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The Groundwater characteristics of a portion of the Eastern Cape are depicted on a General Hydrogeological Map (Queenstown 3126) at 1 :500 000 scale. The purpose of the map and accompanying text is to provide a synoptic overview of the hydrogeology of the area. The "fractured and intergranular" aquifer type predominates in the more humid eastern part of the study area where the lithologies are more highly weathered whereas the fractured type predominates in the drier west. For the bulk of the area borehole yields are in the 0.5 - 2.0 ℓ/sec range. Higher yields (in the 2.0 - 5.0 ℓ/sec range) are common only in a small area in the south-west of the map. Lowest yields (0.1 - 0.5 ℓ/sec) are obtained in an area immediately north of East London and in the Dwyka Group near the NE coast. It is important to note that these yield ranges are merely a measure of the central tendency, and that higher yields - in excess of 3 ℓ/sec - could well be obtainable at optimal hydrogeological target features within these areas. Highest borehole yields are obtained in folded areas (restricted to the southern edge of the study area) followed by rocks with dolerite intrusions (common over the bulk of the study area). Other targets include fractured sedimentary and volcanic rock and unconsolidated deposits. Yields obtained from dolerite contact zones vary across the area; differences correspond to spatial variations in the style of intrusion. Highest success rates are obtained in areas intruded by a combination of dykes, ring-shaped sheets and irregular sheets while poor results are obtained in areas intruded by thick massive sills. Air photo and satellite image interpretation, geological mapping, magnetic, electrical resistivity and electromagnetic geophysical methods can be used to locate drilling target features. Groundwater quality is good since electrical conductivities over much of the area are lower than 70 mS/m and rarely exceed the South African Water quality guideline limit for human consumption of 300 mS/m. The volume of groundwater abstractable ranges between approximately 2 000 m³/km²/annum and 80 000 m³/km²/annum and is limited by either volumes of recharge or subsurface storage.

The Uitenhage artesian aquifer north-west of Port Elizabeth in South Africa, is one of the few artesian groundwater systems in Southern Africa. The Uitenhage - Coega, and Kruis River areas, are the most important portions of the Uitenhage Artesian System in terms of water abstraction and water use. This study concentrates on the Uitenhage - Coega area and in particular, on the Coega Ridge where the Table Mountain Sandstone (TNS) aquifer occurs at relatively shallow depths. The investigation is aimed at assessing the geological, hydrogeological and hydrochemical characteristics of the HIS and any other aquifers present, with the object of providing quantitative data for use in future decisions on the water resource management of the area. In order to achieve these objectives, field work, involving a hydrocensus, geological mapping, geophysical exploration, drilling, aquifer testing and hydrochemical sampling was carried out. Analysis of these data provided information on the extent of the aquifers, their hydrogeological characteristics and the chemical nature of the various groundwater types.

The Grootfontein aquifer is located about 20 km south east of Mahikeng, North West Province, South Africa, and currently supplies about 20% of Mahikeng’s water. Formed in weathered Malmani Subgroup dolomites, the aquifer contains good quality groundwater that could potentially supply more of Mahikeng’s water, as well as provide a strategic reserve of water for use during droughts. Over-abstraction of groundwater from the aquifer, mainly by irrigating farmers but also by the boreholes supplying Mahikeng, has caused the natural groundwater level to drop at a rate of about 0.4 m per year since the 1970s, leading to water level declines of as much as 28 m in parts of the aquifer. Although the Grootfontein aquifer is one of the best studied aquifers in South Africa hydrogeologically, efforts to address these declines since the 1970s have largely failed. This research combines hydrogeological evidence with social research (interviews and participant-observation) and the principles of Earth Stewardship Science to argue that the aquifer functions as a hydro-social system, and that institutional characteristics are the root cause of a collective inability to restore the aquifer to its full potential as a water resource. A sub-optimal and undesirable Nash equilibrium prevails, in which major groundwater users are unable or unwilling to reduce abstraction. The situation has significant cost and risk implications for the environmental, economic and social sectors, and contributes to insecurity, pessimism, inequality and mistrust. An effective local forum with appropriate powers, supported and mandated by the Department of Water and Sanitation, is needed to begin the work of dismantling the sub-optimal equilibrium to realise the potential of the Grootfontein aquifer. Such a forum would require a shared understanding of the hydrogeological mechanisms of the aquifer as well as its social and institutional functioning, since these influence each other in complex ways.

The study concerns an assessment of the hydrogeological impact of an open cast coal mine in the North Western Transvaal Province of South Africa. The hydrogeological impact of the mine is assessed in terms of groundwater quality and levels. A monitoring system was installed to enable the present and future impact of mining operations on the hydrogeological regime to be assessed. Grootegeluk Mine is situated in the Waterberg Coal Field of South Africa and began production in 1980. The mine extracts fifteen million tons of mine material annually from a single open pit. Forty percent of the mined material is saleable product and the remaining sixty percent is stacked on discard dumps. The Daarby fault forms the northern boundary of the open pit and serves to bring the younger Letaba and Clarens Formations into contact with the older Beaufort and Ecca Groups. The mine discards are deposited north of the fault on a different hydrogeological environment from which they are mined. Dewatering of the mine open pit has resulted in a steady decline in water levels in the Ecca Group, south of the Daarby fault. In contrast, water levels north of the Daarby fault in the Letaba and Clarens Formations have risen. The short term hydrochemical impact of the mine discard dumps and slimes dams have resulted in a rise in the calcium, sulphate, chloride, fluoride and nitrate concentrations of the ambient groundwater . The longer term hydrochemical impact from the waste dumps, acid mine drainage, is not evident at present in the groundwater below the waste dumps. However, it is expected to manifest itself during the next ten years. A monitoring system was installed at the mine to allow groundwater levels and quality to be monitored. By measuring groundwater quality and levels the impact of the mine on the regional hydrogeology can be monitored and assessed presently, and during the next forty years of production. Monitoring will also enable the timeous implementation of remedial measures at an early stage and eliminate the need for large late stage "clean up" operations. Future monitoring of both water levels and quality will be crucial in evaluating the mine's impact on the regional groundwater regimes over the next forty years of production. The remedial measures recommended for leachate presently emanating from the waste dumps and slimes dams north of the Daarby fault, are a number of collector wells drilled into the basalts and sandstone north of the Daarby fault. The proposed positions of the wells (boreholes) are as close as possible to the dumps and slimes dams with expansion taken into consideration. The boreholes should be designed to lower the water level in the vicinity of the dumps in order to create a nett groundwater gradient towards the dumps and as a result, halt the spread of leachate away from the dumps. Grootegeluk plans to backfill the open pit with plant discards on completion of the mining of zone 2. The backfilled material will consist of the currently produced plant waste and will be covered with overburden and topsoil. It is expected that the backfilling will have a major impact on groundwater quantity if no remedial measures are implemented. The two remedial measures discussed are chemical treatment of the discard material before backfilling or the continual abstraction of water from the pit resulting in a nett groundwater inflow into the pit. No material from the present waste dumps and slimes dams will be transported into the open pit as backfill material

The Hex River Valley is one of the main centres in South Africa for cultivation of table grapes of export quality. The vines require irrigation water, which must be low in dissolved solids. Approximately two thirds of the annual irrigation requirement is obtained from boreholes and the balance from surface water sources. During the early 1960s a deterioration in the quality of the groundwater was noticed, becoming critical in some areas, and borehole yields also declined. The main objectives of this study were therefore to obtain an understanding of the hydrogeological and hydrogeochemical processes operating in the valley to explain the derogation of the groundwater resource and enable optimum utilisation and management of the resource in the future. To achieve these objectives, field work involving exploration drilling, aquifer tests, hydrocensus, long-term monitoring of groundwater levels and surfacewater flows and extensive sampling of the ground and surface waters was carried out. Analysis of these data gave quantitative information on groundwater occurrence, aquifer hydraulic properties, groundwater recharge and storage, chemical characteristics of the ground and surfacewaters and sources of dissolved species. / KMBT_363 / Adobe Acrobat 9.53 Paper Capture Plug-in

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

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: This study was conducted to assess groundwater characteristics of geologically different fracture rock aquifers, at different depths, by means of chemical, isotope and 14C-dating results and to test for a "deeper seated aquifer", with different characteristics. Jurassic dolerite dykes and sills, Cretaceous kimberlite fissures and pipes, as well as EW trending sinusoidal megafolds, comprise the structural domains of the study area. Fluvial sandstone and mudstone of the Beaufort Group are the dominant lithology of the study area. The main water type found in the area is a water type not dominated by any anions or cations in particular. The second is a water type in which Na-S04 is dominant, followed by a Na-HC03 dominated water and to a lesser extend a Ca-S04 type water. The main cause of groundwater salinity is the infiltration of evaporated water to the subsurface, suggested by the isotopic enrichment of 0180 and 02H, indicating very slow recharge from ponded water during excessive rainfall events. There is a fair difference in isotopic values between surface measurements and measurements taken at depth, enforcing the possibility of a "second deeper seated aquifer". The water with the lower 180 values, for samples at depth suggest that this water has a source further inland, from rainfall on the range to the NE, the Hex River Mountain or Pramberge, which has greatly depleted 180 values relative to SMOW. Most of the groundwater samples taken at depth indicated a 14C~dating of century age (±200 years), although in an evolutionary sequence the water is not such an old (evolved) water type, lending support to the theory about the migration of deeper seated water and thus a "second deeper seated aquifer system". The chemical character of the groundwater is predominantly controlled by the infiltration of evaporated surface and subsurface water, the topographical nature of the catchments, geological influences (i.e. the process of dissolution, precipitation and ion exchange) and the influence of man. Variability in water quality is caused by differences in rainfall, recharge, evaporation, topography, soil type and thickness, vegetation cover and antropogenic activities. Micro-scale differences occur due to the nature of groundwater flow in Karoo rocks, namely the resulting variations within matrix and fracture components of the groundwater flux. The residence times are often different for these two main components and give rise to the differences in mineralization and solute proportion in passing groundwater. This project should be seen as a basis of continuing study to provide the concrete answers needed to manage groundwater projects in the fractured rock aquifers of the Karoo. Enslin (1950) expresses the classical hydrological conceptualisation of Karoo dolerite dykes - lithe effect of induration and crushing of the sedimentary rock is that the permeability has been increased and the contact zone has been changed into an aquifer lying between the solid dyke and the saturated, low permeability country rock". / AFRIKAANSE OPSOMMING: Hierdie studie was onderneem met die doel. om grondwater eienskappe te ondersoek in geologies verskillende gekraakte / genate aquifere en by verskillende dieptes met die hulp van chemiese, isotopiese en 14C-datering resultate, om sodoende te toets vir 'n "tweede dieper liggende aqulfeer", met verskillende eienskappe. Doleriet gange en plate (Jura), kimberliet gange en pype (Kryt), sowel as OW lopende sinusvormige mega-verskuiwings en monoklienes van die Kaapse Plooi Gordel, Vorm die strukturele omgewings in die studie gebied. Die dominante litologie in die studie gebied is fluviaal gedeponeerde sandsteen en moddersteen van die Beaufort Groep. Die opvallendste water-tipe wat in die studie gebied waargeneem word is 'n grondwater wat geen dominante katione of anione toon nie, tweedens is daar 'n Na-S04 tipe grondwater wat gevolg word deur 'n Na-HC03 tipe water en daarna 'n Ca-S04 grondwater tipe. Die hoof oorsaak van saliniteit in the grondwater is die infiltrering van verdampte water na die grondwater-tafel, deur die verryking in 01BOen 02H, wat stadige infiltrasie van water na hewige reënval episodes voorstel. Die verskil van isotoop waardes by vlak en diepper watervlakke, steun die moontlikheid van die aanwesigheid van 'n "tweede dieper liggende aquifeer". Water met die lae 1BO-waardes (met diepte) dui op 'n opvangsgebied meer na die noordoostelike binneland, soos byvoorbeeld die Hex Rivier Berge en die Pramberge. Meeste van die grondwater monsters wat geneem is by 'n redelike diepte toon 'n 14C-datering waarde van ongeveer 200 jaar, alhoewel die water uit 'n evolutionere oogpunt nie so oud is nie en sodoende ondersteuning bied aan die teorie van die beweging van dieper liggende water en die bestaan van 'n "tweede dieper liggende aquifeer". Die chemiese karakter van grondwater word hoofsaaklik beheer deur die infiltrering van verdampte oppervlak water na die grondwater-tafel, die topografiese geaardheid van die opvangsgebied, geologiese invloede (soos die prosesse van presipitering, oplossing en ioon uitruiling), sowel as die infloed van die mens. Wisselvalligheid in die kwaliteit van grondwater word veroorsaak deur verskille in reënval, infiltrasie, evaporasie, topografie, grond tipe en diepte, plantegroei en die aktiwiteite van die mens. Verskille op mikro-vlak word veroorsaak deur die aard van die grondwater vloei deur die Karoo gesteentes, volgens die verskil in hidroliese geleiding tussen vloei in die matriks en vloei in die krake / nate. Daar is ook 'n verskil in die tydsbestek wat grondwater in die twee hoofstrukturele komponente deurbring en so die verskil in mineralisasie en saliniteit in die dinamiese grondwater veroorsaak. Die projek moet gesien word as die basis vir voortdurende studie om konkrete antwoorde te verseker vir die gebruik in grondwater bestuur projekte van die gekraakte / genate rots aquifere in die Karoo. Enslin (1950) konseptualiseer Karoo doleriet gange as volg: "die effek van indringing en verbrokkeling van sedimentêre gesteentes is dat die deurlaatbaarheid verhoog word en dat die kontak sone verander is na 'n aquifeer wat lê tussen die soliede gang en die versadigde, lae deurlaatbare wand-gesteentes".

The aquifer of the study area occupies an escarpment and low lying limestone plain, and exhibits a Vaal River type karst. The four dolomitic formations present fall into two distinct aquifer forming types; chert poor units and chert rich units. The chert poor units of the Oaktree and Lyttelton Formations were deposited in a subtidal environment and were probably dolomi tised in a migrating schizohaline environment during basin subsidence and shoreline trangression. The chert rich units of the Monte Christo and Eccles Formations were deposited in the shallow subtidal to supratidal zones and the interbedded chert and dolomites may result from minor cyclical marine trangressions and regressions or be a geochemical response to the periodic flooding of freshwater carbonate and flats and tidal deltas. These fundamental geological differences are reflected in correspondingly different development of karst. Transmissive zones in the chert poor units are generally discrete solution features in massive dolomite, 1 m to 2 m thick. Transmissive zones in the chert rich units comprise thick (up to 60 m) and extremely weathered chert with a high void content resulting from the dissolution of carbonate material. The relative importance of various geological features to the development of the karst was assessed using information from two extensive hydrogeological investigations of the area. From the results it bas been concluded that lithostratigraphy, including the occurrence of palaeokarstic horizons, is the major control of aquifer properties. All other geological features are of lesser importance but may nevertheless be associated with enhanced transmissivi ties in any given unit. Faults and lineaments are the structural features most widely associated with highly transmissive zones. The knowledge gained in this study is applicable elsewhere as the principal hydrogeological characteristics of the study area are common to many of the Chuniespoort Group aquifers in the Pretoria - Witwatersrand - Vereeniging Region.

This thesis deals with a groundwater investigation conducted in the Van Rynevelds Pass Dam basin, north of Graaff-Reinet, in the Cape Province. The objective of the study was to assess the groundwater potential of the basin in terms of its development and exploitation as a municipal supply. In order to achieve this objective, fieldwork was carried out involving a hydrocensus, geological/geophysical mapping, drilling, aquifer testing and hydrochemical sampling. The fieldwork was conducted during the period January 1983 to February 1984. The investigation revealed that the most significant ground water occurrence in the study area is an alluvial/weathered bedrock aquifer (Graaff-Reinet aquifer ) . The volume of ground water stored in the Graaff-Reinet aquifer is in the order of 27 x 10⁶ m³, while its exploitation potential is conservatively estimated at 9 300 m³/day. However, the quality of this water is poor and should be blended with dam water or better quality groundwater. Two minor fractured aquifer units were also identified.