Mémoire (M.Sc.T.)-- Université du Québec à Chicoutimi, 1993. / Document électronique également accessible en format PDF. CaQCU

Groundwater flow and transport in deep crystalline rock is an important area of research. This is partly due to its relevance for constructing a long term repository for storing radioactive spent nuclear fuel in deep bedrock. Understanding the behavior of flow and transport processes in deep crystalline rock is crucial in developing a sustainable solution to this problem. This study aims to increase the understanding of how channel network models (CNM) can be applied to represent groundwater flow and solute transport in sparsely fractured crystalline rock under site specific conditions. A main objective was to determine how to incorporate structural and hydrogeological site characterization data in the construction of the CNMs. In addition to this, the associated key parameters of the CNMs were investigated to gain further understanding of model site application. To that end, a scripting approach with the python scripting library Pychan3d was used to create alternative channel network representations of a field site. A conceptual discrete fracture network (DFN) model was constructed using field site data obtained from a structural model of the fractures present at the site of the Tracer Retention Understanding Experiments (TRUE) - Block Scale at the Äspö Hard Rock Laboratory (HRL). This conceptual model was used as a base for constructing two different alternatives, denoted respectively as sparse and dense, of a CNM. The sparse CNM consisted of a limited amount of channels for each fracture, while the dense CNM acted as a DFN proxy, taking the full extent of the fracture areas into account and creating a dense, large network of flow channels for each fracture. In order to verify the performance of the generated CNMs, a reproduction of tracer tests performed at the same specific field site was attempted using a particle tracking technique. In addition to this, long term predictions of solute transport without the interference of the pumps used during the tracer tests were done in order to estimate transport time distributions. Pychan3d and the scripting approach was successfully used to create CNMs respecting specific conditions from the TRUE-Block Scale site. The sparse CNM was found to give very adequate flow and transport responses in most cases and to be relatively easier to calibrate than its dense counterpart. The long term transport predictions at the site according to the models seem to follow a channelized pattern, with only a few select paths for transport. The difficulties encountered in matching the dense CNM with the tracer tests most likely stem from difficulties in flow calibration, as well as certain key parameters being assigned too generically.

M.Sc. / Please refer to full text to view abstract

Magister Scientiae - MSc / The Table Mountain group aquifer system has the potential to be an important supply of water. Although the aquifer system is used to some extent, a number of aspects relating to the aquifer system are poorly understood and unquantified. This study aimed to take into consideration the importance of differenct ecosytems, which is essential in predicting the effects of groundwater abstruction. However, the ecological requirements of systems that depend on groundwater are poorly understood. This project identified "type areas" for further detailed research into the impacts of large-scale groundwater abstraction from the Table Mountain group aquifer system based on the nature and functioning of ecosystems across groundwater dependent ecosystem boundaries of a regional scale. / South Africa

Philosophiae Doctor - PhD / The analysis of geologic, hydrologic and hydrogeologic data interpreted to give the characteristics of the Cape Flats aquifer showed the quality of groundwater from the aquifer is suitable for development as a water resource. The conceptual model of the Cape Flats sand shows an unconfined sandy aquifer, grading into semi-confined conditions in some places where thick lenses of clay and peat exists. Recharge rates through the saturated zone of the Cape Flats aquifer have been determined by water table fluctuation (WTF), rainfall-recharge relationship, soil water balance and chloride mass balance methods (CMB). Recharge rates using the WTF vary considerably between wet and dry years and between locations, with a range of 17.3% to 47.5%. Values obtained from empirical rainfall-recharge equation (method 2) agree with those of the WTF. Recharge estimates from the water balance model are comparatively lower but are within the range calculated using empirical method 2 (i.e. 87 - 194 mm or 4 – 21% of MAP). These recharge rates also agree with estimates from the series of other methods applied to sites located in the north-western coast of Western Cape and are comparable to recharge rates obtained elsewhere in the world. / South Africa

This dissertation collates all available data from the Department of Water Affairs and Forestry’s (DWAF’s) National Groundwater Database (NGDB), DWAF’s Groundwater Resource Information Project (GRIP) and tests conducted during the progress of this project in order to evaluate Basement aquifers. The project was commenced at the request of the Water Research Commission (WRC), situated in Pretoria, South Africa. The study area (Limpopo and Luvuvhu-Letaba Water Management Areas, WMA1 and WMA2 respectively) is underlain by fractured, crystalline Basement terrain. The influences of structures (i.e. joints, faults and shear zones) and the neotectonic stress conditions were also studied to address the influence on groundwater flow and occurrence. The aim of the project was to address the determination of the aquifer parameters (essentially transmissivity and sustainable yield) in Basement terrane. Pumping test data was used and analysed via the Flow Characteristic Programme (Institute for Groundwater Studies, University of Free State). The methods of Logan (1964), Theis (1935), Cooper-Jacob (1946) and Birsoy-Summers (1980) were applied for comparative purposes. Statistically, all four methods supplied results within the same order of magnitude, with Theis and Cooper-Jacob correlating extremely well. Results from the Logan and Birsoy-Summers methods correlated very well too, but the T-values calculated via Logan’s method were almost double those obtained from the step-drawdown data analysed via the Birsoy-Summers method. The combined results adhered to a developed model-setting-scenario approach where each borehole can be evaluated based on three parameters. Firstly, the model refers to the potential water-bearing and/or water-barring features. In the study area, it was found that water predominates in the Hout River Shear Zone, and that the neotectonic stress fields have little influence on determining the orientation of favourable water-bearing structures. Geological contacts often resulted in higher yielding boreholes than geological structures. Secondly, the setting refers to the climatic and tectonic setting of the site. This determines the recharge and the orientation of structures. Based on this, supposedly closed structures (due to prevailing neotectonic stress fields) often supplied higher yielding boreholes than the supposedly open structures. Rainfall and climate however had little influence on the results. Finally, the scenario ranks a borehole in terms of high, intermediate or low transmissivity and subsequently potential yield. High T-values typically exceeded 100 m2/d whereas low T-values were generally below 5 m2/d. Significantly low yielding boreholes therefore formed part of the Low T Scenario, and high yielding boreholes of the High T Scenario. Copyright / Dissertation (MSc)--University of Pretoria, 2008. / Geology / unrestricted

>Magister Scientiae - MSc / Deformation of the western part of the Table Mountain Group rocks during the Cape Orogeny created a series of folds and associated fractures. The subsequent continental break-up of Gondwana led to the development of large fault systems. These exert a major influence on deep and shallow groundwater flow. There are 3 main types of structures that are investigated. The geological contacts between hydraulically different lithologies, the primary characteristics of the sediments comprising the main geological units and the secondary structures developed from the tectonic events. These inter-alia include lithological boundaries, bedding and conjugate joints and large faults. Compartmentalisation of the aquifers by lithological and fault boundaries are the main regional level controls on flow in the study area. Joints are important for local control of flow, but cumulatively exert a regional effect as well. These controls exert a strong 3 dimensional impact on flow patterns within the area. Geological cross sections and detailed fieldwork combined with the conceptual models proposed are used to determine groundwater flow and the extent of the flow constraints. There is heterogeneity in the fault characteristics whilst there is consistence in the impermeable aquitards. These effect boundaries at the base of the aquifer, divide the aquifer into upper and lower units and cap the top of the aquifer. Using water level data, EC and pH an attempt is made to establish patterns created by structures, mainly faults. There appears to be some control of these shown by patterns seen on contour plots of the data. Understanding of the structures can significantly alter the way the available data could be interpreted. The integration of all available data into the conceptual model provides an effective research tool, which opens up further avenues for new approaches and methods for continued research in this area.

Thesis is submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, 2016 / Keywords/key concepts: Dolomite, Dolomitic ground, Disaster Risk Management, Physical Vulnerability, Low-income settlements, Housing Policy, Services delivery, Responsibility, Living with risk, Human Behaviour, Basic Human Rights Ground underlain by dolomite may be hazardous to development due to the potential occurrence of subsidence and sinkholes. These potentially disastrous occurrences are in many instances caused by human interaction with the soil through the ponding of water or leaking of wet infrastructure such as water and sanitation services. Construction materials and techniques, as well as effective maintenance of waterborne services have traditionally been acknowledged as having a significant bearing on the level of risk that communities face when living on such potentially dangerous land. The spatial distribution of settlements on dolomite in the Gauteng City Region (GCR) is already widespread and expected to increase as urbanisation intensifies. Similarly, the challenge of considering the physical vulnerability of low-income settlements is expected to intensify. Welldefined procedures and guidelines govern the development of human settlements on dolomitic ground. However, the classification and characterisation of low-income and informal settlements are not as advanced as that of formal residential developments. In addition, the guidelines regarding management of settlements on dolomite focus significantly on geotechnical interventions, leaving a gap in the influence that human behaviour can play in possible disaster risk reduction on such ground. The thesis considers the significance of different low-income settlement types on dolomite, relative to perceived human behaviour in association with principles of disaster risk reduction. It hypothesizes that an understanding of settlement type in relation to human behaviour and a stronger emphasis on monitoring via official channels could address some of the conflicts in the development-on-dolomite debate and thereby reduces settlement vulnerability. The research methods included quantitative and qualitative components, commencing with a literature review that spanned multiple disciplines and sectors. Fieldwork included spatial investigation and consideration of low-income settlement types with regard to, for example building material use, dwelling size and dwelling layout, and wet services infrastructure provision and location. The thesis subsequently identify and explore low-income settlement types in the study area. The research explores a number of sample settlements to consider the physical vulnerability and potential key areas of intervention and risk reduction, outside of the traditional geotechnical arena. The evaluation then applies the Analytical Hierarchy Process (AHP), a form of Multi Criteria Analysis (MCA), to identify important variables and indicators related to human behaviour and the physical vulnerability of settlements on dolomite that can be harnessed to intervene in the debate, and possible improve the safety of communities living with this risk. Although not affecting the research outcome directly, a specific observation during the course of engagement with specialists across disciplines was that experts in even closely related practice areas view low-income settlement development and upgrading on dolomite differently. The differences in viewpoints result in contradictions in approaches between housing officials, disaster managers, socio-environmental practitioners, engineers and geologists. Even small differences in approach have been shown to have significant effects on the practicalities surrounding decision making related to low-income settlements and especially informal settlement relocation or upgrading. The outcome is a set of prioritised indicators that could enable specialists, officials and the public to consider different elements of low-income settlements based on its physical vulnerability. By focussing on the indicators most likely to result in reduced vulnerability, actions that drive settlement development, upgrade and resettlement could be prioritised. Interestingly, one of the findings of the research is that it is not so much the settlement type based on informality that makes a difference in the exposure to risk – physical vulnerability is deemed to be significantly affected by official (municipal-sphere) actions, monitoring and awareness. Finally, the research enables the integration of technical knowledge with behavioural considerations when living on dolomite, thus highlighting opportunities to bring technical and non-technically skilled stakeholders in the debate closer together. / MT2017

In the numerical simulation of fluid flow and solute transport in porous media, finite element method (FEM) has long been utilized and has been proven to be efficient. In this work, an alternative approach called random walk particle tracking (RWPT) method is proposed. In this method, a finite number of particles represent the distribution of a solute mass. Each particle carries a certain fraction of the total mass and moves in the porous media according to the velocity field. The proposed RWPT model is established on a scientific software platform OpenGeoSys (OGS), which is an open source initiative for numerical simulation of thermo-hydro-mechanical-chemical (THMC) processes in porous media. The flow equation is solved using finite element method in OGS. The obtained hydraulic heads are numerically differentiated to obtain the velocity field. The particle tracking method does not solve the transport equation directly but deals with it in a physically stochastic manner by using the velocity field. Parallel computing concept is included in the model implementation to promote computational efficiency. Several benchmarks are developed for the particle tracking method in OGS to simulate solute transport in porous media and pore space. The simulation results are compared to analytical solutions and other numerical methods to test the presented method. The particle tracking method can accommodate Darcy flow as it is the main consideration in groundwater flow. Furthermore, other flow processes such as Forchheimer flow or Richards flow can be combined with as well. Two applications indicate the capability of the method to handle theoretical real-world problems. This method can be applied as a tool to elicit and discern the detailed structure of evolving contaminant plumes. / Bei der numerischen Simulation von Strömung und Stofftransport in porösen Medien hat die Nutzung der Finite-Elemente-Methode (FEM) eine lange Tradition und wird sich als effizient erweisen. In dieser Arbeit wird ein alternativer Ansatz, die random walk particle tracking (RWPT) Methode vorgeschlagen. Bei diesem Verfahren stellt eine endliche Anzahl von Partikeln die Verteilung eines gelösten Stoffes dar. Jedes Teilchen trägt einen bestimmten Bruchteil der Gesamtmasse und bewegt sich in den porösen Medien gemäß des Geschwindigkeitsfeldes. Das vorgeschlagene RWPT Modell basiert auf der wissenschaftlichen Softwareplattform OpenGeoSys (OGS), die eine Open-Source-Initiative für die numerische Simulation thermo-hydro-mechanisch-chemischen (THMC) in porösen Medien darstellt. Die Strömungsgleichung wird in OGS mit der Finite-Elemente-Methode gelöst. Der Grundwasserstand wird numerisch berechnet, um das Geschwindigkeitsfeld zu erhalten. Die Partikel-Tracking-Methode löst die Transportgleichung nicht direkt, sondern befasst sich mit ihr in einer physikalisch stochastische Weise unter Nutzung des Geschwindigkeitsfeldes. Zur Berücksichtigung der Recheneffizienz ist ein Parallel Computing-Konzept in der Modell-Implementierung enthalten. Zur Simulation des Stofftransports in porösen Medien und im Porenraum wurden mehrere Benchmarks für die Partikel-Tracking-Methode in OGS entwickelt. Die Simulationsergebnisse werden mit analytischen Lösungen und andere numerische Methoden verglichen, um die Aussagefähigkeit des vorgestellten Verfahrens zu bestätigen. Mit der Partikel-Tracking-Methode kann die Darcy-Strömung gelöst werden, die das wichtigste Kriterium in der Grundwasserströmung ist. Außerdem bewältigt die Methode auch andere Strömungsprozesse, wie die Forchheimer-Strömung und die Richards-Strömung. Zwei Anwendungen zeigen die Leistungsfähigkeit der Methode bei der prinzipiellen Handhabung von Problemen der realen Welt. Die Methode kann als ein Instrument zur Aufdeckung Erkennung der detaillierte Struktur von sich entwickelnden Schadstofffahnenangewendet werden.

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