Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 101 - 150 of 795 results

Title	Presenter Name	Presenter Surname	Area Sort descending	Conference year	Keywords
Assessing The Role Of Oxygen In The Attenuation Of Petroleum Hydrocarbon Vapours In The Vadose Zone	Samuel	Samuel M?hr		2015
Abstract Vapour intrusion (VI) is the term used to define the encroachment of vapour phase contaminants from subsurface sources into structures such as buildings and basements. It is widely recognized that VI often forms the principal risk of exposure to receptors at petroleum release sites. Petroleum VI (PVI) generally occurs where a release of petroleum hydrocarbon product migrates from its source (e.g. from a leaking underground storage tank) to the groundwater table at which point, given favourable conditions, the hydrocarbon plume may migrate laterally beneath an adjacent building or structure. Subsequent volatilisation of the petroleum product results in the upward diffusion of vapours towards the surface where the vapours may enter into the building or structure at concentrations which may be harmful to human health. The subject of PVI with regards to its fate and transport mechanisms, as well as associated mitigation measures is rapidly gaining attention on a global scale, although to date this exposure pathway remains largely un-assessed in South Africa, with no regulatory guidance currently available. In the late 1990's and early 2000's focus was placed on the development of VI screening criteria by which sites could be screened with respect to their hydrogeological conditions and contamination status so as to determine whether VI could be a potential exposure pathway of concern, with much of the early work being completed by the United States Environmental Protection Agency. For the past decade the majority of the available screening criteria and guidance has had a partially incomplete understanding of hydrocarbon vapour fate and transport processes associated with VI, which has led to doubt over the application of such screening criteria in many cases. Furthermore, recent research conducted abroad has highlighted the importance of the role of oxygen in the vadose zone in the natural attenuation of petroleum hydrocarbon vapours as they diffuse through the soil profile. This research is pointing towards the notion that currently applied screening criteria may be overly conservative, leading to many unnecessary PVI investigations being conducted to the disruption of occupants of the buildings, and at great cost. Over the last two years ERM has compiled a dataset of PVI results from numerous investigations it has conducted throughout Southern Africa and in this paper the authors present data that supports the growing global trend towards recognizing the role that oxygen plays in attenuating petroleum hydrocarbon vapours in the vadose zone. The data also supports the notion that confirmed cases of PVI into buildings have generally been found to be the exception to the rule and not the norm.
Governing Groundwater Wisely To Provide For Current And Future Generations.	Zine	Matshakeni		2015
Abstract POSTER About 97% of the earth's freshwater fraction is groundwater, excluding the amount locked in ice caps (Turton et al 2007) and is often the only source of water in arid and semi-arid regions and plays a critical role in agriculture, this dependency results in over-exploitation, depletion and pollution (Turton et al 2007). Groundwater governance helps prevent these issues. CSIR defines governance as the process of informed decision making that enables trade between competing users of a given resource, as to balance protection and use in such a way as to mitigate conflicts, enhance security, ensure sustainability and hold government officials accountable for their actions (Turton et al 2007). Realising the issues of groundwater governance is a requirement for developing policy recommendations for both national and trans-boundary groundwater governance. Groundwater level decline has led to depletion in storage in both confined and unconfined aquifer systems (Theesfeld 2010). There are about six institutional aspects, namely voluntary compliance, traditional and mental models, administrative responsibility and bureaucratic inertia, conflict resolution mechanisms, political economy and information deficits (Theesfeld 2010). Each of these aspects represents institutional challenges for national and international policy implementation. Traditional local practices should not be disregarded when new management schemes or technological innovations are implemented. The types of policies that impact governance include regulatory instruments, economic instruments and voluntary/advisory instruments. Regulatory or command and control policy instruments such as ownership and property right assignments and regulations for water use are compulsory. Economic policy instruments make use of financial reasons such as groundwater pricing, trading water right or pollution permits, subsidies and taxes. Voluntary /advisory policy instruments are those that influence voluntary actions or behavioural change without agreement or direct financial incentives. These are ideal types though no policy option ever relies purely on one type of instrument. The aim of these policies is to have an impact on governance structures (Theesfeld 2010). The national water act (1998) of the Republic of South Africa is not widely recognized as the most comprehensive water law in the world even though it is the highlight of socio-political events; socially it is still recent in most sites although the law was implemented 15 years ago (Schreiner and Koppen 2002). Regulations for use include quantity limitations, drilling permits and licensing, use licenses, special zone of conservation and reporting and registering requirement. In general when drilling and well construction are done commercially they increasingly fall under the scope of regulatory legislation. This paper will focus mostly on traditional and mental models; procedures that a certain community is dependent on should be taken into account before replacing with technological advanced tools. Consultation of the public can cause conflicts which lead to poor groundwater management. Keywords: Groundwater governance, policy, policy instruments.
Generation Of Multi-Site And Multi-Variate Stochastic Inputs To Support Improved Groundwater Resource Assessment	John Ogony	Odiyo		2019	resource assessment
Abstract In South Africa, the use of stochastic inputs in surface water resources assessments has become the norm while this is rarely done for groundwater resources. Studies that have applied multi-site and multi-variate methods that incorporate stochastic generation of groundwater levels are limited. Stochastic based inputs account for uncertainties attributed to inherent temporal and spatial variability of hydrologic variables and climatic conditions. This study applied variable length block (VLB) stochastic generator for simultaneous generation of multi-site stochastic time series of rainfall, evaporation and groundwater levels. In the study, 100 stochastic sequences with record length of 34 years (1980-2013), similar to the historic one were generated. Performance of VLB was assessed by comparing single statistics of historic time series located within box plots of the 100 annual and monthly stochastically generated time series. The statistics used include mean, median, 25th and 75th percentiles, lowest and highest values, standard deviation, skewness, and serial and cross correlation coefficients. Majority (9 out of 10) of the historical statistics were mostly well preserved by VLB, except for skewness. Historic highest groundwater levels were mostly underestimated. Historic statistics below interquartile range (overestimation) is a common problem of weather generators which can be reduced by including additional covariates that influence atmospheric circulation. The generation of multi-site stochastic sequences support realistic assessment of groundwater resources and generation of groundwater operating rules.
Use Of Environmental Isotopes To Determine Hydraulic Connectivity Across The Surrounding Aquifers At Majuba UCG	Gundo	Mathoho		2015
Abstract Environmental isotope techniques have been successfully applied in the field of hydrogeology over the last couple of decades and have proved useful for understanding groundwater systems. This paper describes a study of the environmental isotopes for Oxygen (18O) and Hydrogen (1H, 2H-Deutrium, 3H-Tritium) obtained from various points in and around the underground coal gasification (UCG) site in Majuba, South Africa. UCG is an alternative mining method, targeting deep coal seams that are regarded as uneconomical to mine. The process extracts the energy by gasifying the coal in-situ to produce a synthetic gas that can be used for various applications. The site consists of shallow, intermediate and deep aquifer systems at a depth of 70m, 180 and 300m respectively. The intermediate aquifer is further divided into the upper and lower aquifer systems. Samples were taken from each aquifer system together with supplementary samples from the Witbankspruit and an on-site water storage dam. A total of 15 samples were submitted for isotope analyses. By investigating the various isotopic signatures from all the samples taken, it will be possible to determine if there are similar or contrasting isotopic compositions by deducing possible water source for each sample due to isotopic fractionation caused by physical, chemical and biological processes. This will also be supported by deducing the mean residence time (MRT) for each water source sampled based on the Tritium data as well as the chemistry data already available for different sources. The chemistry data established linkages between the upper and lower intermediate aquifers.{List only- not presented} Key words: Environmental isotopes, UCG, Water source, Isotope fractionation
The Groundwater Data Acquisition and Management Strategy for the Department of Water and Sanitation	Mxolisi	Mukhawana		2015
Abstract Data acquisition and Management (DAM) is a group of activities relating to the planning, development, implementation and administration of systems for the acquisition, storage, security, retrieval, dissemination, archiving and disposal of data. Data is the life blood of an organization and the Department of Water and Sanitation (DWS) is mandated by the National Water Act (No 36 of 1998) as well as the Water Services Act (No 108 of 1997), to provide useful water related information to decision makers in a timely and efficient manner. In 2009 the DWS National Water Monitoring Committee (NWMC) established the DAM as its subcommittee. The purpose was to ensure coordination and collaboration in the acquisition and management of water related data in support of water monitoring programs. The DAM subcommittee has relatively been inactive over the years and this has led to many unresolved data issues. The data extracted from the DWS Data Acquisition and Management Systems (DAMS) is usually not stored in the same formats. As a result, most of the data is fragmented, disintegrated and not easily accessible, making it inefficient for water managers to use the data to make water related decisions. The lack of standardization of data collection, storage, archiving and dissemination methods as well as insufficient collaboration with external institutions in terms of data sharing, negatively affects the management water resources. Therefore, there is an urgent need to establish and implement a DAM Strategy for the DWS and water sector, in order to maintain and improve data quality, accuracy, availability, accessibility and security. The proposed DAM Strategy is composed of the six main implementation phases, viz. (1) Identification of stakeholders and role players as well as their roles and responsibilities in the DWS DAM. (2) Definition of the role of DAM in the data and information management value chain for the DWS. (3) Development of a strategy for communication of data needs and issues. (4) Development of a DAM life Cycle (DAMLC). (5) Review of existing DAMS in the DWS. (6) Review of current data quality standards. The proposed DAM Strategy is currently being implemented on the DWS Groundwater DAM. The purpose of this paper is to share the interesting results obtained thus far, and to seek feedback from the water sector community.
Effects of Urbanization and Agricultural activities on Aquifer storage and Groundwater quality	Athenkosi	Matshini		2015
Abstract POSTER Aquifer stress arising from urbanization and agricultural activities, these two factors affect aquifer properties when prolonged. Increase in urbanization especially those situated on top unconfined or semi-confined aquifer results in pressure on natural resources, this includes water resources, and changes of land use for agricultural purposes with high economic benefits has an effect on groundwater quality to due to application of Nitrogen- fertilizers during crop rotation and this is largely experienced in developing countries. The effects ranges from groundwater quality to aquifer storage as prolonged aquifer withdrawals due to irrigation, construction, manufacturing affects groundwater storage. Assessment of urbanization and agricultural effects on groundwater requires a complex analysis as integration approaches needs to be discovered for a better analysis of the two more specially when assessing groundwater pollution. The study was conducted to assess the impacts of urbanization and agricultural activities on aquifer storage and groundwater quality: by (a) determining the relationship between the occurrence of contamination due to urbanization by assessing contaminants present in the study area (b) develop groundwater protection, and if any offer recommendation for groundwater management. Multiple-well tests were conducted observing the behavior of drawdown and recovery for assessing groundwater storage. Two aquifer properties were observed to yield information about any changes in aquifer storage (transmissivity and storage coefficient) and groundwater quality lab test focusing on TDS, nitrate and pH were conducted. Historical results reflect that before industrial and urban revolution the groundwater contained small amounts of TDS compared with the present results. Increase in nitrate and pH concentrations observed in location closer to agricultural areas. Prolonged aquifer withdrawals increases expansion of cone of depression and therefore increases aquifer vulnerability and the risk of aquifer being polluted, and this increases storage coefficient. This study can be used to formulate protection zones for water resources and practice towards groundwater management.
Feasibility Of Coal Ash Backfilling In Opencast Mines Using The Darcy Column Experiment.	Bongiwe	Seleka		2019	Poster, coal ash
Abstract The generation of acid mine drainage (AMD), as a result of mining activities, has led to the degradation of groundwater quality in many parts of the world. Coal mining, in particular, contributes to the production of AMD to a large extent in South Africa. Although a vast number of remediation methods exist to reduce the impacts of AMD on groundwater quality, the use of a coal fly ash monolith to act as a reactive and hydraulic barrier has not been extensively explored. This study, therefore, aims to investigate how different ways of packing ash affect the hydraulic conductivity of ash and influence leachate quality when acid-mine drainage filters through the ash. Coal ash is highly alkaline due to the existence of free lime on the surface of the ash particles. Previous studies that investigated alternative uses of coal ash, particularly in AMD treatment, suggest that coal ash has the potential to neutralise pH in acid water and remediate acidic soils. To test the effects of different packing methods of coal ash on the hydraulic conductivity and quality of acid mine leachate flowing through it, several Darcy column tests will be conducted. During the course of these experiments, the following parameters will be measured, electrical conductivity, pH discharge, lime (CaCO3) and selected elements of environmental concern.
The Significance of Collecting Hydrogeological Data and Conceptualising the Groundwater System at the Exploration Stage of the Mine Life Cycle	Jacqueline	Stapelberg		2019	Poster, hydrogeological setting, mine life cycle, exploration drilling, piezometers, budget optimisation
Abstract The hydrogeological setting of a proposed mine site can significantly influence the viability of the mining venture. The management of groundwater inflows, costs of the dewatering technology, construction and maintenance of storage facilities, discharge strategies and anticipated environmental impacts are vital factors for consideration. It is fundamental to assess the hydrogeological setting at an early stage of the mine life cycle and should involve the collection of sufficient hydrogeological data, conceptualisation of the hydrogeological setting and an assessment of planned mine operations and anticipated impacts. Ambient hydrogeological conditions at the deposit area may be identified by conducting a hydrocensus and utilising existing ore exploration drilling data. Information from the hydrocensus and ore exploration drilling can provide valuable preliminary data on groundwater risks, dewatering and available groundwater resources. Potential groundwater/surface water interactions and receptors sensitive to environmental impacts can be identified during a hydrocensus. Similarly, water strikes and fracture density recorded during exploration drilling provide valuable insight to the subterranean environment. It is also possible to obtain aquifer hydraulic properties through packer testing of exploration boreholes. Geochemical test work on exploration borehole-cores could provide valuable information regarding contamination risks from ore deposit and waste material storage. The installation of piezometers within available and accessible exploration holes that extend below the regional groundwater level can pioneer the collection of monitoring data crucial for consideration during the mine life cycle and provide an understanding of the interaction between hydrogeological units and recharge characteristics. Ultimately, mine operations and associated potential impacts on the surrounding groundwater environment can be simulated with the application of numerical hydrogeological flow and contaminant transport models. The numerical models can simulate the regional groundwater flow system and complexities of the mine environment, the accuracy of which is influenced by the type, spatial and temporal distribution of the data collected. It is accordingly suggested that the collection of hydrogeological data and information during the exploration phase would facilitate the timely conceptualisation of potential groundwater risks and effective planning of hydrogeological investigations required during upcoming phases while assisting in the budget optimisation of these future studies.
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.
The Management of Groundwater resources using GIS/Cartography splay)	Freda	Jonck		2015
Abstract The Department of Water Affairs and Sanitation is the custodian of the Water Resource in South Africa. The Western Cape Regional Office, Geotechnical Service Sub Directorate, is responsible for management of groundwater resources in two Water Management Areas (WMA), Olifants Doorn-Berg and Breede-Gouritz. Twenty-nine monitoring routes comprising 800 sites in total are monitored across the Western Cape Region. The purpose of this paper is to create awareness of groundwater related databases and the type of information products used in assessing the status of data bases and groundwater resources. This is to assist and support the scientists, technicians, managers, external stakeholders and/or general public. The main question that needs to be answer is: "What is the current groundwater data management situation in the Regional office?" With the GIS as platform, geographical information was generated from existing data bases to answer questions such as, what is being monitored, where is it being monitored, who is monitoring it, why is it being monitored and when is it being monitored? These questions are applicable to the Region, Water Management Areas, the monitoring route and geosites. Graphical time-series information generated from available data, in combination with the generated geographical information, showed the gaps, hot spots and what is still needed for all the facets of groundwater management (from data acquisition to information dissemination) processes. The result showed the status of data bases, need for data in areas of possible neglect, training gaps, inadequate structure and capacity, instrumentation challenges, need for improvement of commitment and discipline, as well as many other issues. The information generated proves to be an easy tool for Scientists, Technicians and Data Administrators to assist them to be on top of the groundwater resource management in their area of responsibility. The expansion of the use of GIS as a groundwater management tool is highly recommended. This will ensure better understanding of the resource: "The Hidden Treasure".
Remediation of Groundwater at AngloGold Ashanti South Africa	Gawie	van Dyk		2015
Abstract Gold Mining activities the past 60 years at AngloGold Ashanti polluted the groundwater underlain by 4000 ha of land at the Vaal River and West Wits operations in South Africa. Sulphide material in Tailings Storage Facilities, Waste Rock Dumps and extraction plants produce Saline Mine Drainage with Sulphate, minor salts and metals that seep to the groundwater and ultimately into surface water resources. Water regulation requires mines to prevent, minimise/ reduce or eliminate pollution of water resources. The waste philosophy has matured from tolerate and transfer to treat and termination of pollution sources. The impact of the pollution was determined and possible technologies to treat the impact were evaluated. Source controls of proper water management by storm water management, clean dirty water separation, lined water conveyance structures and reduced deposition of water on waste facilities is crucial. The aquifer character determines the possible remediation technology. From the possible technologies phytoremediation, physical interception and re-use of this water was selected. In future possible treatment of the water would be considered. This paper explain the strategy and report on the phased implementation of these plans and the expected results. The establishment of 750 ha of woodlands as phytoremediation, interception trenches of 1250 m, 38 interception boreholes and infrastructure to re-use this water in 10 water management areas is planned. The total volume of 15 Ml/day would be abstracted for re-use from the boreholes and trenches. The woodlands can potentially attenuate and treat 5 ml/day. The established woodlands of 150 ha proof successful to intercept diffused seep over the area of establishment and reduce the water level and base flow. The 2 implemented trenches of 1000 m indicate a local decline in the water level with interception of shallow groundwater within 1-2 m from surface. The 2 production interception well fields abstracting 50 and 30 l/s respectively indicate a water level decline of between 2 to 14 m with regional cones of depression of a few hundred meters to intercept groundwater flow up to 20 meter. Predictions from groundwater modelling indicate that these schemes can minimise pollution during the operational phase and protect downstream water resources. Predictions from modelling indicate that the pollution sources need to be removed to ensure long term clean-up to return the land to save use. The gold and uranium prize is securing the removal of the sources through re-processing of the tailings and waste rock dumps. After removal of the sources of pollution the remediation schemes would have to be operated for 20 years to return the groundwater to an acceptable standard of stock watering and industrial water use. The water quality is observed by a monitoring network of approximately 100 observation boreholes.
Characterising The Hydrological Regime Of The Rietvlei Wetland: Implications For Ecohydrology	Nathasha R	Gariremo		2019	Poster, ecohydrology
Abstract In the following study, the soil and groundwater regime of the Rietvlei wetland near Cape Town are characterised. This has been done by means of logging the subsurface material during the construction of 8 shallow wells, complimented with field observations, and surveying the dug wells. The water stemming from these wells was sampled and analysed for Oxygen 18 and Deterium. Downhole salinity logs of the wells were also undertaken and rainfall samples were analysed for the aforementioned stable isotopes. Results indicate a distinct relationship between elevation and soil structure. Through the use of the water table method, it was found that the relationship between elevation and soil moisture had a direct impact on spatially distributed groundwater recharge on an event basis. Furthermore, higher salinities were found with depth in groundwater in the same wells which had higher recharge values. Isotopic results indicate that groundwater all stems from rainfall, with the exception of Well 8 is influenced by the river due to its proximity to the surface water body. The various water chemistries and soil profiles have a direct impact on the type of flora and its distribution throughout the study area. This study managed to conceptualize the relationship between groundwater, soil profiles and the various plant types surviving in the Rietvlei wetland. Future studies can focus on computer based approaches in order to predict how changes in groundwater characteristics caused by natural or anthropogenic factors would affect other ecohydrological processes within the wetland. These findings can be incorporated in decision making processes concerning groundwater management.
Estimating groundwater availability at catchment scale using streamflow recession and instream flow requirements of rivers	Girma Yimer	Ebrahim		2015	streamflow, RDM
Abstract Groundwater is an important resource for multiple uses in South Africa. Hence, setting limits to its sustainable abstraction while assuring basic human needs is required. Due to prevalent data scarcity related to groundwater replenishment, which is the traditional basis for estimating groundwater availability, the present article presents a novel method for determining allocatable groundwater in quaternary catchments through information on streamflow. Using established methodologies for assessing baseflow, recession flow, and instream ecological flow requirement, the methodology develops a combined stepwise methodology to determine annual groundwater storage volume using linear reservoir theory, essentially linking low flows proportionally to upstream groundwater storages. The approach was trialled for twenty-one perennial and relatively undisturbed quaternary catchments with longterm and reliable streamflow records. Using the Desktop Reserve Model, maintenance low instream flow requirements necessary to meet present ecological state of the streams were determined, and baseflows in excess of these flows were converted into allocatable groundwater storages on an annual basis. Results show that groundwater development potential exists in nineteen of the catchments, with upper limits to allocatable groundwater volumes (including present uses) ranging from 0.02 to 2.60 Mm3/a over the catchments. With a secured availability of these volumes 75% of the years, variability between years is assumed to be manageable. A significant (R2 = 0.86) correlation between baseflow index and the drainage time scale for the catchments underscores the physical basis of the methodology and also enables the reduction of the procedure by one step, omitting recession flow analysis. The method serves as an important complementary tool for the assessment of the groundwater part of the Reserve and the Groundwater Resource Directed Measures in South Africa.
The Colenso Fault System - What Recent Geohydrological Investigations Taught Us	Nicolette	Vermaak		2019	investigations
Abstract A large number of groundwater investigations have been carried out in the Western Cape over the last decade or so. Most of them were related to water supply options for individuals, agriculture, businesses, industries, government departments and municipalities. Some of these developments have confirmed what we already knew about the groundwater characteristics and aquifers of the Western Cape, while others provided us with surprises - surprises so significant that we may have to re-write what we thought we knew. This paper will not be able to cover all the interventions and groundwater studies that have been done. Two case studies linked to the major geological structure in the Western Cape, namely the Colenso Fault (also known as the Franschhoek-Saldanha Fault), will therefore be used as an illustration of the lessons that were learnt by comparing them with our historical understanding of the associated groundwater characteristics. It will also show that there is a need for updated groundwater maps on smaller scale and a reassessment of the aquifers status.
Alluvial Wellfield Optimisation And Management Using Numerical Flow Modelling And Seasonal River Stages	Brendon	Bredenkamp		2017	Alluvial aquifer, wellfield management, numerical modelling, river stages
Abstract Three dimensional numerical flow modelling has become one of the best tools to optimise and management wellfields across the world. This paper presents a case study of simulating an existing wellfield in an alluvial aquifer directly recharged by a major perennial river with fluctuating head stages. The wellfield was originally commissioned in 2010 to provide a supply of water to a nearby Mine. Ten large diameter boreholes capable of abstracting ±2 000 m3 /hour were initially installed in the wellfield. The numerical groundwater flow model was used to evaluate if an additional 500 m3 /hour could be sustainably abstract from the alluvial aquifer system. A probabilistic river flow assessment and surface water balance model was used to quantify low and average flow volumes for the river and used to determine water availability in the alluvial aquifer over time. Output generated indicated that the wellfield demand only exceeded the lowest 2% (98th percentile) of measured monthly river flow over a 59 year period, thereby proving sufficient water availability. Conceptual characterisation of the alluvial aquifer was based on previous feasibility studies and monitoring data from the existing hydrogeological system. Aquifer parameters was translated into the model discretisation grid based on the conceptual site model while the MODFLOW River package was used to represent the river. Actual river stage data was used in the calibration process in addition to water levels of monitoring boreholes and pump tests results. The input of fluctuating river water levels proved essential in obtaining a low model error (RMSE of 0.3). Scenario modelling was used to assess the assurance of supply of the alluvial aquifer for average and drought conditions with a high confidence and provided input into further engineering designs. Wellfield performance and cumulative drawdown were also assessed for the scenario with the projected additional yield demand. Scenario modelling was furthermore used to optimise the placement of new boreholes in the available wellfield concession area.
Observations on seepage from platinum tailings	Terry	Harck		2015	platinum tailings
Abstract Tailings storage facilities are significant contributors of dissolved solids to underlying aquifers and adjacent watercourses. Salt balances indicate estimated seepage loads of the order of 1 500 tonnes of chloride per year. Actual seepage loads will be determined by the hydraulic conductivity of the tailings and mechanisms of flow within the tailings. Field observations and sample analytical results from several platinum tailings facilities are presented. These indicate the development of lenses of clay sized material within coarser silty material and suggest a tortuous seepage flow path, perhaps characterised by zones of preferential flow. The implications of seepage modelling and geochemical data on the salt loads mobilised from tailings are discussed. Results suggest that tailings facilities are effective at retaining salts and that release of accumulated salts after closure may take place at long time scales. {List only- not presented}
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}
An investigation into the effectiveness of underground water pollution mitigation policies	Sibanda	Kin		2015
Abstract Pollution of underground water is fast becoming a global problem and South Africa is not immune to this problem. The principal objective of this paper is to investigate the effectiveness of laws and policies put in place to mitigate underground water pollution. The paper also seeks to examine the causes and types of underground water pollution followed by a closer look into the laws and policies in place to mitigate the pollution levels. Finally, the paper seeks to ascertain whether the current policies are properly implemented. The paper follows content analysis (desk research) to achieve the objectives. Policy recommendations are given based on the findings. {List only- not presented}
Starting From The Problem And Working Backwards	John	Doherty		2019	model calibration, decision-support
Abstract Many groundwater models are commissioned and built under the premise that real world systems can be accurately simulated on a computer - especially if the simulator has been "calibrated" against historical behavior of that system. This premise ignores the fact that natural processes are complex at every level, and that the properties of systems that host them are heterogeneous at every scale. Models are, in fact, defective simulators of natural processes. Furthermore, the information content of datasets against which they are calibrated is generally low. The laws of uncertainty tell us that a model cannot tell us what will happen in the future. It can only tell us what will NOT happen in the future. The ability of a model to accomplish even this task is compromised by a myriad of imperfections that accompany all attempts to simulate natural systems, regardless of the superficial complexity with which a model is endowed. This does not preclude the use of groundwater models in decision-support. However it does require smarter use of models than that which prevails at the present time. It is argued that, as an industry, we need to lift our game as far as decision-support modeling is concerned. We must learn to consider models as receptacles for environmental information rather than as simulators of environmental systems. At the same time, we must acknowledge the defective nature of models as simulators of natural processes, and refrain from deploying them in a way that assumes simulation integrity. We must foster the development of modelling strategies that encapsulate prediction-specific complexity supported by complexity-enabling simplicity. Lastly, modelers must be educated in the mathematics and practice of inversion, uncertainty analysis, data processing, management optimization, and other numerical methodologies so that they can design and implement modeling strategies that process environmental data in the service of optimal environmental management.
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.
The National State of Water in South Africa - the Annual Reporting	Kwazikwakhe	Majola		2015
Abstract POSTER The Department of Water and Sanitation (DWS) is the custodian of South Africa's water and thus is imperative that it reports on its state as the National Water Act of 1998 requires regular reporting to Parliament by the Minister. Hence, the annual compilation of report entitled "The National State of Water in South Africa." This report aims to give an overview of the status and trends of water quality and quantity, further assisting with international water reporting obligations to SADC Region, African Continent, and Globally e.g. the United Nations Commission on Sustainable Development. This information empowers the public and provides knowledge to water managers for informed decision-making. The main purpose is to enhance quality, accessibility and relevance of data and information relating to the goal of Integrated Water Resource Management towards attaining holistic Integrated Water Management, and Integrated Water Cycle Management in future. Three distinct requirements for collecting data by DWS are: (i) assessing and comparing the status and trends for both quantity and quality; (ii) monitoring for water use and (iii) monitoring for compliance to licence conditions. Such information is further used to assess the effectiveness of policies implemented and identify the existing gaps. Various challenges to the country's water demand proper integrated water resources planning and management. The report is divided into Themes such as, Resource Management, Water Services/Delivery, Water Development and Finance, based on selected indicators. The indicators are strategically selected to provide a representative picture of the state, as well as the changes over time to the drivers, pressures, impacts and responses related to the chosen themes. These Indicators include: Climatic Conditions, Water Availability, Water Use, Water Protection, Water Quality, Water Service Delivery, Water Infrastructure, Water Finance, and Sanitation. The report for Hydrological Year 2013/2014 has been completed and it shows that the amount of water available varies greatly between different places and seasons, and from one year to another. The average total storage was around 85% of full supply capacity in September 2014. Surface water quality is generally facing a threat from eutrophication and microbial pollution emanating mainly from mismanaged water (and waste) treatment plants and related landuse activities. Groundwater quality is generally good except in some localised areas where mining and industrial activities are prevalent. With regards to infrastructure; vandalism, lack of maintenance & management skills reflect on/as non-revenue water, highlighting the need for more funding towards maintenance, especially in groundwater which is normally wrongly deemed as an unreliable resource. In the past 20 years, water services delivery to communities has improved as the Millennium Development Goals have been met and surpassed, while the sanitation access goals were likely to be met.
Review of Groundwater Use in Varying Climatic Conditions	Lindelani	Lalumbe		2019	Poster, Climate
Abstract Groundwater levels in E33F quaternary catchment are at their lowest level ever. The impact of climatic variation and increasing abstraction were determined to be the main factor. There are 115 registered groundwater users in E33F and the monthly abstraction volumes are not being measured. There is a need to use land use activities as well as the population to estimate groundwater use. The main objective is to use non-groundwater monitoring data to estimate groundwater use in order to protect the aquifer and ecosystem in general in varying climatic condition. Land use activities information was used to estimate groundwater use in E33F quaternary catchment. The estimated groundwater use volumes were compared to allocated and measured volumes. For domestic groundwater use estimation, population data and an estimation 100 litre per person per day were used. The water requirements for the types of crops being cultivated together with the area (m2) were used to estimate groundwater use volumes for irrigation. The number and type of live stocks were used with the water requirements for each livestock type to estimate the groundwater use volumes. 96 % of groundwater users are using groundwater for irrigation purposes with 9 966 105 m3/a allocated for irrigation. Mining, industries, domestic and livestock are allocated 100 200 m3/a. The estimated groundwater use volume for irrigation is 30 960 000 m3/a, which is three times higher than the allocated volume. Groundwater use volume for domestic use is estimated to be 38 225 m3/a which is higher than the 31 000 m3/a allocated. The total estimated groundwater use volume in E33F is estimated to be 30 998 225 m3/a, which is three times higher than the allocated groundwater use volume of 10 066 305 m3/a. This estimation could be higher as only registered boreholes were used and estimations from mining, Industries and live stocks were excluded due to lack of data
The use Vegetable Oil Substrate's in the treatment of contaminated groundwater	Michelle	Pienaar		2015
Abstract Edible vegetable oil (EVO) substrates have been successfully used to stimulate the in situ anaerobic biodegradation of groundwater contaminated chlorinated solvents as well as numerous other anaerobically biodegradable contaminants like nitrates and perchlorates at a many commercial, industrial and military sites throughout the United States of America and Europe. EVO substrates are classified as a slow release fluid substrate, and comprise of food grade vegetable oil such as canola or soya bean oil. The EVO substrate serves as an easily biodegradable source of carbon (energy) used to create a geochemically favorable environment for the anaerobic microbial communities to degrade specific contaminants of concern. EVO substrate's can either be introduced into the subsurface environment as pure oil, in the form of light non aqueous phase or as an oil/water emulsion. The emulsified vegetable oil substrates holds several benefits over non-emulsified vegetable oil as the fine oil droplet size of the commercially manufactured emulsified oils can more easily penetrate the heterogeneous pore and fracture spaces of the aquifer matrix. The use of this technology to stimulate in situ biodegradation of groundwater contaminants is still relatively unknown in South Africa. This paper will give an overview of the EVO technology and its application, specifically looking at the advantages of using this relatively inexpensive, innocuous substrate based technology to remediate contaminated groundwater within fractured rock environments commonly encountered in South Africa. {List only- not presented}
A methodology for uncertainty quantification of dewatering volumes under the context of open-cast mining	C	Rivera Villarreyes		2023	FEFLOW, Groundwater Modelling, mining, PEST, PESTPP
Abstract Groundwater modelling at the mine sites involves assumptions from the geological model, mining stages, parametrization, and fractures, among others. Modelling work mainly focuses on calibrating against historical measurements before operations (pre-mining) or afterwards (transient calibration). Calibration is carried out mainly with gradient-based algorithms. However, the majorlimitation is the number of model runs, since the number of parameters can easily reach hundreds or more. PEST has become the common tool for parameter estimation. The Jacobin calculation required for the Levenberg Marquardt algorithm requires several model runs. This, a limited factor for the calibration and, subsequently, uncertainty quantification. The next generation of PEST, named PESTPP, is gained popularity in the groundwater community. The great advantage of PESTPP,, compared to the classical PEST, is its new module, Iterative Ensemble Smoother (IES). PESTPP-IES covers both parameter estimation and uncertainty quantification in one goal. Its empirical formulation of the Jacobian matrix reduces the number of runs; thus, the numerical bottleneck can be significantly reduced. PESTPP-IES has been extensively tested in an open-pit mine at the geological complex conditions in the Peruvian Andes. The work involves the task of model simplification, e.g., from a regional model to a detailed local pit model, calibration and uncertainty quantification of pit dewatering volumes. Detailed model was kept calibrated based on hydraulic-head measurements, and dewatering volumes were predicted. All these consider transient changes in the mining plan within the same FEFLOW model. Results validate the methodology and practicability in mining applications.
Comparitive analyses between LAK3 package and the high K techniques used for numerical simulation of lake-aquifer interactions	Jannie	Weitz		2015
Abstract Modelling of groundwater systems and groundwater-surface water interaction using advanced simulation software has become common practice. There are a number of approaches to simulate Lake-aquifer interactions, such as the LAK Package integrated into MODFLOW, the high conductivity and fixed stage approaches. LAK and the high conductivity approaches were applied and compared in simulating Lake- aquifer interaction in the Lake Sibayi Catchment, north-eastern, South Africa using the finite difference three-dimensional groundwater flow model, Visual MODFLOW Flex under steady state conditions. The steady state model consisted of two layers: an upper layer consisting of the Sibayi, KwaMbonambi, Kosi Bay and Port Durnford Formations which have similar characteristics, and a lower model layer representing the karst, weathered and calcareous Uloa Formation. The bottom model boundary is constrained by the impermeable Cretaceous bedrock. The model area covers the surface and groundwater catchments of Lake Sibayi which is constrained in the east by the Indian Ocean. A no-flow boundary condition is assigned to the northern, western and southern sides and a constant head boundary is assigned to the eastern side. The Mseleni River and neighbouring plantations were modelled using the River and Evapotranspiration boundary conditions respectively. Input parameters for the various boundary conditions were obtained from the previously developed high resolution conceptual model, including recharge
Questions Of Scale And Measurements	Nicolette	Vermaak		2019	scale
Abstract Until 1998 groundwater was managed separately from surface water and was seen as a private resource. The National Water Act of 1998 (Act 36 of 1998) (NWA) was forward thinking in that it saw groundwater as an integrated part of the water resource system and as a common resource to be managed by the Department of Water and Sanitation (DWS) as custodian. Various tools had been provided to manage the water resources equitably, sustainably and efficiently. A limited understanding of groundwater and the prevalence to revert to engineering principles when managing water resources had led to an Act that is mostly written with surface water in mind. The tools and principles that had been tested for surface water was used directly for groundwater without considering the practicalities in applying and enforcing the NWA. This did not provide too many problems, as groundwater was not considered a viable, sustainable water resource, and the use of groundwater was mostly limited to private use for garden irrigation, in agriculture for irrigation and for bulk supply in a number of small towns where surface water was not available. This has changed drastically during the recent drought that affected the whole country, but especially the Western Cape. Groundwater was suddenly seen as the solution to the problem of water availability. The problem was that the understanding of groundwater has not increase sufficiently over the years, and water resources management is still skewed to hydrology principles that apply to surface water. Groundwater sustainability is at the heart of the questions of scale and measurements. The Department has been flooded by the large number of water use licence applications that have been submitted by municipalities, industries and agriculture as a result of the drought. This article will look at groundwater resource assessment and allocation methodology in a South African context.
The connectedness of transboundary groundwater researchers: from network analysis to network-building	A	Fernald		2023	network analysis, network-of-networks, transboundary groundwater
Abstract The Transboundary Groundwater Resilience (TGR) Network-of-Networks project brings together researchers from multiple countries to address the challenges of groundwater scarcity and continuing depletion. Improving groundwater resilience through international research collaborations and engaging professionals from hydrology, social science, data science, and related fields is a crucial strategy enabling better decision-making at the transboundary level. As a component of the underlying data infrastructure, the TGR project applies visual analytics and graph-theoretical approaches to explore the international academic network of transboundary groundwater research. This enables the identification of research clusters around specific topic areas within transboundary groundwater research, understanding how the network evolved over the years, and finding partners with matching or complementary research interests. Novel online software for analysing co-authorship networks, built on the online SuAVE (Survey Analysis via Visual Exploration, suave.sdsc.edu) visual analytics platform, will be demonstrated. The application uses OpenAlex, a new open-access bibliographic data source, to extract publications that mention transboundary aquifers or transboundary groundwater and automatically tag them with groundwater-specific keywords and names of studied aquifers. The analytics platform includes a series of data views and maps to help the user view the entire academic landscape of transboundary groundwater research, compute network fragmentation characteristics, focus on individual clusters or authors, view individual researchers’ profiles and publications, and determine their centrality and network role using betweenness, eigenvector centrality, key player fragmentation, and other network measures. This information helps guide the project’s data-driven international networking, making it more comprehensive and efficient.
Monitored Natural Attenuation on-sites with different geological setting	Bongani	Masombuka		2015
Abstract When considering how to reduce contamination of petroleum hydrocarbons in shallow aquifers, it is important to recognize the considerable capacity of natural processes continuously at work within the secondary sources of contamination. This natural processes are technically referred to as Monitored Natural Attenuation (MNA), a process whereby petroleum hydrocarbons are deteriorated naturally by microbes. This approach of petroleum hydrocarbon degradation relies on microbes which utilise oxygen under aerobic processes and progressively utilises other constituents (sulphates, nitrates, iron and manganese) under anaerobic processes. MNA process is mostly evident when light non-aqueous phase liquids (LNAPLs) has been removed while the dissolved phase hydrocarbon compounds are prominent in the saturated zone. The case studies aim at determining feasibility and sustainability of Monitored Natural Attenuation process at different sites with varying geological setting.
Teaching Machines Hydrogeology: Demonstrating The Use Of Machine Learning In Groundwater Science And Management	Rui	Hugman		2019	Machine learning, AI
Abstract The advent of the 'Big Data' age has fast tracked advances in automated data analytics, with significant breakthroughs in the application of artificial intelligence (AI). Machine learning (ML), a branch of AI, brings together statistics and computer science, enabling computers to learn how to complete given tasks without the need for explicit programming. ML algorithms learn to recognize and describe complex patterns and relationships in data - making them useful tools for prediction and data-driven discovery. The fields of environmental sciences, water resources and geosciences have seen a proliferation of the use of AI and ML techniques. Yet, despite practical and commercial successes, ML remains a niche field with many under-explored research opportunities in the hydrogeological sciences. Currently physical-process based models are widely applied for groundwater research and management, being the dominant tool for describing and understanding processes governing groundwater flow and transport. However, they are limited in terms of the high data requirements, costly development and run time. By comparison, ML algorithms are data-driven models that establish relationships between an input (e.g. climate data) and an output (e.g. groundwater level) without the need to understand the underlying physical process, making them most suitable for cases in which data is plentiful but the underlying processes are poorly understood. Combining data-driven and process-based models can provide opportunities to compensate for the limitations of each of these methodologies. We present applications of ML algorithms as knowledge discovery tools and explore the potential and limitations of ML to fill in data gaps and forecast groundwater levels based on climate data and predictions. Results represent the first step in on-going work applying ML as an additional tool in the study and management of groundwater resources, alongside and enhancing conventional techniques such as numerical modelling.
Exploring The Potential Of The GRACE Derived Groundwater Drought Index (GGDI) To Forecast Groundwater Drought In South Africa	Kopano	Mokoena		2019	GRACE, Drought
Abstract Water has been recognized and acknowledged as a fundamental natural resource that sustains environmental diversity, social and economic development (Liu et al., 2017; Fisher et al., 2017). With increasing populations, climate change and limited monitoring networks for both ground and surface water, freshwater resources are becoming difficult to assess due to rapid changes in water supply and uses. Several efforts have been devoted towards the monitoring and management of water resources and discovery of alternative sources of freshwater. One of the more recent efforts is using gravity information to track changes in water storage on the earth's surface. The Gravity Recovery and Climate Experiment (GRACE) mission (https://www.nasa.gov/mission_pages/Grace/index.html) holds great potential for assessing our water resources in areas with little monitoring data. The increasing interest in the use of GRACE as a water resource information and monitoring tool, is due to its cost effectiveness and user-friendly system which affords a broad understanding of the world we live in and its processes, specifically in water resource management and hydrological modelling. South Africa's National Water Act (NWA) of 1998 highlights the importance of the sustainable development of water resources. However, it is difficult to sustainably manage South Africa's groundwater resources due to the difficultly in measuring and understanding our complex aquifers. The challenges in establishing sustainable monitoring of groundwater resources and its Reserve, are due to insufficient knowledge about the contribution that groundwater makes to surface water, and methods which reliably monitor groundwater resources. The GRACE is a joint satellite mission by the Deutschen Zentrum fur Luftund Raumfahrt (DLR) in Germany and the United States National Aeronautics and Space Administration (NASA). The satellite was launched on 17 March 2002 and provides monthly temporal differences of earth's gravity field and its mean gravity field (Schmidt et al., 2008). It can afford insights into the location of groundwater resources, and their changes. GRACE can however, only determine the change in total water storage and therefore information on other components of the water balance are required to isolate the groundwater component. Therefore, the integrated Pitman Model is ideal to be applied together with GRACE and the Model can isolate surface water, soil moisture and groundwater into various components. Many studies have evaluated GRACE-derived groundwater storage changes as a response to drought (Famiglietti et al. 2011; Scanlon et al., 2012), while Thomas et al. (2017b) evaluated a groundwater drought index based on GRACE observations in an effort to understand and identify groundwater drought. Typically, GRACE is applied at scales of 150 000 km2, however Thomas et al., (2017) has developed a recent method that allows for the application of his GRACE derived Groundwater Drought Index (GGDI) at smaller scales. This study applies Thomas et al. 2017 GGDI in South Africa to the Crocodile, Sedgefield and Doring catchments, in hopes to to evaluate drought characterisation using data from GRACE satellites, focusing on the total water storage deficits to characterise groundwater drought occurrence.
Blast curtain optimized with a numerical model for TSF seepage control	Robel	Gebrekristos		2015
Abstract Preventing the spread of seepage from tailings storage facilities (TSF's) in groundwater is necessary as it often contains toxic contaminants. Experience has shown that seepage from TSFs is inevitable and that zero seepage remains difficult even with complex liner systems. Multiple seepage control methods are often required to minimise seepage to ensure that environmental regulations are met. Control methods can be grouped into either barrier or collection systems. Barrier systems are used to hinder seepage whereas collection systems are used to intercept seepage. A blast curtain, which is the focus of this article, is a type of collection system that is still at a conceptual level but has seen little or no application worldwide. It works in principle, similarly to a curtain drain, but is typically extended to greater depths depending on the aquifer vulnerability. Numerical modeling has shown that this mitigation measure could add another line of defence for seepage control. The depth and effectiveness of the curtain can be optimized with a numerical model to ensure optimal interception of contaminated seepage around the TSF. Depths of up to 30 m in fractured aquifers have been simulated in this study. A blast curtain is constructed by drilling a set of boreholes around a TSF in close proximity to one another and then fracturing the rock using either explosives or fracking methods to create a more permeable zone. This is then combined with a series of scavenger wells or natural seepage to abstract the contaminated water. Numerical simulation has shown that blast curtains are effective especially if groundwater flow is horizontal. The effectiveness decreases if the vertical flow component is significant. A blast curtain can result in the lowering of the water table, however, local depression is a less of a concern than potential groundwater contamination. {List only- not presented}
Depth Discrete Multilevel Monitoring In Fractured Rock: State Of The Technology And Implications	John A	Cherry		2017	Monitoring, fractured rock, Hydrochemistry, MLS technologies
Abstract Well-established engineered systems for depth-discrete monitoring in fractured rock boreholes (referred to as a Multilevel System or MLS) are commercially available and offer much diversity in design options, however, they are used infrequently in professional practice and have seen minimal use in groundwater research. MLSs provide information about hydraulic head and hydrochemistry from many different depths in a single borehole and, therefore, magnify greatly the knowledge value of each borehole. Conventional practice globally is devoted to standard monitoring wells, either alone as longer single screened wells or in clusters or nests with a few wells screened at different depth intervals. These are the mainstay of the groundwater science and engineering community and severely limit prospects for each borehole to provide the information needed to solve the complex problems typically posed by fractured rock. This paper outlines the nature and evolution of MLS technologies and points to recent literature showing how MLSs add important insights that cannot be obtained using conventional wells. Also, it reviews commercially available MLS technologies, which present a range of robust options with each system having different characteristics and niches depending on characterization and monitoring goals and site conditions. The paper also describes refined MLS criteria aimed at improving the cost effectiveness and expanding capabilities of MLSs, so as to improve their accessibility for high resolution data acquisition in the context of both groundwater system characterization and long-term monitoring.
Integrated Modelling: A Tool For Urban Groundwater Management On The Cape Flats, Cape Town	Benjamin	Mauck		2015
Abstract There is growing concern that South Africa's urban centres are becoming increasingly vulnerable to water scarcity due to stressed surface water resources, rapid urbanisation, climate change and increasing demand for water. Given South Africa's water scarcity, global trends for sustainable development, and awareness around the issues of environmental degradation and climate change, there is a need to consider alternative water management strategies. Water Sensitive Urban Design (WSUD) is an approach to sustainable urban water management that attempts to achieve the goal of a 'Water Sensitive City'. The concept of a Water Sensitive City seeks to ensure the sustainable management of water using a range of approaches such as the reuse of water (stormwater and wastewater), exploiting alternative available sources of supply, sustainable stormwater management and improving the resource value of urban water through aesthetic and recreational appeal. Therefore, WSUD attempts to assign a resource value to all forms of water in the urban context, viz. stormwater, wastewater, potable water and groundwater. However, groundwater is often the least considered because it is a hidden resource, often overlooked as a form a water supply (potable and non-potable) and it is often poorly protected. The management of urban groundwater and understanding the impacts of WSUD on groundwater in South African cities is challenging, due to complex geology, ambiguous groundwater regulations and management, data limitations, and lack of capacity. Thus, there is a need for an approach to assess the feasibility of management strategies such as WSUD, so that the potential opportunities and impacts can be quantified and used to inform the decision making process. An integrated modelling approach, incorporating both surface and subsurface hydrological processes, allows various urban water management strategies to be tested due to the complete representation of the hydrological cycle. This integration is important as WSUD is used to manage surface water, but WSUD known to utilise groundwater as a means of treatment and storage. This paper assesses the application, calibration and testing of the integrated model, MIKE SHE, and examines the complexities and value of establishing an integrated groundwater and surface water model for urban applications in South Africa. The paper serves to demonstrate the value of the application of MIKE SHE and integrated modelling for urban applications in a South African context and to test the models performance in Cape Town's unique conditions, accounting for a semi-arid climate, complex land use, variable topography and data limitations. Furthermore, this paper illustrates the value of integrated modelling as a management tool for assessing the implementation of WSUD strategies on the Cape Flats, helping identifying potential impacts of WSUD interventions on groundwater and the potential opportunities for groundwater to contribute towards ensuring to Cape Town's water security into the future.
Fly Ash Leaching Dynamics And Implication On Groundwater Contamination	Nadine	Swartz		2019	fly ash, contamination
Abstract South Africa utilizes coal for energy and chemical feedstock thereby generating millions of tons of ash every year. The ash is stockpiled in surface waste facilities where it poses a risk of leaching and contaminating groundwater. This study utilizes standard leaching tests, TLCP and SPLP, to evaluate and predict the mobility of different elements that leach from fly ash. Two different fly ash samples (Ash M and Ash T) were used in the study. A QEMSCAN analysis was also performed on the samples as well as the coal to determine the elementary and mineralogical compositions. Both Ash samples were generated from bituminous coals and had similar physical properties. Both ash samples were mixed respectively with the two different leachates one more acidic (Leachate A) the other more basic (Leachate B). Trace elements are present in ash in small amounts, but still at lower levels still pose threat to the environment and human health. Only three trace elements were found present in both ash samples. The detected trace elements in an increasing concentration order are: Manganese>Chromium>Copper. It appears the leaching behaviour of these trace elements is similar to the other metals, being insoluble at near neutral and alkaline pH range while dissolvable at low pH ranges. The results show that Leachate B was found to extract more material than Leachate A on a milligrams per gram of ash basis. The risk to groundwater contamination can be minimized by understanding the leaching dynamics and water retention of fly ash dumps as the results show.
Investigating the influence of fine ash leaching in a tailings dam on the underlying aquifers	Paul JH	Lourens		2015	primary aquifers
Abstract Groundwater in South Africa is the most important source of potable water for rural communities, farms and towns. Supplying sufficient water to communities in South Africa becomes a difficult task. This is especially true in the semi-arid and arid central regions of South Africa where surface water resources are limited or absent and the communities are only depended on groundwater resources. Due to a growing population, surface water resources are almost entirely being exploited to their limits. These factors, therefore, increases the demand for groundwater resources and a more efficient management plan for water usage. For these reasons, the relation between the geology and geohydrology of South Africa becomes an important tool in locating groundwater resources that can provide sustainable quantities of water for South Africans. It was therefore decided to compile a document that provides valuable geohydrological information on the geological formations of the whole of South Africa. The information was gathered by means of interviews with experienced South African geohydrologists and reviewing of reports and articles of geohydrological studies. After gathering the relevant information, each major geological unit of South Africa together with its geohydrological characteristics was discussed separately. These characteristics include rock/aquifer parameters and behaviour, aquifer types (primary of secondary), groundwater quality, borehole yields and expected striking depths, and geological target features and the geophysical method used to locate these targets. Due to the fact that 90 % of South Africa's aquifers are classified as secondary aquifer systems, groundwater occurrence within the rocks of South Africa is mainly controlled by secondary fractures systems; therefore, understanding the geology and geological processes (faulting, folding, intrusive dyke/sills & weathering) responsible for their development and how they relate is important. However, the primary aquifers of South Africa (Coastal Cenozoic Deposits) should not be neglected as these aquifers can produce significant amounts of groundwater, such as the aquifer units of the Sandveld Group, Western Cape Province. Drilling success rates and possibility of striking higher yielding boreholes can be improved dramatically when an evaluation of the structural geology and geohydrological conditions of an area together with a suitable geophysical method is applied. The ability to locate groundwater has been originally considered (even today) a heavenly gift and can be dated back to the Biblical story of Moses striking the rock to get water: "behold, I will stand there before thee there upon the rocks thou shalt smite the rock and there shall come water out of it" (Exodus 17:6).
A review of groundwater resource protection measures in South Africa	Eberhard	Braune		2015

Modelling recharge in an opencast coal mining environment, applying model parameters on a catchment scale.	Freek	van Devnter		2015
Abstract The provision, usage and discharge of water resources are major concerns for coal mines, both underground and opencast. Water resources in a coal mining environment will often account for a significant portion of the daily operational cost. In order to cut costs, the mine will often collect as much runoff as possible to recycle for future use. This on-going recycling of site water and management of the resource demands a complete site water balance model in order to understand the dynamics of the resource within the boundaries of the mine. To improve the understanding of the dynamics of the resource on a much larger scale, and the effect it will have on recharge in an open cast coal mine environment, one must consider alternative modelling approaches which can compensate for such conditions. This amounts to describing recharge as a modelling component in a physically based distributed model. The main goal of this project is to calculate recharge into the main pit at this specific colliery by applying parameters on a quaternary catchment scale. The colliery is located just west of the town of Ogies, Mpumalanga on the peripheral region of the quaternary catchment B20G. The physiography of the quaternary catchment B20F is described as a central Highveld region gently sloping to the north. The geohydrological modeling application MIKE SHE (developed by DHI) was used to develop a fully integrated catchment model. The model was created mainly to simulate the impact of human activities on the hydrological cycle and hence on water resource development and management. Different modules of MIKE SHE that was used during the modelling stage include saturated- and unsaturated flow and a small degree of overland flow. Key words: Mpumalanga, MIKE SHE, recharge
Groundwater Sampling: Measurement Uncertainties And Their Implications For Decision Making	Modreck	Gomo		2019	sampling
Abstract The uncertainties associated with both the sampling process and laboratory analysis can contribute to the variability of the results. In most cases, it does appear that if the water samples have been analysed by an accredited laboratory, the results are acceptable. While the accreditation of analytical laboratory and therefore its credibility is very important to uphold quality and integrity, the same should be said about the sampling process. The quality and credibility of a sampling process is typically left to the responsibility of the appointed groundwater practitioner without any criteria to evaluate the quality and integrity of the sampling process. Perhaps the quality and integrity of the sampling process is evaluated based on trust or experience of the practitioner. However without any form of scientific criteria to evaluate the quality and integrity of the sampling process, it is difficult for the sampling process to be scrutinized. The quality and integrity of both the sampling process and laboratory analysis must be scientifically evaluated based on the uncertainty of measurements in line with the monitoring goals/requirements. This presentation discusses the aspects of evaluation of measurement uncertainties associated with groundwater sampling as an important component of quality assessment of groundwater sampling processes. The potential implications of the uncertainties on the final results and their use in decision making is also discussed. The credibility of the decisions made also depends on the knowledge about the uncertainties of the final results
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.
Water Monitoring in the Mining Industry: An Overview	Callie	Pickering		2015
Abstract Water monitoring is a key aspect in the mining industry, in terms of gathering baseline data during the pre-construction stage, identifying potential areas of concern and mitigating source pollutants during the operational stage. A proper water monitoring program assists in the monitoring of plume development and water level rebound during the closure phase. The data made available through consistent long term monitoring should not be underestimated. Monitoring the effect that coal mine operations have on the water quality and quantity of surface and groundwater resources is a complex and multidisciplinary task. Numerous methodologies exist for monitoring of this kind. This paper will supply an overview of the water- rock chemistry associated with coal mine environments and the key indicator elements that should be focused on for water monitoring as well a review of the Best Practice Guidelines requirements in terms of water monitoring. Two case studies of coal mines in KwaZulu Natal will be reviewed, the key challenges outlined and mitigation measures implemented. The impact of requirements such as those set out by the Department of Water and Sanitation in terms of strict water quality limits for water containment and waste facilities as specified by Water Use Licences has also created unrealistic non-compliance conditions. The initial approach to creating a water monitoring programme should involve first identifying gaps in previous datasets and delineating potential sources of contamination. The sampling frequency will depend primarily on the water resource being monitored and the water quality analysis will depend on the type of facility. The facilities required for a specific situation will depend on the type and amount of waste generated, potential for leachate formation, vulnerability of groundwater resources and potential for water usage or resource sensitivity.
Evaluating Groundwater Availability Based on Land Cover and Local Hydrogeology - A Groundwater Balance Approach	Hendrik	Botha		2019	land cover, water balance
Abstract The main purpose of this paper is to present a case study where a water balance concept was applied to describe the expected groundwater safe yield on a sub-catchment scale. The balance considers effective recharge based on local hydrogeology and land cover types, basic human needs, groundwater contribution to baseflow, existing abstraction and evaporation. Data is derived from public datasets, including the WRC 90 Water Resources of South Africa 2012 Study, 2013-2014 South African (SA) National Land Cover and Groundwater Resource Assessment Ver. 2 (GRAII) datasets. The result is an attempt to guide a new groundwater user regarding the volume of groundwater that can be abstracted sustainably over the long-term.
Comparative use of groundwater by invasive alien PROSOPIS SPP and co-occurring indigenous V. Karoo in a semi-arid catchment	Sebinasi	Dzikiti		2015
Abstract Groundwater is a vital source of water for many communities in South Africa and elsewhere. Besides the changing climate, rapidly spreading invasive alien plants with deep roots e.g. Prosopis spp, pose a serious threat to this water source. Dense impenetrable thickets of Prosopis occur in the drier parts of the country mainly along river channels in the Northern, Eastern and Western Cape Provinces. Few studies have quantified the actual water use by this species outside of the USA where it is native. Consequently the impacts of Prosopis invasions on groundwater resources are not well documented in South Africa. The aim of this study was to quantify the actual volumes of water used by Prosopis invasions and to establish the effects on groundwater. Because deep rooted indigenous trees that normally replace Prosopis once it has been cleared also use groundwater, we sought to quantify the incremental water use by Prosopis over and above that used by indigenous trees in order to determine the true impacts on groundwater. The study was conducted at a site densely invaded by Prosopis at Brandkop farm near the groundwater dependent town of Nieuwoudtville in the Northern Cape. One in seven trees at the site is the Vachellia karroo (formerly A. karroo) which is the dominant deep rooted indigenous tree species. Actual transpiration rates by five Prosopis and five V. karroo are being measured using the heat pulse velocity (HPV) sap flow technique. Additional HPV sensors were installed on the tap and lateral roots to study the water uptake dynamics of the trees. Groundwater levels are being monitored in four boreholes drilled across the site while sources of water used by the trees (i.e. whether soil or groundwater) is being determined using O/H stable isotopes. For similar size trees, V. karroo had higher transpiration rates than Prosopis because of the larger sapwood to heartwood ratio in V. karroo than in Prosopis. However, at the stand level Prosopis consumed significantly larger amounts of water than V. karroo. This is because Prosopis invasions had a much higher tree density than V. karroo. From August 2013 to July 2014, annual stand transpiration for Prosopis (~ 372 mm) was more than 4 times higher than that of V. karroo (~ 84 mm). Tree water uptake was correlated to changes in groundwater levels (R2 ~ 0.42) with groundwater abstractions of ~ 2600 m3/ha/y by Prosopis compared to ~ 610 m3/ha/y for V. karroo. In addition, Prosopis showed evidence of hydraulic redistribution of groundwater wherein groundwater was deposited in the shallow soil layers while V. karroo did not. Results of this study suggest that clearing of Prosopis to salvage groundwater should target dense stands while less dense stands should be prevented from getting dense. {List only- not presented}
Integrated System Approach To Evaluate Natural Processes And Hydrodynamics Linked To Groundwater-Surface Water Interaction	Teboho	Shakhane		2015
Abstract This study was aimed at developing an integrated groundwater-surface water interaction (GSI) model for a selected stretch of the Modder River by considering the following five different aspects of the GSI: 1) the distribution of different aquifer systems (structural connectivity) along the river 2) the hydraulic connectivity between the aquifer systems, 3) the volumes of water abstracted from the aquifers by streamside vegetation, 4) the volumes of water replenished to the groundwater system through rainfall recharge, and 5) the exchange fluxes between the various components of the groundwater-surface water system. The distribution of the aquifer systems was investigated by means of a) geo-electrical surveys, and b) in situ slug tests while their hydraulic connectivity was investigated by hydrogeochemical routing. The volumes of water abstracted by streamside vegetation were estimated by the quantification of the transpiration from individual plants and the groundwater recharge was estimated by a root zone water balance. The water exchange fluxes between the groundwater and surface water were determined from a simple riparian zone groundwater budget. The results of the geo-electrical surveys and slug tests allowed the delineation of the riparian area aquifers (RAA) and the terrestrial area aquifers (TAA) on both the south-eastern and north-western sides of the river. Based on the results of hydrochemical analyses, saturation indices and inverse mass balance modelling, the GSI involves flow of water from the TAA to the RAA, and finally to the river on the south-eastern side while it involves flow from the river into the RAA with a limited exchange with the TAA on the south-eastern side. The dominant vegetation on the study area was found to be the Acacia karroo and Diospyros lycioides. The close similarities in isotope compositions of the xylem sap and the borehole water samples suggested that the Acacia karroo sourced its water from the groundwater storage while differences in isotope compositions suggested that the Diospyros lycioides did not source water from the groundwater storage at the time of measurement. The results of groundwater recharge estimation in the study area highlighted the fact that both the antecedent moisture and the rainfall amounts determine whether recharge to the groundwater system will take place. Finally, the results of baseflow estimation indicated that the river is a gaining stream along the south-eastern reach while acting as a losing stream along the north-western reach.
Potential for co-disposal of fly-ash and coal discard: Results from geochemical modelling and laboratory studies	Meris	Mills		2015
Abstract Geochemical investigations for a planned coal mine indicated that the coal discard material that would be generated through coal processing would have a significant potential to generate acid rock drainage. A power station is planned to be developed in close proximity to the coal mine, and the potential for co-disposal of coal discard with fly-ash material required examination. Fly-ash is typically highly alkaline and has the potential to neutralise the acidic coal discard material. In order to investigate whether this was a viable option, the geochemical interaction between the coal discard and fly-ash was investigated. Geochemical data, including acid-base accounting, total chemical compositions, leach test data and kinetic test data, were available for the coal discard material and the fly-ash. Using these data as inputs, a geochemical model was developed using Phreeqci to predict the pH of leachate generated by mixing different ratios of coal discard and fly-ash. The ratio of coal discard to fly-ash was established that would result in a leachate of neutral pH. Using this prediction, a kinetic humidity cell test was run by a commercial laboratory for a total of 52 weeks using the optimal modelled ratio of discard and fly-ash. Although leachate pH from the kinetic test initially reflected a greater contribution from fly-ash, the pH gradually decreased to the near-neutral range within the first 20 weeks, and then remained near-neutral for the remainder of the 52-week test. During this period, sulphate and metal concentrations also decreased to concentrations below those generated by either the fly-ash or coal discard individually. The addition of fly-ash to the coal discard material provided sufficient neutralising capacity to maintain the near-neutral pH of the co-disposal mixture until the readily available sulphide minerals were oxidized, and the oxidation rates decreased. At the end of the test, sufficient neutralising potential remained in the humidity cell to neutralise any remaining sulphide material. The results of this investigation suggested that, under optimal conditions, co-disposal of fly-ash with coal discard is a viable option that can result in reduced environmental impacts compared to what would be experienced if the two waste materials were disposed of separately.
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.
Application of GIS Mapping Techniques to Classify Karoo Aquifers	Mildred	Goes		2015
Abstract POSTER As the National Water Act has evolved to provide for more effective and sustainable management of our water resources, there has been a shift in focus to more strategic management practices. With this shift come new difficulties relating to the presentation of sensitivity issues within a spatial context. To this end it is necessary to integrate existing significant spatial layers into one map that retains the context, enables simple interpretation and interrogation and facilitates decision making. This project shows the steps taken to map and identify key groundwater characteristics in the Karoo using Geographic Information Systems (GIS) techniques. Two types of GIS-based groundwater maps have been produced to assist with interpretation of existing data on Karoo Aquifer Systems in turn informing the management of groundwater risks within Shell's applications for shale gas exploration. Aquifer Attribute and Vulnerability maps were produced to assist in the decision making process. The former is an aquifer classification methodology developed by the project team, while the latter uses the well-known DRASTIC methodology. The overlay analysis tool of ESRI's ArcGIS 10.1 software was used, enabling the assessment and spatial integration of extensive volumes of data, without losing the original detail, and combining them into a single output. This process allows for optimal site selection of suitable exploration target areas. Weightings were applied to differentiate the relative importance of the input criteria. For the Attributes maps ten key attributes were agreed by the project team to be the most significant in contributing to groundwater/aquifer characteristics in the Karoo. This work culminated in the production of a series of GIS-based groundwater attributes maps to form the Karoo Groundwater Atlas which can be used to guide groundwater risk management for a number of purposes. The DRASTIC model uses seven key hydrogeological parameters to characterise the hydrogeological setting and evaluate aquifer vulnerability, defined as the tendency or likelihood for general contaminants to reach the watertable after introduction at ground surface.
Impact of urbanization on groundwater quantity and quality in Kabul city, Afghanistan	A	Farahmand	Afghanistan	2023	Kabul basin, Urbanization, ground subsidence, Groundwater Quality, land use, land cover
Abstract Groundwater quantity and quality of shallow aquifers have deteriorated in recent years due to rapid development that has created an increased demand for drinking water, which is increasingly being fulfilled by groundwater abstraction. The study evaluates the hydrogeological framework of the Quaternary aquifer of the Kabul basin, Afghanistan, and the impact of urbanization on the groundwater resources around the Kabul city plain. Time series of Landsat satellite LCLU images indicate that the urban area increased by 40% between 2000 and 2020, while the agricultural area decreased by 32% and bare land decreased from about 67% to 52% during this period. The assumed groundwater overdraft 2019 was 301.4×103 m3 /day, while the recharge was 153.4×103 m3 /day, meaning a negative balance of about 54 million cubic meters (MCM) this year. Due to the long-term decline of water levels at 80 90 cm/year, and locally (Khairkhana, Dasht-e-Barchi) 30-50m during 2005-2019, a considerable groundwater drawdown is shown. Groundwater quality, on the other hand, reveals that chloride concentrations and salinity increased throughout the aquifer between 2005 and 2020. The nitrate concentration decreased in most Kabul Plain places over the period. In conclusion, the quantity and quality situation of urban groundwater in Kabul is worrying; urgent scientific and sustainable solutions and measures should be considered to manage this situation.
Combined effects of seawater intrusion and nitrate contamination on groundwater quality in the coastal agricultural area of El-Nil River, Algeria	Lamine	Boumaiza	Algeria	2023	Coastal aquifer, Groundwater Quality, nitrate contamination, Seawater Intrusion, stable isotopes
Abstract This study focuses on the coastal agricultural area of El-Nil River (Algeria), where anthropogenic activities heavily impact groundwater resources. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δ2HH2O, δ18OH2O, δ15NNO3 and δ18ONO3), is combined with a hydrochemical facies evolution diagram and a Bayesian isotope mixing model (MixSIAR) to assess seawater contamination and distinguish the nitrate sources and their apportionment. A total of 27 groundwater samples and 7 surface water samples distributed over the entire study area were collected. Results show classic inland intrusion combined with an upstream seawater impact through the river mouth connected to the Mediterranean Sea. Results from nitrate isotopic composition, NO3 and Cl concentrations, and the MixSIAR model show that nitrate concentrations chiefly originate from sewage and manure sources. Nitrate derived from sewage is related to wastewater discharge, whereas nitrate derived from manure is attributed to an excessive use of animal manure to fertilise agricultural areas. The outcomes of this study are expected to help decision-makers prepare suitable environmental strategies for effective and sustainable water resources management in the study area.
Micro pore-pressure sensor (MEMs) and analysis technologies – towards a future of multi-scale groundwater monitoring	W	Timms	Australia	2023	multi-scale, pore pressure, sensors, analysis
Abstract Micro-electro-mechanical system (MEMs) technologies coupled with Python data analysis can provide in-situ, multiple-point monitoring of pore pressure at discrete and local scales for engineering projects. MEMs sensors are tiny, robust, inexpensive, and can provide wireless sensing measurements in many electrical and geomechanical engineering applications. We demonstrate the development of MEMs pressure sensors for pore pressure monitoring in open boreholes and grouted in piezometers. MEMs sensors with a 60 m hydraulic head range and centimetre vertical resolution were subject to stability and drawdown tests in open boreholes and in various sand and grouts (permeability 10-8 to 10-2 m/s). The resulting accuracy and precision of the MEMs sensors, with optimal calibration models, were similar to conventional pore pressure sensors. We also demonstrate a framework for estimating in-situ hydrogeological properties for analysis from vented pore pressure sensors. This framework method included Python code analysis of hourly pore pressure data at the millimetre vertical resolution, which was combined with barometric data and modelled earth tides for each borehole. Results for pore pressure analysis in confined boreholes (>50 m depth) included specific storage, horizontal hydraulic conductivity and geomechanical properties. Future improvements in the vertical resolution of MEMs pore pressure sensors and combined these two technologies will enable groundwater monitoring at multiple scales. This could include the deployment of numerous MEMs, at sub-meter discrete scale in boreholes and evaluating local site scale variations in pore pressure responses to recharge, groundwater pumping and excavations in complex sub-surface geological conditions.
Alternative approaches for integrated groundwater management in the rural basins of central Bolivia	I	Rodriguez-Levy	Bolivia	2023	Bolivia, socio-hydrogeology, Geophysics, groundwater recharge, soil water balance
Abstract Due to technical, social, and economic limitations, integrated groundwater management presents a significant challenge in developing countries. The significance of this issue becomes even more pronounced in groundwater management, as this resource is often overlooked and undervalued by decision-makers due to its status as a “hidden resource,” despite the fact that it provides multiple ecosystem services. This study aims to establish the technical hydrogeological foundation in rural basins of central Bolivia through alternative, simplified, and cost-effective methods and tools. The study includes applying geophysical techniques, such as Electrical Resistivity Tomography, to determine the conceptual hydrogeological model of a micro-basin. In addition, a soil water balance approach was applied, characterizing 24 biophysical variables to identify groundwater recharge zones, while global circulation models provided a substitute for unreliable meteorological data. Furthermore, a participatory model was developed to identify recharge areas in upper basin areas within the framework of developing a municipal policy for their protection. The participatory model included local knowledge in all stages of methodology development, considering the characteristics of the local plant communities and the spatial distribution of local rainfall. The research findings have already contributed to resolving socio-environmental conflicts in Bolivia and establishing a foundation for effective water governance by empowering local rural communities. This study has demonstrated the feasibility of using alternative, simplified, and low-cost methods and tools to establish the technical hydrogeological basis, which can inform public policies to promote sustainable groundwater management in developing countries.