Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 1 - 10 of 220 results
Title Presenter Name Presenter Surname Area Conference year Keywords

Abstract

Chow,  R; Watson, A

The frequency, intensity, and duration of droughts are increasing globally, putting severe pressure on water supply systems worldwide. The Western Cape Province suffered from a period of severe water shortages that began around January 2015 and lasted until about July 2018. During this recent drought, there was a forced reduction in water use, predominantly from the agricultural sector. Citizens also reduced water use and increasingly tapped into groundwater for their needs irrespective of whether the hydrogeology was considered favourable or not. Unmonitored and unregulated abstraction of groundwater, especially under unstable climatic conditions, poses a significant risk to the future water security of the Western Cape.
We hypothesize that groundwater enabled the municipalities, residents, and industries of the Western Cape to survive the recent drought. Our aim is to evaluate the change in groundwater storage during the 2015 to 2018 drought and its subsequent recovery. To achieve this, we must gain a comprehensive understanding of the dynamics of separate components of the water cycle, as well as the overall water balance.

While there is data on surface water use during the drought, the impact on groundwater resources has yet to be evaluated. However, the accurate assessment of groundwater use is difficult, especially in data-scarce regions, such as South Africa. In our study, we combine remote sensing from NASA’s Gravity Recovery and Climate Experiment (GRACE), the Global Land Data Assimilation Systems, groundwater level measurements from the National Groundwater Archive, and ancillary datasets from the City of Cape Town’s weekly water dashboard to assess the total change in groundwater storage in the Cape Town Metropolitan area and surrounding cities over an 8-year period, from 2012 to 2020. Preliminary results from GRACE data analysis show a steady decline in aquifer saturated thickness over the drought, indicative of an increase in groundwater use.

Abstract

Veltman, S

It has become increasingly apparent that understanding fractured rock mechanics as well as the interactions and exchanges between groundwater and surface water systems are crucial considering the increase in demand of each in recent years. Especially in a time where long term sustainability is of great importance for many water management agencies, groundwater professionals and the average water users. Previous callow experience has shown that there is a misunderstanding in the correct interpretation and analyses of pumping test data. The fracture characterisation (FC) method software provides a most useful tool in the overall understanding of a fractured rock aquifer, quantification of the aquifer’s hydraulic (flow regime and flow boundary conditions) and physical properties, only if the time-drawdown relationships are correctly interpreted and when the theoretical application principles are applied. Interpretation is not simply a copy and paste of the aquifer test data into the software to get a quick answer (especially when project time constraints are considered), however, recent experiences with numerous field examples, required intricate understanding of the geological environment, intended use and abstraction schedules coupled with the academic applications on which the software was based for correct interpretation. Through the application of correct interpretation principles, a plethora of flow information becomes available, of which examples will be provided in the presentation itself. By achieving this, flow can be conceptualised for inputs into a conservative scale three-dimensional numerical flow model and calibrated based on measurable data in a fraction of the time of a conventional regional model. Although higher confidence levels are achieved with these practical solutions, monitoring programmes are still required to provide better insight of the aquifer responses to long-term abstraction and recovery.

Abstract

The South African government is considering shale gas extraction in the Karoo basin, South Africa. To protect groundwater resources, there is an urgent need to do a groundwater baseline in possible gas extraction areas. Various groundwater samples have therefore been taken at a borehole and 2 soekor wells in the Northern Cape, from 2016 to 2021. The groundwater samples were analysed for dissolved gasses, specifically focussing on methane. As laboratories became more efficient ethane was also included in later analyses. From the analyses we found that drought might influence the dissolved gas concentrations in the groundwater via pressure influences on the groundwater flow and the dissolved gas flow towards the shallow aquifers. Artesian conditions at this site are helping with the flow of dissolved gasses from deep to shallow aquifers via preferential pathways. The possibility of shallow-deep groundwater interconnections and the migration of deep methane to shallow aquifers make it important to establish a groundwater baseline in the Karoo. By focusing on boreholes and wells that are emitting methane, a better understanding of groundwater flow and interaction with geological layers can be determined. If other gasses like propane and butane can be analysed in addition to methane, more information can be gathered to determine the origins of the methane and whether it is thermogenic or biogenic.

Abstract

Israel,S

Surface water resources are under threat of depletion and quality deterioration due to various factors such as climate change, urbanization, and population expansion. Managed aquifer recharge (MAR) is a technique that has been successfully implemented over the last 4 decades to sustain the balance between water demand and availability. The unsaturated zone, where source water is introduced during infiltration, plays a major role in the reduction of contaminants present in water before it naturally percolates and reaches the aquifer. This research aims to evaluate the removal efficiency of contaminants by the unsaturated zone. Three objectives to be accomplished are; to determine and classify the chemical composition of the source water. Secondly, to determine the hydraulic properties of the soil in the area of interest. Lastly to evaluate the contaminants removal efficiency, by tracing the quality of water at the point of recharge and discharge. The Atlantis water resource management scheme in the Western Cape will be used as a case study, in order to assess the relationship between the unsaturated zone and the reduction of contaminants. The current study argues that during the artificial recharge of aquifers, contaminants present in the source water filter through the unsaturated zone, where natural processes, as well as resident microbes, reduce their concentrations to acceptable levels. Assessing the ability of the unsaturated zone to reduce contaminants, will allow for the early warnings of contamination potential and the execution of informed prevention strategies that can be used in decision making of the management and protection of water resources. Additionally, the advanced understanding of the role that the unsaturated zone plays in eliminating contaminants can be used to account for satisfactory groundwater quality in areas where groundwater is not constantly monitored and artificial remedies are not applied.

Abstract

With increasing population growth and a subsequently increased demand for food production, the agricultural sector has had to grow and develop continuously despite drought-stricken water resources in recent years. The expansion in this sector requires increasingly efficient water use management and increases in water supplies, which are often met through groundwater utilization. In the past several years the use of groundwater in the Western Cape has increased exponentially and thus has forced the sharing of resources. The question pertains to how an invisible water resource that is difficult to measure and quantify, can be shared. Issues of varying complexities can arise when submitting a water use licence application (WULA), such as historical water use debates, interactions between groundwater and surface water, seasonal stresses on resources, etc. In one case study in De Doorns, a WULA became side-tracked soon after initiation by a neighbour’s complaint that his production borehole was severely affected by the drilling of the applicant’s boreholes. In the second case study in the Hexriver Valley, a WULA was complicated by a gentleman’s agreement stating that no one in the valley is allowed to abstract groundwater from deeper than 6 m. This gentleman’s agreement stems from past disagreements regarding such practices. The final case study was not a WULA but arose out of concerns for dropping weir levels connected to a new borehole. The borehole was equipped with new casing to case off the alluvium; it was suspected to be the cause of the disturbance. The scientific method was used to evaluate the borehole’s impact on the weir. Case studies such as these will become more prevalent as the demand on water resources will increase. Hydrogeologists needs to more informed of the complexities that can and will arise in the future as a result of shared water resources.

Abstract

The western part of South Africa is experiencing a prolonged drought. In many cases, the effects of drought have been noticed since 2011, putting the western part of the Northern Cape under severe stress to provide water to the communities. In the past 10 years, rainfall has also decreased, and in most cases, the catchments did not receive rain to help with the recharge of groundwater. Various lessons were learned from the change in the climate and environment. But a lot can be done to minimise the impact of these changes on the water supply to communities. This paper addresses what we are noticing in the environment that impacts the way we think groundwater behaves. The changes include the change in rainfall: patterns, lines, and type of rainfall. The collapsing of boreholes with water strikes closing when being over-pumped occurs more often in the last 3 years. Pump test recommendation changes with water level change – deployment output. A combination of the factors mentioned puts more stress on groundwater resources, and a mindset change is needed to give assurance of future supply to the communities.

Abstract

Heller, H

Stringent drinking water standards for constituents like chromium, arsenic, and nitrates, combined with continually higher demand for groundwater resources have led to the need for more efficient and accurate well characterization. Many boreholes are screened across multiple aquifers to maximize groundwater production, and since these aquifers can have different water qualities, the water produced at the wellhead is a blend of the various water qualities. Furthermore, the water entering a well may not be distributed equally across the screened intervals, but instead be highly variable based on the transmissivity of the aquifers, the depth of the pump intake, the pumping rate, and whether any perforations are sealed off due to physical, chemical, or biological plugging. By identifying zones of high and low flows and differing water qualities, well profiling is a proven technology that helps optimize operational groundwater production from water supply boreholes or remediation systems. This frequently results in increased efficiencies and reduced treatment costs. By accurately defining groundwater quantity and quality, dynamic profiling provides the data needed to optimize well designs. Conventional exploration methods frequently rely on selecting well screen intervals based on performing and analyzing drill stem tests for one zone at a time. Using dynamic flow and water quality profiling, the transmissivity and water quality can be determined for multiple production zones in a matter of one to two days. It also allows the location and size of the test intervals to be adjusted in the field, based on real-time measurements. In this paper we discuss dynamic well profiling techniques with project case examples of characterization different types groundwater boreholes for a variety of applications and industries resulting in significant cost saving and sustainable water abstraction.

Abstract

Kanyerere, T

The argument in this paper is that improved understanding of science-policy integration, where physical bases of natural science is combined with practice in managing water resource challenges, becomes critical in translating scientific knowledge into effective and sustainability solutions linked to groundwater resource protection. Such hypothesis should be attested at locally relevant scale where water resources reside and where water utilization takes place. This paper provides a practical case-study of how science-policy integration can directly impacts groundwater resource protection practice from a local, and national perspective using strategies of groundwater resources directed measures. A combination of literature surveys, and desktop record review methods were used for the purpose of data collection from published literature and publicly accessible national databases of the Department of Water and Sanitation (DWS). Collected data were analysed using document analysis, descriptive statistics, and case study analysis methods. Based on the analysis, three types of science-policy nexus theoretical models exist in practice, namely, 1) science-policy integration, 2) policy-science integration, and 3) mixed integration. From a national perspective, the analysis showed that South Africa is able to practically apply science-policy nexus in policy implementation practice for water resources protection, and that such practice depicts a mixed integration model of the nexus. Case study analysis of the Schoonspruit-Koekemoerspruit River Catchment provided insight on how localized operationalization of groundwater resource directed measures facilitates sustained groundwater resources protection for water availability and sustainable utilization. This study provides an exemplary for collaborations between researchers and/or scientists and policy makers to ensure that science research is answering policy-relevant questions and that results from scientific work are readily available for policy implementation. In addition, there is adequate evidence to indicate that science-policy nexus can be designed and prioritized to support sustainable development agenda on groundwater resilience, and visibility at various levels.

Abstract

Approximately 982 km3 /annum of the world’s groundwater reserve is abstracted, providing almost half of all drinking water worldwide. Globally, 70% is used for agricultural purposes while 38% for irrigation.

Most water resources of South Africa are threatened by contamination caused by industrial, agricultural, and commercial activities, and many parts of the country face ongoing drought with an urgent need to find alternative freshwater sources, such as groundwater. Groundwater constitutes approximately 15% of the total volume consumed, hence it is an important resource that supplements insufficient surface water supplies across South Africa.

Very little attention has been afforded to understanding the anthropogenically altered vadose zone as a potential source or buffer to groundwater contamination. This is evident from few research studies that has applied multiple isotopic tracers to characterise this zone. Most subsurface systems in South Africa are characterised by fractures, whereby flow and transport are concentrated along preferential flow paths.

This study aims to evaluate the performance of different tracer classes (environmental and artificial) with one another, and create a better understanding of the hydraulic properties, mean residence time and transport mechanisms of these tracers. The influence of unsaturated zone thickness on recharge mechanisms will also be evaluated.

Site visits will be conducted for the proposed study areas, and the neighbouring sources of contamination will be assessed. The matric potential and unsaturated hydraulic conductivities will be measured using various techniques. Water samples will be collected and analysed for the various tracers from the vadose zone using gravity lysimeters including suction cups. Several tracers will also be injected into boreholes where samples will be collected to calculate tracer residence times (BTC’s) and further constrain the hydraulic properties of the vadose zone. All samples will be analysed, interpreted, and simulated using the numerical finite-element modelling code SPRING, developed by delta h. The software derives quantitative results for groundwater flow and transport problems in the saturated and unsaturated zones of an aquifer.

The research is expected to provide more insight into the selection and use of environmental and artificial tracers as markers for detecting, understanding the transport processes and pathways of contaminants in typical altered South African subsurface environments. The impact derived improved characterisation of the pathways, transport, and migration processes of contaminants, leading to groundwater protection strategies and appropriate conceptual and numerical models. The output from this study will determine the vertical and horizontal flux for both saturated and unsaturated conditions.

Abstract

Kanyerere, T

Groundwater contribution towards improved food security and human health depend on the level of contaminants in the groundwater resource. In rural areas, many people use groundwater for drinking and irrigation purposes without treatment and have no knowledge of contaminants levels in such waters. The reason for such lack of treatment and knowledge is due to the parachute type of research which emphasizes on scientific knowledge and records only and do not develop skills and outputs on groundwater quality for improved human health and food security in communities. This study argued that parachute research type exposes groundwater users to health hazards and threaten food security of communities. Concentration levels of contaminants were measured to ascertain suitability of groundwater for drinking and irrigation use. 124 groundwater quality samples from 12 boreholes and 2 springs with physiochemical data from 1995 to 2017 were assessed. This study found high concentration levels of contaminants such F-, NO3-, Cl- and TDS in certain parts of the studied area when compared to international and national water quality standards. In general, groundwater was deemed suitable for drinking purposes in most part of the studied area. Combined calculated values of SAR, Na%, MH, PI, RSC and TDS determined that groundwater is suitable for irrigation purposes. The discussion in this paper showed that scientific knowledge generated on groundwater quality is not aimed at developing skills and outputs for improved human health and food security but rather for scientific publication and record keeping leaving communities where such knowledge has been taken devoid of knowledge and skills about the groundwater quality. In this study, it was recommended that skills and outputs on groundwater quality should be developed and shared with groundwater users through various initiatives as it will enhance the achievement of SDG’s.