The development potential of Kwazulu-Natal aquifers for rural water supply
- Authors: King, Georgina
- Date: 1997
- Subjects: Aquifers -- South Africa -- KwaZulu-Natal , Water-supply, Rural -- South Africa -- KwaZulu-Natal , Hydrology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4938 , http://hdl.handle.net/10962/d1005550 , Aquifers -- South Africa -- KwaZulu-Natal , Water-supply, Rural -- South Africa -- KwaZulu-Natal , Hydrology -- South Africa
- Description: The supply of water to 'disadvantaged' areas of KwaZulu-Natal has in the past received low priority. Local government is now faced with supplying water to large, sometimes dispersed, rural populations. Groundwater has been utilised informally as a water supply for some years, but the impetus provided by the Department of Water Affairs and Forestry's White Paper has compelled those responsible for water supply to seriously consider groundwater as a sustainable option. The development potential or success of groundwater in its role as a reliable water supply is dependent on acceptance of the resource by the communities, appropriate level of service, yield sustainability and safe quality. Apart from the social aspects, the yield and groundwater quality characteristics of the aquifers under consideration must be used to determine the best hydrogeological features to target during exploration. A total of 993 borehole records, from a recent government drought relief programme, were used to compare the yield, water quality and best geophysical exploration and drilling techniques of the main hydrolithologies in rural KwaZulu-Natal. The results of comparative analysis shows that the competent rocks of the Natal Group and Natal Metamorphic Province and the karstic Uloa Formation of the Maputaland Group have the best overall potential for water supply. The unconsolidated sediments of the Maputaland Group also have good potential, but have some salinity problems. The Karoo Supergroup sediments and volcanics have moderate potential, with the argillaceous rocks having the worst potential of the Karoo rocks. The contacts between the Ecca Group shales and sandstone have the best potential of the Karoo Supergroup sedimentary hydrolithologies. Fractures clearly enhance the groundwater potential of most hydrolithologies, with fractured Dwyka Group tillites rated as having one of the best development potentials of all the hydrogeological targets in KwaZulu-Natal, despite the hydrolithology's poor water-bearing characteristics. Dolerite contacts with sedimentary rocks are commonly targeted features in groundwater development. However, the results from this research showed that, apart from the Natal Group's contact with dolerite, these targets have poor development potential. In general, contacts between different hydro lithologies. Health related quality was found to be adversely affected in argillaceous hydrolithologies, such as the majority of Karoo rocks which had high levels of sodium and chloride and Natal Metamorphic Province schists which had elevated sodium, chloride and fluoride. Crystalline and arenaceous hydrolithologies generally exhibited good quality groundwater. A comparison between the different geophysical methods for each target feature indicates that there are appropriate methods to use to detect anomalies related to water-bearing features. The large number of dry boreholes drilled in locations with recorded geophysical anomalies can be either a function of the water-bearing characteristics of the formation, human error or background noise. The cost of using the different geophysical methods vary considerably. The order of increasing cost is magnetics, VLF, EM-34, electrical resistivity profiling followed by vertical electrical sounding. Drilling has a large influence on the development potential of certain aquifers due to the high costs involved. Most of the secondary aquifers will require percussion drilling which is the cheapest method of drilling commonly used. Some very unstable formations within fractured or highly weathered rock may need ODEX drilling to enable drilling to advance. ODEX drilling in these conditions is very costly and can double the cost of drilling compared to air percussion. The unconsolidated sediments of the Maputaland Group can only be drilled by mud rotary or ODEX techniques. The relative costs of these two methods arer very similar with ODEX being slightly cheaper. Because of the high expense of drilling in the sands it is recommended that alternative sources, possibly from shallow hand-dug wells, be considered as appropriate methods of accessing groundwater. The aspects of groundwater yield and quality of aquifers, appropriate geophysical siting and drilling methods, together with social considerations will all contribute to the success of groundwater development in rural KwaZulu-Natal.
- Full Text:
- Authors: King, Georgina
- Date: 1997
- Subjects: Aquifers -- South Africa -- KwaZulu-Natal , Water-supply, Rural -- South Africa -- KwaZulu-Natal , Hydrology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4938 , http://hdl.handle.net/10962/d1005550 , Aquifers -- South Africa -- KwaZulu-Natal , Water-supply, Rural -- South Africa -- KwaZulu-Natal , Hydrology -- South Africa
- Description: The supply of water to 'disadvantaged' areas of KwaZulu-Natal has in the past received low priority. Local government is now faced with supplying water to large, sometimes dispersed, rural populations. Groundwater has been utilised informally as a water supply for some years, but the impetus provided by the Department of Water Affairs and Forestry's White Paper has compelled those responsible for water supply to seriously consider groundwater as a sustainable option. The development potential or success of groundwater in its role as a reliable water supply is dependent on acceptance of the resource by the communities, appropriate level of service, yield sustainability and safe quality. Apart from the social aspects, the yield and groundwater quality characteristics of the aquifers under consideration must be used to determine the best hydrogeological features to target during exploration. A total of 993 borehole records, from a recent government drought relief programme, were used to compare the yield, water quality and best geophysical exploration and drilling techniques of the main hydrolithologies in rural KwaZulu-Natal. The results of comparative analysis shows that the competent rocks of the Natal Group and Natal Metamorphic Province and the karstic Uloa Formation of the Maputaland Group have the best overall potential for water supply. The unconsolidated sediments of the Maputaland Group also have good potential, but have some salinity problems. The Karoo Supergroup sediments and volcanics have moderate potential, with the argillaceous rocks having the worst potential of the Karoo rocks. The contacts between the Ecca Group shales and sandstone have the best potential of the Karoo Supergroup sedimentary hydrolithologies. Fractures clearly enhance the groundwater potential of most hydrolithologies, with fractured Dwyka Group tillites rated as having one of the best development potentials of all the hydrogeological targets in KwaZulu-Natal, despite the hydrolithology's poor water-bearing characteristics. Dolerite contacts with sedimentary rocks are commonly targeted features in groundwater development. However, the results from this research showed that, apart from the Natal Group's contact with dolerite, these targets have poor development potential. In general, contacts between different hydro lithologies. Health related quality was found to be adversely affected in argillaceous hydrolithologies, such as the majority of Karoo rocks which had high levels of sodium and chloride and Natal Metamorphic Province schists which had elevated sodium, chloride and fluoride. Crystalline and arenaceous hydrolithologies generally exhibited good quality groundwater. A comparison between the different geophysical methods for each target feature indicates that there are appropriate methods to use to detect anomalies related to water-bearing features. The large number of dry boreholes drilled in locations with recorded geophysical anomalies can be either a function of the water-bearing characteristics of the formation, human error or background noise. The cost of using the different geophysical methods vary considerably. The order of increasing cost is magnetics, VLF, EM-34, electrical resistivity profiling followed by vertical electrical sounding. Drilling has a large influence on the development potential of certain aquifers due to the high costs involved. Most of the secondary aquifers will require percussion drilling which is the cheapest method of drilling commonly used. Some very unstable formations within fractured or highly weathered rock may need ODEX drilling to enable drilling to advance. ODEX drilling in these conditions is very costly and can double the cost of drilling compared to air percussion. The unconsolidated sediments of the Maputaland Group can only be drilled by mud rotary or ODEX techniques. The relative costs of these two methods arer very similar with ODEX being slightly cheaper. Because of the high expense of drilling in the sands it is recommended that alternative sources, possibly from shallow hand-dug wells, be considered as appropriate methods of accessing groundwater. The aspects of groundwater yield and quality of aquifers, appropriate geophysical siting and drilling methods, together with social considerations will all contribute to the success of groundwater development in rural KwaZulu-Natal.
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The geology and alteration-mineralisation of the Gamigab Tin Prospect, Damaraland, Namibia
- Authors: Walraven, Felix Caspar
- Date: 1990
- Subjects: Mineralogy -- Namibia -- Damaraland , Geology -- Namibia -- Damaraland , Tin mines and mining -- Namibia -- Damaraland
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4956 , http://hdl.handle.net/10962/d1005568 , Mineralogy -- Namibia -- Damaraland , Geology -- Namibia -- Damaraland , Tin mines and mining -- Namibia -- Damaraland
- Description: The stratigraphy at the Gamigab Sn prospect consists of two mainly schistose units separated by a thick marble unit which have been assigned to the Orusewa, the Karibib and the Kuiseb Formations respectively. Four phases of folding affected the lithologies with the south-south-west trending F2 folds defining the main structures in the region. The area underwent low grades of metamorphism. Temperatures were in the range 420° to 500°C and pressures less than 2 kbars. The effects of contact metamorphism are seen in the south-east and south-west. Regional metamorphism outlasted the deformation and contact metamorphism started late during deformation. Two Karoo-age intrusions penetrated the metasediments north of the mineralisation. One is an altered porphyry plug and the other is a weathered dolerite plug, the latter containing xenoliths of undeformed Karoo sediments. Cassiterite is hosted within east-west trending quartz veins that cross-cut previously altered schistose country rocks. The alteration types include sericitisation, tourmalinisation, carbonatisation and ferruginisation. Preliminary Rb/Sr dating on muscovite from the alteration zone suggests an age of 509 ± 11 Ma. Breccias of probable hydrothermal origin are spatially associated with the mineralisation. These hydraulic breccias occur in antiformal structures within the marble and developed in response to a sudden pressure release due to a build up of fluids at the contact between the schistose Orusewa and carbonate Karibib Formations.
- Full Text:
- Authors: Walraven, Felix Caspar
- Date: 1990
- Subjects: Mineralogy -- Namibia -- Damaraland , Geology -- Namibia -- Damaraland , Tin mines and mining -- Namibia -- Damaraland
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4956 , http://hdl.handle.net/10962/d1005568 , Mineralogy -- Namibia -- Damaraland , Geology -- Namibia -- Damaraland , Tin mines and mining -- Namibia -- Damaraland
- Description: The stratigraphy at the Gamigab Sn prospect consists of two mainly schistose units separated by a thick marble unit which have been assigned to the Orusewa, the Karibib and the Kuiseb Formations respectively. Four phases of folding affected the lithologies with the south-south-west trending F2 folds defining the main structures in the region. The area underwent low grades of metamorphism. Temperatures were in the range 420° to 500°C and pressures less than 2 kbars. The effects of contact metamorphism are seen in the south-east and south-west. Regional metamorphism outlasted the deformation and contact metamorphism started late during deformation. Two Karoo-age intrusions penetrated the metasediments north of the mineralisation. One is an altered porphyry plug and the other is a weathered dolerite plug, the latter containing xenoliths of undeformed Karoo sediments. Cassiterite is hosted within east-west trending quartz veins that cross-cut previously altered schistose country rocks. The alteration types include sericitisation, tourmalinisation, carbonatisation and ferruginisation. Preliminary Rb/Sr dating on muscovite from the alteration zone suggests an age of 509 ± 11 Ma. Breccias of probable hydrothermal origin are spatially associated with the mineralisation. These hydraulic breccias occur in antiformal structures within the marble and developed in response to a sudden pressure release due to a build up of fluids at the contact between the schistose Orusewa and carbonate Karibib Formations.
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