface water and groundwater form a joint system in the upper ~150 m cross-section depth, and there is no preferred regional TB flow direction due to flat topography. This makes cross-border flow highly dependent on pumping close to the border area. The results of recent studies provide valuable information on groundwater’s importance in EE-LV TB areas and a basis for simple conceptual models to make groundwater visible to the general audience and decision-makers. These findings are critical for specialists in managing water resources in the region and will inform decisions related to the use and protection of groundwater in transboundary areas.
Integrated assessment of groundwater potential zones for deep groundwater exploration in hard rock aquifers using GIS and geophysical techniques: A case study of Huai Krachao, Kanchanaburi, western Thailand	Vanachawan	Hunyek	Thailand	2023	Deep groundwater exploration; Hard rock aquifer; groundwater potential zones; Analytical Hierarchy Process; weighted overlay analysis; spring
Abstract Groundwater is an important freshwater supply that has a significant role in the economy. However, water is increasingly becoming scarce in several regions. Huai Krachao Subdistrict in Kanchanaburi Province is an example of an area that has been experiencing a severe drought for decades due to the impacts of climate change. This study was conducted to delineate the groundwater potential zones in hard-rock terrains using geographic information system (GIS) techniques. The study aims to explore deep groundwater resources in challenging areas and propose alternative methods supporting traditional groundwater exploration. This finding revealed that the groundwater potential zones were classified into high, moderate, and low potential zones based on the groundwater potential index (GWPI), integrated using the Weighted Index Overlay Analysis. The computed weights from the Analytical Hierarchy Process were acceptable and consistent. The high potential zones mainly occur in the Silurian-Devonian metamorphic rocks. The GIS-based analytical results were later prepared for detailed field investigation, including collecting well information and conducting the 2-dimensional geophysical survey. To prove the GWPI map, 9 groundwater wells were drilled in the high potential zones. Consequently, well yields obtained from the pumping-test analysis ranged from 24-40 m3 / hr, some of which are springs rich in dissolved minerals. Accordingly, a significant amount of water could meet the water demand, supplying about 1 million m3 /year. Under these circumstances, discovering new groundwater resources can support roughly 5,000 people and agricultural lands no less than 480 hectares (4.8 km2 ).
Exploring Danish experiences for Groundwater mapping in South Africa	Anker Lajer	HØjberg	South Africa, Denmark	2021	mapping , fractured geology, SAGMAA, guidelines
Abstract Kürstein, J; Thorn, P; Vermaak, N; Kotzé, YL; Pedersen, PG; Linneberg, MS; Fourie, F; Magingi, A Water supply relies entirely on groundwater in Denmark. A national groundwater mapping programme was established in 2000 to protect this valuable resource. It builds on a thorough and holistic understanding of the hydrogeological settings, obtained through an extensive data collection, culminating with an identification of threats and aquifer vulnerablility. As part of the programme, new approaches, methods, and instruments have been developed, such as airborne geophysical survey by Sky-TEM that allows the mapping of large areas in a fine resolution. Another key element in the mapping is the development of three-dimensional hydrogeological and numerical models. These are used to understand the groundwater flow paths and delineate wellhead capture zones as well as infiltration areas, which, depending on the assessed vulnerability, may be subject to protective measures. The Danish mapping approach have been tested at selected South African sites through the Strategic Sector Cooperation (SSC) between Denmark and South Africa. The approach was applied in a study supporting Umgeni Water to identify groundwater resources to supply numerous villages near the town of Ladysmith. The study illustrated a high potential for adapting relevant parts of the Danish approach to South Africa, but also revealed some challenges, e.g. related to the fractured geology, where groundwater recharge can be concentrated along dykes, a process very different from what is generally observed in Denmark. The SSC has initialised the project “South African Groundwater Mapping and Assessment Approach (SAGMAA)” to share knowledge gain through the national groundwater mapping programme in Denmark with South Africa and explore the possibility of adapting elements from the Danish approach to South African conditions in a broader context. The objective of the project is to provide recommendations to South African guidelines, and the paper will present results from the comparison of approaches in the two countries and preliminary recommendations to guidelines.
Application of machine learning techniques to improve groundwater level predictions and optimization, West Coast, South Africa	N	Igwebuike	Cape Town, South Africa	2023	Groundwater Modelling, groundwater level., Machine learning, Managed aquifer recharge, Water security
Abstract Groundwater systems are complex and subject to climate change, abstraction, and land use stresses, making quantifying their impacts on aquifers difficult. Groundwater models aim to balance abstraction and aquifer sustainability by simulating the responses of an aquifer to hydrological stresses through groundwater levels. However, these models require extensive spatial data on geological and hydrological properties, which can be challenging to obtain. To address this issue, data-driven machine learning models are used to predict and optimize groundwater levels using available data. This paper argues that using machine learning to model groundwater level data improves predicting and optimizing groundwater levels for setting up a managed aquifer recharge scheme. The West Coast Aquifer System in South Africa was used as a case study. The neural network autoregression model was used for the analysis. Multiple variables such as rainfall, temperature, and groundwater usage were input parameters in the mode to facilitate predictions. Outputs from the model showed how machine learning models can enhance the interpretation of observed and modelled results on groundwater levels to support groundwater monitoring and utilization. In areas with high dependence on groundwater and where data on abstraction (use) and monitoring were scarce, results showed that feasible measures were available to improve groundwater security. Although the simulation results were inconclusive, the results provided insights into how the use of machine learning can provide information to inform setting up a managed aquifer recharge scheme.
'Best Practice' Approach To Undertaking Detailed Groundwater Impact Assessment Studies For Proposed Solar Energy Plants	Sheila	Imrie	Jacobsdal, Free State	2015	Solar energy, EIA, best practice, groundwater management
Abstract South Africa is a country at the forefront of the solar energy revolution. Each solar energy plant implementation results in further supply of clean renewable energy to the South African electric grid, thus playing a part in helping South Africa meet its renewable energy targets, in addition to stimulating long-term economic development and creating new jobs. Active solar techniques include the use of photovoltaic systems, concentrated solar power and solar water heating to harness the energy. Particular focus has recently been on the use of concentrated solar power technology which is better able to address the issues of scalability and electric storage. The process includes the use of a liquid salt solution and also requires a reliable water source. When applying for a new solar energy plant, a geohydrological assessment is required to inform the Environmental Impact Assessment. SolarReserve South Africa (Pty) Ltd responsibly take this one step further by requesting detailed geohydrological assessments including drilling and field testing, numerical modelling and simulations, and detailed impact analysis. Of particular consideration in these assessments is the potential for groundwater to meet the plants water needs, as well as the assessment of risk and potential groundwater contamination impact from failure in the lining of the evaporation ponds. This paper describes the 'best practice' approach that has been formulated and undertaken for some previously proposed sites, and is now recommended for future use in the groundwater impact assessment of future proposed solar energy plants in South Africa. It makes use of a SolarReserve case study example, located at the farm Kalkaar near Jacobsdal in the Free State Province, to explain the main steps in the process and how the results of using this approach are important inputs in the assessment of impacts, decision-making regarding go/no-go, technology used, infrastructure and site layout, and responsible management and monitoring of the groundwater in the future.
eSymon - An Innovative Solution to Monitoring Data Management	Tarika	Isaac	South Africa various	2021	eSymon, Monitoring, data management, data visualization, data security
Abstract The year 2020 will forever be synonymous with the Covid-19 pandemic and the immeasurable impact it has had on all our lives. During this time, there was one avenue that reigned supreme: technology. Whether it was Zoom calls or Netflix, online consultations or video conferencing at work, technology took charge. In light of this, GCS (Pty) Ltd started exploring ways that technology could assist with the most common problem identified in the Water and Environmental sectors, which is the management of large volumes of geodata. Thus, the invention of eSymon. Monitoring of the environment usually generates a significant amount of data. If this data is not systematically stored, problems often arise with: • Limited access to historical data due to poor storage; • Different formats of stored data (if they are kept in digital form at all); • Continuity and integrity of the data; and • Security of the data. Therefore, years of historical data cannot be used or trusted. The solution was to develop eSymon, which is an acronym for Electronic Data Management System for Monitoring. eSymon is primarily designed to: • Systematically import, store, view and manipulate large volumes of monitoring data; • Provide remote and instantaneous access to site-specific information; • Allow data visualization using an interactive GIS interface; and • Create various outputs such as time series graphs, geochemical diagrams and contour maps. The main idea of the software is to have all historical data for a site on one platform and have it be accessible and functional at the touch of a button. This results in several key benefits, including saving time, providing accurate and up to date information, not having to wait for technical reports to assess trends and compliance, providing several means of data visualization and, most importantly, ensuring data security.
Successful field pilot scale nitrate removal using low technology methods	Sumaya	Israel		2015
Abstract Decades of monitoring, characterising, and assessing nitrate concentration distribution and behaviour in the soil profile and it's pathway into groundwater have resulted in a good understanding of its distribution in the country. While the national distribution is of great importance, site specific conditions determine fate, transport, and ultimately concentration in a specific area. Field experimental work included installation of a barrier containing a cheaply available carbon source to treat groundwater. The "reactor"/ tank with dimensions- 1,37m height, 2.15m diameter used for the experiment was slotted for its entire circumference by marking and grinding through the 5mm thick plastic material. The top section was left open to allow for filling and occasional checking of filled material during the experiment. The tank was packed with Eucalyptus globulus woodchips which was freely available at the site. Concentrations of groundwater nitrate at the site were well over what could be expected in any naturally occurring groundwater systems, and would result only by major anthropogenic activities in unconfined aquifer areas of South Africa. The changes in parameter concentrations with time were measured in order to determine the efficiency and life span of the carbon source used for the experiment. This paper considers 35 months of monitoring at a site where a low technology method was implemented. Field implementation was tested at a site which previously experienced some NH4NO3 spills. Main results from the field work showed that nitrate was totally removed at the treatment zone and surrounding boreholes, and even sulphate and NH4+ were removed during the experiment. This shows that the woodchips were successful in affecting denitrification for 35 months. Data also shows that boreholes further downstream from the tank had reduced NO3-, SO42- and NH4+ levels. Using the available biodegradable carbon for the woodchips based on its composition, a barrier lifespan could be determined. The results of calculations showed that the barrier would be effective for at least another 6.9 years from the period of the last sampling date. A total lifespan of about 10 years can thus be estimated.
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.
Development Of A Conceptual Understanding Of Hydrogeological Relationship Between The Skurweberg Aquifer And Wetlands In The Steenbras Catchment	Sinawo	Jack	Skurweberg Aquifer, Steenbras Catchment	2019	Drought, City of Cape Town, Steenbras, Skuweberg Aquifer, Groundwater Abstraction, Ecosystems
Abstract The City of Cape Town (CoCT) commenced a study into the feasibility of the Table Mountain Group aquifers (TMGA) for augmenting the water supply to the city in 2002. It comprised drilling of exploration boreholes in several target areas and the establishment of a hydrogeological and ecological monitoring network. Due to the prolonged drought and associated water crisis, the CoCT decided to fast-track the TMGA development in 2017. The first wellfield is currently developed within the catchment area of the Steenbras Dam comprising production boreholes targeting the Skurweberg and the Peninsula aquifers of the TMGA. Since groundwater abstraction from the Peninsula and Skuweberg aquifers might have a short-term or long-term impact on aquatic ecosystems (i.e. streams and wetlands) that are linked to the TMGA. As a result, evaluation of the potential impact of groundwater abstraction from this aquifer system requires an understanding of the nature and extent of groundwater dependency of the ecosystems. A variety of data sets and parameters have been measured over the last decade at ecological monitoring sites across the study area, of which two sites are located within the Steenbras catchment that are probably connected to the Skurweberg Aquifer. Recently further boreholes and monitoring sites have been added. This paper describes the various methods used and results of the analysis towards a conceptual understanding and quantification of the groundwater dependency of the selected ecosystems. While groundwater contribution is only one factor in ecosystem functioning, sustainable and adaptive management of the groundwater use must be based on the conceptual model and ongoing monitoring of the ecosystem responses.
Upscaling Preferential Flow in Heterogeneous Porous Media from the Laboratory to the Field	T	James Oudega	Austria	2023	Heterogeneity, preferential flow, upscaling
Abstract ue to public health or environmental concerns, performing tracer tests in the field by injecting pathogenic microorganisms or contaminants of emerging concern into groundwater is not permitted. Therefore, examining the effects of preferential flow processes on these contaminants under controlled saturated conditions must be done in the laboratory, but the resulting transport parameters cannot be directly applied to field-scale groundwater models. This research considers how an upscaling relationship can be found using a colloidal tracer and three different scales: small laboratory columns (0.1 m scale), a large intact core (1 m scale), and a real-world gravel aquifer (10 m scale). The small columns were filled with gravel from boreholes at the field site, an alluvial gravel aquifer close to Vienna, Austria. The mesoscale consists of an undisturbed gravel column from a gravel pit near Neuhofen an der Ybbs, Austria. Results showed that a certain pattern emerges after an initial scale-dependent threshold, regardless of differences due to the small columns being repacked with aquifer material and the large column and field site being “undisturbed”. In this way, the mesoscale column allows us to gain insight into upscaling processes by incorporating an in-between step when comparing groundwater transport at the column- to the field scale.
Estimation Of Groundwater Recharge: The Case Of Grasslands Catchment, Marondera, Zimbabwe	Muchanyara	Jarawaza	Grasslands Catchment, Marondera, Zimbabwe	2013	groundwater recharge, hydrochemical
Abstract The study on estimation of groundwater recharge was done in Grasslands Catchment, about 70 km south-east of Harare, Zimbabwe. The catchment is underlain by Archean Granitic rocks intruded by dolerite dykes/sheets and form part of the Basement Complex. The catchment is a stream headwater wetland, at the source of Manyame River. The catchment comprises an upland region or interfluves of area 2.12 km2 and a dambo area of 1.21 km2. The study focused on the assessment of temporal and spatial variability of moisture fluxes based on solute profiling, and groundwater recharge and investigations of moisture transport mechanisms. The methodology involved the use of both hydrometric and hydrochemical techniques. Groundwater recharge rates and moisture fluxes were calculated using a chloride mass balance technique in comparison to the hydrograph separation technique. Groundwater recharge was estimated to be 185 mm/year using the chloride mass balance and 215 mm/year using the hydrograph separation technique. Mechanisms of recharge were investigated using the bimodal flow model that comprised of diffuse flow and preferential flow. The results revealed that preferential flow contributes up to 95% of the recharge in the interfluves, whilst diffuse flow contributes up to 5% of the total recharge. The results reveal that the groundwater hydrograph technique results are in agreement with the chloride mass balance method. The study illustrated how routine observations can improve process understanding on groundwater recharge mechanisms. The techniques are not expensive, are easy to use and can be replicated elsewhere depending on availability of data.
GIS-PMWIN, A Preprocessor In ArcGIS For Groundwater Modeling With PMWIN	Haili	Jia		2015
Abstract PMWIN5.3 has been one of the most commonly used software for groundwater modeling because of its free source and the adoption of popular core program MODFLOW. However, the fixed formats required for data input and lack of GIS data support have posted big challenges for groundwater modelers who are dealing with large areas with complicated hydrogeological conditions. In South Africa, most geological and hydrogeological data have been captured and stored in GIS format during various national research projects such as WR2005, NGA and etc. Therefore, a proper linkage between PMWIN and ArcGIS is expected to do the preprocessing for modeling in PMWIN. Visual Basic for Application (VBA) embedded in ArcGIS 9.3 was used to develop the linkage. Based on the conceptualization of the study area, the model dimension, discretization and many value setting processes can be easily carried out in ArcGIS other than directly in PMWIN. Then the grid specification file and other input files can be exported as the PMWIN-compatible files. The functions of move, rotation, refinement, sub-model, deleting and inserting row(s) or column(s) of the model have also been developed to avoid the inconvenience aroused from model modification. The linkage can be used with a higher version of PMWIN or ArcGIS. It has been applied to several gold fields in the Witwatersrand gold basin to simulate the groundwater flow and mass transportation for various conditions and scenarios. One of the applications will be presented in this paper. It has been proved that the linkage is efficient and easy to use. {List only- not presented}
Assessing The Temporal Change In Hydro-Geochemical Properties Of Fly Ash When Disposed Into Opencast Coal Mines In Mpumalanga, South Africa	Angelo	Johnson	Mpumalanga	2019	hydrochemical, fly ash
Abstract This study focus on the feasibility of coal ash backfill into historical and future, acid generating coal mines. However, there is limited knowledge of how South African ash would behave in these acidic opencast mines. Therefore the aim is to improve the understanding of the change in hydro-geochemical properties of coal ash with reference to acid mine drainage (AMD). Fly ash from two power stations in Mpumalanga were assessed in the laboratory. The hydraulic properties of ash were determined through the use of Darcy up flow column tests, where ash was continuously leached with natural AMD. The influent and effluent was monitored for pH, EC and metal concentrations to investigate the chemical changes in the AMD, flowing through ash. The laboratory results exhibited decreasing trends in K over time, from 10-1 m/d to 10-3 m/d. These changes in hydraulic conductivity are initially subjected to the pozzolanic bindings that formed during the curing phase of the experiment. Subsequently, secondary mineralization occurs induced by calcium rich minerals which are deposited in the flow paths, causing a further decrease in K towards 10-2 m/d. Lastly, the Fe (>130 mg/L) and SO4 (>2000 mg/L) concentrations in the AMD together with the low pH = 2.5 causes a clogging effect at the front face of the ash columns, ultimately causing the K to decrease towards 10-3 m/d. Calcium was the dominant cation that leached out and sulphate the dominant anion, which was due to high concentrations in both the ash and AMD. It was observed that most of the leachate water was of a better quality than the influent AMD water quality. Based on the research findings, an ash monolith deposited at the decanting position of an opencast mine may have positive impacts. Ultimately, reducing AMD decant volumes and improving water quality.
Geochemical investigations to improve the prediction of mine water impacts: A case study in the Elandsfontein Aquifer System, West Coast.	Angelo	Johnson	West Coast	2021	Phosphate mine, waste sreams, mine water impacts, PHREEQC, geochemical
Abstract The impact of the future closure of the KROPZ phosphate mine in the West Coast on the various potential receptors including the underlying Elandsfontein Aquifer System (EAS), Langebaan Lagoon (RAMSAR-site) and wetlands were assessed. This abstract/paper describes the geochemical characterization and management options related to the waste streams from the mining activity, to assess the post closure contribution to groundwater flow from the mine towards potential receptors. The PHREEQC geochemical modelling code was used to predict potential mine water impacts. The input water quality parameters used in the model included: background groundwater quality, pit water and processed water generated from phosphate separation process at the mine. Various scenarios were simulated combining the different process water streams with the tailings and soft stockpile material at the mine. The geochemical predictions showed some management options that should be prevented, while also providing guidance to promising options where most of the chemical parameters does not exceed the WUL stage 1 thresholds. There is however, an increase in sulphate concentrations that need attending to before the mine goes into production phase. Currently there seems to be no immediate concern on the Lagoon relating to the prediction of mine water impacts post mine closure. Some of the management scenarios do however show low levels of potential impacts on SANParks property 100 years post closure. These predictions do however correlate to areas where limited calibration data is available. At the time of this abstract the sites for new boreholes have been selected and the initial boreholes are being drilled to confirm aquifer properties in areas with limited data.
Assessing The Change In Hydraulic Properties Of Fly Ash Over Time When Disposed Into Opencast Coal Mines In Mpumalanga, South Africa	Angelo	Johnson	Mpumalanga	2017	AMD, leaching, Darcy column tests, trace tests, fly ash
Abstract Large volumes of fly ash are generated by the coal-fired power stations and is currently disposed onto waste dumps, with already limited space. Therefore, a need for an alternative ash disposal method arises. This study evaluates the feasibility of fly ash disposed as backfill into opencast coal mines. The change in the hydraulic properties of the ash under different conditions and over time play an important role in determining this feasibility. Leachate and tracer tests are conducted in the laboratory through Darcy column tests where; (i) fly ash will be leached with acid mine water, (ii) fly ash will be leached with saline mine water, and (iii) fly ash will be leached with natural groundwater. These experiments will be conducted with fly ash of different moisture content and ages (3 days, 28 days and 90 days old ash) to establish the change in hydraulic properties and porosity over time. Infiltration tests will also be conducted on the existing ash dumps in the field and results will be compared to that of the laboratory tests. Conceptual models will then be generated from a combination of the laboratory and field results. The study is still in progress, but the literature review suggests that the possible outcomes are: 1) hydraulic conductivity of the fly ash will be lower than that of the backfill spoils and is expected to further decrease over time, therefore acting as a barrier to the movement of groundwater, 2) general groundwater levels within the backfill are expected to rise; resulting in the decrease of the unsaturated zone and therefore limits oxygen exposure to backfill spoils, and (3) the alkaline nature of fly ash might potentially neutralize acidic levels of AMD. Fly ash, when disposed as backfill into opencast coal mines, might aid in the mitigation/prevention of AMD formation.
Mine dewatering case study at a gold mine in Mandiana Region, Eastern Guinea	Angelo	Johnson	Eastern Guinea	2023	mine dewatering, Monitoring
Abstract A hydrogeological investigation was conducted at a gold mine in the Mandiana region, northeast Guinea. The objectives of the investigation included: 1) Review the efficiency of the current dewatering system and 2) Assess potential dewatering impacts on neighbouring groundwater users. Historical and current hydrogeological information were reviewed and assessed to address the project objectives. The site geological succession contains laterites, saprolites, saprock, dolorite sill and fresh fractured bedrock below. A review of the borehole lithological logs, pump test and monitoring data confirmed that the contact zone between the saprock and the dolorite sill is the major aquifer zone with hydraulic conductivity up to 25 m/d, with a minor alluvial aquifer with hydraulic conductivity ~ 0.05 m/d. The current dewatering system is not as effective as it should be due to electrical issues causing seepage into the current pit floor. A combination of in-pit sumps and dewatering boreholes is recommended to ensure the mine pit’s dry working conditions. The neighbouring groundwater users tap into the alluvial aquifer with water levels ranging between 0-10 mbgl and are not at risk from mine dewatering impacts due to the dewatering boreholes tapping into the deeper saprock-dolorite contact zone. The shallow and deeper aquifers are hydraulically disconnected. The following is recommended: 1) Drilling of replacement dewatering boreholes and implementing continuous water level and abstraction rate monitoring, and 2) Discharge the in-pit sumps (alluvial aquifer inflow and rainfall) into the river downgradient of the mine to supplement recharge to the alluvial aquifer.
Aquifer structure and extent based on Airborne Geophysical investigation: A case study based in Saldanha Bay Local Municipality, West Coast.	Angelo	Johnson	Saldanah Bay	2021	Poster, Skytem, 3D mapping survey, MAR, interpretation, aquifer management
Abstract Saldanha Bay Local Municipality appointed Skytem to conduct an airborne geophysical 3D aquifer mapping survey. As part of improving the sustainable management of the groundwater resources and exploring the options of Managed Aquifer Recharge, a better understanding of the aquifers is required. The Skytem technology unlocked a rich understanding of the subsurface geology and the groundwater contained in it. Before the main survey commenced, a trial survey was conducted to investigate the quality of the data that may be expected from the main survey. The trial survey was conducted over the existing water supply wellfield where there were existing groundwater data including borehole lithology from drilling and ground geophysics. Consequently, the main survey commenced and consisted of the following: 1) Magnetic survey providing information regarding bedrock composition and where it changes due to faults or deposition, 2) Time Domain Electromagnetic survey providing conductivity/resistivity of the subsurface, 3) Detailed elevation along flight paths, and 4) 50Hz signal to understand where interferences can be due to power lines. The survey interpretation showed the following important aquifer characteristics that will be useful for future management of the aquifer system: 1) Bedrock elevation and paleo topography, 2) Areas with different bedrock composition, 3) Geological faults in the bedrock, 4) Bedrock below the surface, 5) Areas with thick dry sand, 6) Clay layer extent and area without clay, 7) Areas with different water quality, and 8) Areas with very high concentrations of salt. The survey output and interpretations are regarded as very useful for the update of the conceptual models for the area. Data can now be used to update the numerical models and improve the management of the wellfields.
Groundwater Stratification And Impact On Coal Mine Closure	Andrew	Johnstone	National	2013	Groundwater, coal mine
Abstract To date, South Africa has mined approximately 3.2 billion tons of coal from a number of different coal reserves located in various parts of the country. A large number of the mines have reached the end of their productive life, resulting in numerous mine closures. With closures, groundwater levels have rebounded, resulting in decant of mine water into the environment. This paper describes a case study of a closed underground coal mine, the rebound of water levels, the evolution of the groundwater quality and the impact it has had on the management of the potential decant. On closure of the Ermelo Mines in 1992, initial water quality monitoring indicated that a water treatment plant would be required to treat the mine decant. However, as the groundwater levels in the mine rebounded, the water quality in the mine void evolved from sulphate type water to sodium type water. The evolution of the water quality can be attributed to sulphate reducing bacteria, vertical recharge from the hanging aquifer and stratification. Water level and quality monitoring have shown that the water in the old mine void will not decant to surface due to the depth of the mine void, hydrogeological conditions, a "hanging aquifer" and the recharge mechanisms. As a result, no water treatment will be required and the mine will not impact on the surface water. The main applications from this paper are: Design of a correct monitoring procedure to allow for monitoring of water quality stratification in rebounding mines. Identifying the role of sulphate reducing bacteria in the evolution of groundwater quality in a methane rich coal mine void. The role of a hanging aquifer in recharging of a coal mine void and resultant stratification. Designing of a mine taking into consideration mine closure. The main contribution of this paper is the use of hydrogeological information in design of a coal mine so as not to decant on closure.
The Management of Groundwater resources using GIS/Cartography splay)	Freda	Jonck		2015
Abstract The Department of Water Affairs and Sanitation is the custodian of the Water Resource in South Africa. The Western Cape Regional Office, Geotechnical Service Sub Directorate, is responsible for management of groundwater resources in two Water Management Areas (WMA), Olifants Doorn-Berg and Breede-Gouritz. Twenty-nine monitoring routes comprising 800 sites in total are monitored across the Western Cape Region. The purpose of this paper is to create awareness of groundwater related databases and the type of information products used in assessing the status of data bases and groundwater resources. This is to assist and support the scientists, technicians, managers, external stakeholders and/or general public. The main question that needs to be answer is: "What is the current groundwater data management situation in the Regional office?" With the GIS as platform, geographical information was generated from existing data bases to answer questions such as, what is being monitored, where is it being monitored, who is monitoring it, why is it being monitored and when is it being monitored? These questions are applicable to the Region, Water Management Areas, the monitoring route and geosites. Graphical time-series information generated from available data, in combination with the generated geographical information, showed the gaps, hot spots and what is still needed for all the facets of groundwater management (from data acquisition to information dissemination) processes. The result showed the status of data bases, need for data in areas of possible neglect, training gaps, inadequate structure and capacity, instrumentation challenges, need for improvement of commitment and discipline, as well as many other issues. The information generated proves to be an easy tool for Scientists, Technicians and Data Administrators to assist them to be on top of the groundwater resource management in their area of responsibility. The expansion of the use of GIS as a groundwater management tool is highly recommended. This will ensure better understanding of the resource: "The Hidden Treasure".
GIS and Groundwater Monitoring	Freda	Jonck	Western Cape	2017	monitoring network, resource assessment
Abstract The Department of Water Affairs and Sanitation is the custodian of the Water Resources in South Africa. The Western Cape Provincial Office, Geotechnical Services (Geohydrology) Sub Directorate, is responsible for management of groundwater resources in two Water Management Areas (WMA), Berg Olifants and Breede- Gouritz. Thirty-eight monitoring routes comprising 700 sites in total are monitored across the Western Cape Province. The purpose of this paper is to show the use of GIS as a management tool for groundwater monitoring in the Western Cape. This is to assist and support the scientists, technicians, managers, external stakeholders and/or general public. The main question that needs to be answered is: “What is the current groundwater monitoring and data management situation in the Provincial office” With GIS as platform, geographical information was generated from existing data bases to answer questions such as, what is being monitored, where is it being monitored, who is monitoring it, why is it being monitored, when is it being monitored, are instruments installed, what instruments are installed, what equipment is involved and what energy source is used? These questions are applicable to the Region, Water Management Areas, the relevant monitoring route and geosites. Generated geographical information showed the gaps, hot spots and what is still needed for all the facets of groundwater management (from data acquisition to information dissemination) processes. The result showed the status of data bases, need for data in areas of possible neglect, training gaps, inadequate structure and capacity, instrumentation challenges, need for improvement of commitment and discipline, as well as many other issues. The information generated proves to be an easy tool for Scientists, Technicians and Data Administrators to assist them to be on top of the groundwater resource management in their area of responsibility. The expansion of the use of GIS as a groundwater management tool is highly recommended. This will ensure better understanding of the “The Hidden Treasure” resource.
Sustainability Of Shallow Groundwater Irrigation On Emerging Farms In The Limpopo Province: Case Study In The Molototsi Catchment	Nebo	Jovanovic	Limpopo	2017	Shallow groundwater, modelling, MODFLOW, Irrigation
Abstract A cycle of research is under way to investigate sustainable farming practices and business development on emerging farms in the lowveld of the Limpopo Province of South Africa. One of the main limiting factors for intensive agricultural production in this region is water availability. The objectives of this study were: i) to determine the spatial extent of occurrence of shallow groundwater (<20 m deep), in particular along dry river beds; and ii) to determine the sustainability of shallow groundwater abstraction for irrigation on emerging farms. A case study was investigated in the Molototsi River catchment, a torrential tributary of the Letaba River. The geology consists of well-developed, medium-textured alluvial/colluvial soils overlying predominantly Goudplaats gneiss. Geophysical surveying and mapping was carried out with a Model G5 proton memory magnetometer and an EM-34 electrical resistivity meter. Groundwater level data were collected from the GRIP database (Groundwater Resource Information Project - Department of Water and Sanitation) and selected boreholes were monitored with Solinst water level loggers. Groundwater abstraction data, borehole logs and digital elevation models were also collected. A methodology was developed to map the extent of shallow groundwater using measured groundwater levels, a National Land Cover map (NLC 2013/14), the wetland map of the National Freshwater Ecosystem Priority Areas (NFEPA), satellite remote sensing (MOD16 evapotranspiration data) and ground-truthing. Groundwater level monitoring indicated that the water bearing features may not be directly connected to the alluvium and sand river bed (alluvial aquifer), resulting in limited baseflow estimated to be ~15 m3 a -1 for a river reach of 100 m. Episodic recharge of the alluvial aquifer occurs predominantly via surface runoff. The hydraulic conductivity of the river sand aquifer was estimated to be >20 m d-1 , and one order of magnitude smaller in the fractured rock aquifers. Groundwater modelling with MODFLOW was done at farms abstracting groundwater from fractured bedrock aquifers and directly from the sand bed of the Molototsi River to investigate how much water can be abstracted for sustainable irrigation. Both modelling and monitoring results indicated that there is limited scope for large scale expansion of irrigation, given the competition for water in the area, in particular for drinking water supply. However, the volume of water stored in the dry river bed could represent a useful reserve during periods of severe drought, with recharge from occasional flood events being essential. Given the porosity of the river bed aquifer of about 40%, it was estimated that a 100 m reach of the Molototsi River would retain about 7,200 m3 of water that could be abstracted if numerous wells are established and recovery periods are allowed. A water volume of 7,200 m3 is sufficient to irrigate 1.8 ha of vegetables for one season. This volume could be augmented to a certain extent by establishing river bed sand dams.
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.
Optimizing borehole performance through dynamic flow and chemistry profiling	Steve	Kalule		2021	Drinking water standards, Groundwater Quality, supply boreholes, remediation system, optimised well design, well profiling
Abstract Stringent drinking water standards for constituents like chromium, arsenic, and nitrates, combined with continually higher demand for groundwater resources have led to the need for more efficient and accurate well characterization. Many boreholes are screened across multiple aquifers to maximize groundwater production, and since these aquifers can have different water qualities, the water produced at the wellhead is a blend of the various water qualities. Furthermore, the water entering a well may not be distributed equally across the screened intervals, but instead be highly variable based on the transmissivity of the aquifers, the depth of the pump intake, the pumping rate, and whether any perforations are sealed off due to physical, chemical, or biological plugging. By identifying zones of high and low flows and differing water qualities, well profiling is a proven technology that helps optimize operational groundwater production from water supply boreholes or remediation systems. This frequently results in increased efficiencies and reduced treatment costs. By accurately defining groundwater quantity and quality, dynamic profiling provides the data needed to optimize well designs. Conventional exploration methods frequently rely on selecting well screen intervals based on performing and analyzing drill stem tests for one zone at a time. Using dynamic flow and water quality profiling, the transmissivity and water quality can be determined for multiple production zones in a matter of one to two days. It also allows the location and size of the test intervals to be adjusted in the field, based on real-time measurements. In this paper we discuss dynamic well profiling techniques with project case examples of characterization different types groundwater boreholes for a variety of applications and industries resulting in significant cost saving and sustainable water abstraction.
The impact of groundwater temperature on water quality in the urban aquifer of the city of Vienna	E	Kaminsky	Vienna	2023	groundwater temperature, groundwater-surface water interaction, trends, Water chemistry
Abstract Rising shallow groundwater temperatures are observed in many cities worldwide and are expected to increase further over the next century due to anthropogenic activities and climate change. The impact of groundwater temperature increase on groundwater quality is poorly understood. This study conducted two high-spatial-resolution campaigns in Vienna (Austria, autumn 2021/ spring 2022). At 150 wells, a comprehensive parameter set (e.g. major ions, nutrients, and water stable isotopes) was analyzed in groundwater collected, and at 812 wells, the water temperature was measured. Results are compared to available long-term data on groundwater chemistry (1991-2020). In theory, temperature triggers a cascade of effects, where, finally, the depletion of dissolved oxygen (DO) causes a switch to anaerobic microbial processes and a deterioration of water quality. No direct relation between DO and water temperature was observed between 10 and 20 °C. However, many wells delivered anoxic groundwater, including the one with the highest measured temperature (27 °C). The highest temperatures were consistently observed near potential heat sources (local scale), with a rapid decrease in temperature with increasing distance from these sources. Long-term data from particular high-temperature wells revealed decreased dissolved oxygen after sudden temperature changes of > 5 K. On a regional scale, it is observed that groundwater-surface water interactions and aquifer properties play a pivotal role in oxygen availability and redox conditions. In conclusion, high-spatial-resolution sampling combined with long-term data analysis is needed to determine the impact of temperature on water quality.
Using Hydrogeologic Conceptual Model To Implement A Successful Iwrm Approach In Limphasa River Catchment, Malawi	Thokozani	Kanyerere	Limphasa River Catchment, Malawi	2013	Hydrogeological, IWRM, conceptual model
Abstract This study examined the effective use of the hydrogeologic conceptual model (HCM) to implement the integrated water resource management (IWRM) approach. While research focuses on using hydrogeologic models in groundwater for planning, few studies show how to use HCM for a successful IWRM approach, especially in resource poor catchments. This is largely due to t he lack of adequate data to showcase such models. Despite the lack of numerical groundwater data, the HCM was used in this study and it provided the scientific and visual presentation of key issues for practical understanding by stakeholders. For the first time, HCM provided a practical understanding of t he groundwater system in the Limphasa River catchment. By using HCM and physical factors qualitatively, the study revealed that, apart from storage, abstraction mechanisms significantly contributes to regional initiatives of groundwater supply whose central objective is to utilise and manage such water sustainably. The model is based on the relationship between groundwater availability and its related hydrogeologic factors. Findings suggest improvement in quantifying the studied parameters through field experiments to provide a better estimation on storage and abstraction of groundwater in relation to impacts of a future changing climate. Since using HCM has shown practical usage, replicating it in catchments with similar physical and socioeconomic environments, would be desirable as refining the model progresses.
Spatial and temporal assessment of groundwater-surface water interaction, Skoonspruit River catchment, North West, South Africa	Thokozani	Kanyerere	North-West	2015
Abstract POSTER The poster presents the spatial-temporal assessment of groundwater-surfacewater (GW-SW) aspects in Skoonspruit River catchment, North West of South Africa. Despite the common use of quantitative methods to assess various aspects of GW-SW interaction, the use of qualitative methods remains poorly understood in assessing aspects of GW-SW interaction especially in the context of developing countries such as South Africa. While quantitative methods are envisaged to provide reliable and valid results,the use of qualitative methods are exploratory, site specific and more revealing to provide insights for more robust confirmatory methods. Such approach remains fundamental to comprehensive assessments that facilitate relevant generation of information to decision makers to enable them develop and improve interventions for the desired water utilization and management practice. However, the use of such qualitative methods in GW-SW interaction studies has not been applied, a situation which limit the basis for applying quantitative methods and that make quantitative methods not yield the desired results in most studies. The current study argues that the use of quantitative methods should be informed by the results from the qualitative methods and that the poor results from the GW-SW interaction studies is partly due to lack of implementing the qualitative methods prior to using the quantitative methods, especially in the context of developing countries such as South Africa. The current study established spatial variation in the water-type of the upper and lower catchment for both groundwater and surface water. Characterized water-type for several site specific reaches and determined the temporal trends for GW-SW interaction process in order to produce a comprehensive scenario for spatial-temporal pattern for GW-SW interaction in the Skoonspruit River catchment of North West to inform desired interventions for water use and management. Key Words: Qualitative methods, Quantitative methods, Spatial-temporal assessment, GW-SW interaction, Water use and management, Skoonspruit River catchment, North West
The Use Of Derivative Analysis To Choose And Refine Conceptual Models Of Groundwater Flow Systems	Thokozani	Kanyerere	Western Cape	2019	modelling, flow systems
Abstract Groundwater flow system responses have been understood using derivative analysis. The argument is that the use of derivative analysis derived from pumping test data improves the understanding of aquifer types and curve matching in a hydrogeologic setting. The different aquifer systems encountered in Western Cape Government Business Continuity Programme (WCBCP) of South Africa was used as case study where the analysis of the time versus draw-down derivative plots were applied to validate the aquifer characteristics to explaining the groundwater flow systems. Key findings showed that analysis from the time versus draw-down derivative plots can be used to infer conditions within the wellbore, groundwater flow to boreholes and boundary conditions within the aquifer to provide insights. In addition, results confirmed that the archetypal time vs draw-down responses enabled characterizing the aquifer types and such analysis showed unique responses to the pumping. Lastly, long term operation of boreholes for water supply were ascertained when the analysis was interpreted. The analysis was enhanced when the geological information that was collected during drilling operations, were added to the conceptual understanding of groundwater flow studied aquifer system. However, due to costs implications of conducting long-term aquifer hydraulic pumping tests, deviations from the conventional draw-down responses are expected. In this study, it is suggested that due to complexities associated with heterogeneous flow in aquifer types, it is essential to combine derivative analysis with pumping methods to improve interpretation and assessing long term operation of boreholes for water supply
Contribution of gravel pit lakes in reducing the groundwater nitrate contamination originating from agricultural land	Igor	Karlović	Croatia	2023	Varaždin aquifer, gravel pit lakes, Groundwater, groundwater remediation, Nitrate
Abstract The alluvial aquifer in the Varaždin region has a long-standing problem with high groundwater nitrate concentrations, mainly from agricultural activities. Since groundwater is used in public water supply networks, it is important to ensure its sustainable use. The aquifer is also used to exploit gravel and sand, and the increased demand for this valuable construction material causes the excavation of gravel pit lakes, making groundwater more vulnerable. Although engineered processes can remove nitrate from groundwater, natural attenuation processes should be investigated to understand the nitrogen behaviour and additional mechanisms for groundwater remediation. Previous research has shown nitrate is a conservative contaminant in the critical zone. Aerobic conditions within an aquifer system prevent significant denitrification. Thus, nitrification is the main process controlling nitrogen dynamics in groundwater. Since groundwater and gravel pit lakes are hydraulically connected, and natural nitrate attenuation exists in these lakes, an additional mechanism for groundwater remediation is possible. This work used isotope hydrochemistry and groundwater modelling to investigate gravel pit lakes as possible sites to reduce nitrate concentration in groundwater. Based on the isotopic composition of groundwater and nitrate concentrations, water balance and solute mass balance were calculated, which made it possible to estimate the nitrate attenuation rate in gravel pit lakes. The gained retardation factor was applied to the groundwater flow and nitrate transport model through several scenarios to evaluate the contribution of gravel pit lakes in reducing the groundwater nitrate concentrations
Groundwater overuse and water quality challenges in a large metropolitan catchment	B	Karthikeyan	India	2023	Managed aquifer recharge, megacity, persistent organic pollutants, urban catchment
Abstract Conjunctive use of surface water and groundwater plays a pivotal role in sustainably managing water resources. An increase in population, especially in the cities, increases the demand for water supply. Additional infrastructure to meet the needs and treatment techniques to remove the pollutants should be updated from time to time. Closing the urban water cycle by recycling and reusing treated sewage in the water sector can significantly reduce excessive groundwater extraction. However, this method is being implemented in only a few cities in developed countries. In the closed urban water cycle, treated sewage is discharged to rivers or other surface water bodies and used for managed aquifer recharge (MAR). Bank filtration, soil aquifer treatment and infiltration ponds are available MAR methods that augment the groundwater resources and remove pollutants during the natural infiltration process. These cost-effective natural treatment methods serve as a pre-treatment technique before public water supply to remove turbidity, algal toxins, bulk dissolved organic carbon and pathogenic microorganisms. The successful performance of these treatment methods depends on the need and feasibility for MAR, suitable hydrogeological conditions, sub-surface storage capacity of the aquifers, availability of suitable areas for MAR, type of MAR, source of recharge water, quality criteria, assessing the past, present and future climatic conditions. Case studies on groundwater resources management and water quality assessment, including for organic micropollutants from a large urban catchment in India, are presented.
Peculiarities of the chemical composition of the Ordovician aquifer as a source of potable water supply (St. Petersburg, Russia)	E	Kayukova	St. Petersburg, Russia	2023	aquifer properties, ground water contamination, radon, saturation index
Abstract The Ordovician aquifer of the Izhora deposit is widely used for drinking by the population of St. Petersburg and its suburbs. Carbonate Ordovician rocks are intensively karstified. The water is fresh (0,5-0,8 g/l), bicarbonate-calcium on the predominant ions, pH 7.6; calcium content is 50-80 mg/l, magnesium content is 30-60 mg/l and the total hardness is 7,6-8,0 mg-equ./l. Western, northern and northeastern boundaries of the Izhora deposit go along the Baltic Klint, which is evident on the relief. Its southern boundary is along the zone of the dip of Ordovician limestone beneath the Devonian sandstone. The territory of the Izhora plateau belongs to the areas of intensive economic activity. Often, objects of human economic activity are located near drinking water intakes. Almost all sites are marked by excess sanitary norms of chemical elements. Pollution of groundwater in the Ordovician aquifer has been identified in some areas. Priority substances have been identified for assessing the quality of groundwater: total hardness, Fe, Mn, Ba, and B. According to hydrochemical modelling data, Ordovician groundwater is saturated with calcite over most territory. There are many springs of underground water along the Baltic Klint, for example, near the village of Lopukhinka, Duderhof springs and others. The springs waters have natural radioactivity (due to the contact of groundwater with dictyonema shales), which makes their use hazardous to human health.
Investigating groundwater and surface water interactions using stable isotopes and hydrochemistry in the Notwane River Catchment, South East Botswana.	Piet	Kenabatho	Botswana	2021	Gw-Sw interaction, Isotopes, Hydrochemistry, HCA
Abstract Modie LT; Stephens M Stable isotopes and hydrochemical analysis were undertaken to investigate groundwater-surface water (GW-SW) interactions and their possible implications on the quality and quantity of water in the karstified dolomite-dominated Notwane River Catchment (NRC) in semi-arid South East (SE) Botswana. Stable isotopes (δ18O & δ2H) and other hydrochemical parameters were analyzed from water samples (groundwater, river water and rain) collected in the upstream, middle stream and downstream of the Ramotswa Wellfields to investigate the potential GW-SW relationship in the study area. In addition field observation were also undertaken to support results obtained through stable isotopes and hydrochemical methods. Similarity in isotopic signatures taken during the dry and wet seasons respectively for groundwater (δ18O -1.4‰, δ2H -10.8‰; δ18O 1.4-‰, δ2H -10.9‰) and surface water(δ18O -2.04‰, δ2H -6.2 ‰; δ18O -2.56‰, δ2H -7.1‰) suggests groundwater recharge through the streambed at a site further downstream in the study area. In upstream study sites the average groundwater isotopic signature values of (δ2H -24.1,δ18O -4.1) suggests a more direct link to the Meteoric Water Line(MWL) indicating possibility of a rapid infiltration and quick watershed response to heavier rainfall events(δ2H -51.7, δ18O -8.6) rather than recharge through the riverbed. A further assessment on the GW-SW hydrochemistry was provided using Hierarchical Cluster Analysis (HCA) to investigate the influence of groundwater on stream water. The median EC values from the clusters are in an increasing order Cluster A-B2-B1 indicating cluster A(all river samples) as the most dilute samples with the shortest resident time relative to the groundwater clusters(B2 and B1). These results therefore rules out groundwater discharge through the streambed into the river as not a dominant process for GW-SW interaction in the study area. The study has concluded that GW-SW interactions in the NRC part under study vary from connected to no connection from one site to another.
Securing Water Supplies – Participatory Groundwater Monitoring and Management in Botswana and Uganda	Piet Kebuang	Kenabatho	Botswana, Uganda	2023	Livelihoods and Pollution, Participatory groundwater monitoring
Abstract Groundwater resources in Africa face increasing threats of over-exploitation and pollution due to urbanization, agricultural and mining activities, yet monitoring remains challenging. Conventional approaches to monitoring groundwater at the exclusion of communities have not been successful. To overcome this, it is important to fully engage and train local communities in monitoring Groundwater Levels (GWLs), Rainfall and Water Quality (RWQ), which are important for understanding groundwater dynamics in wellfields. In this way, villagers can better understand groundwater issues and convey this information to others to cooperatively manage groundwater. A pilot program to monitor GWLs and RWQ by locals was initiated in two villages each in Botswana and Uganda to learn about its effectiveness. Through continuous stakeholder engagement, the local communities in the two case studies have been facilitated, trained and supported in monitoring groundwater and using the information collected to understand groundwater trends and their sustainability. Preliminary results indicate improvement in understanding the importance of groundwater monitoring by the communities and the implications on groundwater sustainability for improved livelihoods. This has become useful to one of the communities engaged in a village-level irrigation project which depends on groundwater resources. This project builds on a successful village-level participatory approach developed in the MARVI project (www.marvi.org.in ). It seeks to contribute to the United Nation’s 2022 call on “Groundwater: making the invisible visible” to highlight the importance of better monitoring and managing this vital resource.
Pock Marks as a Nature-based solution for enhancing water availability in African marginal drylands?	D	Kibirige	South Africa	2023	Pockmarks, Groundwater, nature-based solutions
Abstract Nearly 1.9 billion people live in marginal environments, including drylands, semiarid, arid, and hyperarid environments. Obscure but ubiquitous circular pockmark depressions dot these lands. These circular depressions can range from a few meters to kilometers, and the depth of these depressions varies from a few centimeters to over 10 m. However, the genesis of the circles has been investigated among scientists for many years because of their obscure nature. Some researchers believe that termites cause fairy circles, while others believe they are caused by plants competing for water and nutrients. This study documented the Africa-wide prevalence and extent of the pockmarks for the first time, and it further classified the pockmarks according to their genesis and hydrological roles. We further investigated their relevance in serving as nature-based solutions to overcome water scarcity in dryland regions. So far, field evidence in Ethiopia and Somalia showed that these features potentially have water security significance in a) organizing surface water flows over arid/semi-arid landscapes, b) serving as the site of temporary surface water storage, and c) serving as the site of focused groundwater recharge into the underlying aquifers. This presentation will highlight the spatial prevalence, extent, and genesis model of the pockmarks across the drylands in Africa (South Africa, Namibia, Somalia, Ethiopia, Kenya, Chad, Senegal, Mali, Niger, etc.).
An investigation into the effectiveness of underground water pollution mitigation policies	Sibanda	Kin		2015
Abstract Pollution of underground water is fast becoming a global problem and South Africa is not immune to this problem. The principal objective of this paper is to investigate the effectiveness of laws and policies put in place to mitigate underground water pollution. The paper also seeks to examine the causes and types of underground water pollution followed by a closer look into the laws and policies in place to mitigate the pollution levels. Finally, the paper seeks to ascertain whether the current policies are properly implemented. The paper follows content analysis (desk research) to achieve the objectives. Policy recommendations are given based on the findings. {List only- not presented}