Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 351 - 400 of 795 results

Title Sort descending	Presenter Name	Presenter Surname	Area	Conference year	Keywords
Groundwater and Surface Water Interaction Study for the Ingula Wetland	Christie	Terrell		2015
Abstract The Bedford Dam is the upper storage dam for the Ingula Pumped Storage Scheme and is situated in the Ingula/Bedford Wetland. This wetland has a high structural diversity which supports a unique assemblage of plants and invertebrates. The flow regulation and water purification value is of particular importance as the wetland falls within the Greater Vaal River catchment. Concern was raised with respect to the potential negative impact of the newly constructed dam on the dynamic water balance within the wetland. An assessment of the extent to which groundwater drives / sustains the wetland systems and the water requirements needed to sustain the wetland processes was determined. This includes establishing the impact of the Bedford Dam on the groundwater and wetland systems as well as providing recommendations on management and monitoring requirements. The hydropedological interpretations of the soils within the study area indicate that baseflow to the wetland is maintained through perennial groundwater, mainly recharged from infiltration on the plateau, and was confirmed through isotope sampling and hydrometric measurements. It is apparent that the surface flows in the main wetland are fed by recent sources, while the subsurface layers in the wetland are sustained by the slower moving near-surface and bedrock groundwater. The movement of groundwater towards the wetland is hindered by the numerous dykes creating a barrier to flow. Nevertheless, there seems to be a good connection between the groundwater sources in the upland and the surface drainage features that conduct this water to the contributing hillslopes adjacent to the main wetland. The surface flows of the main wetland are sustained by contributions from tributary fingers. The discharge out of the wetland is highly seasonal
Groundwater and mining on the West African shield: application of mineralogical and weathering profiling	David	Love	West Africa	2015
Abstract The Birimian and Tarkwaian rocks of the Paleoproterozoic West African Shield host some of the most important gold reserves in the world, with Ghana the world's 10th largest gold producer and the region collectively producing more gold than all but five countries in the world. The gold was deposited during successive hydrothermal sulphide alteration events, which were channelled by shear zones and thrusts formed during the regional progressive Eburnean tectono-thermal deformation event. The hydrothermal fluids were auriferous and sulphide-rich, resulting in two distinct types of gold and sulphide mineralisation: (1) gold-bearing quartz- and quartz-ankerite veins, occurring in NNE-SSW trending shear zones or thrust folds, usually in Birimian metasediments, with associated sulphides deposited on the fragmented wall rock and (2) disseminated gold-bearing pyrite and arsenopyrite, occurring in halos within the same shear zones or thrust folds as the quartz veins. The sulphidic nature of the gold deposit leads to a high risk of acid rock drainage (ARD). During operations, inflowing groundwater may carry the ARD into underground workings and opencast pits. Post-closure, as the groundwater rebounds, there is a risk of acidic pit lakes forming or acidic decant of underground mines. However, the occurrence of ARD in such systems can be predicted by a combination of weathering profiling, mineralogical profiling and conventional acid base accounting (ABA). The weathering profile can be divided into three zones, readily distinguishable in borehole core: (i) Oxide Zone, from which both the acid-generating sulphide minerals and the acid-neutralising carbonate minerals have been largely leached, (ii) Transitional Zone, from which the carbonate minerals have been largely leached but the sulphide minerals remain, (iii) a Fresh/Primary Zone, where both sulphide and carbonate minerals occur. The Oxide Zone is generally non acid-generating, the Transitional Zone is acid-generating and the Fresh Zone is potentially acid-generating, depending upon the balance of sulphide vs carbonate minerals. Mineralogical profiles can be prepared from the relative abundance of macroscopic sulphide and carbonate minerals in the borehole core, again providing an assessment of ARD risk. Combined logs can then be prepared from these profiles with acid-generation and neutralisation data from ABAs, illustrating in space where the highest ARD risk zones are located. Using this information, groundwater and mine water management options can be developed for operations and closure, such as prioritisation of open pit backfilling or which levels of an underground mine water should be preferentially excluded from.
Groundwater and surface water interaction in farming areas in the Rawsonville area of the Western Cape.	Siphumelelo	Mbali	Western Cape	2015
Abstract The understanding of groundwater and surface water interaction is important for the planning of water resources in particular for farming areas. The interactions between groundwater and surface water are complex. To understand the relationship of groundwater and surface water interactions it is important to have a good understanding of the relation of climate, landform, geology, and biotic factors, a sound hydrogeoecological framework. Surface-water and groundwater ecosystems are viewed as linked components of a hydrologic continuum leading to related sustainability issues. In this study the Gevonden farm in Rawsonville will be used as the study site. This study site forms part of the Table Mountain Group (TMG). The methods to establish the relationship of groundwater and surface water interaction are collection of rainfall data monthly, river channel parameters at the farm such as the discharge on a monthly bases, chemistry of the water in the stream and groundwater were also be analyzed and pumping tests will be conducted twice to get the hydraulic parameters of the aquifer. The aquifer parameters will be analyzed using the Theis and Cooper-Jacob methods. The river has lower water levels in the summer months and this is also the case in the water levels in the boreholes on the farm, however in winter the opposite is true. The chemical analyses which are identical indicate that there is groundwater and surface water interaction in the farm. The degree of the interaction differs throughout the year. The results show that the interaction is influenced by the rainfall. The results clearly suggests that the farmers need to construct dams and drill pumping borehole in order to have enough water to water their crops in the summer season as by that time the river is almost dry. {List only- not presented}
Groundwater and surface water interdependencies in a water-scarce arid system, Sandveld, South Africa	L	Smit	South Africa	2023	Catchment, coastal wetlands, Groundwater, Hydrogeology, Management, surface water
Abstract The largely groundwater-dependent Sandveld region’s water resources have been put under severe strain due to increased agricultural and town development and recent increased interest in mineral exploration within these catchments. The area known locally as the Sandveld consists of the coastal plain along the west coast of South Africa, bordered by the Olifants River to the north and east, the Berg River to the south and the Atlantic Ocean coastline to the west. Groundwater is considered an essential source of fresh water for the town and agricultural supply. It also plays a major role in maintaining the functionality of the natural environment, especially concerning the coastal wetlands, such as the Verlorenvlei Wetland, designated as a Wetland of International Importance (Ramsar Site). Monitoring boreholes displayed a general drop in water levels, and a decrease in surface water flow has been reported. This has resulted in the drying up of wetland areas within the catchments. This investigation focused on conceptualising the geohydrological setting and defining the groundwater-surface water interactions and interdependencies. The assessment entailed a complete review and analyses of available hydrogeological and hydrochemical data and reports obtained through Stellenbosch University, the Department of Water and Sanitation and the private consulting sector. The priority groundwater areas were delineated, and recommendations on the regional management of these aquifers were made. The research characterised the geohydrological setting and outlined the Sandveld surface water systems’ dependency on groundwater baseflow and spring flow.
Groundwater as bulk water supply option to an open pit mine	Christo	Gouws	Mozambique	2015	Open pit mines, Water supply
Abstract A multi seam open pit coal mine is planned to be developed in the Moatize Basin of Mozambique. The proposed project includes a new coal mine and coal handling facility to produce up to six million tons per annum of coking and thermal coal for the export market, which will have a life of mine of approximately 30 years. The mine will require 65 l/s for the first five years to supplement their process water make-up. Geo Pollution Technologies Ltd was appointed to investigate the feasibility of supplying groundwater to the mine. Due to the complexity of the Revuboe River during flooding and other difficulties abstracting water directly from the river, abstraction of groundwater from the alluvial aquifer next to the Revuboe River was selected as bulk water supply to the mine as it proved to be a sustainable source of water at other mining operations in the area. The benefits of the alluvial aquifer is the potential volume of water in storage and the zero losses to evaporation and seepage. Taking into consideration the information gathered from previous groundwater and geophysical studies done in the area, a number of boreholes were sited based on geophysical results, alluvial material thickness and the energy of the river. Four of the six initial borehole positions had to be changed due to unforeseen access restrictions and concerns from the community. After the borehole positions were cleared and finalised, six boreholes were drilled up to a depth of roughly two meters below the bottom of the alluvial aquifer, which is on average 20 meters thick. The boreholes were logged in terms of geology and hydrogeology and cased to allow maximum water inflow from the aquifer. Due to one of the six boreholes being dry, five of the boreholes were subjected to 24 hour pump testing. The discharge rates varied between 4 and 20 l/s. The pump test results were interpreted using the Flow Characteristic method and final yields of between 5 and 30 l/s were achieved. The bulk water supply target of 65 l/s were exceeded by 9 l/s, with a final supply from the five holes combined of 74 l/s sustainably for the next five years.
Groundwater chemical evolution at an underground coal gasification pilot plant in Majuba	Lehlohonolo	Mokhahlane	KwaZulu-Natal	2015
Abstract Underground coal gasification (UCG) is technology that aspires to exploit coal reserves using in-situ gasification. This mining method gasifies coal seams while extracting a syngas that can be used for electricity generation. Since the bulk of this process occurs in the subsurface, there is a possibility of impacting on regional groundwater quality. This paper seeks to assess this impact on groundwater across different aquifers while taking into account the chemical evolution of these aquifers. Three aquifer systems were identified namely the shallow, intermediate and the deep aquifer which comprises of the coal seam. The water chemistry was reviewed over a two year period during which the gasifier was still active. Alkaline conditions were prevalent across the three aquifers with minor seasonal changes. High levels of dissolved solids were observed especially in the deep aquifer but the quality of water was poor even in background samples. The impact of gasification does have small variation in already unusable water in the deep aquifer which was also characterized by low hydraulic conductivity. Higher hydraulic conductivity values were established in the shallow aquifer. No significant groundwater chemistry change was detected in this aquifer as a result of gasification process.
Groundwater circulation and hydrogeochemical evolution in the coastal zone of Xiamen, southeast China	Y	Li	China	2023	groundwater flow, Hydrogeochemical evolution, Seawater Intrusion
Abstract This study aims to investigate the groundwater circulation and hydrogeochemical evolution in the coastal zone of Xiamen, southeast China, which can provide a reference for the development of water resources and the protection of soil and water environment in the coastal areas. A close connection between mountains and the sea characterizes the southeast coast of China. Although rainfall is abundant, the topography limits it, and water resources quickly run into the sea. Coupled with a concentrated population, water is scarce. In addition, this area’s water and sediment environment are influenced by human activities and geological conditions. Its changing trend also needs further study. Therefore, using hydrochemical analysis, isotope technology, numerical simulation and other techniques, this study took Xiamen City on the southeast coast as an example to study the groundwater circulation and the environmental evolution of water and sediment. The results show that although the aquifer is thinner, there is still deep groundwater circulation, and the seawater intrusion range of deep aquifer is much further than that of shallow aquifer. In addition to geological causes, human activities have become the main factors affecting groundwater quality, especially nitrate and lead. The nitrate content even exceeds the content of the major ionic components. Introducing land-based pollutants has also contributed to declining seawater and sediment quality in the Bay area. In general, the main pollutants in coastal areas include nutrients, heavy metals and new pollutants.
Groundwater dependency and the plight of Loeriesfontein	Dale	Barrow	Northern Cape	2015	mini-wellfield, mixing model
Abstract The town of Loeriesfontein, situated in the northern Cape, is entirely groundwater dependent, and is currently facing a serious water shortage. Low rainfall and the lack of storm events have resulted in groundwater levels dropping drastically. The current supply boreholes have been over abstracted and cannot meet the required demand. Water levels are close to pump depth for some of the municipal boreholes, and yields are decreasing. The town at one stage was trucking in water in order to supply its residents. Additional supplies are therefore urgently required. A number of measures were implemented to monitor and manage the current demand and the limited supply. Thereafter GEOSS investigated the occurrence of groundwater within a 20 km radius of Loeriesfontein, and found that dolerite represents the primary target formation for groundwater exploration. Groundwater occurrence is found at the lower dolerite contact with the host rock, or in fractures in the dolerite itself. Based on an extensive hydrocensus, geophysical surveys, drilling and yield testing, the Rheeboksfontein area was identified as a suitable water source. Initially water was being trucked into Loeriesfontein from Rheeboksfontein and later an innovative arrangement of solar driven borehole pumps and reservoir pumps resulted in water being transported much closer to Loeriesfontein, reducing the transportation distances and costs. During this first Phase of exploration the projected supply still did not meet the water demand and water quality targets. A number of high yielding boreholes were drilled, however the water quality was such that it would have required treatment and disposal of brine in that area is problematic. The extent of the exploration was then increased to a distance of 40 km from Loeriesfontein. A detailed hydrocensus was completed, followed up with further geophysical surveys, drilling and yield testing. Successful boreholes were drilled and the required demand and water quality standards could just be met. This finding is being verified with numerical modelling. A process is underway to develop a mini-wellfield and then the environmental processes are being followed so that a pipeline can be built delivering water directly into the reservoirs at Loeriesfontein. On-going monitoring and maintenance is crucial to the long-term success of the groundwater supply.
Groundwater development for Municipal water supply in response to drought of 2015 to 2019.	Dale	Barrow	Western Cape	2019	Drought, TMG
Abstract The geographic positioning of the Western Cape results in a Mediterranean climate - receiving majority of its rainfall during the winter months. A demand on the water supply throughout the year is typically met by storing water from winter rainfall in large dams. The Western Cape experienced a significant drought between 2015 and 2019. As a result, the supply dams have not been filled to capacity and drastic water restrictions had to be implemented. In the search for alternative water sources, groundwater exploration became a priority. Groundwater development projects were implemented rapidly in attempt to alleviate the implications caused by severe water restrictions and ultimately prevent running out of water. As a local groundwater institution, GEOSS got involved in several fast-tracked groundwater development projects for Department of local government, local municipalities, as well as other industrial and agricultural corporations. For obtaining the required water volumes, alternative measures were implemented. Previously under developed aquifers were targeted. In certain instances, in order to target the Table Mountain Group Aquifer (TMG), horizontal exploration drilling was conducted. The results of exploration and drilling yielded valuable learnings in terms of relevant hydrostratigraphy within the study areas. Additionally, there were learnings in terms of managing projects of this nature. In fast-tracked projects, careful management of the contractors, data collation (and storage) and public perception is critical to the success of the project. In this paper on water supply development for Municipalities, the various components of groundwater development are detailed along with relevant learnings from the recent emergency drought response measures.
Groundwater discharge and climate change: The application of RCMs to assess long-term effects of climate change on spring flow along the Apennines	Tommaso	Casati	Italy	2023	Climate change, downscaling, forecasting, GCMs, groundwater discharge
Abstract Global warming affects atmospheric and oceanic energy budgets, modifying the Earth’s water cycle with consequent changes to precipitation patterns. The effects on groundwater discharge are still uncertain at a global and local scale. The most critical step to assess future spring flow scenarios is quantifying the recharge-discharge connection. This research aims to predict the long-term effects of climate change on the discharge of seven main springs with long hydrologic series of discharge values located in different hydrogeological settings along the Apenninic chain (Italy). The investigated springs are strategic for either public water supply or mineral water bottling. The Apennines stretch along the Italian peninsula in a Northwest-Southeast direction, crossing the Mediterranean area that represents a critical zone for climate change due to a decreased recharge and increased frequency and severity of droughts over the last two to three decades. In this communication, the data of one of the chosen springs, called Ermicciolo (42°55’25.8”N, 11°38’29.5”E; 1020 m ASL), discharging out from the volcanic aquifer of Mount Amiata, are presented. Statistical and numerical tools have been applied to analyse the time series of recharge-related parameters in the spring’s contribution area and the spring discharge from 1939 to 2022. To estimate the impact of climate change on the Ermicciolo’s outflow, a regional atmospheric circulation model has been downscaled to the spring catchment area and used to derive the expected discharge at the 2040-2060 time span, according to the build-up data-driven model of the recharge-discharge relationship in the past.
Groundwater fingerprinting for identifying potential project risks	Meris	Mills		2015
Abstract Implementation of a mining project in South Africa involved dewatering of a fractured rock aquifer at considerable depth below ground level. Groundwater quality within this aquifer is not suitable for domestic use due to high levels of salinity. Numerous geological investigations in the area indicate that the target aquifer is confined, with a different piezometric head to the shallower aquifers. However, regulators and other interested and affected parties expressed concern regarding the potential mixing of more saline groundwater from the deeper aquifer to be dewatered with groundwater from shallower aquifers, which are extensively used for farming and domestic purposes. A large database of groundwater quality monitoring data collected over 16 years was available to investigate the degree of mixing between the deeper more saline and shallower freshwater aquifers. The groundwater chemistry of selected boreholes with known geological profile, depth and construction was used to develop groundwater fingerprinting criteria for each of the aquifers in the area. These fingerprinting criteria were then applied to private and exploration boreholes in the area in order to identify the main aquifer from which groundwater was being sourced. Once the boreholes were classified in terms of groundwater origin, an attempt was made to identify indicators of mixing with deeper, more saline groundwater from the aquifer being dewatered. Groundwater fingerprinting allowed identification of impacts related to the mining operations. The data showed that there was no upward mixing of water related to dewatering operations, but rather that surface spillages and disposal schemes may have resulted in minor changes in shallow groundwater quality. {List only- not presented}
Groundwater flow paths dictate terrestrial carbon inputs into a groundwater-dominated stream	Y	Xie	China	2023	Groundwater discharge; groundwater flowpaths; dissolved carbon; environmental tracers
Abstract Groundwater discharge is crucial for transporting terrestrial carbon into streams and rivers, but the effects of groundwater flow paths on terrestrial carbon inputs are poorly understood. Here, we investigated environmental tracers (EC, Cl-, 2H, 18O, 220Rn, and 222Rn) and carbon concentrations in riparian groundwater, streambed groundwater, and stream water over six groundwater-stream monitoring sites. Significantly high 220Rn and 222Rn activities in the stream and endmember analysis results of the environmental tracers reveal that vertical groundwater discharge from the streambed (VGD) and lateral groundwater discharge from the riparian zone (LGD) is of equal importance for the stream. We quantified VGD by modelling the detailed 222Rn and Cl- profiles at the streambed and then combined differential flow gauging to estimate LGD. VGD (2.9 ± 1.4 m2 d-1) prevailed in relatively wide and shallow channels, while LGD (2.6 ± 2.6 m2 d-1) dominated narrow and deep channels. Carbon measurements indicate that LGD had the highest CO2, CH4, DIC, and DOC, while VGD had relatively higher CO2 but lower CH4, DIC, and DOC than stream water. Our findings suggest that LGD is the primary carbon source for the stream, while VGD mainly dilutes the stream (except CO2). Finally, we observed that groundwater discharge and temperature overrode metabolism in controlling stream carbon dynamics, implying the importance of groundwater discharge for understanding stream carbon cycling. Overall, this study identified the impacts of groundwater flow paths on carbon exchanges between terrestrial and stream ecosystems.
Groundwater for people and the environment: A globally threatened resource	H	Loaiciga		2023	Groundwater, groundwater sustainability, overdraft, population growth, recharge, safe yield
Abstract Groundwater is an essential source of water worldwide. The increased reliance on groundwater has caused the mining of many aquifers, a situation compounded by climate change, rising surface-air temperature, declining precipitation, and reduced groundwater recharge in many regions. The global annual intensity of groundwater use rose from 128 to 155 m3 per capita between 1950 (when the world population was 2.5 billion people) and 2021 (when the population was 7.9 billion people) and is herein projected to rise to 178 m3 per capita by 2050 as the world’s population is projected to increase (to 9.7 billion people by 2050) throughout the rest of the 21st century and beyond. This study projects a global annual groundwater depletion of 1,008 km3 by 2050, representing a 256% rise from the estimated 2010 depletion. This projection is most likely a lower bound of the actual groundwater depletion that would be realized considering environmental flows, historical trends of global economic growth, and climate-change impacts, thus being a harbinger of rising environmental degradation (e.g., land subsidence, seawater intrusion, streamflow reduction, aridification). Measures to achieve groundwater sustainability are herein identified.
Groundwater governance: where science, economics and politics meet	Nicolette	Vermaak		2015	groundwater governance
Abstract POSTER Researching a subject on the internet the slogan "Water flows upstream to money" popped up. The context was drought, and the meaning clear. If politics come into play as well, it would seem that science is relegated to a distant third place. The proclamation of the National Water Act, of 1998 (Act 36 of 1998), recognized the importance of groundwater and its role in the hydrological cycle and water supply issues. Groundwater governance has grown since then and is becoming increasingly important. One of the most important tenets on which groundwater based is the concept of sustainability. Various definitions of sustainability is used with the best know being "?development which meets the needs and aspirations of the present generation without compromising the ability of future generations to meet their own needs." Even though the basic understanding of sustainability may have been around for much longer than the term, it is the application of the theory in our current context that present us with challenges. Concepts like the precautionary principle, corporate governance and other buzz words that is being used does not always ensure good groundwater governance. One of the greatest problems is often the lack of scientific understanding and knowledge. Groundwater systems tend to be more complex and thus more difficult to manage than surface water. Understanding how groundwater and surface water interact, and that it is actually a linked water resource adds to the complexity. Add to this its importance in the functioning of groundwater dependent ecosystems that is still poorly understood. This article will look at principles for good groundwater governance and the tools that are needed to achieve it. It will finally look at real case studies where scientific considerations fall by the wayside for the requirements of the economy and political goals.
Groundwater models for water resources assessment at regional, local and site scales	V	Price	England	2023	England, Groundwater/surface-water relations, numerical modelling, scale, water-resources Management
Abstract For 25 years, the UK’s Environment Agency has commissioned groundwater flow models of the main aquifers in England. These regional-scale models are regularly updated, occasionally recalibrated and used for water resources management, regulatory decisions and impact assessment of groundwater abstractions. This range of uses requires consideration of the appropriate scale of data collection and modelling and adaptation of the groundwater models, with refinement where local impacts on individual springs and seasonal streams are considered and combination and simplification for strategic national water resources planning. The Cretaceous Chalk, a soft white limestone, is the major aquifer of southern and eastern England, supplying up to 80% of the drinking water in this densely populated region. Springs and baseflow of good quality groundwater feed Chalk streams, which are a rare and valuable habitat with a high public profile, but face significant challenges in the 21st century, worsened by climate change and population growth. The modelling informs strategic planning and regulatory decisions, but the model’s scale needs to be appropriate for each issue. The presentation defines these issues and presents examples, ranging from the large-scale, strategic Water Resources East to impact assessment for individual groundwater abstractions and more bespoke local investigations, including simulation of groundwater flood risks. As the scale of investigations reduces, there is increasing importance on the accuracy of information, both temporally and spatially. Model refinement made during local investigations can be incorporated into larger-scale models to ensure that this understanding is captured.
Groundwater monitoring of South Africa through numerical model	Akhona	Maqhubela	Sutherland	2021	Monitoring, numerical modelling, GRACE, SG measurements, MODFLOW, SAGOS
Abstract Monitoring groundwater storage is conducted in the study. World Health Organisation estimates, about 55 million people affected by drought yearly. However, Surface water holds 0.3 percent of the freshwater, and groundwater holds 30.1 percent of the freshwater. Hence, monitoring groundwater storage is vital. Though the GRACE (Gravity Recovery And Climate Experiment) satellite provides global-scale groundwater data, but does not provide any information about changes in groundwater flow systems and has uncertainties, due to large noise produced. A correlation has to be established between gravity changes and groundwater storage variations through a program that simulates the flow of groundwater. The relationship between developed numerical models and data derived from superconducting gravity is imperative. This study is conducted in South African Geodynamic Observatory Sutherland (SAGOS) area at Sutherland, South Africa. The study aims to develop a numerical geohydrological model to monitor subsurface variations in water distribution through superconducting gravimeters (SG) records. The interpretation of the SG measurements to directly compare to one another at a higher resolution is considered in the study, through the correlation of the developed model and installed superconducting gravimetric residual data. A numerical groundwater flow model is developed using model muse on MODFLOW. Assigned boundary conditions, fractured rocks were activated by the model. Hydraulic conductivities were simulated for any layer, including storage coefficient. Hence, hydraulic conductivity is an important aspect of the study. In conclusion, gravity is an excellent tool for measuring groundwater recharge within the immediate vicinity of the SAGOS. This implies that gravity can aid in monitoring groundwater recharge and discharge in semi-arid areas. The application of the hydrological model at various scales comparing the Superconducting Gravimeter and GRACE satellite data is paramount to improve modelling groundwater dynamics. The consideration of developing numerical hydrological to monitor groundwater storage will add much value to missing information.
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.
Groundwater porosities and effective porosities: definitions, physical relevance, and scale issues	Alain	Dassargues	Belgium	2023	REV, drainage effective porosity, effective porosity, porosity, scale issue, transport effective Porosity
Abstract Porosity describes the ratio between the volume of pores, cracks, and fissures and the total volume of a studied geological medium. This notion implies a volume averaging of the medium characteristics using the concept of Representative Elementary Volume (REV). Small volumes can contain only pores, while larger volumes typically contain both pores and fissures. Porosity can be highly scale-dependent, and different porosity values can be measured for the same geological formation. Furthermore, groundwater in the pores and cracks can be partly immobile or mobile. So, the porosity actively involved in groundwater flow can be discussed. A ‘mobile water porosity’ can be defined, but this remains highly dependent on the existing pressure conditions in the geological medium. In unconfined conditions, the term ‘effective porosity’ usually corresponds to the drainage porosity corresponding to the specific yield or storage coefficient. When dealing with solute transport and remediation of contaminated sites, another ‘effective porosity’ is needed to describe the advection velocity of the contaminant. This ‘mobile water porosity’ acting in solute transport processes typically takes lower values than drainage’s ‘effective porosity’. Scale issues must also be expected, as shown by field and lab tracer tests. The term ‘Darcy velocity’ will be banished herein because it induces much confusion. For clarity, we propose to distinguish ‘drainage effective porosity’ and ‘transport effective porosity’. The physical meaning of both terms is discussed, and examples of supporting observations are presented for illustration and discussion.
Groundwater potential and lateral connectivity of the Limpopo sand river system mitigating water scarcity and salinity in semi-arid Mozambique	P	Saveca	Mozambique	2023	Limpopo, aquifer connectivity, groundwater potential, salinity mitigation, sand river, semi-arid regions
Abstract In this study, we assess the potential of large riverbed aquifers in semi-arid Africa, known as sand rivers, to mitigate water scarcity and salinity for multiple-use water supply through a case study of the Limpopo River in Mozambique. Such sand river systems are widespread and still heavily underused at a regional scale, particularly in Mozambique, with the riparian vegetation currently being the primary user, though only consuming a minor fraction of available water. At a local scale, we performed geoelectrical surveys, water level measurements (in river and groundwater), as well as field physicochemical measurements and hydrochemical and isotopic sampling at 38 locations in the river channel, margins and up to 6 km away from the river, over five years. Results show that these shallow systems can be up to a kilometer wide and 15 m thick and, at some locations, can extend laterally beyond the river channel, below thin layers of clay and silt. Large areas of the sand river channel carry runoff yearly, providing optimal conditions for rapid recharge into the coarse sands with a high storage capacity. Connectivity between the river margin and channel is clearly shown at the local scale, even though sand pockets located further away appear isolated (revealed by geophysics), isotopically different and more brackish. Recharge, evapotranspiration and mixing processes are confirmed through hydrogeochemical modelling. The proven connectivity is highly relevant as groundwater is abstracted locally, promoting socio-economic development in water-scarce regions.
Groundwater recharge in sub-humid drylands under different agricultural systems	D	Mudimbu	SADC (Malawi, Zambia, Zimbabwe)	2023	groundwater recharge, basement aquifers, Southern Africa Development Community (SADC
Abstract Groundwater is a strategic long-term water resource used by an estimated 70% of the populations in sub-Saharan Africa for drinking, irrigation and a wide range of economic activities. Understanding groundwater recharge processes is key for effectively using and managing water resources. Very few studies have used direct groundwater observations to assess the impact of different farming systems on groundwater recharge processes. This study focused on assessing basement aquifer recharge in 4 instrumented catchments in Malawi (Chitedze), Zambia (Liempe and Kabeleka) and Zimbabwe (Domboshawa) within the SADC region between 2019-2022. Employing a range of methods, including direct field observations (groundwater hydrographs, precipitation data, stable isotopes, chloride mass balance and residence time tracer data), we quantify the amount of groundwater recharge as well as the timing and nature of recharge processes under both conservation and conventional tillage systems in these four study sites. Groundwater recharge was measured in most years across the study sites. The study reveals the strong climate controls on seasonal groundwater recharge volumes, the influence of low permeability layers in the unsaturated zone, and the likely magnitude of impact from different farming practices. Groundwater residence times are high (i.e. low fractions of modern recharge, interquartile range 1-5%, n=46), even in shallow piezometers, suggesting these unpumped systems may be highly stratified. The results provide an evidence-based suite of data that reveals much about key controls on groundwater recharge in basement aquifers in sub-humid drylands and will inform the development and management of such groundwater systems.
Groundwater resource assessment and delineation of resource unit for the Komati catchment within the Inkomati Usuthu Management Catchment area – Mpumalanga Province, South Africa	Collen	Monokofala	South Africa	2023	Catchment scale integrated surface water and groundwater studies
Abstract The recent uncertainties in rainfall patterns have resulted in shortages in the availability of water resources, posing significant risk to the sustainability of all living organisms, livelihoods and economic prosperity. The fact that hidden groundwater resources in semi-arid regions present a challenge to understanding and managing the resources. Various groundwater studies have been undertaken; however, the quantification is generally over-simplified due to a limited understanding of the groundwater flow regime and consideration being mostly given to water supply. Thus, the data is often not comprehensive enough and generally limited in determining how much groundwater is available to supply rural areas. The Komati catchment area is dominated by coal mining in the upper reaches and irrigation and agriculture in the lower reaches, with human settlements competing for these water resources. Five significant dams in the Komati catchment are constructed to deal with the increasing water demand for commercial agriculture in the region. However, given uncertain weather patterns, the water mix approach is imperative. This study focused on understanding the groundwater potential, characterised the aquifer system, delineated the groundwater resource units, quantified baseflow and calculated the groundwater balance that can be used as a guide for the groundwater management protocol for the catchment area. The box model approach (surface-groundwater interaction) was used to characterize the groundwater regime and understand the spatial distribution of the aquifer types, water quality and significant aquifers of interest to protect this important resource.
Groundwater resources of the Danakil Depression – hydrogeology in the hottest place on Earth	L	Towers	Umvoto	2023	Danakil Depression, Alluvial aquifer, potash, rift basin, solution mining
Abstract he Danakil Depression of the Afar Rift forms part of the north/south-trending Ethiopia-Eritrean arm of the East African Rift System, whereas the western margin of the depression forms part of an active plate boundary between the western Nubian and eastern Danakil tectonic blocks. Dallol (within the Danakil Depression) currently holds the record for the highest average temperature for an inhabited place on Earth, with annual average temperatures of ~35-36°C. The isolated area was initially explored geologically in the late 1960s, with recent geological and hydrogeological interest in its northeast Ethiopian portion due to easier access, geo-tourism and potash-ore exploration. Potash mining is proposed via solution-extraction techniques, requiring large volumes of water in one of the driest hyper-arid regions. Various hydrogeological investigations were therefore conducted between 2014 and 2016 as part of a feasibility and water resource study towards developing a water resource estimate for the region and proposed mining operations. Alluvial fans on the west side of the rift basin form a major, regional primary aquifer – fan boreholes have yields of 50 litres per second, although groundwater is highly saline (up to 3-5 times the salinity of seawater) and can reach temperatures of 50°C. Groundwater yields of hundreds of millions of cubic metres per annum are potentially available from the saline alluvial fan primary aquifers for potash solution mining. In contrast, groundwater from karstic limestone aquifers could provide a freshwater resource to settlements within the Lelegheddi River basin and the Danakil.
Groundwater transport modelling: A fractional/fractal perspective	Amy	Allwright		2019	modelling
Abstract The complexity of real world systems inspire scientists to continually advance methods used to represent these systems as knowledge and technology advances. This fundamental principle has been applied to groundwater transport, a real world problem where the current understanding often cannot describe what is observed in nature. There are two main approaches to improve the simulation of groundwater transport in heterogeneous systems, namely 1) improve the physical characterisation of the heterogeneous system, or 2) improve the formulation of the governing equations used to simulate the system. The latter approach has been pursued by incorporating fractal and fractional derivatives into the governing equation formulation, as well as combining fractional and fractal derivatives. A fractal advection-dispersion equation, with numerical integration and approximation methods for solution, is explored to simulate anomalous transport in fractured aquifer systems. The fractal advection-dispersion equation has been proven to simulate superdiffusion and subdiffusion by varying the fractal dimension, without explicit characterisation of fractures or preferential pathways. A fractional-fractal advection-dispersion equation has also been developed to provide an efficient non-local modelling tool. The fractional-fractal model provides a flexible tool to model anomalous diffusion, where the fractional order controls the breakthrough curve peak, and the fractal dimension controls the position of the peak and tailing effect. These two controls potentially provide the tools to improve the representation of anomalous breakthrough curves that cannot be described by the classical-equation model. In conclusion, the use of fractional calculus and fractal geometry to achieve the collective mission of resolving the difference between modelled and observed is explored for the better understanding and management of fractured systems.
Groundwater trend analysis at an active underground coal gasification plant	L	Mokhahlane	Johannesburg, South Africa	2023	underground coal gasification, gasifier, groundwater risk assessment model, spent georeactor
Abstract Underground coal gasification (UCG) is a high-temperature mining method that gasifies coal in situ to produce a synthetic gas that can be used as feedstock for industrial purposes. Coal conversion leads to mineral transformation in the gasifier, which ultimately interacts with the rebounding groundwater post-gasification. This poses a groundwater contamination risk, the biggest environmental risk from a UCG geo reactor. There is currently no model for UCG operators and regulators to assess the total risk of groundwater contamination from UCG operations. This study collates literature on groundwater contamination from UCG operations and presents a workable but comprehensive groundwater risk assessment model for a spent UCG chamber. The model follows the source-pathway-receptor arrangement where groundwater contamination sources are identified as ash, char, roof and floor. All possible pathways are assessed for hydraulic connections with the spent geo-reactor via acceptable geochemical tests, including stable isotopes, hydrochemistry and stratification analysis. Finally, the receptor aquifers (e.g. shallow aquifers) are monitored periodically to determine if contamination has occurred.
Groundwater-dependent ecosystem dynamics in transboundary aquifer settings - a case study in the Tuli-Karoo aquifer	Kwazikwakhe	Majola	South Africa	2023	Groundwater-Dependent Ecosystem, Interactions, Transboundary aquifer
Abstract Knowledge of the nature and extent of groundwater-dependent ecosystems (GDE) at an aquifer scale enables incorporating ecological water requirements in integrated groundwater resource management activities, including transboundary aquifer cases (TBA). This way, sustainable groundwater management and functional ecosystem services can be achieved. Therefore, understanding groundwater- ecosystems-surface water interactions is crucial for assessing resources’ resilience or susceptibility towards certain impacts. Unfortunately, this subject is widely under-researched with fragmented information, especially in southern Africa. This study was thus initiated to understand groundwater processes controlling the maintenance of Tuli-Karoo TBA (Botswana, South Africa, Zimbabwe) GDEs towards developing a model that can be utilised in impact assessments, especially in climate change. The employed approach included stable isotope analysis (mainly 2 H and 18O) for groundwater, streams, springs, rainwater, vegetation, and soil; spatial imagery and GIS classification (incl. NDVI, NDRE, NDWI); and plant moisture stress techniques. Identified GDEs in the study area (characterized by intergranular alluvium aquifer underlain by the Karoo sandstone of intergranular and fractured secondary aquifer type) are riparian vegetation, floodplain and depression wetlands, and springs. Precipitation recharged alluvium aquifer’s contribution to Limpopo River baseflow is negligible as the discharge is mainly through springs and evapotranspiration. Monitoring data scarcity and skewed availability among sharing countries hamper research and its output applicability to TBA’s entirety. Therefore, data generation, exchange, and joint databases development are crucial for sustainable comanagement of groundwater and supported ecosystems and science-based decision-making.
Groundwater/Wetland Interactions In A Coastal Aquifer In The Eastern Cape Province Of South Africa.	Desmond	Visser	Eastern Cape	2013	Groundwater, coastal wetland, coastal aquifers, aquifer, surface water
Abstract This study, near Thyspunt between St. Francis and Oyster Bay in the Eastern Cape Province of South Africa, focused on identification and quantification of surface water–groundwater links between the mobile Oyster Bay dune field and the coast. The specific objective was to establish the extent to which important wetlands such as the Langefonteinvlei and the numerous coastal seeps along the coast are directly or indirectly dependent on groundwater as their main water source. A further objective was to establish the extent to which any of the coastal seeps derive their water from the Langefonteinvlei, and are thus interdependent on the integrity of this system. The study also investigated the contribution of the Algoa and Table Mountain Group aquifers to these wetlands. The monitoring network established as part of this study focused on unpacking the interrelationships between surface and groundwater flows, aquifer hydrochemistry and wetland function, as related to the Langefonteinvlei and the coastal seeps in particular. Results indicate that the Langefonteinvlei is fed by groundwater flowing from the mobile Oyster Bay dune field in the north and the water divide in the northeast, which emerges at the foot of the high dune in the north and northeast of the wetland. However, the majority of the vlei area is ‘perched’ above the local water table on a layer of organic-rich sediment. The coastal springs located southwest and west of the Langefonteinvlei are not fed by water from the Langefonteinvlei. They emerge near the coast, where the bedrock lies close to the surface, and are fed by groundwater draining directly from the Algoa and Table Mountain Group aquifers to the Indian Ocean.
HALF FULL OR HALF EMPTY ? Groundwater surface water interactions – An ever-increasing focus for water resource management.	Sonia	Veltman	South Africa various	2021	Gw-Sw interaction, wellfield testing, resource management, numerical model
Abstract More often these days we hear concerns from water users regarding “how much water is the newly drilled borehole of a neighbor extracting from “their” river water”. These are serious question with serious repercussions for sustainable use and economic development. No one wants to lose what they have invested in. On the other hand, from a groundwater perspective, this is very one sided. Numerical modelling solutions are often proposed to clients as a more accurate method of determining the groundwater surface water interaction, with the addition of volumes removed from the modelling domain, to present to decision makers the changes in volumes of discharge into streams or volumes of infiltration of stream water into the aquifer. However, this is an expensive and time-consuming exercise, and will most likely incur additional costs to accumulate sufficient meaningful data sets for input into these detailed models. A robust combination of analytical and numerical solutions is proposed, while keeping aquifer assumptions conservative, where a lack of regional data exist. This is useful in quantifying this interaction and associated volumes better without the full time and cost associated with calibrated regional flow and transport models. Analytical calculations assist in the quantification of the aquifer’s hydraulic and physical properties and is used to conceptualize flow better and determine the inputs for a conservative well field scale numerical model, in which the change in flow between groundwater and surface water system are also evaluated. The well field scale model is calibrated in a fraction of the time as a conventional flow model (less than 20%), while volumes derived is defendable and based on measurable data. This combination is viewed to be a critical step in providing time effective solutions
Harmonized groundwater data in International River Basins under the Water Framework Directive (2000/60/EC) – Challenges	Belinda	Flem	Norway	2023	Harmonized data; monitoring; sampling techniques; analysis
Abstract Transboundary aquifers in Europe are managed according to the Water Framework Directive (WFD) through international river basin districts (IRBD) management plans. Paragraph 11 in the WFD states that each Member State shall ensure the establishment of a programme of measures, PoM, for each river basin district, RBD, or part of an IRBD within its territory. Easy access to harmonized data from neighbouring countries part of the aquifer is essential to analyse the groundwater status and make proper PoMs. The datasets must be available in machine-readable format via an Application Programming Interface (API) and, where relevant, as a bulk download. The metadata describing the data shall be within the scope of the Infrastructure for Spatial Information in the European Community (INSPIRE) data themes set. The datasets must also be described in a complete and publicly available online documentation describing the data structure. Using a questionnaire survey of nine European countries, groundwater sampling and analysis routines are compared to evaluate if data are comparable and accessible across borders.
High Resolution Site Characterisation (HRSC) In South Africa: Challenges, Successes And Lessons Learned	Samuel D	Mohr		2015
Abstract Inadequate characterization of contaminated sites often leads to the development of poorly constructed conceptual site models and consequently, the design and implementation of inappropriate risk management strategies. As a result, the required remedial objectives are not achieved or are inefficient in addressing the identified risks. Unfortunately, it is all too common to find remedial intervention strategies that run for lengthy periods of time at great cost while generating little environmental benefit due to inadequate characterization of site conditions. High resolution site characterization (HRSC) can provide the necessary level of information to allow for development of rigorous conceptual site models, which can be used to develop and implement appropriate risk management solutions for environmental problems. At the outset, the HRSC approach generally has comparatively higher costs than traditional state-of-the-practice assessment methods. However, the project lifecycle costs can be substantially reduced due to development of optimal risk management strategies. In developing countries where there is a lack of legislation relating to soil and groundwater contamination or, a lack of enforcement of legislation which is present, the long-term liabilities related to contaminated sites are often not immediately apparent to the parties responsible for the sites. This often creates a reticence to employ HRSC techniques due to their increased cost, especially when much of the technology must be imported on a project specific basis from either Europe or the United States. The Authors provide information from several case studies conducted in South Africa where HRSC techniques have been employed to gain a greater understanding of subsurface conditions. Techniques employed have included surface-based geophysical techniques such as electrical resistivity tomography (ERT) and multi-channel analysis of seismic waves (MASW), passive soil gas surveys, deployment of Flexible Underground Technologies (FLUTe?) liners, diamond core drilling, fluid electrical conductivity profiling, downhole geophysical logging tools, the Waterloo Advanced Profiling System (APS), and the use of field laboratories. Several of the techniques required importing equipment and personnel from Europe or the US, and in several case studies, were a first to be employed in South Africa, or the continent of Africa for that matter. The Authors present data obtained using the HRSC techniques from the case studies and elaborate on how the information obtained was used to drive effective decision making in terms of managing long term environmental risks at the various sites, which has been positively embraced by local clients. The authors also highlight key challenges in conducting HRSC investigations in an emerging market context.
High Resolution Site Characterisation Assessment Of A Chlorinated Solvent Plume In A Shallow Unconfined Aquifer	Kate	Naude		2015
Abstract Identifying and characterising the vertical and horizontal extent of chlorinated volatile organic compound (CVOC) plumes can be a complex undertaking and subject to a high degree of uncertainty as dense non-aqueous phase liquid (DNAPL) movement in the subsurface is governed most notably by geologic heterogeneities. These heterogeneities influence hydraulic conductivity allowing for preferential flow in areas of higher conductivity and potential pooling or accumulation in areas of lower conductivity. This coupled with the density-induced sinking behaviour of DNAPL itself and the effects of groundwater recharge in the aquifer result in significant challenges in assessing the distribution and extent of CVOC plumes in the subsurface. It has been recognized that high resolution site characterization (HRSC) can provide the necessary level of information to allow for appropriate solutions to be implemented to mitigate the effects of subsurface contamination. Although the initial cost of HRSC is higher, the long-term costs can be substantially reduced and the remedial benefits far greater by obtaining a better understanding of the plume characteristics upfront. The authors will discuss a case study site in South Africa, where ERM has conducted HRSC of a CVOC plume to characterise the distribution of the source area and plume architecture in order to assess the potential risk to receptors on and off-site. The source of impact resulted from the use of a tetrachloroethene (PCE)-based solvent in an on-site workshop. The following methods of characterization were employed: - Conducting a passive soil gas survey to identify and characterise potential source zones and groundwater impacts; - Vertical characterisation of the hydrostratigraphy, contaminant distribution and speciation in real time using a Waterloo Advanced Profiling System (APS) with a mobile on-site laboratory; - Using the Waterloo APS data to design and install groundwater monitoring wells to delineate the vertical and lateral extent of contamination; and - Conducting a vapour intrusion investigation including sub-slab soil gas, indoor and outdoor air sampling to estimate current risk to on-site employees. In less than a year, the risk at the site is now largely understood and the strategies for mitigating the effects of the contamination can be targeted and optimised based on the information gained during the HRSC assessment.
Highly productive geophysical mapping of groundwater systems in water-scare countries	D	Grombache	Africa	2023	Geophysics, Groundwater, Hydrogeology, transient electromagnetics
Abstract Groundwater is a hidden resource, so as part of making it more visible, geophysical methods can be very useful in inferring the delineation of aquifers and/or more productive zones to target in fractured rock environments. The most commonly used techniques to assist groundwater studies or exploration are still resistivity profiles or sections known as ERT or electrical resistivity tomography and vertical electrical soundings or VES. One of the limiting factors with this technique is the scale of what surveys can be conducted, resulting in, at best, some kilometers per day. The Hydrogeophysics group of Aarhus University have developed the towed transient electromagnetic (tTEM) system as a cost-efficient tool for characterizing regional hydrological systems to depths of up to 70 m as an alternative to these more traditional methods - which is highly productive in that collection of 40- to-80-line kilometers of data per day is feasible. The system is based on the transient electromagnetic (TEM) method, which involves using a transmitter and receiver coil to measure the electrical resistivity of the subsurface. The hydrological value in electrical resistivity images stems from the ability to delineate different hydrogeological units based on their contrasting electrical properties. Consequently, 3D electrical resistivity images can infer the subsurface hydrogeology and enhance the success of installing productive boreholes. This work presents case studies from several African countries (e.g., South Africa, Zimbabwe, Ethiopia, Senegal, and Togo). It demonstrates how the tTEM method can identify reliable drinking water sources in these countries.
How Good Is Your Consultant? A Laymens’ Guide To Critically Assessing Consultants	ME	Convery	National	2013	Consultant
Abstract With increasing focus on wasted expenditure within local government and recent media reports on the money spent on poor quality service, it is becoming progressively important for those in a position of engaging consultants, either for groundwater supply or environmental work, to have confidence in the company or person they have employed. This paper focuses on how to assess consultants before they walk through the door based on qualifications, CVs, professional registrations and previous work experience. It goes through the project lifestyle, explaining in a non- technical fashion the different processes involved in a groundwater supply or groundwater contamination assessment and provide simple indicators of good practice that should be evident in the consultant's work. Topics covered include assessing proposals, gathering background information, health and safety, appointing sub-contractors, data quality, the use of appropriate published procedural guidelines, the use of relevant quality guidelines and what deliverables should be provided.
How Ground Gets Wet: Physical Experiments Of Variably Saturated Flow	Matthys A	Dippenaar	National	2019	saturated flow
Abstract Hydrogeology no longer only relies on understanding of phreatic systems. Highly heterogeneous and anisotropic conditions in soil and rock comprising intergranular, fractured and karstic porosity affect groundwater vulnerability, recharge rates, drainage and dewatering practices, soil corrosivity, natural attenuation of contaminants, and integrity of infrastructure, to name a few examples. Movement of water at partial and highly variable saturation is very complex, depending on very small-scale variations in ground conditions as well as very subtle changes in moisture content. In contributing to this, a number of research projects were conducted, focused around physical experiments in the laboratory or mimicked in the field, and subjected to differing conditions pertaining to gravitational acceleration to scale the vertical dimension. Studies contribute to flow mechanisms and flow regimes of variably saturated soils and rocks, as well as the interface between, and link available theoretical understanding and empirical approaches to physical experiments and field verification experiments. Where possible, hydraulic parameters are estimated to improve the quantification of said parameters at discreet scale rather than assuming single values for bulk systems. Obvious limitations and assumptions are understood to the extent that updated flow scenarios are proposed to contribute to variably saturated flow systems. Behaviour is inferred for fractures of changing orientation, changes in medium from soil to rock, and for alternation between wetting and drying of different media. Selected experiments will be presented to highlight novel findings and the way forward
How alluvial storage controls surface water – groundwater interactions in dryland intermittent and ephemeral streams: A case study from semi-arid Australia	M	Zarate	Australia	2023	Groundwater, groundwater recharge, drylands, ephemeral streams, focused recharge, intermittent, semi-arid, streamflow, surface water, water balance
Abstract Water balance partitioning within dryland intermittent and ephemeral streams controls water availability to riparian ecosystems, the magnitude of peak storm discharge and groundwater replenishment. Poorly understood is how superficial geology can play a role in governing the spatiotemporal complexity in flow processes. We combine a new and unusually rich set of integrated surface water and groundwater observations from a catchment in semi-arid Australia with targeted geophysical characterisation of the subsurface to elucidate how configurations of superficial geology surrounding the stream control the variability in streamflow and groundwater responses. We show how periods of stable stream stage consistently follow episodic streamflow peaks before subsequent rapid recession and channel drying. The duration of the stable phases increases in duration downstream to a maximum of 44±3 days before reducing abruptly further downstream. The remarkable consistency in the flow duration of the stable flow periods, regardless of the size of the preceding streamflow peak, suggests a geological control. By integrating the surface water, groundwater and geological investigations, we developed a conceptual model that proposes two primary controls on this behaviour which influence the partitioning of runoff: (1) variations in the permeability contrast between recent channel alluvium and surrounding deposits, (2) the longitudinal variations in the volume of the recent channel alluvial storage. We hypothesise optimal combinations of these controls can create a ‘Goldilocks zone’ that maximises riparian water availability and potential for groundwater recharge in certain landscape settings and that these controls likely exist as a continuum in many dryland catchments globally.
How can collective groundwater resource management solutions benefit water governance at various levels? An example in a volcanic watershed in East Java, Indonesia	E	Cut	Indonesia	2023	groundwater governance, district level, collective solutions, stakeholders, volcanic watershed, Java Indonesia
Abstract On the slopes of Mount Bromo, East Java (Indonesia), the land use of the Rejoso watershed is dominated by rice fields and sugarcane ( lowland area ), agroforestry (midstream) and horticulture and pine plantation in the upstream part. During the last three decades, some land changes driven by socio-economic development, with conversion of agroforests to rice fields, tree monoculture and horticulture, and the development of urban areas nearby, increased pressure on the watershed. Intensive irrigated rice cultivation is using groundwater from free-flowing artesian wells. Due to a lack of management, the hydraulic head and discharge of the major spring are decreasing. Rejoso watershed, like others in urban and rural areas in Indonesia, is facing challenges to guarantee sustainable integrated water resources management. Collective solutions have been implemented between 2016 and 2022 within this watershed. In the downstream, sustainable paddy cultivation and wells management with local stakeholders, aiming at improving water efficiency, have been piloted on 65 ha with 184 farmers. Water governance at the district level was re-activated and strengthened thanks to the project. Various capacity-building tools were used via radio talk shows and workshops. Members of the watershed forum of Pasuruan took some actions to reshape the structure and set up a roadmap. The implementation of collective solutions in the field was a real catalyst and serves all levels of water governance, as it is replicable. This example will be explained and illustrated after the presentation of the socio-hydrogeological context.
How groundwater temperature is affected by climate change: a systematic review and meta-analysis	Elena	Egidio	Italy	2023	Climate change, Groundwater, groundwater temperature, review, temperature
Abstract Groundwater (GW) is a target of climate change (CC), and the effects become progressively more evident in recent years. Many studies reported the effects on GW quantity, but of extreme interest is also the assessment of qualitative impacts, especially on GW temperature (GWT), because of the consequences they could have. This study aims to systematically review the published papers dealing with CC and GWT, to determine the impacts of CC on GWT, and to highlight possible consequences. Scopus and Web of Science databases were consulted, obtaining 144 papers. However, only 45 studies were considered for this review after a screening concerning eliminating duplicate papers, a first selection based on title and abstract, and an analysis of topic compatibility through examination of the full texts. The analysed scientific production from all five continents covers 1995-2023 and was published in 29 journals. As a result of the review, GWT variations due to CC emerged as of global interest and have attracted attention, especially over the past two decades, with a multidisciplinary approach. A general increase in GWTs is noted as a primary effect of CC (especially in urban areas); furthermore, the implications of the temperature increase for contaminants and groundwater-dependent ecosystems were analysed, and various industrial applications for this increase (e.g. geothermy) are evaluated. It’s evident from the review that GWT is vulnerable to CC, and the consequences can be serious and worthy of further investigation.
How to manage the Plitvice Lakes National Park (Croatia) as part of transboundary groundwater resources?	H	Meaški	Croatia	2023	Karstic water resources, Plitvice Lakes, Transboundary aquifer
Abstract The National Park Plitvice Lakes (NPPL) in the Republic of Croatia was declared in 1949 due to its exceptional natural beauty. However, in addition to its attraction, the NPPL also encompasses an area of significant karstic water resources in the Dinaric karst region, on the border between the Black Sea and the Adriatic Sea catchment. In some parts, groundwater connections to the Klokot Spring and Una River in Bosnia and Herzegovina have been assumed by hydrogeological research and proven by tracing tests, which confirm transboundary aquifer. Assessing transboundary aquifer systems already presents challenges in managing this area, considering not only the well-defined physical catchment. Therefore, comprehensive protection is necessary, which must reconcile people’s aspirations for spatial development with the sustainability of natural systems. Protecting karstic water resources can be achieved through separate analyses of the natural vulnerability of surface and groundwater and their integration into a comprehensive protection system. Protection should be layered through three levels: (1) protecting the area from the impact of the upstream catchment, (2) protecting surface water in the catchment that is most affected by anthropogenic influences, and (3) protecting the surrounding area from the impact of the NPPL, which with numerous visitors every year and tourist facilities, also represents significant pressure on downstream catchments. The ultimate goal is a scientifically based proposal for sustainable development of the protected area, in line with the needs of protection and spatial use, and based on an assessment of the overall risk to water resources.
Hydraulic Fracturing Of Coal Bed Methane In The Springbok Flats	Gerrit	van Tonder		2015
Abstract It is estimated that the three coal layers in the Springbok Flats contain about 5 TCF of coal bed methane (CBM). Two sedimentary basins, namely the southern Tuinplaas basin and the northern Roedtan basin, exist with coal layers with a total thickness of 7m which occurs mainly in three mayor seams. The coal layers are located between 20 m to more than 600m. Farmers in the Flats are concerned about the environmental impact of fracking the coal beds. They are mostly worried about the risk of groundwater pollution; the drawdown of the water table and the producing of a bad quality water during the mining process. They set up an EPA for the Springbok Flats in 2010 and until now, they have stopped more than 6 companies to conducted exploration (stopped strictly on account of the different laws in SA that were not adhered too). On average, 1000 liters of water is produced for every 2000 cubic feet coal bed methane mined in the USA. The quality of the produced water is not good (with typical Na values of more than 5 000 mg/l) and cannot be used for irrigation purposes. It is thus expected that about 500 million m3 of bad quality water will be produced for every 1 TCF mined in the Flats. This groundwater will be removed from the system and it is expected that a drawdown of up to 30m will be evident at places in the Springbok Flats. There are also a large number of dykes and faults in the Flats which imply that the upward movement of methane and water will be very probable after abandonment of each coal methane well.
Hydraulic Tests Of Strong Artesian Boreholes: Well-Head Construction And Test Design	Kornelius	Riemann	National	2013	hydraulic tests, artesian conditions, aquifer
Abstract Artesian boreholes are a common feature worldwide in confined aquifers. However, the hydraulic testing of these boreholes and estimation of aquifer properties from such tests still pose a challenge for hydrogeologists. Common hydraulic tests, such as step-drawdown or constant discharge rate tests require a static water level at the start of the test, and the measurement of drawdown (increasing over time) and abstraction rate (fixed for a period of time). Usually, when undertaking a pumping test in an artesian borehole, the drawdown is measured from ground level, and the drop in hydraulic head between static pressure and ground level is often ignored. This also implies that the starting time of the test is not at the static water level. A constant head test, set at ground level, is the other option. However, the decrease in flow rate is not only dependent on the hydraulic properties of the aquifer, but also masked by pipe hydraulic effects within the well. This kind of test would also limit the available drawdown to be utilised for the test. Hence, it was required to develop a method for undertaking hydraulic tests in strong artesian boreholes allowing for the drawdown to fluctuate between above and below ground and avoiding the pitfalls described above. The solution is a specially designed and constructed well-head for the installation of the pump and monitoring equipment prior to the hydraulic test. The standard tests are slightly modified and will only be carried out after sealing the well-head and reaching static hydraulic pressure. The recommended well-head construction and subsequent hydraulic tests were carried out at a strong artesian borehole in the Blossoms Well-field, south of Oudtshoorn in the Western Cape of South Africa.
Hydraulic fracturing and Water Resources: Separating fact from fiction	Lizanne	Bredenkamp	Karoo	2015	Shale gas, Dolerite Intrusions
Abstract Shale gas in South Africa can be a game changer for the Karoo and South Africa economy but it may have a devastating effect on the environment. The Karoo communities is highly reliable on groundwater for their stock, irrigation and also for domestic use. Knowing the process and the potential impacts of gas-well drilling and fracturing on shallow groundwater systems beforehand different appropriate studies can be done before any hydraulic fracturing can took place in South Africa. The biggest concerns with hydraulic fracturing is that the fracturing fluids will flow and discharge into shallow aquifers due to the high pressure used or the produced water mixed with deep saline water may discharge into the environment. This paper presents a baseline dataset that will be a reference point against which any future changes in groundwater concentrations can be measured. The Karoo basin with its numerous dolerite intrusions make it unique and different from other countries. These dolerite intrusions are associated with high yielding boreholes because of the fractured contact. The Karoo Basin may be under artesian conditions, which imply that any pollutant might migrate upwards in the Karoo. The understanding of key attributes for characterising groundwater of Karoo Aquifers is most importantly the depth to water level, the yield, and groundwater quality.. The understanding of these characteristics will help to close possible legislative loopholes regarding fracturing. This paper establish an interactive database to obtain full understanding of the hydrogeology of the Karoo to be able to quantify how much water is available in the Karoo and who is the users. Not only the quantity of the water in the Karoo, but also quality and age/origin by making use of different isotopes in conjunction with basic macro chemistry. This will allow for a broader picture before any unconventional gas mining in the Karoo takes place and it can be used to identify any future changes in groundwater quality and quantity of the Karoo aquifers.
Hydraulic tests of strong artesian boreholes; wellhead construction and test design	Kornelius	Riemann		2015
Abstract Artesian boreholes are a common feature worldwide in confined aquifers, but the hydraulic testing of these boreholes, and estimation of aquifer properties from such tests, still poses a challenge for hydrogeologists. Common hydraulic tests, such as step-drawdown or constant-discharge rate tests require a static water level at the start of the test, and the measurement of drawdown (increasing over time) and abstraction rate (fixed for a period of time). Usually, when undertaking a pumping test in an artesian borehole, the drawdown is measured from ground level, and the drop in hydraulic head between static pressure and ground level is often ignored. This procedure also implies that the starting time of the test is not at the static water level. A constant-head test, set at ground level, is the other option. However, the decrease in flow rate is not only dependent on the hydraulic properties of the aquifer, but also masked by pipe hydraulic effects within the well. This kind of test would also limit the available drawdown to be utilized for the test. Hence, it was required to develop a method for undertaking hydraulic tests in strong artesian boreholes, allowing for the drawdown to fluctuate between levels both above and below ground and avoiding the pitfalls described above. The solution is a specially designed and constructed wellhead for the installation of the pump and monitoring equipment prior to the hydraulic test. The standard tests are slightly modified and are only undertaken after sealing the wellhead and reaching static hydraulic pressure. The recommended wellhead construction and subsequent hydraulic tests were implemented at a strong artesian borehole in the Blossoms Wellfield, south of Oudtshoorn in the Western Cape province of South Africa.
Hydrocarbon Remediation – Practical Low Cost And Low Maintenance Solutions	Jennifer A	Pretorius	National	2013	Hydrocarbon, contamination
Abstract In recent years there is an increased awareness of hydrocarbon contamination in South Africa, and the need for remediating sites affected by these contaminants. Hydrocarbon contamination of groundwater can be caused by a large variety of activities at industrial, mining or residential areas. Once these contaminants are discovered in groundwater where it poses risks to human health and/or the environment, remediation is often required. Remediation of groundwater has become a booming industry for groundwater practitioners and often there is an attitude of more sophisticated and expensive solutions are better. This paper will show that this attitude is not always the best solution, but rather recommend an approach where a combination of low cost/low maintenance system need to be investigated and applied to reach clean-up goals. Determination of natural attenuation potential and on-going monitoring forms an integral part of this type of solution.
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.
Hydrocarbon plume delineation using a Hydrogeological and Geophysical approach	Albert	Kruger		2015
Abstract Simple and cost-effective techniques are needed for land managers to assess and quantify the environmental impacts of hydrocarbon contamination. During the case study, hydrocarbon plume delineation was carried out using hydrogeological and geophysical techniques at a retail filling station located in Gauteng. Laboratory and controlled spill experiments, using fresh hydrocarbon product, indicate that fresh hydrocarbons generally have a high electrical resistivity, whilst biodegraded hydrocarbons have a lower resistivity. This is attributed to the changes from electrically resistive to conductive behaviour with time due to biodegradation. As such, it should be possible to effectively delineate the subsurface hydrocarbon plume using two-dimensional (2D) Electrical Resistivity Tomography (ERT). As part of the case study, two traverses were conducted using an Electric Resistivity Tomography (ERT) survey with an ABEM SAS1000 Lund imaging system. The resultant 2D tomographs were interpreted based on the resistivity characteristics and subsurface material properties to delineate the plume. Localised resistivity highs were measured in both models and are representative of fresh hydrocarbons whereas areas of low resistivity represented areas of biodegraded hydrocarbons. More conventional plume delineation techniques in the form of intrusive soil vapour and groundwater vapour surveys as well as hydrochemical anlayses of the on-site monitoring wells were used to compare the results and to construct the detailed Conceptual Site Model. During the investigation, four existing monitoring wells located on the site and additional two wells were installed downgradient of the Underground Storage Tanks (USTs) in order to determine the extent of the plume. In conclusion, a comparison was found between the groundwater results and geophysical data obtained during the case study and it was concluded that ERT added a significant contribution to the Conceptual Site Model.
Hydrochemical Analysis Of Groundwater In The Danakil Depression, Northern Ethiopia	David C	McGibbon	Ethiopia	2017	hydrostratigraphy, hydrochemical, hydrothermal influx
Abstract An investigation of surface and groundwater chemistry was undertaken as part of a resource assessment of water-supply for potash solution-mining in the Danakil Depression of the Afar Rift, situated in northern Ethiopia on the N/S-trending Ethiopia-Eritrean arm of the East African Rift System. Four hydrostratigraphic units are recognised in the area: 1) Basement Tsaliet Group rocks, low yielding and with poor water quality; 2) Adigrat Formation and Antalo Group fractured sandstones and karstic limestones, high yielding with good water quality; 3) Danakil Group and Zariga Formation fine-grained sediments, forming a good regional aquifer; 4) Dogua Formation alluvial fans, forming a major, regional, primary aquifer with high yields and poor water quality (yields of >50 l/s but 3 times the salinity of sea water). In the mining concession area the only available target for groundwater exploration is the Dogua alluvial-fan system that extends off the Dogua Mountain range to the west. During 2015 and 2016, 5 production and 5 exploration/monitoring boreholes were drilled into the fans, thereafter test pumped and sampled for hydrochemical and isotope analysis. The aquifer stress test proved that there is sufficient groundwater available for the life of mining, but that the water quality is poor. The hydrochemical analysis found that in general, water quality is poor (brine with TDS values >100 000 mg/l and a density >1.05 g/cm3 ) and with temperatures of ~50°C. Water quality degrades from south to north, possibly due to recharge of fresh water from the Antalo limestones in the south and lesser quality water from the Tsaliet basement in the north. The high salinity and temperature found throughout the fans is due to hydrothermal influx along rift-boundary faults that extend downwards into the thermally active, volcanic rift zone. Prolonged pumping results in the degradation of the water quality in the southern boreholes and improvement of quality in the northern boreholes; this is likely as the groundwater heads towards equilibrium, with a similar hydrochemical signature to that of the dominant hydrothermal influx. Stable and radiogenic isotope sampling and analysis was undertaken to determine the source of the recharge, the results showing that it is likely a combination of evaporation from fresh water, lateral recharge of ancient sea water along faults from the Red Sea, and hydrothermal recharge from the sub-surface leaching of young Afar and Red Sea Basalts in the active rift zone.
Hydrochemical Characterisation Of Groundwater In The Evander Goldfields, Mpumalanga, South Africa	Humberto	Saeze	Mpumalanga	2019	hydrochemical
Abstract The hydrochemical, water stable isotopes of groundwater have been determined around Evander Goldfields Mine in Mpumalanga. Based on the stratigraphy of the study area four major aquifer systems can be identified namely Karoo Supergroup, Transvaal Supergroup, Ventersdorp Supergroup and Witwatersrand Supergroup. Hydrochemical and isotope in groundwater were assessed for Karoo and Witwatersrand Supergroup aquifer systems. The results show that in Karoo, groundwater chemistry evolve in two ways: the shallower recently recharged groundwater depicts Ca-Mg-HCO3 water type and the relatively deeper circulation and older governed by ionic exchange present Na-HCO3 water type. In the study area boreholes around tailing facilities constructed to monitor groundwater in the immediate vicinity of these structures show Na-Cl and Ca-Mg-Cl, and this is highly mineralized groundwater. Water samples collected underground mine workings between 1500 and 2080 mbgl in Wtwatersrand Supergroup aquifer system present Na-Cl water type. All groundwater samples analysed for isotopes ?18O and ?2H plot on and/or close to the Global Meteoric Water and Pretoria Meteoric Water Lines. However, groundwater from the deeper part of the underground workings in the Evander mine plot shifting toward negative values of ?18O in relation to the rest of the groundwater in this study. This fraction of groundwater may originate from precipitation isotopically different from the present day rainfall as suggested by deuterium excess values which are above 21.75?. However, the probability that the shifting of ?18O signature may result from groundwater exchange with CO2 gas has to be considered. Hence, analysis of ?18O and ?13C in groundwater CO2 gas has to be performed in order to clarify the hydrochemical processes evolving groundwater in the study area.
Hydrodynamic and Hydrochemical characterization of groundwater resources of a municipality in Switzerland	Cedric	Meier	Switzerland	2015
Abstract The study characterized the hydrodynamic and hydrochemical properties of the quaternary porous aquifer which supplies the municipality of Pont-en-Ogoz (Department of Fribourg in Switzerland) with drinking water. The hydrostratigraphic series is composed of a thin overburden material, a porous aquifer composed of gravel and sand, a thin silt-clay layer and sandstone that forms the deeper aquifer. Pumping tests of a borehole nearby the well PSG1 and well PSG1 itself was used to calculate a mean hydraulic conductivity of the aquifer. The hydraulic conductivity from the test varies between 7.4?10-7 m/s and 2.4?10-5 m/s. The values of hydraulic conductivities are typical for sedimentary rocks as silt, fine sandstone and fine sand. The main physical and chemical parameters like concentration in cations and anions, as well the pH, the dissolved oxygen, the electrical conductivity and the alkalinity were measured and saturation indices were calculated. The analysis of the physical and chemical parameters shows that the type of water is Ca-HCO3 and that it contain mixture of old water coming from a regional groundwater flow system, probably from the deeper aquifer, and from recently infiltrated water as local groundwater flow system. The quality of water is generally good, but the effect of the purification of it through the thin overburden layer is limited. An initial one dimension steady state models based on the hypothesis of Dupuits for an unconfined and confined aquifer was used to calculate the mean recharge. This model gives us a recharge values from 24.8 cm/year and 12.1 cm/year, respectively. A second, two dimensional, confined, homogeneous and isotropic model has been calibrated in order to represent the spatial distribution of the piezometric surface. All the models have been calibrated as a steady state. Two groups of predictive scenarios were done to evaluate the drawdown in the well PSG1 using the 2D model. The maximum drawdown calculated was 40 m for the first group of scenarios and 3-4 m for the second group. The second group of scenarios considered from the deeper sandstone aquifer contributing to the well PSG1. The results of the second group of scenarios fit the field results better and the capture zone is much smaller than the one from the first model. The reality is probably between those two models. In order to lower the uncertainty, spatial variation should be added
Hydrogeochemical And Environmental Isotope Characteristics Of The Thyspunt Area, Eastern Cape, South Africa.	Seeke	Mohuba	Thyspunt, Eastern Cape	2019	Environmental Isotopes, Hydrogeochemistry, Seawater Intrusion, Hydrochemical Evolution, Regional Recharge And Hydraulic Link
Abstract Hydrogeochemical and environmental isotope investigation of the Thyspunt area, located in Eastern Cape South Africa, has been undertaken to understand the hydrogeological conditions in the area. Fifty-nine water samples from springs, wells, streams and ocean were collected for major ions, metals, and environmental isotope analyses. The hydrogeochemical and environmental isotope signatures were used to identify the interaction between various waters bodies, major hydrogeochemical processes, and possible sources of moisture in the Thyspunt area. The groundwater is characterised by electrical conductivity (EC) that varies between 286 and 7040 ?S/cm, dominant alkaline pH conditions and calcium-magnesium-bicarbonate hydrochemical water type. Hydrochemical evolution of groundwater is observed along the groundwater flow direction (west to east), from fresh calcium-magnesium-bicarbonate water type to saline sodium-chloride water type. Furthermore, mixing of calcium-magnesium-bicarbonate and sodium-chloride type groundwater is apparent in the analysed spring samples, indicating deep circulation. Gibbs plot of major ion hydrochemical data indicates that the groundwater hydrochemistry is primarily controlled by water-rock interactions (mineral dissolution) and evaporation processes. Isotopically, water samples from springs and wells have depleted isotope signatures indicative of rainfall recharge from either high attitude moisture source or recharge during colder seasons or both. None of the groundwater samples have isotope signatures similar to ocean water, signifying that there is no seawater intrusion in any of the sampled aquifers. Deuterium excess values range between -0.71 ? and 22.64 ?, suggesting the presence of numerous moisture sources. Tritium activity in groundwater varies between 0.2 T.U and 3.2 T.U, showing submodern to modern (5 - 10 years) recharge. Hydrochemical and environmental isotope similarities between spring and borehole samples confirm the fact that springs are a surface manifestation of the local groundwater flow conditions.
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.
Hydrogeochemical Footprint As A Result Of Mining Activities In The Johannesburg Area	Tamiru	Abiye	Johannesburg	2013	hydrochemical
Abstract The water quality in the crystalline rocks of the Johannesburg and its environs has been severely altered by the mining activity. Due to freshwater scarcity and dependency of the people on the groundwater, it is important to understand the extent of hydrogeochemical footprint in the area. The water quality characteristic has been thoroughly assessed in the crystalline aquifers based on the input from hydrogeochemical characteristics and environmental isotopes. The results show that the calculated dilution factor for acid-mine decant is in the range of 68% as a result of interaction with surrounding fresh water. The SO4/Cl ratio has a wide range of values that falls between 0 and 306.37, while that of Fe/Ca ratio falls between 0 and 5.59. High SO4/Cl values potentially indicate the interference of acid-mine decant with the groundwater system traced through sulphate concentration. Similarly, a high Fe/Ca ratio also indicates the impact of acid-mine decant on the groundwater system where iron is traced with respect to calcium concentration. In this regard the ratios above 0,25 (with the assumption of 1 to 4 natural abundance for Fe:Ca in water in the area) could potentially represent acid-mine decant source.The results confirm that most of the water- supply wells have heterogeneous chemistry with distinctive hydrogeochemical footprint represented by abnormally high Fe, SO4 and Si as a result of acid-mine decant.