- Title
- The investigation of groundwater potential zones in the Neotectonic area of Ntabankulu Local Municipality, Eastern Cape Province, South Africa
- Creator
- Nonkula, Zenande https://orcid.org/0000-0002-3858-7703
- Subject
- Groundwater
- Subject
- Water-supply
- Subject
- Neotectonics
- Date
- 2021-09
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/22875
- Identifier
- vital:53068
- Description
- Ntabankulu extends from latitude 30° 51' 09"S to 31° 09' 10" S and from longitude 29° 06' 51"E to 29° 23' 49"E in the Eastern Cape Province of South Africa. Ntabankulu Local Municipality has 141 villages with 125 976 population size. About 36% of villages do not have water sources, 38% have partial functional water sources, 6% have non-functional water sources, and 20 % have reliable water sources, primarily rivers (Mnceba, Caba and Mzimvubu). Water is scarce in this area, especially in the dry season when perennial rivers and springs become dry. This research investigates groundwater potential zones and identifies suitable aquifers that can be developed to augment the water resources. The study involved: literature review, remote sensing, borehole and springs data, geological, petrographic and geophysical (gravity, magnetic and electrical resistivity) analyses. Each method has its purpose in finding the potential groundwater zones. Ntabankulu Local Municipality is located on the Karoo Supergroup in Ecca and Beaufort Group, Adelaide Subgroup and Balfour Formation. During field analysis, it was observed that this area consists of sandstone, shale and dolerite sills, dykes and complex rings. Fining up sequences, massive bedding, concretions, and spheroidal weathering were observed in sandstone, shale, and dolerite, respectively. Groundwater seepages are found within these structures. Sandstones are yellow due to the presence of limonite because of the continuous seepage. Red coloured laminated shale reflects that the rock has an iron oxidation state with hematite (Fe2O3) on the sediments. The Geographical Information Systems (GIS) method was used to extract lineaments. Lineaments dominate Ntabankulu with an NW-SE direction. Some of the lineaments are due to Karoo igneous intrusions, and others are due to neotectonic activities. Ntabankulu is located on the eastern and northern neotectonic belts. Geological maps and lineament maps were compared; it was observed that sandstones and shales are found on high liinament density areas. High yielding boreholes and springs coincide with lineaments, and some lineaments are faults. Hence areas that have high lineaments density could be groundwater potential zones. There are geological structures (faults, joints, and fractures) that are present. Systematic and non-systematic joints are found on sandstones which are due to extensional stress. These joints have been reactivated and acted as strike-slip faults. All these geological structures increase the porosity and permeability of the rocks. It was observed that the area of Ntabankulu consists of coarse-grained and medium-grained sandstone with quartz and orthoclase minerals. Dolerite consists of labradorite, clinopyroxene, olivine, oxide minerals with twinning formed during cooling and magma crystallisation. The gravity and magnetic methods were used to study the subsurface rock density contrasts and susceptibilities, respectively. The gravity and magnetic maps were generated in Geosoft Oasis 8.3 software. High gravity zones coincide with some of the mapped Karoo intrusions. Unmapped dolerite intrusions, lineaments and faults were inferred. The magnetic method delineated the subsurface structures (lineaments and faults), which are known to control groundwater accumulation. These structures and inferred dolerite intrusions helped in identifying groundwater potential zones. Groundwater potential zones were inferred in sedimentary rocks between dolerite intrusions and areas where sills and dykes intersect. A total of six vertical electrical soundings (VES) were conducted at Mzalwaneni and Tabankulu town areas using the Schlumberger configuration array with a maximum penetration depth of about 25- 33 m. The VES data were modelled in Winresist and Surfer 9 software to obtain 1D models and geoelectric sections, respectively. These 1D models have three layers with response curves of H-type. The top layer is about 0.4 - 0.7 m thick, with resistivity values from 12.3 – 1885.9 Ωm and is topsoil (sand and clay). The second layer of thickness 5.2 – 13.3 m has low resistivity values from 23.1- 44.9 Ωm. This layer is interpreted to be fractured shales and sandstones possibly containing water. The third layer of high resistivity values of 145.9 – 727.4 Ωm is inferred to be sandstone. The simultaneous interpretation of resistivity and normalised chargeability revealed that groundwater potential zones are characterised by low resistivity values and low normalised chargeability values for layers from 0.7 - 13.3 m depth. The groundwatwer in the area of Ntabankulu can be found on unconfined aquifers.
- Description
- Thesis (MSc) -- Faculty of Science and Agriculture, 2021
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (xiii, 176 pages)
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- rights holder
- Rights
- All Rights Reserved
- Rights
- Open Access
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UFH Department of Geology
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details | SOURCE1 | Nonkula MSc Geology dissertation.pdf | 6 MB | Adobe Acrobat PDF | View Details |