Groundwater is an important natural resource and ought to be protected. Groundwater recharge and contamination are two important aspects in groundwater management. Both these aspects apply to the vadose zone. The research aimed to narrow the knowledge gap between practising geohydrologists and engineering geologists, both frequently involved in vadose zone investigations for geohydrological and engineering purposes respectively. The vadose zone is the portion of the geological profile above the groundwater surface and is usually characterised by unsaturated conditions. Matrix forces counteract the force of gravitation to hold liquid in the porous medium and are reflected by hydraulic heads lower than atmospheric pressure (suction). The unique relationship between soil-water content and suction is presented by soil-water characteristic curves. Flow of liquids is directly proportional to the hydraulic gradient and the hydraulic conductivity and is affected by the geometric properties of the pore channels. In unsaturated soils, flow is governed by both matrix and gravitational forces. Preferential flow is the process by which water and solutes move along preferred pathways through a porous medium. Important hydrogeological properties, such as porosity, hydraulic conductivity and soil-water retention characteristics, can be estimated from geotechnical data. Unsaturated hydraulic conductivity can also be estimated from soil-water characteristic curves and saturated hydraulic conductivity. The experimental procedures comprised analyses of existing hydrogeological data, laboratory tests and field experiments. The geotechnical data were used to predict important hydrogeological properties and these predictions were compared to experimentally derived hydrogeological properties. The effects of preferential flow and soil variability were also investigated. Predictions of porosity, hydraulic conductivity and soil-water retention characteristics lack precision, owing mostly to the natural variability in hydrogeological properties and inherent errors of the empirical models. Accurate predictions of unsaturated hydraulic conductivity were based on experimentally derived saturated hydraulic conductivity and soil water characteristic data. The study area is located in Midrand and is underlain by granitoid rocks that had been subjected to a number of geomorphologic events. The land system classification approach was used to delineate the hydrogeological units. The different hydrogeological characteristics can be attributed mainly to the position of the hydrogeological units in respect of the topographical setting, the geomorphologic history and the underlying geology. A conceptual hydrogeological model was constructed for each of the hydrogeological zones and its significance in respect of groundwater recharge and vulnerability discussed. The research has shown that geohydrological properties can be estimated from geotechnical data with various degrees of accuracy. Predictions of hydraulic conductivity, soil water retention characteristics and porosity are not suitable for site-specific investigations, but it can be used during the feasibility phases. In cases where saturated hydraulic conductivity and soil-water retention characteristics have been experimentally derived, estimations of unsaturated hydraulic conductivity are adequate for site-specific investigations. The land system approach can be used to delineate areas of similar geohydrological characteristics and these can be used in the compilation of aquifer vulnerability and groundwater recharge maps. / Thesis (PhD)--University of Pretoria, 2006. / Geology / Unrestricted

The Swartkops River and Sundays River Estuaries are different in terms of morphology and the level of human impact. Budget models of DIP and DIN were constructed for each estuary at different riverine flow rates, using the Land-Ocean Interactions in the Coastal Zone (LOICZ) protocol. Nutrient dynamics in the estuaries were investigated using nutrient data and the results of the models. The Swartkops River Estuary acted as a sink of DIP and DIN, while being net heterotrophic. The Sundays River Estuary acted as a source of DIP and DIN, while being net autotrophic. Both systems were net denitrifying. The Swartkops River Estuary shows greater anthropogenic impacts in terms of nutrient loads than the Sundays River Estuary. A shift in nutrient concentration trends and system properties occurred between conditions of low and high riverine flow rates. The Swartkops River and Sundays River Estuaries were shown to be ‘outwellers’ of DIN and DIP, while having an important influence on the ratio of DIN:DIP exported to the adjacent ocean. Comparisons with other estuaries suggested that riverine flow into estuaries in the Eastern Cape region may display natural DIN:DIP ratios which are lower than the global average for “pristine” systems. Such ratios would be decreased further by increased water extraction for human activities.

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 isconsistence 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.

<p>The Table Mountain Group (TMG) Aquifer is the second largest aquifer system in South Africa, after dolomites. This aquifer has the potential to be a signinficant source of water for the people of the Western Cape. The occurrence of hot water springs in the TMG in relation with the main geological fault systems in SOuth Africa shows that deep flow systmes do exist. Little is known about these deep aquifer systems in South Africa (i.e. flow mechanisms). To close the above-mentioned knowledge gap, this study was initiated. The current study gave a review of some of the aspects that needs to be considered when distinguishing deep groundwater from shallow groundwater.</p>

<p>Understanding of Groundwater Dependent Ecosystems (GDEs) and their extent within the Table Mountain Group (TMG) aquifer is poor. To understand the dependence to basic ecological and hydrogeological concepts need explanation. The use of current literature aided in identification and classification. From the literature it has come clear that groundwater dependence centers around two issues, water source and water use determination. The use of Geographical Information System (GIS) showed its potential in proof of water sources. Rainfall data and a Digital Elevation Model (DEM) for the Uniondale area have been used to do watershed delineation, which is in line with locating GDEs on a landscape. Thus the conceptual approach should be a broad one that sets a basis for both investigation (scientific research) and institutional arrangements (management).</p>

Previous studies found that during a rainfall event, pre-event water, which exists in the catchment before the event, may appear in significant amounts in the stream stormflow hydrograph. Pre-event water is predominantly groundwater. Among the mechanisms that have been proposed to explain the rapid mobilization of pre-event water from hillslopes are: (1) groundwater ridging (GWR) i.e. the rapid rise of a water table in environments, where the capillary fringe, or the zone of tension saturation, is very close to the ground surface and (2) the Lisse Effect (LE) i.e. the rapid response of a groundwater level to pressurized pore air in the unsaturated zone. Published literature explains that GWR is caused by the application of a small amount of water on the ground surface. On the LE, it is explained that pressurized pore air acts at the water table, resulting in a rapid rise of the water level in a well, screened below the water table. These explanations are insufficient on the physical processes involved in GWR and the LE. The objectives of this study were: (1) to use the commonly observed catchment hydrological processes i.e. tensiometric pore water pressure, shallow groundwater levels, rainfall data and the hydraulic properties of soils, to quantify and describe the physical processes involved in GWR and the LE mechanisms; (2) to perform laboratory experiments, in order to understand the physical processes involved in the LE; and (3) to develop a mathematical theory that can describe the physical processes in the LE. Results indicated that GWR and the LE are caused by the addition (elevation) of potential energy in water within the capillary fringe. In GWR, the additional energy is from the intense rainfall. In the LE, the additional energy is from compressed pore air in the unsaturated zone. In both mechanisms, the added energy diffuses through the capillary fringe, as a downward pressure wave, releasing the tension forces in water. As soon as the downward pressure wave-front arrives at the water table, the water table begins to ascend, as an upward pressure wave. The ascending water table steepens the hydraulic gradient, which results in the rapid groundwater fluxes, without the recharge of the water table by the infiltration profile. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2013.

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 isconsistence 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.

<p>Understanding of Groundwater Dependent Ecosystems (GDEs) and their extent within the Table Mountain Group (TMG) aquifer is poor. To understand the dependence to basic ecological and hydrogeological concepts need explanation. The use of current literature aided in identification and classification. From the literature it has come clear that groundwater dependence centers around two issues, water source and water use determination. The use of Geographical Information System (GIS) showed its potential in proof of water sources. Rainfall data and a Digital Elevation Model (DEM) for the Uniondale area have been used to do watershed delineation, which is in line with locating GDEs on a landscape. Thus the conceptual approach should be a broad one that sets a basis for both investigation (scientific research) and institutional arrangements (management).</p>

<p>The Table Mountain Group (TMG) Aquifer is the second largest aquifer system in South Africa, after dolomites. This aquifer has the potential to be a signinficant source of water for the people of the Western Cape. The occurrence of hot water springs in the TMG in relation with the main geological fault systems in SOuth Africa shows that deep flow systmes do exist. Little is known about these deep aquifer systems in South Africa (i.e. flow mechanisms). To close the above-mentioned knowledge gap, this study was initiated. The current study gave a review of some of the aspects that needs to be considered when distinguishing deep groundwater from shallow groundwater.</p>

Magister Scientiae - MSc / Understanding of Groundwater Dependent Ecosystems (GDEs) and their extent within the Table Mountain Group (TMG) aquifer is poor. To understand the dependence to basic ecological and hydrogeological concepts need explanation. The use of current literature aided in identification and classification. From the literature it has come clear that groundwater dependence centers around two issues, water source and water use determination. The use of Geographical Information System (GIS) showed its potential in proof of water sources. Rainfall data and a Digital Elevation Model (DEM) for the Uniondale area have been used to do watershed delineation, which is in line with locating GDEs on a landscape. Thus the conceptual approach should be a broad one that sets a basis for both investigation (scientific research) and institutional arrangements (management). / South Africa