Evaluation of groundwater potential based on hybrid approach of geology, geophysics, and geoinformatics: Case study of Buffalo Catchment area, Eastern Cape, South Africa
- Authors: Owolabi,Solomon T
- Date: 2019
- Subjects: Hydrogeology Geology
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12238 , vital:39218
- Description: This study focuses on the feasibility of exploring potential groundwater zones through assessment of catchment geo-hydrodynamic processes, using hydro-statistic principles and geographic information system-based approaches. The research work integrated analysis of hydrologic variables, geologic structures, and geomorpho-tectonic processes that provide information on spatial variability of hydrologic units in a watershed. The study is aimed at improving conceptual knowledge and presenting the technical feasibility of exploring potential groundwater zones through geo-hydrodynamic perspectives in hydrogeologically challenged environments. The study adopted a case design approach at the Buffalo hydrologic basin headwater in Eastern Cape, South Africa. The methods used in this study include: field mapping of geologic units and structures, digital processing of aeromagnetic map, cross-section profiling of borehole logs, auto-extraction of lineament, streamflow variability and recession assessment, geomorpho-tectonic analysis of surficial drainage pattern, vertical electrical sounding for imaging shallow subsurface layers, and geospatial integration of thematic maps of groundwater multi-influencing factors. The results indicate that the hydrogeological settings of Buffalo watershed comprised of good, moderate, fair, poor and very poor groundwater potential zones which cover 187 km2 , 338 km2 , 406 km2 , 185 km2 , and 121 km2 respectively. The results report that the groundwater system of Buffalo watershed is mainly hosted by the well-drained fractured dolerite and the shallow unconfined sandstone aquifer. The aquifer is bounded by two parallel impermeable valley walls in the north and south. Also, the Buffalo drainage system constitutes a variable head boundary as a groundwater discharge zone. The groundwater discharge which mostly occurs at the Tshoxa upper course, Mgqakwebe, Quencwe, Yellowwoods upper course and the Buffalo River center influence the status of the Buffalo River as a perennial river system. vi The groundwater recharge occurs through the networks of surficial lineaments and fractures concentrated on the sandstone lithosome, mostly in the northern half of the watershed. The surficial tectonic features trend in a WNW-ESE and E-W direction. The groundwater flow system is controlled by the subsurface lineaments which are oriented in west-northwest – eastsoutheast direction. Most of the groundwater recharge is driven by rain which is extreme at the north. The hydro-climatic pattern of the region influences the dendritic drainage system of Buffalo watershed. The geologic characterization and geomorpho-tectonic analysis indicate that the geologic settings are made up of upward-fining lithologic material and siliciclastic materials that were deposited as fill in paleochannels by braided and meandering fluvial systems. The variability in dissection property and the fluvial system indicates that Buffalo hydrologic and geomorphic systems are heterogeneous and complex. The possible impact of these variabilities aligns with the report of geoelectric sections which revealed the heterogeneity of the aquifer intrinsic properties and variability in groundwater yield. The electric resistivity tomography revealed the existence of a fault system and variation in the thickness of the aquifer. Hydrologic characterization indicates the vulnerability status of the rivers within the watershed. In particular, the Ngqokweni River is vulnerable to diminution while Quencwe River has the potential for a flash flood. Buffalo station is an important surface water capture zone. Delineation of groundwater potential zone should incorporate geologic, hydrologic, geophysical, geomorphotectonic, and environmental perspectives due to the inherent relationship among influencing factors. The study therefore identifies groundwater capture zones which can be further explored for groundwater development and to mitigate the stake of water shortage. The study therefore recommends the approach here to the department of water affairs for adoption to map the zones of groundwater potential at a regional scale. The study also provides resourceful information on vii groundwater recharge zones and therefore recommends that the environment and water stakeholders work together to protect the recharge zones from groundwater contamination due to land use
- Full Text:
- Date Issued: 2019
- Authors: Owolabi,Solomon T
- Date: 2019
- Subjects: Hydrogeology Geology
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12238 , vital:39218
- Description: This study focuses on the feasibility of exploring potential groundwater zones through assessment of catchment geo-hydrodynamic processes, using hydro-statistic principles and geographic information system-based approaches. The research work integrated analysis of hydrologic variables, geologic structures, and geomorpho-tectonic processes that provide information on spatial variability of hydrologic units in a watershed. The study is aimed at improving conceptual knowledge and presenting the technical feasibility of exploring potential groundwater zones through geo-hydrodynamic perspectives in hydrogeologically challenged environments. The study adopted a case design approach at the Buffalo hydrologic basin headwater in Eastern Cape, South Africa. The methods used in this study include: field mapping of geologic units and structures, digital processing of aeromagnetic map, cross-section profiling of borehole logs, auto-extraction of lineament, streamflow variability and recession assessment, geomorpho-tectonic analysis of surficial drainage pattern, vertical electrical sounding for imaging shallow subsurface layers, and geospatial integration of thematic maps of groundwater multi-influencing factors. The results indicate that the hydrogeological settings of Buffalo watershed comprised of good, moderate, fair, poor and very poor groundwater potential zones which cover 187 km2 , 338 km2 , 406 km2 , 185 km2 , and 121 km2 respectively. The results report that the groundwater system of Buffalo watershed is mainly hosted by the well-drained fractured dolerite and the shallow unconfined sandstone aquifer. The aquifer is bounded by two parallel impermeable valley walls in the north and south. Also, the Buffalo drainage system constitutes a variable head boundary as a groundwater discharge zone. The groundwater discharge which mostly occurs at the Tshoxa upper course, Mgqakwebe, Quencwe, Yellowwoods upper course and the Buffalo River center influence the status of the Buffalo River as a perennial river system. vi The groundwater recharge occurs through the networks of surficial lineaments and fractures concentrated on the sandstone lithosome, mostly in the northern half of the watershed. The surficial tectonic features trend in a WNW-ESE and E-W direction. The groundwater flow system is controlled by the subsurface lineaments which are oriented in west-northwest – eastsoutheast direction. Most of the groundwater recharge is driven by rain which is extreme at the north. The hydro-climatic pattern of the region influences the dendritic drainage system of Buffalo watershed. The geologic characterization and geomorpho-tectonic analysis indicate that the geologic settings are made up of upward-fining lithologic material and siliciclastic materials that were deposited as fill in paleochannels by braided and meandering fluvial systems. The variability in dissection property and the fluvial system indicates that Buffalo hydrologic and geomorphic systems are heterogeneous and complex. The possible impact of these variabilities aligns with the report of geoelectric sections which revealed the heterogeneity of the aquifer intrinsic properties and variability in groundwater yield. The electric resistivity tomography revealed the existence of a fault system and variation in the thickness of the aquifer. Hydrologic characterization indicates the vulnerability status of the rivers within the watershed. In particular, the Ngqokweni River is vulnerable to diminution while Quencwe River has the potential for a flash flood. Buffalo station is an important surface water capture zone. Delineation of groundwater potential zone should incorporate geologic, hydrologic, geophysical, geomorphotectonic, and environmental perspectives due to the inherent relationship among influencing factors. The study therefore identifies groundwater capture zones which can be further explored for groundwater development and to mitigate the stake of water shortage. The study therefore recommends the approach here to the department of water affairs for adoption to map the zones of groundwater potential at a regional scale. The study also provides resourceful information on vii groundwater recharge zones and therefore recommends that the environment and water stakeholders work together to protect the recharge zones from groundwater contamination due to land use
- Full Text:
- Date Issued: 2019
Geological and geophysical assessment of groundwater vulnerability to contamination in selected general landfill sites in the Eastern Cape Province, South Africa
- Authors: Mepaiyeda, Seyi
- Date: 2019
- Subjects: Groundwater -- Pollution Sanitary landfills
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12227 , vital:39217
- Description: Increasing expansion, population and urbanization have resulted in high volume of waste generated daily in South Africa. Most municipalities in the Eastern Cape are experiencing challenges in effective waste disposal, thus resulting in pollution of the air, soil and groundwater by the percolation of harmful contaminants into the environment from landfill leachate. Groundwater resources are limited in South Africa due to itssemi-arid nature. Also, there islimited information available, not only about where it occurs but how to manage it so that its quality does not depreciate to unacceptable levels. A combination of these factors coupled with a gap between waste policy and its subsequent implementation may be disastrous to South Africa. This research examines the impact of landfill sites on groundwater resources at three selected sites in the Eastern Cape Province using an integrated geological and geophysical approach. The methodology adopted include: an exhaustive literature review on waste management policies and practices in South Africa and Eastern Cape specifically. It also involved remote sensing for the study of geomorphology and structural interpretations of lineaments. Field excursions, analysis of physico-chemical and geochemical properties of groundwater obtained from monitoring boreholes and leachate pond in the vicinity of the landfill sites was also carried out. Combined induced polarization (IP) and electrical resistivity measurements for geophysical assessment of groundwater vulnerability and petrographical analysis was alos adopted. Data analysis and interpretation of the obtained results showed that the selected landfill sites are generally characterized by a 4-layer Earth structure with an average depth to top of the bedrock between 15 m - 30 m. Plant-rock association observed from the aerial photo-interpretation showed groundwater potential around the locality of the landfill sites with a dendritic to poorly drained x patterns and moderate to high topography. Structural controls such as the presence of lineaments and a fractured bedrock beneath, which are excellent pathways for the migration of leachate, particularly at the Berlin and King Williams Town landfill sites were observed. Analysis of physico-chemical and geochemical properties of water samples showed contamination of the groundwater by heavy metals and some of the physico-chemical properties were above the generally acceptable limits (WHO). These include high electrical conductivity (EC) and total dissolved solid (TDS) values observed in the groundwater samples from the King Williams Town landfill which indicated a downward transfer of leachate into the groundwater. The difference in EC and TDS values for boreholes BH2 and BH1 (9892 µS/cm, 4939 mg/L and 6988 µS/cm, 3497 mg/L respectively), showed that concentration of contaminants increased towards the centre of the landfill. Interpretation of the obtained results from the Berlin landfill showed the presence of heavy metals in groundwater samples in high concentrations. This indicated the dumping of toxic and hazardous waste substances on the landfill, contrary to the landfill design and classification. This could have harmful effect on plants and animals. Integrated geophysical assessment showed the presence of leachate plumes on pseudosections across the landfill sites. This was further corroborated on the chargeability pseudosections. Resistivity and IP pseudosections from the Berlin landfill showed a 4-layered Earth structure and anomalous zones of resistivity (≤ 112 Ώ-m) and low chargeability (≤1.25 ms) in the top layers. This is indicative of percolating leachate plume in the unsaturated zone. Contaminants ranging from unsaturated waste with high ion content to dense aqueous phase liquid contaminants, characterized by low resistivity (34 Ώm to 80 Ώ-m) and low chargeability values (0.05 ms to 5.75 ms) were identified across the Alice landfill. Results from the King Williams Town Landfill revealed plume contamination to a depth of about 75 m, well within the aquiferous zone. xi It is suggested that waste disposal practices should be improved by proper waste inspection and classification at landfills prior to disposal, use of lining and cap material to prevent leaching of contaminants into the groundwater below and the construction of waste cells and containment structures. This will go a long way in mitigating groundwater contamination due to landfilling at the study areas
- Full Text:
- Date Issued: 2019
- Authors: Mepaiyeda, Seyi
- Date: 2019
- Subjects: Groundwater -- Pollution Sanitary landfills
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12227 , vital:39217
- Description: Increasing expansion, population and urbanization have resulted in high volume of waste generated daily in South Africa. Most municipalities in the Eastern Cape are experiencing challenges in effective waste disposal, thus resulting in pollution of the air, soil and groundwater by the percolation of harmful contaminants into the environment from landfill leachate. Groundwater resources are limited in South Africa due to itssemi-arid nature. Also, there islimited information available, not only about where it occurs but how to manage it so that its quality does not depreciate to unacceptable levels. A combination of these factors coupled with a gap between waste policy and its subsequent implementation may be disastrous to South Africa. This research examines the impact of landfill sites on groundwater resources at three selected sites in the Eastern Cape Province using an integrated geological and geophysical approach. The methodology adopted include: an exhaustive literature review on waste management policies and practices in South Africa and Eastern Cape specifically. It also involved remote sensing for the study of geomorphology and structural interpretations of lineaments. Field excursions, analysis of physico-chemical and geochemical properties of groundwater obtained from monitoring boreholes and leachate pond in the vicinity of the landfill sites was also carried out. Combined induced polarization (IP) and electrical resistivity measurements for geophysical assessment of groundwater vulnerability and petrographical analysis was alos adopted. Data analysis and interpretation of the obtained results showed that the selected landfill sites are generally characterized by a 4-layer Earth structure with an average depth to top of the bedrock between 15 m - 30 m. Plant-rock association observed from the aerial photo-interpretation showed groundwater potential around the locality of the landfill sites with a dendritic to poorly drained x patterns and moderate to high topography. Structural controls such as the presence of lineaments and a fractured bedrock beneath, which are excellent pathways for the migration of leachate, particularly at the Berlin and King Williams Town landfill sites were observed. Analysis of physico-chemical and geochemical properties of water samples showed contamination of the groundwater by heavy metals and some of the physico-chemical properties were above the generally acceptable limits (WHO). These include high electrical conductivity (EC) and total dissolved solid (TDS) values observed in the groundwater samples from the King Williams Town landfill which indicated a downward transfer of leachate into the groundwater. The difference in EC and TDS values for boreholes BH2 and BH1 (9892 µS/cm, 4939 mg/L and 6988 µS/cm, 3497 mg/L respectively), showed that concentration of contaminants increased towards the centre of the landfill. Interpretation of the obtained results from the Berlin landfill showed the presence of heavy metals in groundwater samples in high concentrations. This indicated the dumping of toxic and hazardous waste substances on the landfill, contrary to the landfill design and classification. This could have harmful effect on plants and animals. Integrated geophysical assessment showed the presence of leachate plumes on pseudosections across the landfill sites. This was further corroborated on the chargeability pseudosections. Resistivity and IP pseudosections from the Berlin landfill showed a 4-layered Earth structure and anomalous zones of resistivity (≤ 112 Ώ-m) and low chargeability (≤1.25 ms) in the top layers. This is indicative of percolating leachate plume in the unsaturated zone. Contaminants ranging from unsaturated waste with high ion content to dense aqueous phase liquid contaminants, characterized by low resistivity (34 Ώm to 80 Ώ-m) and low chargeability values (0.05 ms to 5.75 ms) were identified across the Alice landfill. Results from the King Williams Town Landfill revealed plume contamination to a depth of about 75 m, well within the aquiferous zone. xi It is suggested that waste disposal practices should be improved by proper waste inspection and classification at landfills prior to disposal, use of lining and cap material to prevent leaching of contaminants into the groundwater below and the construction of waste cells and containment structures. This will go a long way in mitigating groundwater contamination due to landfilling at the study areas
- Full Text:
- Date Issued: 2019
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