Taxonomic and trait-based responses of the orders Ephemeroptera, Plecoptera, Odonata, And Trichoptera (EPOT) to sediment stress in the Tsitsa River and its tributaries, Eastern Cape, South Africa
- Akamagwuna, Frank Chukwuzuoke
- Authors: Akamagwuna, Frank Chukwuzuoke
- Date: 2019
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68082 , vital:29196
- Description: Increased urbanization and industrialisation due to human population growth and associated high demand for food have led to widespread disturbances of freshwater ecosystems and associated resources. A widely recognised consequence of these disturbances is the excessive delivery of sediments into the freshwater ecosystems, which severely affects the functioning and integrity of these systems.. The major water quality impairment in the Tsitsa River and its tributaries, situated in the Mzimvubu catchment in the Eastern Cape Province of South Africa, is known to be excessive sediment input. In this study, the application of macroinvertebrates taxonomic-based and trait-based approaches was used to assess the responses and vulnerability of Ephemeroptera, Plecoptera, Odonata and Trichoptera (EPOT) species to settled and suspended sediments stress in eight selected sampling sites in the Tsitsa River and its tributaries. The eight selected sites were Site 1 (Tsitsa upstream), Site 2 (Tsitsa downstream), Site 3 (Qurana tributary), Site 4 (Pot River upstream), Site 5 (Pot River downstream), Site 6 (Little Pot River), Site 7 (Millstream upstream) and Site 8 (Millstream downstream). The methods used in this study involved the analysis of water physico-chemical variables as well as sediment characteristics, derivation of five EPOT metrics, EPOT species-level taxonomic analysis, individual EPOT trait analysis and the development of a novel trait-based approach using a combination of traits. The sampling of EPOT taxa was done using the SASS5 protocols. Identification of EPOT was done to genus/species level and all data were subjected to relevant statistical analysis. The results of ecological categories derived for the physico-chemical variables generally indicated the ecological categories A and B, which was indicative of good water quality conditions. The result of sediment particle analysis revealed four distinct site groups: site group 1 (Tsitsa River upstream and Qurana tributary), site group 2 (Tsitsa River downstream and Millstream upstream), site group 3 (Pot River, both upstream and downstream, and Millstream downstream) and site group 4 (Little Pot River). The species-level taxonomic analysis of EPOT revealed that site group 1 was the most sediment-influenced sites whereas site group 4 was the least sediment-influenced. Species such as Paragopmhus sp., Aeshna sp. and Baetis sp. were considered sediment-tolerant with strong positive association with site group 1. The novel trait-based approach developed in this study proved useful in predicting the responses of EPOT species to sediment stress, and further discriminated between the study sites. The approach was used to group EPOT species into four vulnerability classes. The result showed that filter feeding EPOT species that have filamentous gills, preferring stone biotopes and feeding on detritus (FPOM) were mostly classified as highly vulnerable to sediment stress and indicated no significant association with the highly sediment-influenced site group 1. The TBA largely corresponded well to the predictions made with the relative abundance of the vulnerable class decreasing in the sediment-influenced sites compared to the tolerant and highly tolerant classes. Overall, the study revealed the importance of the complementary use of taxonomic and trait-based approaches to biomonitoring.
- Full Text:
- Date Issued: 2019
- Authors: Akamagwuna, Frank Chukwuzuoke
- Date: 2019
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68082 , vital:29196
- Description: Increased urbanization and industrialisation due to human population growth and associated high demand for food have led to widespread disturbances of freshwater ecosystems and associated resources. A widely recognised consequence of these disturbances is the excessive delivery of sediments into the freshwater ecosystems, which severely affects the functioning and integrity of these systems.. The major water quality impairment in the Tsitsa River and its tributaries, situated in the Mzimvubu catchment in the Eastern Cape Province of South Africa, is known to be excessive sediment input. In this study, the application of macroinvertebrates taxonomic-based and trait-based approaches was used to assess the responses and vulnerability of Ephemeroptera, Plecoptera, Odonata and Trichoptera (EPOT) species to settled and suspended sediments stress in eight selected sampling sites in the Tsitsa River and its tributaries. The eight selected sites were Site 1 (Tsitsa upstream), Site 2 (Tsitsa downstream), Site 3 (Qurana tributary), Site 4 (Pot River upstream), Site 5 (Pot River downstream), Site 6 (Little Pot River), Site 7 (Millstream upstream) and Site 8 (Millstream downstream). The methods used in this study involved the analysis of water physico-chemical variables as well as sediment characteristics, derivation of five EPOT metrics, EPOT species-level taxonomic analysis, individual EPOT trait analysis and the development of a novel trait-based approach using a combination of traits. The sampling of EPOT taxa was done using the SASS5 protocols. Identification of EPOT was done to genus/species level and all data were subjected to relevant statistical analysis. The results of ecological categories derived for the physico-chemical variables generally indicated the ecological categories A and B, which was indicative of good water quality conditions. The result of sediment particle analysis revealed four distinct site groups: site group 1 (Tsitsa River upstream and Qurana tributary), site group 2 (Tsitsa River downstream and Millstream upstream), site group 3 (Pot River, both upstream and downstream, and Millstream downstream) and site group 4 (Little Pot River). The species-level taxonomic analysis of EPOT revealed that site group 1 was the most sediment-influenced sites whereas site group 4 was the least sediment-influenced. Species such as Paragopmhus sp., Aeshna sp. and Baetis sp. were considered sediment-tolerant with strong positive association with site group 1. The novel trait-based approach developed in this study proved useful in predicting the responses of EPOT species to sediment stress, and further discriminated between the study sites. The approach was used to group EPOT species into four vulnerability classes. The result showed that filter feeding EPOT species that have filamentous gills, preferring stone biotopes and feeding on detritus (FPOM) were mostly classified as highly vulnerable to sediment stress and indicated no significant association with the highly sediment-influenced site group 1. The TBA largely corresponded well to the predictions made with the relative abundance of the vulnerable class decreasing in the sediment-influenced sites compared to the tolerant and highly tolerant classes. Overall, the study revealed the importance of the complementary use of taxonomic and trait-based approaches to biomonitoring.
- Full Text:
- Date Issued: 2019
Macroplastics in the environment: are they suitable habitats for macroinvertebrates in riverine systems?
- Authors: Ali, Andrew Abagai
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424153 , vital:72128
- Description: Emerging pollutants, such as plastics are threat to freshwater ecosystems, and may negatively impact riverine systems. They can modify riverine habitats and affect aquatic organism distribution and composition. Knowledge of how macroplastics alter riverine habitat heterogeneity, and their effects on macroinvertebrate assemblage structure is sparse, especially in Africa. This study examines the effect of hydraulic biotopes on the colonisation, establishment and succession patterns of macroinvertebrates on macroplastic and natural substrates based on the taxonomic and trait-based approach. Four experimental sites from minimally impacted upper reaches of the Buffalo, Kat, Kowie, and Swartkops Rivers in the Eastern Cape of South Africa were selected for the deployment of plastic substrates. Plastics materials, including polyethylene terephthalate (PET) bottles and natural substrate composed of stone and vegetation, were used to formulate three substrate groups: Group 1: 100% natural substrates (NS), Group 2: 50% natural substrates and 50% plastic material (NP), and Group 3: 100% plastic materials (PD). These substrates were placed in litter bags of equal dimension (25 cm by 35 cm, with 2.5 cm mesh) and deployed randomly in three hydraulic biotopes (pools, riffles, runs) over a period of 180 days (October 2021 to April 2022). A total of 216 substrate bags, 54 bags per substrate were deployed per site in the four experimental sites. Twelve bags from each substrate group were retrieved at an interval of 30 days beginning on day 30 after deployment, and analysed for the establishment of macroinvertebrate communities. Based on composite hydraulic biotope data, Simpson index was significantly higher (P < 0.05) for macroinvertebrate assemblage structure on the 50% and 100% macroplastic substrate groups compared to natural substrates. With the exception of Tabanidae, Glossosomatidae, and Psephenidae, all macroinvertebrate taxa recorded showed non-significant positive correlations with all three substrate groups. However, Tabanidae, Glossosomatidae, and Psephenidae showed significant positive correlation with the 100% natural substrates, 50% plastic substrates and 100% plastic substrates, respectively. The parsimony analysis reveal that, within 30 days, all substrate groups underwent similar succession, with high abundance of pioneer taxa which increased on days 60 and 90, and then decreased from days 120 to 180. For the the pool biotope, Shannon and Simpson indices were significantly higher (P < 0.05) for the macroinvertabrates collected over the natural substates compared with those collected on the macroplastic substrate groups. However, in the riffle and run biotopes, all diversity indices were similar for all substrate groups and no statistically significant difference was observed. Statistically significant higher values for taxonomic richness, diversity, and evenness were found on day 30 to 90 for the riffle biotopes, and day 30 to 60 for the run biotopes. The run biotope presented temporal statistical significant variability in taxonomic composition with different macroinvertebrate communities recorded on days 30 and 60 compared with days 90 to 180. However, in pools and riffles, no temporal variation was observed in the taxonomic composition of macroinvertebrates on all three substrate groups. The trait-based fuzzy correspondence analysis revealed differential spatial-temporal distribution of macroinvertebrate traits on all three substrate group. The early colonisers i.e. day 30 – 60, were dominated by group of taxa characterised by medium (>10 – 20 mm) and large (20 > 40) body size, flat body, collector-gatherers, free-living, and predators. The late colonisers, collected mainly on day 150 and 180 were dominated by taxa with a preference for high flow velocity (0.3 - 0.6 m/s), permanent attachment, and filter-feeding mode. Traits such as oval and flat body shape, medium body size (>10 - 20 mm), skating and clinging/climbing mobility, temporal attachment, shredders, predators, prey, and plastron and spiracle respiration showed positive correlation with the 100% macroplastic substrates. Filter feeding, crawling, permanent attachment, a preference for fast velocity (0.3-0.6 m/s), and coarse particle organic matter were positively correlated with the 50% macroplastic substrates. Overall, the results provided critical insights on the impact of macroplastics on the assemblage structure of biological communities by acting as suitable habitats in stream ecosystems. The study elucidated the role of traits of aquatic organisms in mediating the colonisation of plastics substrates, providing insights into the impact of plastics proliferation on riverine ecosystem functioning. Furthermore, the finding provides a baseline insight into the influence of hydraulic biotopes on the colonisation and establishment of macroinvertebrates on macroplastic acting as artificial riverine habitat. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Ali, Andrew Abagai
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424153 , vital:72128
- Description: Emerging pollutants, such as plastics are threat to freshwater ecosystems, and may negatively impact riverine systems. They can modify riverine habitats and affect aquatic organism distribution and composition. Knowledge of how macroplastics alter riverine habitat heterogeneity, and their effects on macroinvertebrate assemblage structure is sparse, especially in Africa. This study examines the effect of hydraulic biotopes on the colonisation, establishment and succession patterns of macroinvertebrates on macroplastic and natural substrates based on the taxonomic and trait-based approach. Four experimental sites from minimally impacted upper reaches of the Buffalo, Kat, Kowie, and Swartkops Rivers in the Eastern Cape of South Africa were selected for the deployment of plastic substrates. Plastics materials, including polyethylene terephthalate (PET) bottles and natural substrate composed of stone and vegetation, were used to formulate three substrate groups: Group 1: 100% natural substrates (NS), Group 2: 50% natural substrates and 50% plastic material (NP), and Group 3: 100% plastic materials (PD). These substrates were placed in litter bags of equal dimension (25 cm by 35 cm, with 2.5 cm mesh) and deployed randomly in three hydraulic biotopes (pools, riffles, runs) over a period of 180 days (October 2021 to April 2022). A total of 216 substrate bags, 54 bags per substrate were deployed per site in the four experimental sites. Twelve bags from each substrate group were retrieved at an interval of 30 days beginning on day 30 after deployment, and analysed for the establishment of macroinvertebrate communities. Based on composite hydraulic biotope data, Simpson index was significantly higher (P < 0.05) for macroinvertebrate assemblage structure on the 50% and 100% macroplastic substrate groups compared to natural substrates. With the exception of Tabanidae, Glossosomatidae, and Psephenidae, all macroinvertebrate taxa recorded showed non-significant positive correlations with all three substrate groups. However, Tabanidae, Glossosomatidae, and Psephenidae showed significant positive correlation with the 100% natural substrates, 50% plastic substrates and 100% plastic substrates, respectively. The parsimony analysis reveal that, within 30 days, all substrate groups underwent similar succession, with high abundance of pioneer taxa which increased on days 60 and 90, and then decreased from days 120 to 180. For the the pool biotope, Shannon and Simpson indices were significantly higher (P < 0.05) for the macroinvertabrates collected over the natural substates compared with those collected on the macroplastic substrate groups. However, in the riffle and run biotopes, all diversity indices were similar for all substrate groups and no statistically significant difference was observed. Statistically significant higher values for taxonomic richness, diversity, and evenness were found on day 30 to 90 for the riffle biotopes, and day 30 to 60 for the run biotopes. The run biotope presented temporal statistical significant variability in taxonomic composition with different macroinvertebrate communities recorded on days 30 and 60 compared with days 90 to 180. However, in pools and riffles, no temporal variation was observed in the taxonomic composition of macroinvertebrates on all three substrate groups. The trait-based fuzzy correspondence analysis revealed differential spatial-temporal distribution of macroinvertebrate traits on all three substrate group. The early colonisers i.e. day 30 – 60, were dominated by group of taxa characterised by medium (>10 – 20 mm) and large (20 > 40) body size, flat body, collector-gatherers, free-living, and predators. The late colonisers, collected mainly on day 150 and 180 were dominated by taxa with a preference for high flow velocity (0.3 - 0.6 m/s), permanent attachment, and filter-feeding mode. Traits such as oval and flat body shape, medium body size (>10 - 20 mm), skating and clinging/climbing mobility, temporal attachment, shredders, predators, prey, and plastron and spiracle respiration showed positive correlation with the 100% macroplastic substrates. Filter feeding, crawling, permanent attachment, a preference for fast velocity (0.3-0.6 m/s), and coarse particle organic matter were positively correlated with the 50% macroplastic substrates. Overall, the results provided critical insights on the impact of macroplastics on the assemblage structure of biological communities by acting as suitable habitats in stream ecosystems. The study elucidated the role of traits of aquatic organisms in mediating the colonisation of plastics substrates, providing insights into the impact of plastics proliferation on riverine ecosystem functioning. Furthermore, the finding provides a baseline insight into the influence of hydraulic biotopes on the colonisation and establishment of macroinvertebrates on macroplastic acting as artificial riverine habitat. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2023
- Full Text:
- Date Issued: 2023-10-13
An erosion and sediment delivery model for semi-arid catchments
- Authors: Bryson, Louise Kay
- Date: 2016
- Subjects: Sedimentation and deposition , Erosion , Watershed management -- South Africa , Water-supply -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6056 , http://hdl.handle.net/10962/d1020331
- Description: Sedimentation has become a significant environmental threat in South Africa as it intensifies water management problems in the water-scarce semi-arid regions of the country. As South Africa already allocates 98% of available water, the loss of storage capacity in reservoirs and degraded water quality has meant that a reliable water supply is compromised. The overall aim of this thesis was to develop a catchment scale model that represents the sediment dynamics of semi-arid regions of South Africa as a simple and practically applicable tool for water resource managers. Development of a conceptual framework for the model relied on an understanding of both the sediment dynamics of South African catchments and applicable modelling techniques. Scale was an issue in both cases as most of our understanding of the physical processes of runoff generation and sediment transport has been derived from plot scale studies. By identifying defining properties of semi-arid catchments it was possible to consider how temporal and spatial properties at higher levels emerged from properties at lower levels. These properties were effectively represented by using the Pitman rainfall-runoff model disaggregated to a daily timescale, the Modified Universal Soil Loss Equation (MUSLE) model incorporating probability function theory and through the representation of sediment storages across a semi-distributed catchment. The model was tested on two small and one large study catchment in the Karoo, South Africa, with limited observed data. Limitations to the model were found to be the large parameter data set and the dominance of structural constraints with an increase in catchment size. The next steps in model development will require a reduction of the parameter data set and an inclusion of an in-stream component for sub-catchments at a larger spatial scale. The model is applicable in areas such as South Africa where water resource managers need a simple model at the catchment scale in order to make decisions. This type of model provides a simple representation of the stochastic nature of erosion and sediment delivery over large spatial and temporal scales.
- Full Text:
- Date Issued: 2016
- Authors: Bryson, Louise Kay
- Date: 2016
- Subjects: Sedimentation and deposition , Erosion , Watershed management -- South Africa , Water-supply -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6056 , http://hdl.handle.net/10962/d1020331
- Description: Sedimentation has become a significant environmental threat in South Africa as it intensifies water management problems in the water-scarce semi-arid regions of the country. As South Africa already allocates 98% of available water, the loss of storage capacity in reservoirs and degraded water quality has meant that a reliable water supply is compromised. The overall aim of this thesis was to develop a catchment scale model that represents the sediment dynamics of semi-arid regions of South Africa as a simple and practically applicable tool for water resource managers. Development of a conceptual framework for the model relied on an understanding of both the sediment dynamics of South African catchments and applicable modelling techniques. Scale was an issue in both cases as most of our understanding of the physical processes of runoff generation and sediment transport has been derived from plot scale studies. By identifying defining properties of semi-arid catchments it was possible to consider how temporal and spatial properties at higher levels emerged from properties at lower levels. These properties were effectively represented by using the Pitman rainfall-runoff model disaggregated to a daily timescale, the Modified Universal Soil Loss Equation (MUSLE) model incorporating probability function theory and through the representation of sediment storages across a semi-distributed catchment. The model was tested on two small and one large study catchment in the Karoo, South Africa, with limited observed data. Limitations to the model were found to be the large parameter data set and the dominance of structural constraints with an increase in catchment size. The next steps in model development will require a reduction of the parameter data set and an inclusion of an in-stream component for sub-catchments at a larger spatial scale. The model is applicable in areas such as South Africa where water resource managers need a simple model at the catchment scale in order to make decisions. This type of model provides a simple representation of the stochastic nature of erosion and sediment delivery over large spatial and temporal scales.
- Full Text:
- Date Issued: 2016
The application of a simple decision support system to address water quality contestations in the Vaal Barrage catchment, South Africa
- Authors: Chili, Asanda Sandra
- Date: 2022-04
- Subjects: Vaal Barrage (South Africa : Reservoir) , Decision support systems South Africa Vaal Barrage (Reservoir) , Water Pollution Law and legislation South Africa , Water quality South Africa Vaal Barrage (Reservoir) , Water use Law and legislation South Africa Vaal Barrage (Reservoir) , Urban watersheds South Africa Vaal Barrage (Reservoir) , Watershed management South Africa Vaal Barrage (Reservoir) , Water use licences (WUL)
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232204 , vital:49971
- Description: Deteriorating environmental water quality is one of the complex challenges in South Africa that threaten freshwater ecosystem health and functionality. An emerging concern is the contestation of water quality regulatory instruments such as standards in water use licences (WUL), and the resource quality objectives. In the Vaal Barrage catchment where this study was undertaken these contestations were evident, suggesting the need for both technical and social solutions to water quality changes in socio-ecological systems. The Vaal Barrage catchment within the lower section of the Upper Vaal is a highly developed, urbanised, and complex catchment supporting and contributing to the social-economic development of Gauteng Province and the entire country, as the Upper Vaal contribute 20% to the Gross Domestic Product of South Africa. This study explores the motivations for stakeholders’ contestations of water quality regulatory instruments in order to contribute to ways in which water resource users and regulators can collaboratively address water quality challenges in the Vaal Barrage catchment. The study also explores water quality scenarios and their ecological and management implications. Document analysis, participant observations and a semi-structured questionnaire were deployed to explore stakeholders’ motivations, values, and perceptions of the water quality regulatory instruments. The results were triangulated to gain better insights into research participants responses. To explore water quality management scenarios, the study applied a water quality systems assessment model Decision Support System (DSS). The DSS was recently developed as part of a bigger project within the Vaal Barrage catchment. Regarding stakeholders’ motivation for contesting water quality regulatory instruments in the catchment, the results revealed a perceived lack of scientific credibility and defensibility in the processes used for deriving standards in WUL, a lack of transparent linkage between the WUL and resource quality objectives, and the increased need for stakeholder engagement in the resource quality objective formulation process. Furthermore, the study revealed punitive measures, education and awareness, self-regulation as mechanisms to encourage compliance. The applied DSS results showed that high nutrient loads, sulphate and total dissolved solids sourced from upstream catchments contribute to water quality deterioration in the Vaal Barrage catchment. The results also showed that the Vaal Barrage catchment could not host additional licence emitters because of TDS, phosphate and nitrate levels, which pose a serious risk to the ecology of the Vaal Barrage catchment, indicating that system had exceeded its assimilative capacity for critical water quality variables. Lastly, the results evidenced the need for collaborative action by the waste emitters within the Vaal Barrage catchment, particularly collaboration between upstream and downstream waste emitters. The study has far-reaching implications for water quality management in South Africa. These include i) the need for transparent and open processes and methods for deriving standards in water use licence, ii) the need for a water quality DSS that recognises catchment hydrological complexity in deriving standards in WUL, and for linking WUL and Resource Quality Objectives (RQOs), iii) collaboration between resources users, and between the resources users and the regulators to bring pollution to acceptable levels and iv) both social and technical solutions are necessary for managing water quality challenge, particularly in a highly developed catchment such as the Vaal Barrage system. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Chili, Asanda Sandra
- Date: 2022-04
- Subjects: Vaal Barrage (South Africa : Reservoir) , Decision support systems South Africa Vaal Barrage (Reservoir) , Water Pollution Law and legislation South Africa , Water quality South Africa Vaal Barrage (Reservoir) , Water use Law and legislation South Africa Vaal Barrage (Reservoir) , Urban watersheds South Africa Vaal Barrage (Reservoir) , Watershed management South Africa Vaal Barrage (Reservoir) , Water use licences (WUL)
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232204 , vital:49971
- Description: Deteriorating environmental water quality is one of the complex challenges in South Africa that threaten freshwater ecosystem health and functionality. An emerging concern is the contestation of water quality regulatory instruments such as standards in water use licences (WUL), and the resource quality objectives. In the Vaal Barrage catchment where this study was undertaken these contestations were evident, suggesting the need for both technical and social solutions to water quality changes in socio-ecological systems. The Vaal Barrage catchment within the lower section of the Upper Vaal is a highly developed, urbanised, and complex catchment supporting and contributing to the social-economic development of Gauteng Province and the entire country, as the Upper Vaal contribute 20% to the Gross Domestic Product of South Africa. This study explores the motivations for stakeholders’ contestations of water quality regulatory instruments in order to contribute to ways in which water resource users and regulators can collaboratively address water quality challenges in the Vaal Barrage catchment. The study also explores water quality scenarios and their ecological and management implications. Document analysis, participant observations and a semi-structured questionnaire were deployed to explore stakeholders’ motivations, values, and perceptions of the water quality regulatory instruments. The results were triangulated to gain better insights into research participants responses. To explore water quality management scenarios, the study applied a water quality systems assessment model Decision Support System (DSS). The DSS was recently developed as part of a bigger project within the Vaal Barrage catchment. Regarding stakeholders’ motivation for contesting water quality regulatory instruments in the catchment, the results revealed a perceived lack of scientific credibility and defensibility in the processes used for deriving standards in WUL, a lack of transparent linkage between the WUL and resource quality objectives, and the increased need for stakeholder engagement in the resource quality objective formulation process. Furthermore, the study revealed punitive measures, education and awareness, self-regulation as mechanisms to encourage compliance. The applied DSS results showed that high nutrient loads, sulphate and total dissolved solids sourced from upstream catchments contribute to water quality deterioration in the Vaal Barrage catchment. The results also showed that the Vaal Barrage catchment could not host additional licence emitters because of TDS, phosphate and nitrate levels, which pose a serious risk to the ecology of the Vaal Barrage catchment, indicating that system had exceeded its assimilative capacity for critical water quality variables. Lastly, the results evidenced the need for collaborative action by the waste emitters within the Vaal Barrage catchment, particularly collaboration between upstream and downstream waste emitters. The study has far-reaching implications for water quality management in South Africa. These include i) the need for transparent and open processes and methods for deriving standards in water use licence, ii) the need for a water quality DSS that recognises catchment hydrological complexity in deriving standards in WUL, and for linking WUL and Resource Quality Objectives (RQOs), iii) collaboration between resources users, and between the resources users and the regulators to bring pollution to acceptable levels and iv) both social and technical solutions are necessary for managing water quality challenge, particularly in a highly developed catchment such as the Vaal Barrage system. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2022
- Full Text:
- Date Issued: 2022-04
Evaluation of low-cost technology options for sustainable water supply and sanitation in two peri-urban areas of Lusaka, Zambia: opportunities and constraints
- Authors: Chiliboyi, Yvonne
- Date: 2017
- Subjects: Toilets -- Technological innovations -- South Africa , Sanitary engineering -- Technological innovations -- South Africa , Water resoures development -- Technological innovations -- South Africa , Water-supply -- Technological innovations -- South Africa , Household surveys -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7960 , vital:21328
- Description: Presently, at least 70% of the total urban population in Zambia resides in peri-urban areas. Peri-urban settlements are characterized by high population growth, high poverty levels and inadequate access to water and sanitation which often result in increased prevalence of diseases. The situation is even made worse because of the position that many local authorities have taken regarding the implementation of infrastructure and service development in these settlements. Local authorities in developing countries have continuously focused on implementation of traditional and unsustainable technologies for service provision to meet the demand despite the technologies’ inability to serve the rapidly growing peri-urban areas. These technologies have high costs, lack proper operation and maintenance, and are not affordable to majority of peri-urban residents. Therefore, this study was set out to identify and evaluate the existing and possible low-cost technology options for sustainable water supply and sanitation in two selected peri-urban areas of Lusaka, Zambia, namely Kanyama and Chazanga. This was achieved through a household survey conducted in the selected communities. Questionnaires and focus group discussions were held in the respective areas to obtain baseline data on the current water supply and sanitation situation, the type of technologies used, challenges faced regarding water and sanitation technologies, and to get the communities perceptions and preferences of different technology options. Thereafter, a Multi-Criterion Analysis methodological approach was used to assess the selected technologies by the communities, taking into consideration of the economic, socio-cultural, technical, institutional and environmental aspects. Results from the study revealed that a few low-cost water supply and sanitation technologies are feasible for peri-urban areas. For Chazanga, communal taps, boreholes, protected wells, and rain water harvesting were found to be feasible for water supply. For sanitation, on-site sanitation services such as compost toilets, dry toilets, as well as Ventilated Improved Pits (VIP) and Pour-flush, Fossa Alterna and the Urine Diversion Dry Toilet (UDDT) are some of the low-cost technologies that can be implemented in the area. The VIP is suitable for households that rely on water from communal taps for their use. As majority of households in the area have taps on their plots, the Pour-flush can be an alternative. The Fossa Alterna and the Urine Diversion Dry Toilet (UDDT) have low initial cost and can accommodate different households. Additionally, the area has a lower household size and majority of the residents in the area landlords, which makes it easy to teach users how the toilet operates as well as its maintenance. For Kanyama, feasible and sustainable low-cost water supply facilities include boreholes and communal taps. Kanyama has limited plot sizes thereby causing the challenge of implementing infrastructure such as rainwater harvesting. Additionally, continuous increase in urban population in the area, coupled with the construction of unregulated households and sanitation facilities, renders protected wells not feasible to implement in Kanyama. In terms of sanitation, wet on-site sanitation facilities such as Ventilated Improved Pit (VIP) latrines are accepted by the community. The VIP does not require water for use and if properly constructed can be used as a bathroom. The Pour-flush toilet is also another alternative for provision of sanitation in the area. However, the latrine can be expensive to construct for majority of the residents. Dry sanitation such as the Urine Diversion Dry Toilet (UDDT) is not feasible for Kanyama. The UDDT requires continuous awareness on its use especially in rented households where tenants are constantly changing. The method of evaluating appropriate technology options for peri-urban areas and thereafter letting the users from the communities choose from the proposed technologies ensures a participatory approach. Results from Multi-Criterion Analysis (MCA) showed that stakeholders’ influence is essential for the selection of sustainable technology options. However, it is important that the implementation process of any technology in peri-urban areas consider different aspects including the local environmental, socio-cultural, economic, technical, and institutional conditions. Finally, the outcome of this study will not only provide baseline data for successful implementation of appropriate low-cost water supply and sanitation technology options in Chazanga and Kanyama, but also other peri-urban communities in Zambia.
- Full Text:
- Date Issued: 2017
- Authors: Chiliboyi, Yvonne
- Date: 2017
- Subjects: Toilets -- Technological innovations -- South Africa , Sanitary engineering -- Technological innovations -- South Africa , Water resoures development -- Technological innovations -- South Africa , Water-supply -- Technological innovations -- South Africa , Household surveys -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7960 , vital:21328
- Description: Presently, at least 70% of the total urban population in Zambia resides in peri-urban areas. Peri-urban settlements are characterized by high population growth, high poverty levels and inadequate access to water and sanitation which often result in increased prevalence of diseases. The situation is even made worse because of the position that many local authorities have taken regarding the implementation of infrastructure and service development in these settlements. Local authorities in developing countries have continuously focused on implementation of traditional and unsustainable technologies for service provision to meet the demand despite the technologies’ inability to serve the rapidly growing peri-urban areas. These technologies have high costs, lack proper operation and maintenance, and are not affordable to majority of peri-urban residents. Therefore, this study was set out to identify and evaluate the existing and possible low-cost technology options for sustainable water supply and sanitation in two selected peri-urban areas of Lusaka, Zambia, namely Kanyama and Chazanga. This was achieved through a household survey conducted in the selected communities. Questionnaires and focus group discussions were held in the respective areas to obtain baseline data on the current water supply and sanitation situation, the type of technologies used, challenges faced regarding water and sanitation technologies, and to get the communities perceptions and preferences of different technology options. Thereafter, a Multi-Criterion Analysis methodological approach was used to assess the selected technologies by the communities, taking into consideration of the economic, socio-cultural, technical, institutional and environmental aspects. Results from the study revealed that a few low-cost water supply and sanitation technologies are feasible for peri-urban areas. For Chazanga, communal taps, boreholes, protected wells, and rain water harvesting were found to be feasible for water supply. For sanitation, on-site sanitation services such as compost toilets, dry toilets, as well as Ventilated Improved Pits (VIP) and Pour-flush, Fossa Alterna and the Urine Diversion Dry Toilet (UDDT) are some of the low-cost technologies that can be implemented in the area. The VIP is suitable for households that rely on water from communal taps for their use. As majority of households in the area have taps on their plots, the Pour-flush can be an alternative. The Fossa Alterna and the Urine Diversion Dry Toilet (UDDT) have low initial cost and can accommodate different households. Additionally, the area has a lower household size and majority of the residents in the area landlords, which makes it easy to teach users how the toilet operates as well as its maintenance. For Kanyama, feasible and sustainable low-cost water supply facilities include boreholes and communal taps. Kanyama has limited plot sizes thereby causing the challenge of implementing infrastructure such as rainwater harvesting. Additionally, continuous increase in urban population in the area, coupled with the construction of unregulated households and sanitation facilities, renders protected wells not feasible to implement in Kanyama. In terms of sanitation, wet on-site sanitation facilities such as Ventilated Improved Pit (VIP) latrines are accepted by the community. The VIP does not require water for use and if properly constructed can be used as a bathroom. The Pour-flush toilet is also another alternative for provision of sanitation in the area. However, the latrine can be expensive to construct for majority of the residents. Dry sanitation such as the Urine Diversion Dry Toilet (UDDT) is not feasible for Kanyama. The UDDT requires continuous awareness on its use especially in rented households where tenants are constantly changing. The method of evaluating appropriate technology options for peri-urban areas and thereafter letting the users from the communities choose from the proposed technologies ensures a participatory approach. Results from Multi-Criterion Analysis (MCA) showed that stakeholders’ influence is essential for the selection of sustainable technology options. However, it is important that the implementation process of any technology in peri-urban areas consider different aspects including the local environmental, socio-cultural, economic, technical, and institutional conditions. Finally, the outcome of this study will not only provide baseline data for successful implementation of appropriate low-cost water supply and sanitation technology options in Chazanga and Kanyama, but also other peri-urban communities in Zambia.
- Full Text:
- Date Issued: 2017
Exploring and modelling the effects of agricultural land management and climate change on agroecosystem services in the Eastern Cape, South Africa
- Authors: Choruma, Dennis Junior
- Date: 2020
- Subjects: Agricultural ecology -- South Africa -- Eastern Cape , Agriculture -- Environmental aspects -- South Africa -- Eastern Cape , Crops and climate -- South Africa -- Eastern Cape , Corn -- Climatic factors -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146756 , vital:38554
- Description: The aims of this study were to evaluate the impacts of agricultural land management strategies and climate change on irrigated maize production in the Eastern Cape, South Africa. To achieve these aims, the study was guided by two overarching research questions, subsequently broken down into more specific questions. The first research question examined the reasons behind farmers’ current agricultural land management practices, the values they assigned to different agroecosystem services, their perceptions of climate change and the adaptation strategies they used to address challenges associated with agricultural crop production and climate change. To answer these questions, a survey of conventional farmers in the Eastern Cape was carried out. The survey targeted farmers who used fertilisers and irrigation water in their day to day farming. Results showed that farmers recognised the different benefits that agroecosystems provided even though they were not familiar with the term ‘ecosystem services.’ Farmers assigned a high value to food provisioning compared to other agroecosystem services and managed their farms for maximum crop yields or maximum crop quality. Fertiliser and irrigation water management decisions were based on multiple factors such as cost, availability of farming equipment and crop yield or crop quality considerations. Survey results showed that while most farmers were able to state the amount of fertiliser used per growing season, the majority of farmers did not know the amount of water they used per growing season. From the farmers’ survey it was recommended that extension services and agricultural education programmes be strengthened in the region to increase farmers’ knowledge on effective agricultural land management strategies that support sustainable intensification. The second research question investigated the effects of agricultural land management strategies and climate change on crop yields in the Eastern Cape. This investigation was done in three steps. First, a crop model, the Environmental Policy Integrated Climate (EPIC) model was calibrated and validated using limited field data from maize variety trials carried out at the Cradock Research Farm in the Eastern Cape. Calibration and validation results proved satisfactory with model efficiencies (Nash Sutcliffe, NSE) greater than 0.5 for both calibration and validation. It was concluded that limited data from field trials on maize that only included grain yield and agricultural land management dates can be used for the calibration of the EPIC model to simulate maize production under South African conditions. In the second step, the calibrated model was applied to simulate different irrigation and fertiliser management strategies for maize production in the Eastern Cape. Different irrigation and Nitrogen (N) fertiliser levels were compared to find optimal irrigation and N fertiliser management strategies that would increase maize yields while minimising environmental pollution (nitrate leaching). Model outputs were also compared to the average yields obtained in the field trials (baseline) and to maize yields reported by farmers in the farmers’ survey. Results showed that improved management of irrigation water and N fertiliser could improve farmers’ maize yields from approximately 7.2 t ha-1 to approximately 12.2 t ha-1, an increase of approximately 69%. Results also revealed a trade-off between food provision and nitrate leaching. Simulations showed that increasing N fertiliser application under sufficient irrigation water levels would increase maize yields, however, this would be accompanied by an increase in N leaching. Lastly, the EPIC model was then applied to simulate the effects of future climate change on irrigated maize production in the Eastern Cape. For these simulations, the model was driven by statistically downscaled climate data derived from three General Circulation Models (GCMs) for two future climate periods, (2040-2069) and (2070-2099), under two Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. Future maize yields were compared to the baseline (1980-2010) maize yield average. All three climate models predicted a decline in maize yields, with yields declining by as much as 23.8% in RCP 8.5, 2070-2099. Simulations also predicted increases in average daily maximum and minimum temperatures for both the two future climate periods under both RCPs. Results also indicated a decrease in seasonal irrigation water requirements. Nitrate leaching was projected to significantly increase towards the end of the century, increasing by as much as 373.8% in RCP 8.5 2070-2099. Concerning farmers’ perceptions of climate change, results showed that farmers were aware of climate change and identified temperature and rainfall changes as the most important changes in climate that they had observed. To adapt to climate change, farmers used a variety of adaptation strategies such as crop rotations and intercropping. Apart from challenges posed by climate change, farmers also faced other challenges such as access to markets and access to financial credit lines, challenges that prevented them from effectively adapting to climate change. The study therefore recommended that appropriate and adequate strategies be designed to help farmers in the region offset the projected decrease in maize production and increase crop yields while minimising negative environmental impacts.
- Full Text:
- Date Issued: 2020
- Authors: Choruma, Dennis Junior
- Date: 2020
- Subjects: Agricultural ecology -- South Africa -- Eastern Cape , Agriculture -- Environmental aspects -- South Africa -- Eastern Cape , Crops and climate -- South Africa -- Eastern Cape , Corn -- Climatic factors -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146756 , vital:38554
- Description: The aims of this study were to evaluate the impacts of agricultural land management strategies and climate change on irrigated maize production in the Eastern Cape, South Africa. To achieve these aims, the study was guided by two overarching research questions, subsequently broken down into more specific questions. The first research question examined the reasons behind farmers’ current agricultural land management practices, the values they assigned to different agroecosystem services, their perceptions of climate change and the adaptation strategies they used to address challenges associated with agricultural crop production and climate change. To answer these questions, a survey of conventional farmers in the Eastern Cape was carried out. The survey targeted farmers who used fertilisers and irrigation water in their day to day farming. Results showed that farmers recognised the different benefits that agroecosystems provided even though they were not familiar with the term ‘ecosystem services.’ Farmers assigned a high value to food provisioning compared to other agroecosystem services and managed their farms for maximum crop yields or maximum crop quality. Fertiliser and irrigation water management decisions were based on multiple factors such as cost, availability of farming equipment and crop yield or crop quality considerations. Survey results showed that while most farmers were able to state the amount of fertiliser used per growing season, the majority of farmers did not know the amount of water they used per growing season. From the farmers’ survey it was recommended that extension services and agricultural education programmes be strengthened in the region to increase farmers’ knowledge on effective agricultural land management strategies that support sustainable intensification. The second research question investigated the effects of agricultural land management strategies and climate change on crop yields in the Eastern Cape. This investigation was done in three steps. First, a crop model, the Environmental Policy Integrated Climate (EPIC) model was calibrated and validated using limited field data from maize variety trials carried out at the Cradock Research Farm in the Eastern Cape. Calibration and validation results proved satisfactory with model efficiencies (Nash Sutcliffe, NSE) greater than 0.5 for both calibration and validation. It was concluded that limited data from field trials on maize that only included grain yield and agricultural land management dates can be used for the calibration of the EPIC model to simulate maize production under South African conditions. In the second step, the calibrated model was applied to simulate different irrigation and fertiliser management strategies for maize production in the Eastern Cape. Different irrigation and Nitrogen (N) fertiliser levels were compared to find optimal irrigation and N fertiliser management strategies that would increase maize yields while minimising environmental pollution (nitrate leaching). Model outputs were also compared to the average yields obtained in the field trials (baseline) and to maize yields reported by farmers in the farmers’ survey. Results showed that improved management of irrigation water and N fertiliser could improve farmers’ maize yields from approximately 7.2 t ha-1 to approximately 12.2 t ha-1, an increase of approximately 69%. Results also revealed a trade-off between food provision and nitrate leaching. Simulations showed that increasing N fertiliser application under sufficient irrigation water levels would increase maize yields, however, this would be accompanied by an increase in N leaching. Lastly, the EPIC model was then applied to simulate the effects of future climate change on irrigated maize production in the Eastern Cape. For these simulations, the model was driven by statistically downscaled climate data derived from three General Circulation Models (GCMs) for two future climate periods, (2040-2069) and (2070-2099), under two Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. Future maize yields were compared to the baseline (1980-2010) maize yield average. All three climate models predicted a decline in maize yields, with yields declining by as much as 23.8% in RCP 8.5, 2070-2099. Simulations also predicted increases in average daily maximum and minimum temperatures for both the two future climate periods under both RCPs. Results also indicated a decrease in seasonal irrigation water requirements. Nitrate leaching was projected to significantly increase towards the end of the century, increasing by as much as 373.8% in RCP 8.5 2070-2099. Concerning farmers’ perceptions of climate change, results showed that farmers were aware of climate change and identified temperature and rainfall changes as the most important changes in climate that they had observed. To adapt to climate change, farmers used a variety of adaptation strategies such as crop rotations and intercropping. Apart from challenges posed by climate change, farmers also faced other challenges such as access to markets and access to financial credit lines, challenges that prevented them from effectively adapting to climate change. The study therefore recommended that appropriate and adequate strategies be designed to help farmers in the region offset the projected decrease in maize production and increase crop yields while minimising negative environmental impacts.
- Full Text:
- Date Issued: 2020
Fire and water : a transdisciplinary investigation of water governance in the lower Sundays River Valley, South Africa
- Authors: Clifford-Holmes, Jai Kumar
- Date: 2015
- Subjects: Lower Sundays River Valley Municipality (Eastern Cape, South Africa) , Water -- Law and legislation -- South Africa , Water-supply -- Management , Municipal services -- South Africa -- Eastern Cape , Fire extinction -- South Africa -- Eastern Cape , Integrated water development -- South Africa -- Eastern Cape , Water quality management -- South Africa -- Eastern Cape , Water resources development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6047 , http://hdl.handle.net/10962/d1017870
- Description: The implementation of water policy and the integrated management of water face multiple challenges in South Africa (SA), despite the successes of post-apartheid government programmes in which some significant equity, sustainability and efficiency milestones have been met. This study uses a series of intervention processes into municipal water service delivery to explore the context, constraints, and real-world messiness in which local water authorities operate. The equitable provision of drinking water by local government and the collaborative management of untreated water by ‘water user associations’ are two sites of institutional conflict that have been subjected to broad ‘turnaround’ and ‘transformation’ attempts at the national level. This thesis seeks to explore and understand the use of transdisciplinary research in engaging local water authorities in a process of institutional change that increases the likelihood of equitable water supply in the Lower Sundays River Valley (LSRV). Fieldwork was conducted as part of a broader action research process involving the attempted ‘turnaround’ of the Sundays River Valley Municipality (SRVM) between 2011 and 2014. A multi-method research approach was employed, which drew on institutional, ethnographic, and systems analyses within an evolving, transdisciplinary methodology. In the single case study research design, qualitative and quantitative data were collected via participant observation, interviews and documentary sources. Analytical methods included system dynamics modelling and an adapted form of the ethnographic tool of ‘thick description’, which were linked in a governance analysis. Government interventions into the SRVM failed to take account of the systemic complexity of the municipal operating environment, the interactions of which are described in this study as the ‘modes of failure’ of local government. These modes included the perpetual ‘firefighting’ responses of municipal officials to crises, and the simultaneous underinvestment in, and over-extension of, water supply infrastructure, which is a rational approach to addressing current water shortages when funds are unavailable for maintenance, refurbishment, or the construction of new infrastructure. The over-burdening of municipalities with technocratic requirements, the presence of gaps in the institutional arrangements governing water supply in the LSRV, and the lack of coordination in government interventions are analysed in this study, with policy recommendations resulting. The primary contribution of this study is in providing a substantively-contextualised case study that illustrates the value of systemic, engaged, extended, and embedded transdisciplinary research.
- Full Text:
- Date Issued: 2015
- Authors: Clifford-Holmes, Jai Kumar
- Date: 2015
- Subjects: Lower Sundays River Valley Municipality (Eastern Cape, South Africa) , Water -- Law and legislation -- South Africa , Water-supply -- Management , Municipal services -- South Africa -- Eastern Cape , Fire extinction -- South Africa -- Eastern Cape , Integrated water development -- South Africa -- Eastern Cape , Water quality management -- South Africa -- Eastern Cape , Water resources development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6047 , http://hdl.handle.net/10962/d1017870
- Description: The implementation of water policy and the integrated management of water face multiple challenges in South Africa (SA), despite the successes of post-apartheid government programmes in which some significant equity, sustainability and efficiency milestones have been met. This study uses a series of intervention processes into municipal water service delivery to explore the context, constraints, and real-world messiness in which local water authorities operate. The equitable provision of drinking water by local government and the collaborative management of untreated water by ‘water user associations’ are two sites of institutional conflict that have been subjected to broad ‘turnaround’ and ‘transformation’ attempts at the national level. This thesis seeks to explore and understand the use of transdisciplinary research in engaging local water authorities in a process of institutional change that increases the likelihood of equitable water supply in the Lower Sundays River Valley (LSRV). Fieldwork was conducted as part of a broader action research process involving the attempted ‘turnaround’ of the Sundays River Valley Municipality (SRVM) between 2011 and 2014. A multi-method research approach was employed, which drew on institutional, ethnographic, and systems analyses within an evolving, transdisciplinary methodology. In the single case study research design, qualitative and quantitative data were collected via participant observation, interviews and documentary sources. Analytical methods included system dynamics modelling and an adapted form of the ethnographic tool of ‘thick description’, which were linked in a governance analysis. Government interventions into the SRVM failed to take account of the systemic complexity of the municipal operating environment, the interactions of which are described in this study as the ‘modes of failure’ of local government. These modes included the perpetual ‘firefighting’ responses of municipal officials to crises, and the simultaneous underinvestment in, and over-extension of, water supply infrastructure, which is a rational approach to addressing current water shortages when funds are unavailable for maintenance, refurbishment, or the construction of new infrastructure. The over-burdening of municipalities with technocratic requirements, the presence of gaps in the institutional arrangements governing water supply in the LSRV, and the lack of coordination in government interventions are analysed in this study, with policy recommendations resulting. The primary contribution of this study is in providing a substantively-contextualised case study that illustrates the value of systemic, engaged, extended, and embedded transdisciplinary research.
- Full Text:
- Date Issued: 2015
Development of a hydraulic sub-model as part of a desktop environmental flow assessment method
- Authors: Desai, Ahmed Yacoob
- Date: 2012
- Subjects: Hydrologic models -- Research -- South Africa Hydraulic engineering -- South Africa Rivers -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6041 , http://hdl.handle.net/10962/d1006200
- Description: Countries around the world have been developing ecological policies to protect their water resources and minimise the impacts of development on their river systems. The concept of ‘minimum flows’ was initially established as a solution but it did not provide sufficient protection as all elements of a flow regime were found to be important for the protection of the river ecosystem. “Environmental flows” were developed to determine these flow regimes to maintain a river in some defined ecological condition. Rapid, initial estimates of the quantity component of environmental flows may be determined using the Desktop Reserve Model in South Africa. However, the Desktop Reserve Model is dependent upon the characteristics of the reference natural hydrology used. The advancements in hydraulic and ecological relationships from the past decade have prompted the development of a Revised Desktop Reserve Model (RDRM) that would incorporate these relationships. The research in this thesis presents the development of the hydraulic sub-model for the RDRM. The hydraulic sub-model was designed to produce a realistic representation of the hydraulic conditions using hydraulic parameters/characteristics from readily available information for any part of South Africa. Hydraulic data from past EWR studies were used to estimate the hydraulic parameters. These estimated hydraulic parameters were used to develop hydraulic estimation relationships and these relationships were developed based on a combination of regression and rule-based procedures. The estimation relationships were incorporated into the hydraulic sub-model of the integrated RDRM and assessments of the hydraulic outputs and EWR results were undertaken to assess the ‘applicability’ of the hydraulic sub-model. The hydraulic sub-model was assessed to be at a stage where it can satisfactorily be incorporated in the RDRM and that it is adequately robust in many situations. Recommendations for future work include the refinement of estimation of the channel forming discharge or the use of spatial imagery to check the maximum channel width estimation. It is also proposed that a future version of the hydraulic sub-model could include flow regime change impacts on channel geomorphology and sedimentology so that flow management scenarios can be more effectively assessed.
- Full Text:
- Date Issued: 2012
- Authors: Desai, Ahmed Yacoob
- Date: 2012
- Subjects: Hydrologic models -- Research -- South Africa Hydraulic engineering -- South Africa Rivers -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6041 , http://hdl.handle.net/10962/d1006200
- Description: Countries around the world have been developing ecological policies to protect their water resources and minimise the impacts of development on their river systems. The concept of ‘minimum flows’ was initially established as a solution but it did not provide sufficient protection as all elements of a flow regime were found to be important for the protection of the river ecosystem. “Environmental flows” were developed to determine these flow regimes to maintain a river in some defined ecological condition. Rapid, initial estimates of the quantity component of environmental flows may be determined using the Desktop Reserve Model in South Africa. However, the Desktop Reserve Model is dependent upon the characteristics of the reference natural hydrology used. The advancements in hydraulic and ecological relationships from the past decade have prompted the development of a Revised Desktop Reserve Model (RDRM) that would incorporate these relationships. The research in this thesis presents the development of the hydraulic sub-model for the RDRM. The hydraulic sub-model was designed to produce a realistic representation of the hydraulic conditions using hydraulic parameters/characteristics from readily available information for any part of South Africa. Hydraulic data from past EWR studies were used to estimate the hydraulic parameters. These estimated hydraulic parameters were used to develop hydraulic estimation relationships and these relationships were developed based on a combination of regression and rule-based procedures. The estimation relationships were incorporated into the hydraulic sub-model of the integrated RDRM and assessments of the hydraulic outputs and EWR results were undertaken to assess the ‘applicability’ of the hydraulic sub-model. The hydraulic sub-model was assessed to be at a stage where it can satisfactorily be incorporated in the RDRM and that it is adequately robust in many situations. Recommendations for future work include the refinement of estimation of the channel forming discharge or the use of spatial imagery to check the maximum channel width estimation. It is also proposed that a future version of the hydraulic sub-model could include flow regime change impacts on channel geomorphology and sedimentology so that flow management scenarios can be more effectively assessed.
- Full Text:
- Date Issued: 2012
Developing macroinvertebrate trait- and taxonomically-based approaches for biomonitoring wadeable riverine systems in the Niger delta, Nigeria
- Authors: Edegbene, Ovie Augustine
- Date: 2020
- Subjects: Water – Pollution -- Nigeria -- Niger River Delta , Stream health -- Nigeria -- Niger River Delta , Water -- Pollution -- Measurement , Environmental monitoring -- Nigeria -- Niger River Delta , Water quality -- Nigeria -- Niger River Delta , Water quality biological assessment -- Nigeria -- Niger River Delta , Aquatic invertebrates -- Nigeria -- Niger River Delta , Stream restoration -- Nigeria -- Niger River Delta , Urban agriculture -- Nigeria -- Niger River Delta , Stream ecology -- Nigeria -- Niger River Delta
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/140660 , vital:37907
- Description: Riverine systems are increasingly subjected to pollution due to rapid urbanisation, industrialisation, and agricultural activities. Increasing pollution in freshwater systems impairs water quality, causes biodiversity loss and impairs aquatic ecosystem functionality and supply of ecosystem services. Rivers in the Niger Delta region of Nigeria are particularly vulnerable to urban pollution and agricultural activities as natural forests are increasingly replaced by urbanisation and agriculture. The differential effects of these pressures on the ecological processes of these river systems are poorly explored, as is the development of appropriate biomonitoring tools for routine monitoring of river health. In this study, a physico-chemically-based approach and macroinvertebrate trait- and taxonomic- approaches were developed to better understand the effects of multiple pressures on riverine systems, while developing multimetric indices to enable sustainable management of rivers within the region. Sixty-six stations in 20 river systems within the Edo and Delta States of the Niger Delta ecoregion were monitored seasonally for a period of five (2008–2012) years. The physico-chemically based approach makes apparent the extent of degradation of rivers and streams in the Niger Delta. For each dominant land use type, river stations were classified into least impacted stations (LIS), moderately impacted stations (MIS) or heavily impacted stations (HIS). Of 11 stations within urban catchments, only two were considered least impacted, suggesting that urgent measures are necessary to revise the current trajectories of urban rivers within the region. Most of the stations designated as MIS and HIS in the urban and urban-agriculture catchments were found to be significantly correlated with increased nutrients, EC and BOD5. Characteristics of most of the MIS and HIS within rivers in urban catchments evidenced the so-called urban stream syndrome, a state of persistent degradation of urban streams. The results of the traits and ecological preferences approach showed traits sensitive to urban and urban-agriculture pollution. Traits and ecological preferences that were associated with the LIS include the possession of hardshell, moderate and high sensitivities to oxygen depletion, very large body sized individuals (>20-40mm), swimmers, flattened body shape, a preference for temporary attachment, crawling, respiration with aerial/vegetation, possession of breathing tubes, possession of strap or other apparatus for respiration, streamlined body, and a high sensitivity to oxygen depletion. Permanent attachment as an ecological preference associated with LIS was also positively correlated with increasing dissolved oxygen (DO) and was deemed a pollution sensitive ecological preference. The possession of very small body size (<5mm), associated with HIS, was deemed a pollution-tolerant trait and was negatively correlated with DO, confirming the deteriorating state of the urban and urban-agricultural rivers. The impact of urban-forestry pollution on the distribution pattern of macroinvertebrate traits and ecological preferences was also explored in the selected rivers. Traits and ecological preferences such as possession of hard-shell, large body size, and grazing as a feeding preference which were significantly positively associated with the LIS, were also either significantly positively correlated with DO, or significantly negatively correlated with increasing any two of flow velocity, water temperature, BOD5 and nutrient. These traits and ecological preferences were deemed sensitive in forested rivers receiving urban pollution. Further, burrowing, the pupa aquatic stage, and predation which were significantly positively associated with HIS on the RLQ ordination, were also significantly negatively associated with DO. These traits were deemed tolerant of forested systems receiving urban pollution. Multimetric indices (MMI) were developed, validated and applied for urban, urban-agriculture and urban-forested (MMI-urban, MMI-urban-agric and urban-forest) areas. Of the 26 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban, only five metric were retained for integration into MMI-urban, they are log VeL, Hemiptera abundance, % Coleoptera + Hemiptera, % Chironomidae + Oligochaeta and Evenness index. Further, of the 18 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban-agric, only 12 metrics were retained and nine proved to be redundant. The nine metrics represent different measures; two of them were retained in addition to Chironomidae/Diptera abundance, % Odonata and Oligochaeta richness. The two metrics selected in addition to the hironomidae/Diptera abundance, % Odonata and Oligochaeta richness were the Margalef index and the logarithm of relative abundance of sprawler. For the MMI-urban-forest, 14 metrics satisfactorily discriminated between the LIS, the MIS, and the HIS, and 12 metrics were retained and 11 proved to be redundant. The non-redundant metric was Trichoptera abundance. Three metrics were further selected in addition to the Trichoptera abundance which include % Chironomidae + Oligochaeta, Coleoptera + Hemiptera richness and Shannon diversity. The MMI-urban and MMI-urban-agric indices performed better for LIS designated stations compared to the MIS and HIS deignated stations. The developed indices proved effective as biomonitoring tools for assessing the ecological health of rivers in the urban and urban-agriculture catchments within the Niger Delta. Overall, the results of the macroinvertebrate traits and ecological preferences, and taxonomic approaches showed the strength in the complementarity of both approaches in developing biomonitoring tools for assessing levels of deterioration in riverine systems. The study contributes significantly to understanding the ecology of riverine systems in the Niger Delta, particularly those subject to urban stresses, agricultural activities and urban pollution in forested systems, and thus makes an important contribution to the science and practice of biomonitoring in Nigeria where such studies are sparse.
- Full Text:
- Date Issued: 2020
- Authors: Edegbene, Ovie Augustine
- Date: 2020
- Subjects: Water – Pollution -- Nigeria -- Niger River Delta , Stream health -- Nigeria -- Niger River Delta , Water -- Pollution -- Measurement , Environmental monitoring -- Nigeria -- Niger River Delta , Water quality -- Nigeria -- Niger River Delta , Water quality biological assessment -- Nigeria -- Niger River Delta , Aquatic invertebrates -- Nigeria -- Niger River Delta , Stream restoration -- Nigeria -- Niger River Delta , Urban agriculture -- Nigeria -- Niger River Delta , Stream ecology -- Nigeria -- Niger River Delta
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/140660 , vital:37907
- Description: Riverine systems are increasingly subjected to pollution due to rapid urbanisation, industrialisation, and agricultural activities. Increasing pollution in freshwater systems impairs water quality, causes biodiversity loss and impairs aquatic ecosystem functionality and supply of ecosystem services. Rivers in the Niger Delta region of Nigeria are particularly vulnerable to urban pollution and agricultural activities as natural forests are increasingly replaced by urbanisation and agriculture. The differential effects of these pressures on the ecological processes of these river systems are poorly explored, as is the development of appropriate biomonitoring tools for routine monitoring of river health. In this study, a physico-chemically-based approach and macroinvertebrate trait- and taxonomic- approaches were developed to better understand the effects of multiple pressures on riverine systems, while developing multimetric indices to enable sustainable management of rivers within the region. Sixty-six stations in 20 river systems within the Edo and Delta States of the Niger Delta ecoregion were monitored seasonally for a period of five (2008–2012) years. The physico-chemically based approach makes apparent the extent of degradation of rivers and streams in the Niger Delta. For each dominant land use type, river stations were classified into least impacted stations (LIS), moderately impacted stations (MIS) or heavily impacted stations (HIS). Of 11 stations within urban catchments, only two were considered least impacted, suggesting that urgent measures are necessary to revise the current trajectories of urban rivers within the region. Most of the stations designated as MIS and HIS in the urban and urban-agriculture catchments were found to be significantly correlated with increased nutrients, EC and BOD5. Characteristics of most of the MIS and HIS within rivers in urban catchments evidenced the so-called urban stream syndrome, a state of persistent degradation of urban streams. The results of the traits and ecological preferences approach showed traits sensitive to urban and urban-agriculture pollution. Traits and ecological preferences that were associated with the LIS include the possession of hardshell, moderate and high sensitivities to oxygen depletion, very large body sized individuals (>20-40mm), swimmers, flattened body shape, a preference for temporary attachment, crawling, respiration with aerial/vegetation, possession of breathing tubes, possession of strap or other apparatus for respiration, streamlined body, and a high sensitivity to oxygen depletion. Permanent attachment as an ecological preference associated with LIS was also positively correlated with increasing dissolved oxygen (DO) and was deemed a pollution sensitive ecological preference. The possession of very small body size (<5mm), associated with HIS, was deemed a pollution-tolerant trait and was negatively correlated with DO, confirming the deteriorating state of the urban and urban-agricultural rivers. The impact of urban-forestry pollution on the distribution pattern of macroinvertebrate traits and ecological preferences was also explored in the selected rivers. Traits and ecological preferences such as possession of hard-shell, large body size, and grazing as a feeding preference which were significantly positively associated with the LIS, were also either significantly positively correlated with DO, or significantly negatively correlated with increasing any two of flow velocity, water temperature, BOD5 and nutrient. These traits and ecological preferences were deemed sensitive in forested rivers receiving urban pollution. Further, burrowing, the pupa aquatic stage, and predation which were significantly positively associated with HIS on the RLQ ordination, were also significantly negatively associated with DO. These traits were deemed tolerant of forested systems receiving urban pollution. Multimetric indices (MMI) were developed, validated and applied for urban, urban-agriculture and urban-forested (MMI-urban, MMI-urban-agric and urban-forest) areas. Of the 26 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban, only five metric were retained for integration into MMI-urban, they are log VeL, Hemiptera abundance, % Coleoptera + Hemiptera, % Chironomidae + Oligochaeta and Evenness index. Further, of the 18 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban-agric, only 12 metrics were retained and nine proved to be redundant. The nine metrics represent different measures; two of them were retained in addition to Chironomidae/Diptera abundance, % Odonata and Oligochaeta richness. The two metrics selected in addition to the hironomidae/Diptera abundance, % Odonata and Oligochaeta richness were the Margalef index and the logarithm of relative abundance of sprawler. For the MMI-urban-forest, 14 metrics satisfactorily discriminated between the LIS, the MIS, and the HIS, and 12 metrics were retained and 11 proved to be redundant. The non-redundant metric was Trichoptera abundance. Three metrics were further selected in addition to the Trichoptera abundance which include % Chironomidae + Oligochaeta, Coleoptera + Hemiptera richness and Shannon diversity. The MMI-urban and MMI-urban-agric indices performed better for LIS designated stations compared to the MIS and HIS deignated stations. The developed indices proved effective as biomonitoring tools for assessing the ecological health of rivers in the urban and urban-agriculture catchments within the Niger Delta. Overall, the results of the macroinvertebrate traits and ecological preferences, and taxonomic approaches showed the strength in the complementarity of both approaches in developing biomonitoring tools for assessing levels of deterioration in riverine systems. The study contributes significantly to understanding the ecology of riverine systems in the Niger Delta, particularly those subject to urban stresses, agricultural activities and urban pollution in forested systems, and thus makes an important contribution to the science and practice of biomonitoring in Nigeria where such studies are sparse.
- Full Text:
- Date Issued: 2020
Social-ecological resilience for well-being : a critical realist case study of Boksburg Lake, South Africa
- Authors: Fox, Helen Elizabeth
- Date: 2015
- Subjects: Boksburg Lake and Wetland project , Reservoirs -- South Africa -- Boksburg , Water -- Pollution -- South Africa -- Boksburg , Human ecology -- South Africa -- Boksburg , Social learning -- South Africa -- Boksburg , Critical realism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6048 , http://hdl.handle.net/10962/d1017872
- Description: This thesis is based on a case study of the degraded Boksburg Lake social-ecological system and an environmental education initiative that aimed to support its transformation. This initiative aimed to involve local people in reclaiming the lake’s social and ecological value, through a process of collectively reimagining possibilities, shaping identities, gaining knowledge and developing local human agency. The focus was on social learning processes in schools and churches to explore opportunities for co-engaged reflexivity that might produce transformation. Schools and Christian churches, two institutions that reflect modern, western socialecological worldviews also have the potential to bring about change. Critical Realism was chosen as my philosophical framework as it provided the tools to explore deeper mechanisms beyond empirical reality, both influencing the degrading trajectory as well as providing possibilities for transformation. It also legitimised case study research as a means to understand more generalised processes characterising modern social-ecological systems. The choice of Critical Realism informed the scope of my primary research question: What generative mechanisms constrain and enable the development of social-ecological resilience for well-being, in the modern social-ecological system of Boksburg Lake? The following three goals were formulated to address this primary question. Goal 1: Based on a multitheoretical perspective of social-ecological literature, develop conceptual tools that have explanatory power to probe generative mechanisms operating in the Boksburg Lake social-ecological system. Goal 2: Identify generative mechanisms driving the current degradation of the Boksburg Lake social-ecological system. Goal 3: Identify learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system. By addressing the primary question and research goals I aimed to gain insights into modern global socialecological systems, the mechanisms that drive high social-ecological risk and the requirements for and possibilities of global systemic change. Drawing on a broad reading of social-ecological literature from different vantage points, tools with explanatory power were developed to probe for generative mechanisms in the Boksburg Lake social-ecological system (goal 1). The human capacity for symbolic representation is identified as an emergent property of coevolving human-ecological systems. These symbolic representations become expressed in culture and worldviews, and influence patterns of identifying, types of knowledge and forms of agency. The nature of these will determine the degree that cultural systems are embedded within ecological reality and the extent of cultural-ecological coupling. A cultural system closely coupled with ecological realities is likely to value ecological systems and manage them for their health, while less coupled cultural-ecological systems are likely to lead to the opposite. Because of their integrated nature, the extent of ecological health and value will affect the decline or sustainability of cultural-ecological systems. There are numerous examples of the learning that can take place when cultural-ecological systems are facing decline. This learning can enhance or reduce biophyllic instincts that become encoded in patterns of identifying, types of knowledge and forms of agency. This in turn affects the strength of cultural-ecological coupling and the extent that human societies co-evolve with ecological systems. , Normalising ideologies is a concept coined in the thesis to refer to symbolic representations of reality that have become integral to a social fabric and determine meaning, while maintaining the domination of the powerful. These ideologies determine patterns of identifying, knowledge and agency and are recognised as having a fundamental influence on the resilience of social-ecological systems. Four normalising ideologies are identified that promote apparent human progress at the expense of ecological integrity and social equality and thus alienation with each other and the ecological world. These are human-ecological dualism, anthropocentrism, nature is mechanised and nature is to be controlled. There are also a number of ideologies promoting connectedness with the ecological world that, if they became normalised, would support greater social-ecological resilience for well-being. Generative mechanisms driving the current degradation of the Boksburg Lake socialecological system were identified (goal 2). Drawing on critical methodology, the main method adopted was document analysis of the Boksburg Advertiser archives, Boksburg’s local newspaper. Four generative mechanisms are recognised as most influential. Two of these have been named hegemonic symbolic systems. The primary symbolic system consists of the four normalising ideologies, mentioned above, that promote human progress at the expense of ecological health. The secondary, more explicit symbolic system, built on this, consists of the following normative ideologies: economic growth is imperative, unrestrained development is promoted, competition is the necessary means and consumerism is the good life. These two symbolic systems have had causal influence on the systematic erosion of ecological processes and biological diversity that has occurred in Boksburg, with the consequent undermining of social-ecological resilience for well-being. The third mechanism that constrains resilience is the power dynamics that have shaped Boksburg’s economic history and social-ecological system. This has resulted in a society built on inequality and injustice with all its associated social and environmental ills, expressed as externalities. The fourth mechanism resides in Boksburg’s political and municipal dynamics. These structures are not designed to tackle complex social-ecological problems and they hold considerable agential power, yet seem dysfunctional at present. Learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system were identified (goal 3). By adopting the role of a reflexive practitioner, supported by action research, case study and interpretivist methodologies, data on the empirical manifestations of the environmental educational initiative were collected. Methods included semistructured interviews, focus groups, document analysis and participant observation. Findings indicate that schools and churches are important institutions that can positively influence patterns of identifying, knowledge about and agency for Boksburg Lake and can thus play a role in transforming hegemonic normalising ideologies. Important learning mechanisms identified included: Learning reflexively together within communities of practice that provide opportunities for active rather than passive learning; involving the youth as they are a group of people with notable enthusiasm, vision, energy and motivation; learning through information acquisition, investigation, action and deliberation; learning about abstract concepts and theoretical knowledge but embedding this in local realities; and learning that provides reference markers for how things can be different.
- Full Text:
- Date Issued: 2015
- Authors: Fox, Helen Elizabeth
- Date: 2015
- Subjects: Boksburg Lake and Wetland project , Reservoirs -- South Africa -- Boksburg , Water -- Pollution -- South Africa -- Boksburg , Human ecology -- South Africa -- Boksburg , Social learning -- South Africa -- Boksburg , Critical realism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6048 , http://hdl.handle.net/10962/d1017872
- Description: This thesis is based on a case study of the degraded Boksburg Lake social-ecological system and an environmental education initiative that aimed to support its transformation. This initiative aimed to involve local people in reclaiming the lake’s social and ecological value, through a process of collectively reimagining possibilities, shaping identities, gaining knowledge and developing local human agency. The focus was on social learning processes in schools and churches to explore opportunities for co-engaged reflexivity that might produce transformation. Schools and Christian churches, two institutions that reflect modern, western socialecological worldviews also have the potential to bring about change. Critical Realism was chosen as my philosophical framework as it provided the tools to explore deeper mechanisms beyond empirical reality, both influencing the degrading trajectory as well as providing possibilities for transformation. It also legitimised case study research as a means to understand more generalised processes characterising modern social-ecological systems. The choice of Critical Realism informed the scope of my primary research question: What generative mechanisms constrain and enable the development of social-ecological resilience for well-being, in the modern social-ecological system of Boksburg Lake? The following three goals were formulated to address this primary question. Goal 1: Based on a multitheoretical perspective of social-ecological literature, develop conceptual tools that have explanatory power to probe generative mechanisms operating in the Boksburg Lake social-ecological system. Goal 2: Identify generative mechanisms driving the current degradation of the Boksburg Lake social-ecological system. Goal 3: Identify learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system. By addressing the primary question and research goals I aimed to gain insights into modern global socialecological systems, the mechanisms that drive high social-ecological risk and the requirements for and possibilities of global systemic change. Drawing on a broad reading of social-ecological literature from different vantage points, tools with explanatory power were developed to probe for generative mechanisms in the Boksburg Lake social-ecological system (goal 1). The human capacity for symbolic representation is identified as an emergent property of coevolving human-ecological systems. These symbolic representations become expressed in culture and worldviews, and influence patterns of identifying, types of knowledge and forms of agency. The nature of these will determine the degree that cultural systems are embedded within ecological reality and the extent of cultural-ecological coupling. A cultural system closely coupled with ecological realities is likely to value ecological systems and manage them for their health, while less coupled cultural-ecological systems are likely to lead to the opposite. Because of their integrated nature, the extent of ecological health and value will affect the decline or sustainability of cultural-ecological systems. There are numerous examples of the learning that can take place when cultural-ecological systems are facing decline. This learning can enhance or reduce biophyllic instincts that become encoded in patterns of identifying, types of knowledge and forms of agency. This in turn affects the strength of cultural-ecological coupling and the extent that human societies co-evolve with ecological systems. , Normalising ideologies is a concept coined in the thesis to refer to symbolic representations of reality that have become integral to a social fabric and determine meaning, while maintaining the domination of the powerful. These ideologies determine patterns of identifying, knowledge and agency and are recognised as having a fundamental influence on the resilience of social-ecological systems. Four normalising ideologies are identified that promote apparent human progress at the expense of ecological integrity and social equality and thus alienation with each other and the ecological world. These are human-ecological dualism, anthropocentrism, nature is mechanised and nature is to be controlled. There are also a number of ideologies promoting connectedness with the ecological world that, if they became normalised, would support greater social-ecological resilience for well-being. Generative mechanisms driving the current degradation of the Boksburg Lake socialecological system were identified (goal 2). Drawing on critical methodology, the main method adopted was document analysis of the Boksburg Advertiser archives, Boksburg’s local newspaper. Four generative mechanisms are recognised as most influential. Two of these have been named hegemonic symbolic systems. The primary symbolic system consists of the four normalising ideologies, mentioned above, that promote human progress at the expense of ecological health. The secondary, more explicit symbolic system, built on this, consists of the following normative ideologies: economic growth is imperative, unrestrained development is promoted, competition is the necessary means and consumerism is the good life. These two symbolic systems have had causal influence on the systematic erosion of ecological processes and biological diversity that has occurred in Boksburg, with the consequent undermining of social-ecological resilience for well-being. The third mechanism that constrains resilience is the power dynamics that have shaped Boksburg’s economic history and social-ecological system. This has resulted in a society built on inequality and injustice with all its associated social and environmental ills, expressed as externalities. The fourth mechanism resides in Boksburg’s political and municipal dynamics. These structures are not designed to tackle complex social-ecological problems and they hold considerable agential power, yet seem dysfunctional at present. Learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system were identified (goal 3). By adopting the role of a reflexive practitioner, supported by action research, case study and interpretivist methodologies, data on the empirical manifestations of the environmental educational initiative were collected. Methods included semistructured interviews, focus groups, document analysis and participant observation. Findings indicate that schools and churches are important institutions that can positively influence patterns of identifying, knowledge about and agency for Boksburg Lake and can thus play a role in transforming hegemonic normalising ideologies. Important learning mechanisms identified included: Learning reflexively together within communities of practice that provide opportunities for active rather than passive learning; involving the youth as they are a group of people with notable enthusiasm, vision, energy and motivation; learning through information acquisition, investigation, action and deliberation; learning about abstract concepts and theoretical knowledge but embedding this in local realities; and learning that provides reference markers for how things can be different.
- Full Text:
- Date Issued: 2015
The value of locally isolated freshwater micro-algae in toxicity testing for water resource management in South Africa
- Authors: Gola, Nontutuzelo Pearl
- Date: 2015
- Subjects: Microalgae -- South Africa , Toxicity testing , Water resources development -- South Africa , Aquatic habitats -- South Africa , Water -- Pollution -- Toxicology , Water quality management -- South Africa , Sewage disposal in rivers, lakes, etc. -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6049 , http://hdl.handle.net/10962/d1017873
- Description: The ecological position of micro-algae at the base of the aquatic food web makes them critical components of aquatic ecosystems. Their short generation time also makes them useful biological indicators because they respond quickly to changes in environmental condition, enabling timely identification and assessment of water quality changes. The inclusion of micro-algae as indicators in water resource regulation and management in South Africa has started recently, their more extensive use in biomonitoring and ecotoxicology programmes for water resource management would contribute to the South African policy if water resource protection. The standard algal growth inhibition assay with the species Pseudokirchneriella subcapitata is currently used for monitoring toxicity of in-stream and industrial wastewater discharges to freshwater micro-algae. The relevance of the data generated by standard toxicity bioassays has been questioned, since micro-algae in particular are extremely variable in their sensitivity to a range of contaminants and these standard species used may not occur in the local aquatic environment. As a result, international regulatory agencies, have recommended algal growth inhibition tests be changed from a single standard species to tests with a number of species. One recommendation, in addition to the use of standard toxicity tests, is the use of species isolated from the local environment which may be more relevant for assessing site specific impacts. This study investigated the value and application of locally isolated South African freshwater micro-algae in toxicity tests for water resource management and was carried out in three phases. The first phase involved isolating micro-algae from South African aquatic resources. Micro-algae suitable for toxicity testing were identified and selected using as set of criteria. Three (Scenedesmus bicaudatus, Chlorella sorokiniana and Chlorella vulgaris) out of eight successfully isolated species satisfied the prescribed selection criteria and these were selected as potential toxicity test species. The second phase focused on refining and adapting the existing algal toxicity test protocol (the algal growth inhibition assay) for use on the locally isolated algal species. The refinement of the test protocol was achieved by exposing the locally isolated species to reference toxicants in order to assess and compare their growth and sensitivity to the toxicants under the prescribed toxicity test conditions with that of the standard toxicity test species (Pseudokirchneriella subcapitata) and a commercial laboratory species (Chlorella protothecoides). During this phase, one of the three local species (Scenedesmus bicaudatus) was eliminated as a potential toxicity test species due to inconsistent growth. The third phase of the study involved assessing the sensitivity of the two remaining species (C. vulgaris and C. sorokiniana) to a range of toxicants (reference toxicants, salts, effluents and a herbicide) and comparing it to that of the standard toxicity test species P. subcapitata and C. protothecoides. The toxicants were selected based on their relative importance in the South African context, as well as the practicality of using these local micro-algae to routinely determine the impact of these toxicants on local aquatic resources. The growth of the four micro-algae was stimulated by the selected effluents. The standard toxicity test species P. subcapitata was ranked the most sensitive and of the four species to two reference toxicants and two inorganic salts. Chlorella sorokiniana was ranked the most sensitive of the three Chlorella species to two reference toxicants and two inorganic salts. The herbicide stimulated the growth of C. vulgaris while inhibiting the growth of the other species. Pseudokirchneriela subcapitata and C. sorokiniana showed high intra-specific variability in growth, which made it difficult to determine the effective concentrations of the herbicide and therefore compare the sensitivity of the species. This varied response of micro-algal species to toxicants may result in the biodiversity shifts in aquatic ecosystems, and also supports the recommendation of using a battery of different species to support more informed decisions in water resource management.
- Full Text:
- Date Issued: 2015
- Authors: Gola, Nontutuzelo Pearl
- Date: 2015
- Subjects: Microalgae -- South Africa , Toxicity testing , Water resources development -- South Africa , Aquatic habitats -- South Africa , Water -- Pollution -- Toxicology , Water quality management -- South Africa , Sewage disposal in rivers, lakes, etc. -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6049 , http://hdl.handle.net/10962/d1017873
- Description: The ecological position of micro-algae at the base of the aquatic food web makes them critical components of aquatic ecosystems. Their short generation time also makes them useful biological indicators because they respond quickly to changes in environmental condition, enabling timely identification and assessment of water quality changes. The inclusion of micro-algae as indicators in water resource regulation and management in South Africa has started recently, their more extensive use in biomonitoring and ecotoxicology programmes for water resource management would contribute to the South African policy if water resource protection. The standard algal growth inhibition assay with the species Pseudokirchneriella subcapitata is currently used for monitoring toxicity of in-stream and industrial wastewater discharges to freshwater micro-algae. The relevance of the data generated by standard toxicity bioassays has been questioned, since micro-algae in particular are extremely variable in their sensitivity to a range of contaminants and these standard species used may not occur in the local aquatic environment. As a result, international regulatory agencies, have recommended algal growth inhibition tests be changed from a single standard species to tests with a number of species. One recommendation, in addition to the use of standard toxicity tests, is the use of species isolated from the local environment which may be more relevant for assessing site specific impacts. This study investigated the value and application of locally isolated South African freshwater micro-algae in toxicity tests for water resource management and was carried out in three phases. The first phase involved isolating micro-algae from South African aquatic resources. Micro-algae suitable for toxicity testing were identified and selected using as set of criteria. Three (Scenedesmus bicaudatus, Chlorella sorokiniana and Chlorella vulgaris) out of eight successfully isolated species satisfied the prescribed selection criteria and these were selected as potential toxicity test species. The second phase focused on refining and adapting the existing algal toxicity test protocol (the algal growth inhibition assay) for use on the locally isolated algal species. The refinement of the test protocol was achieved by exposing the locally isolated species to reference toxicants in order to assess and compare their growth and sensitivity to the toxicants under the prescribed toxicity test conditions with that of the standard toxicity test species (Pseudokirchneriella subcapitata) and a commercial laboratory species (Chlorella protothecoides). During this phase, one of the three local species (Scenedesmus bicaudatus) was eliminated as a potential toxicity test species due to inconsistent growth. The third phase of the study involved assessing the sensitivity of the two remaining species (C. vulgaris and C. sorokiniana) to a range of toxicants (reference toxicants, salts, effluents and a herbicide) and comparing it to that of the standard toxicity test species P. subcapitata and C. protothecoides. The toxicants were selected based on their relative importance in the South African context, as well as the practicality of using these local micro-algae to routinely determine the impact of these toxicants on local aquatic resources. The growth of the four micro-algae was stimulated by the selected effluents. The standard toxicity test species P. subcapitata was ranked the most sensitive and of the four species to two reference toxicants and two inorganic salts. Chlorella sorokiniana was ranked the most sensitive of the three Chlorella species to two reference toxicants and two inorganic salts. The herbicide stimulated the growth of C. vulgaris while inhibiting the growth of the other species. Pseudokirchneriela subcapitata and C. sorokiniana showed high intra-specific variability in growth, which made it difficult to determine the effective concentrations of the herbicide and therefore compare the sensitivity of the species. This varied response of micro-algal species to toxicants may result in the biodiversity shifts in aquatic ecosystems, and also supports the recommendation of using a battery of different species to support more informed decisions in water resource management.
- Full Text:
- Date Issued: 2015
Assessing the effect of a laundry detergent ingredient (LAS) on organisms of a rural South African river
- Authors: Gordon, Andrew K
- Date: 2012
- Subjects: Detergent pollution of rivers, lakes, etc. -- Research -- South Africa -- Eastern Cape Water -- Pollution -- Research -- South Africa -- Eastern Cape Stream health -- Research -- South Africa -- Eastern Cape Stream ecology -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6042 , http://hdl.handle.net/10962/d1006201
- Description: Powdered laundry detergents are consumed in high volumes worldwide. Post use, they are directed toward water resources via wastewater treatment works or, as is the situation in many rural areas of South Africa, they enter the environment directly as a result of laundry washing activity undertaken alongside surface waters. Within wastewater treatment works, the main ingredient in powdered laundry detergents, the narcotic toxin linear alkylbenzene sulfonate (LAS), is mostly removed, rendering the waste stream a negligible risk to the aquatic biota of receiving waters. In contrast, the biological and ecological impacts of direct LAS input to the aquatic environment, as a consequence of near-stream laundry washing, are yet to be fully realised. Consequently, this thesis posed two research questions: 1) 'What are the LAS concentrations in a small rural South African river'? and 2) 'Is the in-stream biological community negatively affected at these concentrations?' The chosen study area, the community of Balfour in the Eastern Cape Province, is like many rural areas of South Africa where inadequate provision of piped water to homesteads necessitates laundry washing alongside the nearby Balfour River. The first research question was addressed in two ways: by predicting LAS concentrations in Balfour River water by assessing detergent consumption and laundry washing behaviour of residents living alongside the river; and measuring actual in- stream LAS concentrations on different days of the week and during different seasons. Results indicated that LAS concentrations were highly variable temporally and spatially. High peak concentrations of LAS occurred infrequently and were limited to the immediate vicinity of near-stream laundry washing activity with the highest measured concentration being 342 μg.L ⁻¹ and the average 21 μg.L ⁻¹ over the sampling period. The second research question was addressed by integrating the chemical evidence, determined from the first research question, with the biological evidence of stress responses measured in macroinvertebrates collected downstream of near-stream laundry washing activity on the Balfour River. Predicted and measured LAS exposure concentrations from the Balfour River were compared to a water quality guideline for LAS (304 μg.L ⁻¹), specifically derived in this thesis. Biological stress responses were measured at different levels of organisation: two sub-cellular responses (lipid peroxidation and cholinesterase activity); three measures of macroinvertebrate tolerance to water quality impairment; five measures of community composition; three measures of community richness; and a surrogate measure of ecosystem function (functional feeding groups). Weight-of-evidence methodology was utilised to assess, integrate and interpret the chemical and biological evidence, and at its conclusion, determined no effect on the in-stream biological community of the Balfour River downstream of laundry washing activity.
- Full Text:
- Date Issued: 2012
- Authors: Gordon, Andrew K
- Date: 2012
- Subjects: Detergent pollution of rivers, lakes, etc. -- Research -- South Africa -- Eastern Cape Water -- Pollution -- Research -- South Africa -- Eastern Cape Stream health -- Research -- South Africa -- Eastern Cape Stream ecology -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6042 , http://hdl.handle.net/10962/d1006201
- Description: Powdered laundry detergents are consumed in high volumes worldwide. Post use, they are directed toward water resources via wastewater treatment works or, as is the situation in many rural areas of South Africa, they enter the environment directly as a result of laundry washing activity undertaken alongside surface waters. Within wastewater treatment works, the main ingredient in powdered laundry detergents, the narcotic toxin linear alkylbenzene sulfonate (LAS), is mostly removed, rendering the waste stream a negligible risk to the aquatic biota of receiving waters. In contrast, the biological and ecological impacts of direct LAS input to the aquatic environment, as a consequence of near-stream laundry washing, are yet to be fully realised. Consequently, this thesis posed two research questions: 1) 'What are the LAS concentrations in a small rural South African river'? and 2) 'Is the in-stream biological community negatively affected at these concentrations?' The chosen study area, the community of Balfour in the Eastern Cape Province, is like many rural areas of South Africa where inadequate provision of piped water to homesteads necessitates laundry washing alongside the nearby Balfour River. The first research question was addressed in two ways: by predicting LAS concentrations in Balfour River water by assessing detergent consumption and laundry washing behaviour of residents living alongside the river; and measuring actual in- stream LAS concentrations on different days of the week and during different seasons. Results indicated that LAS concentrations were highly variable temporally and spatially. High peak concentrations of LAS occurred infrequently and were limited to the immediate vicinity of near-stream laundry washing activity with the highest measured concentration being 342 μg.L ⁻¹ and the average 21 μg.L ⁻¹ over the sampling period. The second research question was addressed by integrating the chemical evidence, determined from the first research question, with the biological evidence of stress responses measured in macroinvertebrates collected downstream of near-stream laundry washing activity on the Balfour River. Predicted and measured LAS exposure concentrations from the Balfour River were compared to a water quality guideline for LAS (304 μg.L ⁻¹), specifically derived in this thesis. Biological stress responses were measured at different levels of organisation: two sub-cellular responses (lipid peroxidation and cholinesterase activity); three measures of macroinvertebrate tolerance to water quality impairment; five measures of community composition; three measures of community richness; and a surrogate measure of ecosystem function (functional feeding groups). Weight-of-evidence methodology was utilised to assess, integrate and interpret the chemical and biological evidence, and at its conclusion, determined no effect on the in-stream biological community of the Balfour River downstream of laundry washing activity.
- Full Text:
- Date Issued: 2012
The further development, application and evaluation of a sediment yield model (WQSED) for catchment management in African catchments
- Authors: Gwapedza, David
- Date: 2021-04
- Subjects: Sedimentation and deposition -- South Africa , Sedimentation and deposition -- Zimbabwe , Watersheds -- South Africa , Watersheds -- Zimbabwe , Watershed management -- Africa , Water quality -- South Africa , Water quality -- Zimbabwe , Modified Universal Soil Loss Equation (MUSLE) , Water Quality and Sediment Model (WQSED) , Soil and Water Assessment Tool (SWAT)
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/178376 , vital:42934 , 10.21504/10962/178376
- Description: Erosion and sediment transport are natural catchment processes that play an essential role in ecosystem functioning by providing habitat for aquatic organisms and contributing to the health of wetlands. However, excessive erosion and sedimentation, mostly driven by anthropogenic activity, lead to ecosystem degradation, loss of agricultural land, water quality problems, reduced reservoir storage capacity and damage to physical infrastructure. It is reported that up to 25% of dams in South Africa have lost approximately 30% of their initial storage capacity to sedimentation. Therefore, excessive sedimentation transcends from an ecological problem to a health, livelihood and water security issue. Erosion and sedimentation occur at variable temporal and spatial scales; therefore, monitoring of these processes can be difficult and expensive. Regardless of all these prohibiting factors, information on erosion and sediment remains an urgent requirement for the sustainable management of catchments. Models have evolved as tools to replicate and simulate complex natural processes to understand and manage these systems. Several models have been developed globally to simulate erosion and sediment transport. However, these models are not always applicable in Africa because 1) the conditions under which they were developed are not as relevant for African catchments 2) they have high data requirements and cannot be applied with ease in our data-scarce African catchments 3) they are sometimes complicated, and there are little training available or potential users simply have no time to dedicate towards learning these models. To respond to the problems of erosion, sedimentation, water quality and unavailability of applicable models, the current research further develops, applies and evaluates an erosion and sediment transport model, the Water Quality and Sediment Model (WQSED), for integration within the existing water resources framework in South Africa and application for practical catchment management. The WQSED was developed to simulate daily suspended sediment loads that are vital for water quality and quantity assessments. The WQSED was developed based on the Modified Universal Soil Loss Equation (MUSLE), and the Pitman model is a primary hydrological model providing forcing data, although flow data from independent sources may be used to drive the WQSED model. The MUSLE was developed in the United States of America, and this research attempts to improve the applicability of the MUSLE by identifying key issues that may impede its performance. Assessments conducted within the current research can be divided into scale assessment and application and evaluation assessment. The scale assessment involved evaluating spatial and temporal scale issues associated with the MUSLE. Spatial scale assessments were conducted using analytical and mathematical assessments on a hypothetical catchment. Temporal scale issues were assessed in terms of the vegetation cover (C) factor within the Tsitsa River catchment in South Africa. Model application and evaluation involved applying and calibrating the model to simulate daily time-series sediment yield. The model was applied to calibrated and validated (split-sample validation) in two catchments in South Africa, two catchments in Zimbabwe and three catchments were selected from the USA and associated territories for further testing as continuous daily time-series observed sediment data could not be readily accessed for catchments in the Southern African region. The catchments where the model was calibrated and validated range in size from 50 km2 to 20 000 km2. Additionally, the model was applied to thirteen ‘ungauged’ catchments selected from across South Africa, where only long-term reservoir sedimentation rates were available to compare with long term model simulations converted to sediment yield rates. The additional thirteen catchments were selected from areas of different climatic, vegetation and soils conditions characterising South Africa and range in size from 30 km2 to 2 500 km2. The current research results are split into a) MUSLE scale dependency and b) WQSED testing and evaluation. Scale dependency testing showed that the MUSLE could be spatially scale-dependent, particularly when a lumped approach is used, resulting in simulations of up to 30% more sediment. Spatial scale dependence in the MUSLE was found to be related to the runoff and topographic factors used and how they are calculated. The current study resorted to adopting a reference grid in applying the MUSLE, followed by scaling up the outputs to the total catchment area. Using a reference grid resulted in a general avoidance of the problem of spatial scale. The adoption of a seasonal vegetation cover factor was shown to significantly account for temporal changes of vegetation cover within a year and reduce over-estimations in sediment output. The temporal scale evaluation demonstrated the uncertainties associated with using a fixed vegetation cover factor in a catchment with variable rainfall and runoff pattern. The WQSED model evaluation showed that the model could be calibrated and validated to provide consistent results. Satisfactory model evaluation statistics were obtained for most catchments to which the model was applied, based on general model evaluation guidelines (Nash Sutcliffe Efficiency and R2 > 0.5). The model also performed generally well compared to established models that had been previously applied in some of the study catchments. The highest sediment yields recorded per country were 153 t km-2 year-1 (Tsitsa River; South Africa), 90 t km-2 year-1 (Odzi River; Zimbabwe) and 340 t km-2 year-1 (Rio Tanama; Puerto Rico). The results also displayed consistent underestimations of peak sediment yield events, partly attributed to sediment emanating from gullies that are not explicitly accounted for in the WQSED model structure. Furthermore, the calibration process revealed that the WQSED storage model is generally challenging to calibrate. An alternative simpler version of the storage model was easier to calibrate, but the model may still be challenging to apply to catchments where calibration data are not available. The additional evaluation of the WQSED simulated sediment yield rates against observed reservoir sediment rates showed a broad range of differences between the simulated and observed sediment yield rates. Differences between WQSED simulated sediment and observed reservoir sediment ranges from a low of 30% to a high of > 40 times. The large differences were partly attributed to WQSED being limited to simulating suspended sediment from sheet and rill processes, whereas reservoir sediment is generated from more sources that include bedload, channel and gully processes. Nevertheless, the model simulations replicated some of the regional sediment yield patterns and are assumed to represent sheet and rill contributions to reservoir sediment in selected catchments. The outcome of this study is an improved WQSED model that has successfully undergone preliminary testing and evaluation. Therefore, the model is sufficiently complete to be used by independent researchers and water resources managers to simulate erosion and sediment transport. However, the model is best applicable to areas where some observed data or regional information are available to calibrate the storage components and constrain model outputs. The report on potential MUSLE scale dependencies is relevant globally to all studies applying the MUSLE model and, therefore, can improve MUSLE application in future studies. The WQSED model offers a relatively simple, effective and applicable tool that is set to provide information to enhance catchment, land and water resources management in catchments of Africa. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Gwapedza, David
- Date: 2021-04
- Subjects: Sedimentation and deposition -- South Africa , Sedimentation and deposition -- Zimbabwe , Watersheds -- South Africa , Watersheds -- Zimbabwe , Watershed management -- Africa , Water quality -- South Africa , Water quality -- Zimbabwe , Modified Universal Soil Loss Equation (MUSLE) , Water Quality and Sediment Model (WQSED) , Soil and Water Assessment Tool (SWAT)
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/178376 , vital:42934 , 10.21504/10962/178376
- Description: Erosion and sediment transport are natural catchment processes that play an essential role in ecosystem functioning by providing habitat for aquatic organisms and contributing to the health of wetlands. However, excessive erosion and sedimentation, mostly driven by anthropogenic activity, lead to ecosystem degradation, loss of agricultural land, water quality problems, reduced reservoir storage capacity and damage to physical infrastructure. It is reported that up to 25% of dams in South Africa have lost approximately 30% of their initial storage capacity to sedimentation. Therefore, excessive sedimentation transcends from an ecological problem to a health, livelihood and water security issue. Erosion and sedimentation occur at variable temporal and spatial scales; therefore, monitoring of these processes can be difficult and expensive. Regardless of all these prohibiting factors, information on erosion and sediment remains an urgent requirement for the sustainable management of catchments. Models have evolved as tools to replicate and simulate complex natural processes to understand and manage these systems. Several models have been developed globally to simulate erosion and sediment transport. However, these models are not always applicable in Africa because 1) the conditions under which they were developed are not as relevant for African catchments 2) they have high data requirements and cannot be applied with ease in our data-scarce African catchments 3) they are sometimes complicated, and there are little training available or potential users simply have no time to dedicate towards learning these models. To respond to the problems of erosion, sedimentation, water quality and unavailability of applicable models, the current research further develops, applies and evaluates an erosion and sediment transport model, the Water Quality and Sediment Model (WQSED), for integration within the existing water resources framework in South Africa and application for practical catchment management. The WQSED was developed to simulate daily suspended sediment loads that are vital for water quality and quantity assessments. The WQSED was developed based on the Modified Universal Soil Loss Equation (MUSLE), and the Pitman model is a primary hydrological model providing forcing data, although flow data from independent sources may be used to drive the WQSED model. The MUSLE was developed in the United States of America, and this research attempts to improve the applicability of the MUSLE by identifying key issues that may impede its performance. Assessments conducted within the current research can be divided into scale assessment and application and evaluation assessment. The scale assessment involved evaluating spatial and temporal scale issues associated with the MUSLE. Spatial scale assessments were conducted using analytical and mathematical assessments on a hypothetical catchment. Temporal scale issues were assessed in terms of the vegetation cover (C) factor within the Tsitsa River catchment in South Africa. Model application and evaluation involved applying and calibrating the model to simulate daily time-series sediment yield. The model was applied to calibrated and validated (split-sample validation) in two catchments in South Africa, two catchments in Zimbabwe and three catchments were selected from the USA and associated territories for further testing as continuous daily time-series observed sediment data could not be readily accessed for catchments in the Southern African region. The catchments where the model was calibrated and validated range in size from 50 km2 to 20 000 km2. Additionally, the model was applied to thirteen ‘ungauged’ catchments selected from across South Africa, where only long-term reservoir sedimentation rates were available to compare with long term model simulations converted to sediment yield rates. The additional thirteen catchments were selected from areas of different climatic, vegetation and soils conditions characterising South Africa and range in size from 30 km2 to 2 500 km2. The current research results are split into a) MUSLE scale dependency and b) WQSED testing and evaluation. Scale dependency testing showed that the MUSLE could be spatially scale-dependent, particularly when a lumped approach is used, resulting in simulations of up to 30% more sediment. Spatial scale dependence in the MUSLE was found to be related to the runoff and topographic factors used and how they are calculated. The current study resorted to adopting a reference grid in applying the MUSLE, followed by scaling up the outputs to the total catchment area. Using a reference grid resulted in a general avoidance of the problem of spatial scale. The adoption of a seasonal vegetation cover factor was shown to significantly account for temporal changes of vegetation cover within a year and reduce over-estimations in sediment output. The temporal scale evaluation demonstrated the uncertainties associated with using a fixed vegetation cover factor in a catchment with variable rainfall and runoff pattern. The WQSED model evaluation showed that the model could be calibrated and validated to provide consistent results. Satisfactory model evaluation statistics were obtained for most catchments to which the model was applied, based on general model evaluation guidelines (Nash Sutcliffe Efficiency and R2 > 0.5). The model also performed generally well compared to established models that had been previously applied in some of the study catchments. The highest sediment yields recorded per country were 153 t km-2 year-1 (Tsitsa River; South Africa), 90 t km-2 year-1 (Odzi River; Zimbabwe) and 340 t km-2 year-1 (Rio Tanama; Puerto Rico). The results also displayed consistent underestimations of peak sediment yield events, partly attributed to sediment emanating from gullies that are not explicitly accounted for in the WQSED model structure. Furthermore, the calibration process revealed that the WQSED storage model is generally challenging to calibrate. An alternative simpler version of the storage model was easier to calibrate, but the model may still be challenging to apply to catchments where calibration data are not available. The additional evaluation of the WQSED simulated sediment yield rates against observed reservoir sediment rates showed a broad range of differences between the simulated and observed sediment yield rates. Differences between WQSED simulated sediment and observed reservoir sediment ranges from a low of 30% to a high of > 40 times. The large differences were partly attributed to WQSED being limited to simulating suspended sediment from sheet and rill processes, whereas reservoir sediment is generated from more sources that include bedload, channel and gully processes. Nevertheless, the model simulations replicated some of the regional sediment yield patterns and are assumed to represent sheet and rill contributions to reservoir sediment in selected catchments. The outcome of this study is an improved WQSED model that has successfully undergone preliminary testing and evaluation. Therefore, the model is sufficiently complete to be used by independent researchers and water resources managers to simulate erosion and sediment transport. However, the model is best applicable to areas where some observed data or regional information are available to calibrate the storage components and constrain model outputs. The report on potential MUSLE scale dependencies is relevant globally to all studies applying the MUSLE model and, therefore, can improve MUSLE application in future studies. The WQSED model offers a relatively simple, effective and applicable tool that is set to provide information to enhance catchment, land and water resources management in catchments of Africa. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-04
Modelling plant water use of the grassland and thicket biomes in the Eastern Cape, South Africa: towards an improved understanding of the impact of invasive alien plants on soil chemistry, biomass production and evapotranspiration
- Authors: Gwate, Onalenna
- Date: 2018
- Subjects: Grasslands -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Rangelands -- South Africa -- Eastern Cape , Range ecology-- South Africa -- Eastern Cape , Rangelands -- Water-supply , Rangelands -- Weed control , Evapotranspiration , Plant-water relationships
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54800 , vital:26617
- Description: It is imperative to understand the strong coupling between the carbon capture process and water use to sustainably manage rangelands. Woody encroachment is undermining rangelands grass production. Evapotranspiration (ET) highlights the links between ecosystem carbon capture process and water use. It forms the biggest flux of the hydrological cycle after precipitation yet it is not well understood. The Grassland and the Albany Thicket (AT) biomes in the Eastern Cape, South Africa, provide an interesting space to study the dynamics in rangelands biomass production and the associated water use. Therefore, the main purpose of this study was to contribute towards management of rangelands by understanding the dynamics in rangeland grass production and water use. To achieve this aim, the impact of Acacia mearnsii, an invasive alien plant, on soil chemical properties and rangelands grass production was investigated. This was achieved by analysing the biophysical attributes of A. mearnsii as they related to grass production. Secondly, selected soil variables that could be used as a prognosis for landscape recovery or deterioration were evaluated. In addition, aboveground grass biomass was measured in areas cleared of A. mearnsii and regression equations were prepared to help model aboveground grass biomass in areas cleared of A. mearnsi. The thesis also explored dynamics in water vapour and energy fluxes in these two biomes using an eddy covariance system. Consequently, water vapour and energy fluxes were evaluated in order to understand landscape water use and energy partitioning in the landscape. The study also tested the application of Penman-Monteith equation based algorithms for estimating ET with micrometeorological techniques used for validation. Pursuant to this, the Penman- Monteith-Leuning (PML) and Penman-Monteith-Palmer (PMP) equations were applied. In addition, some effort was devoted to improving the estimates of ET from the PMP by incorporating a direct soil evaporation component. Finally, the influence of local changes in catchment characteristics on ET was explored through the application of a variant of the Budyko framework and investigating dynamics in the evaporative index as well as applying tests for trends and shifts on ET and rainfall data to detect changes in mean quaternary catchment rainfall and ET. Results revealed that A. mearnsii affected soil chemical properties and impaired grass production in rangelands. Hence, thinning of canopies provided an optimal solution for enhanced landscape water use to sequestrate carbon, provide shade, grazing, and also wood fuel. It was also shown that across sites, ET was water limited since differences between reference ET and actual ET were large. ET was largely sensitive to vapour pressure deficit and surface conductance than to net radiation, indicating that the canopies were strongly coupled with the boundary layer. Rangeland ET was successfully simulated and evaporation from the soil was the dominant flux, hence there is scope for reducing the so-called ‘unproductive’ water use. Further, it was shown that the PML was better able to simulate ET compared to the PMP model as revealed by different model evaluation metrics such as the root mean square error, absolute mean square error and the root mean square observations standard deviation ratio. The incorporation of a soil evaporation component in the PMP model improved estimates of ET as revealed by the root mean square error. The results also indicated that both the catchment parameter (w) and the evaporative index were important in highlighting the impacts of land cover change on ET. It was also shown that, despite changes in the local environment such as catchment characteristics, global forces also affected ET at a local scale. Overall, the study demonstrated that combining remote sensing and ground based observations was important to better understand rangeland grass production and water use dynamics.
- Full Text:
- Date Issued: 2018
- Authors: Gwate, Onalenna
- Date: 2018
- Subjects: Grasslands -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Rangelands -- South Africa -- Eastern Cape , Range ecology-- South Africa -- Eastern Cape , Rangelands -- Water-supply , Rangelands -- Weed control , Evapotranspiration , Plant-water relationships
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54800 , vital:26617
- Description: It is imperative to understand the strong coupling between the carbon capture process and water use to sustainably manage rangelands. Woody encroachment is undermining rangelands grass production. Evapotranspiration (ET) highlights the links between ecosystem carbon capture process and water use. It forms the biggest flux of the hydrological cycle after precipitation yet it is not well understood. The Grassland and the Albany Thicket (AT) biomes in the Eastern Cape, South Africa, provide an interesting space to study the dynamics in rangelands biomass production and the associated water use. Therefore, the main purpose of this study was to contribute towards management of rangelands by understanding the dynamics in rangeland grass production and water use. To achieve this aim, the impact of Acacia mearnsii, an invasive alien plant, on soil chemical properties and rangelands grass production was investigated. This was achieved by analysing the biophysical attributes of A. mearnsii as they related to grass production. Secondly, selected soil variables that could be used as a prognosis for landscape recovery or deterioration were evaluated. In addition, aboveground grass biomass was measured in areas cleared of A. mearnsii and regression equations were prepared to help model aboveground grass biomass in areas cleared of A. mearnsi. The thesis also explored dynamics in water vapour and energy fluxes in these two biomes using an eddy covariance system. Consequently, water vapour and energy fluxes were evaluated in order to understand landscape water use and energy partitioning in the landscape. The study also tested the application of Penman-Monteith equation based algorithms for estimating ET with micrometeorological techniques used for validation. Pursuant to this, the Penman- Monteith-Leuning (PML) and Penman-Monteith-Palmer (PMP) equations were applied. In addition, some effort was devoted to improving the estimates of ET from the PMP by incorporating a direct soil evaporation component. Finally, the influence of local changes in catchment characteristics on ET was explored through the application of a variant of the Budyko framework and investigating dynamics in the evaporative index as well as applying tests for trends and shifts on ET and rainfall data to detect changes in mean quaternary catchment rainfall and ET. Results revealed that A. mearnsii affected soil chemical properties and impaired grass production in rangelands. Hence, thinning of canopies provided an optimal solution for enhanced landscape water use to sequestrate carbon, provide shade, grazing, and also wood fuel. It was also shown that across sites, ET was water limited since differences between reference ET and actual ET were large. ET was largely sensitive to vapour pressure deficit and surface conductance than to net radiation, indicating that the canopies were strongly coupled with the boundary layer. Rangeland ET was successfully simulated and evaporation from the soil was the dominant flux, hence there is scope for reducing the so-called ‘unproductive’ water use. Further, it was shown that the PML was better able to simulate ET compared to the PMP model as revealed by different model evaluation metrics such as the root mean square error, absolute mean square error and the root mean square observations standard deviation ratio. The incorporation of a soil evaporation component in the PMP model improved estimates of ET as revealed by the root mean square error. The results also indicated that both the catchment parameter (w) and the evaporative index were important in highlighting the impacts of land cover change on ET. It was also shown that, despite changes in the local environment such as catchment characteristics, global forces also affected ET at a local scale. Overall, the study demonstrated that combining remote sensing and ground based observations was important to better understand rangeland grass production and water use dynamics.
- Full Text:
- Date Issued: 2018
Assessment of fluctuating asymmetry as an indicator of water quality stress in South Africa
- Authors: Holland, Alexandra Jennifer
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/430 , vital:19958
- Description: South Africa’s freshwater resources are facing numerous water quality challenges and need to be protected from degradation and pollution by appropriate management strategies as they are a limited and shared resource. The South African Scoring System (SASS5), which assesses macroinvertebrate communities at family level, is used in routine monitoring of riverine ecosystems in South Africa. Assessing the condition of these ecosystems is limited as SASS5 does not allow for changes at lower levels of biological organisation to be detected. Fluctuating asymmetry (FA) - small random deviations from perfect symmetry - is considered a direct measure of developmental instability. This phenotypical response results from numerous internal and external factors and has a low level of heritability. FA is based on sound scientific principles, easy to measure, biologically robust and cost-effective. It reflects synergistic interactions between stressors and provides an integrated measure of several anthropogenic stresses, which strengthens the assertion that FA is an environmental indicator of water quality stress, and can potentially be used to detect stress in populations before irreversible effects manifest. FA responses were investigated by (1) exposing freshwater shrimp to increasing concentrations of cadmium chloride in a long-term experiment and (2) comparing FA responses to water quality changes and macroinvertebrate community responses in two case studies (Kwazulu-Natal and Limpopo Province) in South Africa. Although no consistent concentration-response curve could be established, this study suggests that FA responses can be used as a sublethal endpoint in exposure experiments. Determining water quality parameters causing FA responses was not possible in field collected freshwater shrimp in either case study. Although FA did not specifically respond to any of the measured water quality parameters identified in the case studies, it has potential as a general indicator of water quality stress in freshwater shrimp. This study shows that FA responses are potentially more sensitive than macroinvertebrate community responses to pollution since it is not affected by habitat. Since FA has the potential to be a general indicator of population quality, particularly where there are natural habitat differences, it can be useful at the level of biomonitoring required for routine basic river status assessments in South Africa. However, in order for FA to become a robust tool that can be used routinely in conjunction with SASS5 more research is required.
- Full Text:
- Date Issued: 2016
- Authors: Holland, Alexandra Jennifer
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/430 , vital:19958
- Description: South Africa’s freshwater resources are facing numerous water quality challenges and need to be protected from degradation and pollution by appropriate management strategies as they are a limited and shared resource. The South African Scoring System (SASS5), which assesses macroinvertebrate communities at family level, is used in routine monitoring of riverine ecosystems in South Africa. Assessing the condition of these ecosystems is limited as SASS5 does not allow for changes at lower levels of biological organisation to be detected. Fluctuating asymmetry (FA) - small random deviations from perfect symmetry - is considered a direct measure of developmental instability. This phenotypical response results from numerous internal and external factors and has a low level of heritability. FA is based on sound scientific principles, easy to measure, biologically robust and cost-effective. It reflects synergistic interactions between stressors and provides an integrated measure of several anthropogenic stresses, which strengthens the assertion that FA is an environmental indicator of water quality stress, and can potentially be used to detect stress in populations before irreversible effects manifest. FA responses were investigated by (1) exposing freshwater shrimp to increasing concentrations of cadmium chloride in a long-term experiment and (2) comparing FA responses to water quality changes and macroinvertebrate community responses in two case studies (Kwazulu-Natal and Limpopo Province) in South Africa. Although no consistent concentration-response curve could be established, this study suggests that FA responses can be used as a sublethal endpoint in exposure experiments. Determining water quality parameters causing FA responses was not possible in field collected freshwater shrimp in either case study. Although FA did not specifically respond to any of the measured water quality parameters identified in the case studies, it has potential as a general indicator of water quality stress in freshwater shrimp. This study shows that FA responses are potentially more sensitive than macroinvertebrate community responses to pollution since it is not affected by habitat. Since FA has the potential to be a general indicator of population quality, particularly where there are natural habitat differences, it can be useful at the level of biomonitoring required for routine basic river status assessments in South Africa. However, in order for FA to become a robust tool that can be used routinely in conjunction with SASS5 more research is required.
- Full Text:
- Date Issued: 2016
Modelling water quality : complexity versus simplicity
- Authors: Jacobs, Haden
- Date: 2017
- Subjects: Water quality management -- Mathematical models , Water quality -- Measurement , Water quality biological assessment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4754 , vital:20721
- Description: Water quality management makes use of water quality models as decision making tools. Water quality management decisions need to be informed by information that is as reliable as possible. There are many situations where observational data are limited and therefore models or simulation methods have a significant role to play in providing some information that can be used to guide management decisions. Water quality modelling is the use of mathematical equations and statistics to represent the processes affecting water quality in the natural environment. Water quality data are expensive and difficult to obtain. Nutrient sampling requires a technician to obtain ‘grab samples’ which need to be kept at low temperatures and analysed in a laboratory. The laboratory analyses of nutrients is expensive and time consuming. The data required by water quality models are seldom available as complete datasets of sufficient length. This is especially true for ungauged regions, either in small rural catchments or even major rivers in developing countries. Water quality modelling requires simulated or observed water quantity data as water quality is affected by water quantity. Both the water quality modelling and water quantity modelling require data to simulate the required processes. Data are necessary for both model structure as well as model set up for calibration and validation. This study aimed to investigate the simulation of water quality in a low order stream with limited observed data using a relatively complex as well as a much simpler water quality model, represented by QUAL2K and an in-house developed Mass Balance Nutrient (MBN) model, respectively. The two models differ greatly in the approach adopted for water quality modelling, with QUAL2K being an instream water quality fate model and the MBN model being a catchment scale model that links water quantity and quality. The MBN model uses hydrological routines to simulate those components of the hydrological cycle that are expected to differ with respect to their water quality signatures (low flows, high flows, etc.). Incremental flows are broken down into flow fractions, and nutrient signatures are assigned to fractions to represent catchment nutrient load input. A linear regression linked to an urban runoff model was used to simulate water quality entering the river system from failing municipal infrastructure, which was found to be a highly variable source of nutrients within the system. A simple algal model was adapted from CE-QUAL-W2 to simulate nutrient assimilation by benthic algae. QUAL2K, an instream water quality fate model, proved unsuitable for modelling diffuse sources for a wide range of conditions and was data intensive when compared to the data requirements of the MBN model. QUAL2K did not simulate water quality accurately over a wide range of flow conditions and was found to be more suitable to simulating point sources. The MBN model did not provide accurate results in terms of the simulation of individual daily water quality values; however, the general trends and frequency characteristics of the simulations were satisfactory. Despite some uncertainties, the MBN model remains useful for extending data for catchments with limited observed water quality data. The MBN model was found to be more suitable for South African conditions than QUAL2K, given the data requirements of each model and water quality and flow data available from the Department of Water and Sanitation. The MBN model was found to be particularly useful by providing frequency distributions of water quality loads or concentrations using minimal data that can be related to the risks of exceeding management thresholds.
- Full Text:
- Date Issued: 2017
- Authors: Jacobs, Haden
- Date: 2017
- Subjects: Water quality management -- Mathematical models , Water quality -- Measurement , Water quality biological assessment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4754 , vital:20721
- Description: Water quality management makes use of water quality models as decision making tools. Water quality management decisions need to be informed by information that is as reliable as possible. There are many situations where observational data are limited and therefore models or simulation methods have a significant role to play in providing some information that can be used to guide management decisions. Water quality modelling is the use of mathematical equations and statistics to represent the processes affecting water quality in the natural environment. Water quality data are expensive and difficult to obtain. Nutrient sampling requires a technician to obtain ‘grab samples’ which need to be kept at low temperatures and analysed in a laboratory. The laboratory analyses of nutrients is expensive and time consuming. The data required by water quality models are seldom available as complete datasets of sufficient length. This is especially true for ungauged regions, either in small rural catchments or even major rivers in developing countries. Water quality modelling requires simulated or observed water quantity data as water quality is affected by water quantity. Both the water quality modelling and water quantity modelling require data to simulate the required processes. Data are necessary for both model structure as well as model set up for calibration and validation. This study aimed to investigate the simulation of water quality in a low order stream with limited observed data using a relatively complex as well as a much simpler water quality model, represented by QUAL2K and an in-house developed Mass Balance Nutrient (MBN) model, respectively. The two models differ greatly in the approach adopted for water quality modelling, with QUAL2K being an instream water quality fate model and the MBN model being a catchment scale model that links water quantity and quality. The MBN model uses hydrological routines to simulate those components of the hydrological cycle that are expected to differ with respect to their water quality signatures (low flows, high flows, etc.). Incremental flows are broken down into flow fractions, and nutrient signatures are assigned to fractions to represent catchment nutrient load input. A linear regression linked to an urban runoff model was used to simulate water quality entering the river system from failing municipal infrastructure, which was found to be a highly variable source of nutrients within the system. A simple algal model was adapted from CE-QUAL-W2 to simulate nutrient assimilation by benthic algae. QUAL2K, an instream water quality fate model, proved unsuitable for modelling diffuse sources for a wide range of conditions and was data intensive when compared to the data requirements of the MBN model. QUAL2K did not simulate water quality accurately over a wide range of flow conditions and was found to be more suitable to simulating point sources. The MBN model did not provide accurate results in terms of the simulation of individual daily water quality values; however, the general trends and frequency characteristics of the simulations were satisfactory. Despite some uncertainties, the MBN model remains useful for extending data for catchments with limited observed water quality data. The MBN model was found to be more suitable for South African conditions than QUAL2K, given the data requirements of each model and water quality and flow data available from the Department of Water and Sanitation. The MBN model was found to be particularly useful by providing frequency distributions of water quality loads or concentrations using minimal data that can be related to the risks of exceeding management thresholds.
- Full Text:
- Date Issued: 2017
Constraining simulation uncertainties in a hydrological model of the Congo River Basin including a combined modelling approach for channel-wetland exchanges
- Authors: Kabuya, Pierre Mulamba
- Date: 2021-04
- Subjects: Congo River Watershed , Watersheds -- Congo (Democratic Republic) , Hydrologic models , Rain and rainfall -- Mathematical models , Runoff -- Mathematical models , Wetland hydrology
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177997 , vital:42897 , 10.21504/10962/177997
- Description: Compared to other large river basins of the world, such as the Amazon, the Congo River Basin appears to be the most ungauged and less studied. This is partly because the basin lacks sufficient observational hydro-climatic monitoring stations and appropriate information on physiographic basin properties at a spatial scale deemed for hydrological applications, making it difficult to estimate water resources at the scale of sub-basins (Chapter 3). In the same time, the basin is facing the challenges related to rapid population growth, uncontrolled urbanisation as well as climate change. Adequate quantification of hydrological processes across different spatial and temporal scales in the basin, and the drivers of change, is essential for prediction and strategic planning to ensure sustainable management of water resources in the Congo River Basin. Hydrological models are particularly important to generate the required information. However, the shortness of the available streamflow records, lack of spatial representativeness of the available streamflow gauging stations and the lack of understanding of the processes in channel-wetland exchanges, are the main challenges that constrain the use of traditional approaches to models development. They also contribute to increased uncertainty in the estimation of water resources across the basin (Chapter 1 and 2). Given this ungauged nature of the Congo River Basin, it is important to resort to hydrological modelling approaches that can reasonably quantify and model the uncertainty associated with water resources estimation (Chapter 4) to make hydrological predictions reliable. This study explores appropriate methods for hydrological predictions and water resources assessment in ungauged catchments of the Congo River Basin. In this context, the core modelling framework combines the quantification of uncertainty in constraint indices, hydrological modelling and hydrodynamic modelling. The latter accounts for channel-wetland exchanges in sub-basins where wetlands exert considerable influence on downstream flow regimes at the monthly time scale. The constraint indices are the characteristics of a sub-basin’s long-term hydrological behaviour and may reflect the dynamics of the different components of the catchment water balance such as climate, water storage and different runoff processes. Currently, six constraint indices namely the mean monthly runoff volume (MMQ in m3 *106), mean monthly groundwater recharge depth (MMR in mm), the 10th, 50th and 90th percentiles of the flow duration curve expressed as a fraction of MMQ (Q10/MMQ, Q50/MMQ, Q90/MMQ) and the percentage of time that zero flows are expected (%Zero), are used in the modelling approach. These were judged to be the minimum number of key indices that can discriminate between different hydrological responses. The constraint indices in the framework help to determine an uncertainty range within which behavioural model parameters of the expected hydrological response can be identified. Predictive equations of the constraint indices across all climate and physiographic regions of the Congo Basin were based only on the aridity index because it was the most influential sub-basin attribute (Chapter 5) for which quantitative information was available. The degree of uncertainty in the constraint Q10/MMQ and Q50/MMQ indices is less than 41%, while it is somewhat higher for the mean monthly runoff (MMQ) and Q90/MMQ constraint indices. The established uncertainty ranges of the constraint indices were tested in some selected sub-basins of the Congo Basin, including the Lualaba (93 sub-basins), Sangha (24 sub-basins), Oubangui (19 sub-basins), Batéké plateaux (4 sub-basins), Kasai (4 sub-basins) and Inkisi (3 sub-basins). The results proved useful through the application of a 2-stage uncertainty approach of the PITMAN model. However, it comes out of this study that the application of the original constraint indices ranges (Chapter 5) generated satisfactory simulation results in some areas, while in others both small and large adjustments were required to fully capture some aspects of the observed hydrological responses (Chapter 6). Part of the reason is attributed to the availability and quality of streamflow data used to develop the constraint indices ranges (Chapter 5). The main issue identified in the modelling process was whether the changes made to the original constraints at headwater-gauged sub-basins can be applied to ungauged upstream sub-basins to match the observed flow at downstream gauging stations. Ideally, only gauged sub-basin’s constraints can be easily revised based on the observed flow. However, the refinement made to gauged sub-basins alone may fail to substantially affect the results if ungauged upstream sub-basins exert a major impact on defining downstream hydrological response. The majority of gauging stations used in this analysis are located downstream of many upstream ungauged sub-basins and therefore adjustments were required in ungauged sub-basins. These adjustments consist of shifting the full range of a constraint index either towards higher or lower values, depending on the degree to which the simulated uncertainty bounds depart from the observed flow. While this modelling approach seems effective in capturing many aspects of the hydrological responses with a reduced level of uncertainty compared to a previous study, it is recommended that the approach be extended to the remaining parts of the Congo Basin and assessed under current and future development conditions including environmental changes. A 2D hydrodynamic river-wetland model (LISFLOOD-FP) has been used to explicitly represent the inundation process exchanges between river channels and wetland systems. The hydrodynamic modelling outputs are used to calibrate the PITMAN wetland sub-model parameters. The five hydrodynamic models constructed for Ankoro, Kamalondo, Kundelungu, Mweru and Tshiangalele wetland systems have been partially validated using independent estimates of inundation extents available from Landsat imagery. Other sources of data such as remote sensing of water level altimetry, SAR images and wetland storage estimates may be used to improve the validation results. However, the important objective in this study was to make sure that flow volume exchanges between river channels and their adjacent floodplains were being simulated realistically. The wetland sub-model parameters are calibrated in a spreadsheet version of the PITMAN wetland routine to achieve visual correspondence between the LISFLOOD-FP and PITMAN wetland sub-model outputs (Storage volumes and channel outputs). The hysteretic patterns of the river-wetland processes were quantified using hysteresis indices and were associated with the spill and return flow parameters of the wetland sub-model and eventually with the wetland morphometric characteristics. One example is the scale parameter of the return flow function (AA), which shows a good relationship with the average surface slope of the wetland when the coefficient parameter (BB) of the same function is kept constant to a value of 1.25. The same parameter (AA) is a good indicator of the wetland emptying mechanism. A small AA indicates a wetland that slowly releases its flow, resulting in a highly delayed and attenuated hydrological response in downstream sub-basins. This understanding has a practical advantage for the estimation of the PITMAN wetland parameters in the many areas where it is not possible, or where the resources are not available, to run complex hydrodynamic models (Chapter 7). The inclusion of these LISFLOOD-FP informed wetland parameters in the basin-scale hydrological modelling results in acceptable simulations for the lower Lualaba drainage system. The small wetlands, like Ankoro and Tshiangalele, have a negligible impact on downstream flow regimes, whereas large wetlands, such as Kamalondo and Mweru, have very large impacts. In general, the testing of the original constraint indices in the region of wetlands and further downstream of the Lualaba drainage system has shown acceptable results. However, there remains an unresolved uncertainty issue related to the under and over-estimation of some aspects of the hydrological response at both Mulongo and Ankoro, two gauging stations in the immediate downstream of the Kamalondo wetland system. It is difficult to attribute this uncertainty to Kamalondo wetland parameters alone because many of the incremental sub-basins contributing to wetland inflows are ungauged. The issue at Mulongo is the under simulation of low flow, while the high flows at the Ankoro gauging station are over-simulated. However, the pattern of the calibrated constraint indices in this region (Chapter 8) shows that the under simulation of low flow at Mulongo cannot be attributed to incremental sub-basins (between Bukama, Kapolowe and Mulongo gauging stations), because their Q90/MMQ constraint indices are even slightly above the original constraint ranges, but maintain a spatial consistency with sub-basins of other regions. Similarly, sub-basins located between Mulongo, Luvua and Ankoro gauging stations have high flow indices slightly below the original constraint ranges and therefore they are unlikely to be responsible for the over simulation of high flow at the Ankoro gauging station. These facts highlight the need for a further understanding of the complex wetland system of Kamalondo. Short-term data collection and monitoring programme are required. Important tributaries that drain to this wetland need to be monitored by installing water level loggers and periodically collecting flow data and river bathymetry. This programme should lead to the development of rating curves of wetland input tributaries. This would partially solve the unresolved uncertainty issues at the Ankoro and Mulongo gauging stations. The integrated modelling approach offers many opportunities in the Congo Basin. The quantified and modelled uncertainty helps to identify regions with high uncertainty and allows for the identification of various data collection and management strategies that can potentially contribute to the uncertainty reduction. The quantified channel-wetland exchanges contribute to the improvement of the overall knowledge of water resources estimation within the regions where the effects of wetlands are evident even at the monthly time scale. In contrast, ignoring uncertainty in the estimates of water resources availability means that water resources planning and management decisions in the Congo Basin will continue to be based on inadequate information and unquantified uncertainty, thus increasing the risk associated with water resources decision making. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Kabuya, Pierre Mulamba
- Date: 2021-04
- Subjects: Congo River Watershed , Watersheds -- Congo (Democratic Republic) , Hydrologic models , Rain and rainfall -- Mathematical models , Runoff -- Mathematical models , Wetland hydrology
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177997 , vital:42897 , 10.21504/10962/177997
- Description: Compared to other large river basins of the world, such as the Amazon, the Congo River Basin appears to be the most ungauged and less studied. This is partly because the basin lacks sufficient observational hydro-climatic monitoring stations and appropriate information on physiographic basin properties at a spatial scale deemed for hydrological applications, making it difficult to estimate water resources at the scale of sub-basins (Chapter 3). In the same time, the basin is facing the challenges related to rapid population growth, uncontrolled urbanisation as well as climate change. Adequate quantification of hydrological processes across different spatial and temporal scales in the basin, and the drivers of change, is essential for prediction and strategic planning to ensure sustainable management of water resources in the Congo River Basin. Hydrological models are particularly important to generate the required information. However, the shortness of the available streamflow records, lack of spatial representativeness of the available streamflow gauging stations and the lack of understanding of the processes in channel-wetland exchanges, are the main challenges that constrain the use of traditional approaches to models development. They also contribute to increased uncertainty in the estimation of water resources across the basin (Chapter 1 and 2). Given this ungauged nature of the Congo River Basin, it is important to resort to hydrological modelling approaches that can reasonably quantify and model the uncertainty associated with water resources estimation (Chapter 4) to make hydrological predictions reliable. This study explores appropriate methods for hydrological predictions and water resources assessment in ungauged catchments of the Congo River Basin. In this context, the core modelling framework combines the quantification of uncertainty in constraint indices, hydrological modelling and hydrodynamic modelling. The latter accounts for channel-wetland exchanges in sub-basins where wetlands exert considerable influence on downstream flow regimes at the monthly time scale. The constraint indices are the characteristics of a sub-basin’s long-term hydrological behaviour and may reflect the dynamics of the different components of the catchment water balance such as climate, water storage and different runoff processes. Currently, six constraint indices namely the mean monthly runoff volume (MMQ in m3 *106), mean monthly groundwater recharge depth (MMR in mm), the 10th, 50th and 90th percentiles of the flow duration curve expressed as a fraction of MMQ (Q10/MMQ, Q50/MMQ, Q90/MMQ) and the percentage of time that zero flows are expected (%Zero), are used in the modelling approach. These were judged to be the minimum number of key indices that can discriminate between different hydrological responses. The constraint indices in the framework help to determine an uncertainty range within which behavioural model parameters of the expected hydrological response can be identified. Predictive equations of the constraint indices across all climate and physiographic regions of the Congo Basin were based only on the aridity index because it was the most influential sub-basin attribute (Chapter 5) for which quantitative information was available. The degree of uncertainty in the constraint Q10/MMQ and Q50/MMQ indices is less than 41%, while it is somewhat higher for the mean monthly runoff (MMQ) and Q90/MMQ constraint indices. The established uncertainty ranges of the constraint indices were tested in some selected sub-basins of the Congo Basin, including the Lualaba (93 sub-basins), Sangha (24 sub-basins), Oubangui (19 sub-basins), Batéké plateaux (4 sub-basins), Kasai (4 sub-basins) and Inkisi (3 sub-basins). The results proved useful through the application of a 2-stage uncertainty approach of the PITMAN model. However, it comes out of this study that the application of the original constraint indices ranges (Chapter 5) generated satisfactory simulation results in some areas, while in others both small and large adjustments were required to fully capture some aspects of the observed hydrological responses (Chapter 6). Part of the reason is attributed to the availability and quality of streamflow data used to develop the constraint indices ranges (Chapter 5). The main issue identified in the modelling process was whether the changes made to the original constraints at headwater-gauged sub-basins can be applied to ungauged upstream sub-basins to match the observed flow at downstream gauging stations. Ideally, only gauged sub-basin’s constraints can be easily revised based on the observed flow. However, the refinement made to gauged sub-basins alone may fail to substantially affect the results if ungauged upstream sub-basins exert a major impact on defining downstream hydrological response. The majority of gauging stations used in this analysis are located downstream of many upstream ungauged sub-basins and therefore adjustments were required in ungauged sub-basins. These adjustments consist of shifting the full range of a constraint index either towards higher or lower values, depending on the degree to which the simulated uncertainty bounds depart from the observed flow. While this modelling approach seems effective in capturing many aspects of the hydrological responses with a reduced level of uncertainty compared to a previous study, it is recommended that the approach be extended to the remaining parts of the Congo Basin and assessed under current and future development conditions including environmental changes. A 2D hydrodynamic river-wetland model (LISFLOOD-FP) has been used to explicitly represent the inundation process exchanges between river channels and wetland systems. The hydrodynamic modelling outputs are used to calibrate the PITMAN wetland sub-model parameters. The five hydrodynamic models constructed for Ankoro, Kamalondo, Kundelungu, Mweru and Tshiangalele wetland systems have been partially validated using independent estimates of inundation extents available from Landsat imagery. Other sources of data such as remote sensing of water level altimetry, SAR images and wetland storage estimates may be used to improve the validation results. However, the important objective in this study was to make sure that flow volume exchanges between river channels and their adjacent floodplains were being simulated realistically. The wetland sub-model parameters are calibrated in a spreadsheet version of the PITMAN wetland routine to achieve visual correspondence between the LISFLOOD-FP and PITMAN wetland sub-model outputs (Storage volumes and channel outputs). The hysteretic patterns of the river-wetland processes were quantified using hysteresis indices and were associated with the spill and return flow parameters of the wetland sub-model and eventually with the wetland morphometric characteristics. One example is the scale parameter of the return flow function (AA), which shows a good relationship with the average surface slope of the wetland when the coefficient parameter (BB) of the same function is kept constant to a value of 1.25. The same parameter (AA) is a good indicator of the wetland emptying mechanism. A small AA indicates a wetland that slowly releases its flow, resulting in a highly delayed and attenuated hydrological response in downstream sub-basins. This understanding has a practical advantage for the estimation of the PITMAN wetland parameters in the many areas where it is not possible, or where the resources are not available, to run complex hydrodynamic models (Chapter 7). The inclusion of these LISFLOOD-FP informed wetland parameters in the basin-scale hydrological modelling results in acceptable simulations for the lower Lualaba drainage system. The small wetlands, like Ankoro and Tshiangalele, have a negligible impact on downstream flow regimes, whereas large wetlands, such as Kamalondo and Mweru, have very large impacts. In general, the testing of the original constraint indices in the region of wetlands and further downstream of the Lualaba drainage system has shown acceptable results. However, there remains an unresolved uncertainty issue related to the under and over-estimation of some aspects of the hydrological response at both Mulongo and Ankoro, two gauging stations in the immediate downstream of the Kamalondo wetland system. It is difficult to attribute this uncertainty to Kamalondo wetland parameters alone because many of the incremental sub-basins contributing to wetland inflows are ungauged. The issue at Mulongo is the under simulation of low flow, while the high flows at the Ankoro gauging station are over-simulated. However, the pattern of the calibrated constraint indices in this region (Chapter 8) shows that the under simulation of low flow at Mulongo cannot be attributed to incremental sub-basins (between Bukama, Kapolowe and Mulongo gauging stations), because their Q90/MMQ constraint indices are even slightly above the original constraint ranges, but maintain a spatial consistency with sub-basins of other regions. Similarly, sub-basins located between Mulongo, Luvua and Ankoro gauging stations have high flow indices slightly below the original constraint ranges and therefore they are unlikely to be responsible for the over simulation of high flow at the Ankoro gauging station. These facts highlight the need for a further understanding of the complex wetland system of Kamalondo. Short-term data collection and monitoring programme are required. Important tributaries that drain to this wetland need to be monitored by installing water level loggers and periodically collecting flow data and river bathymetry. This programme should lead to the development of rating curves of wetland input tributaries. This would partially solve the unresolved uncertainty issues at the Ankoro and Mulongo gauging stations. The integrated modelling approach offers many opportunities in the Congo Basin. The quantified and modelled uncertainty helps to identify regions with high uncertainty and allows for the identification of various data collection and management strategies that can potentially contribute to the uncertainty reduction. The quantified channel-wetland exchanges contribute to the improvement of the overall knowledge of water resources estimation within the regions where the effects of wetlands are evident even at the monthly time scale. In contrast, ignoring uncertainty in the estimates of water resources availability means that water resources planning and management decisions in the Congo Basin will continue to be based on inadequate information and unquantified uncertainty, thus increasing the risk associated with water resources decision making. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-04
Revised parameter estimation methods for the Pitman monthly rainfall-runoff model
- Authors: Kapangaziwiri, Evison
- Date: 2008
- Subjects: Rain and rainfall -- Mathematical models , Runoff -- Mathematical models , Hydrology -- Mathematical models , Water supply -- South Africa , Water resources development -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6033 , http://hdl.handle.net/10962/d1006172 , Rain and rainfall -- Mathematical models , Runoff -- Mathematical models , Hydrology -- Mathematical models , Water supply -- South Africa , Water resources development -- South Africa
- Description: In recent years, increased demands have been placed on hydrologists to find the most effective methods of making predictions of hydrologic variables in ungauged basins. A huge part of the southern African region is ungauged and, in gauged basins, the extent to which observed flows represent natural flows is unknown, given unquantified upstream activities. The need to exploit water resources for social and economic development, considered in the light of water scarcity forecasts for the region, makes the reliable quantification of water resources a priority. Contemporary approaches to the problem of hydrological prediction in ungauged basins in the region have relied heavily on calibration against a limited gauged streamflow database and somewhat subjective parameter regionalizations using areas of assumed hydrological similarity. The reliance of these approaches on limited historical records, often of dubious quality, introduces uncertainty in water resources decisions. Thus, it is necessary to develop methods of estimating model parameters that are less reliant on calibration. This thesis addresses the question of whether physical basin properties and the role they play in runoff generation processes can be used directly in the estimation of parameter values of the Pitman monthly rainfall-runoff model. A physically-based approach to estimating the soil moisture accounting and runoff parameters of a conceptual, monthly time-step rainfall-runoff model is proposed. The study investigates the physical meaning of the model parameters, establishes linkages between parameter values and basin physical properties and develops relationships and equations for estimating the parameters taking into account the spatial and temporal scales used in typical model applications. The estimationmethods are then tested in selected gauged basins in southern Africa and the results of model simulations evaluated against historical observed flows. The results of 71 basins chosen from the southern African region suggest that it is possible to directly estimate hydrologically relevant parameters for the Pitman model from physical basin attributes. For South Africa, the statistical and visual fit of the simulations using the revised parameters were at least as good as the current regional sets, albeit the parameter sets being different. In the other countries where no regionalized parameter sets currently exist, simulations were equally good. The availability, within the southern African region, of the appropriate physical basin data and the disparities in the spatial scales and the levels of detail of the data currently available were identified as potential sources of uncertainty. GIS and remote sensing technologies and a widespread use of this revised approach are expected to facilitate access to these data.
- Full Text:
- Date Issued: 2008
- Authors: Kapangaziwiri, Evison
- Date: 2008
- Subjects: Rain and rainfall -- Mathematical models , Runoff -- Mathematical models , Hydrology -- Mathematical models , Water supply -- South Africa , Water resources development -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6033 , http://hdl.handle.net/10962/d1006172 , Rain and rainfall -- Mathematical models , Runoff -- Mathematical models , Hydrology -- Mathematical models , Water supply -- South Africa , Water resources development -- South Africa
- Description: In recent years, increased demands have been placed on hydrologists to find the most effective methods of making predictions of hydrologic variables in ungauged basins. A huge part of the southern African region is ungauged and, in gauged basins, the extent to which observed flows represent natural flows is unknown, given unquantified upstream activities. The need to exploit water resources for social and economic development, considered in the light of water scarcity forecasts for the region, makes the reliable quantification of water resources a priority. Contemporary approaches to the problem of hydrological prediction in ungauged basins in the region have relied heavily on calibration against a limited gauged streamflow database and somewhat subjective parameter regionalizations using areas of assumed hydrological similarity. The reliance of these approaches on limited historical records, often of dubious quality, introduces uncertainty in water resources decisions. Thus, it is necessary to develop methods of estimating model parameters that are less reliant on calibration. This thesis addresses the question of whether physical basin properties and the role they play in runoff generation processes can be used directly in the estimation of parameter values of the Pitman monthly rainfall-runoff model. A physically-based approach to estimating the soil moisture accounting and runoff parameters of a conceptual, monthly time-step rainfall-runoff model is proposed. The study investigates the physical meaning of the model parameters, establishes linkages between parameter values and basin physical properties and develops relationships and equations for estimating the parameters taking into account the spatial and temporal scales used in typical model applications. The estimationmethods are then tested in selected gauged basins in southern Africa and the results of model simulations evaluated against historical observed flows. The results of 71 basins chosen from the southern African region suggest that it is possible to directly estimate hydrologically relevant parameters for the Pitman model from physical basin attributes. For South Africa, the statistical and visual fit of the simulations using the revised parameters were at least as good as the current regional sets, albeit the parameter sets being different. In the other countries where no regionalized parameter sets currently exist, simulations were equally good. The availability, within the southern African region, of the appropriate physical basin data and the disparities in the spatial scales and the levels of detail of the data currently available were identified as potential sources of uncertainty. GIS and remote sensing technologies and a widespread use of this revised approach are expected to facilitate access to these data.
- Full Text:
- Date Issued: 2008
Regional application of the Pitman monthly rainfall-runoff model in Southern Africa incorporating uncertainty
- Authors: Kapangaziwiri, Evison
- Date: 2011
- Subjects: Water supply -- Africa, Southern Water supply -- Measurement -- Africa, Southern Hydrology -- Mathematical models -- Africa, Southern Hydrologic models Rain and rainfall -- Mathematical models -- Africa, Southern Runoff -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6037 , http://hdl.handle.net/10962/d1006178
- Description: Climate change and a growing demand for freshwater resources due to population increases and socio-economic changes will make water a limiting factor (in terms of both quantity and quality) in development. The need for reliable quantitative estimates of water availability cannot be over-emphasised. However, there is frequently a paucity of the data required for this quantification as many basins, especially in the developing world, are inadequately equipped with monitoring networks. Existing networks are also shrinking due mainly to shortages in human and financial resources. Over the past few decades mathematical models have been used to bridge the data gap by generating datasets for use in management and policy making. In southern Africa, the Pitman monthly rainfall-runoff model has enjoyed relatively popular use as a water resources estimation tool. However, it is acknowledged that models are abstractions of reality and the data used to drive them is imperfect, making the model outputs uncertain. While there is acknowledgement of the limitations of modelled data in the southern African region among water practitioners, there has been little effort to explicitly quantify and account for this uncertainty in water resources estimation tools and explore how it affects the decision making process. Uncertainty manifests itself in three major areas of the modelling chain; the input data used to force the model, the parameter estimation process and the model structural errors. A previous study concluded that the parameter estimation process for the Pitman model contributed more to the global uncertainty of the model than other sources. While the literature abounds with uncertainty estimation techniques, many of these are dependent on observations and are therefore unlikely to be easily applicable to the southern African region where there is an acute shortage of such data. This study focuses on two aspects of making hydrologic predictions in ungauged basins. Firstly, the study advocates the development of an a priori parameter estimation process for the Pitman model and secondly, uses indices of hydrological functional behaviour to condition and reduce predictive uncertainty in both gauged and ungauged basins. In this approach all the basins are treated as ungauged, while the historical records in the gauged basins are used to develop regional indices of expected hydrological behaviour and assess the applicability of these methods. Incorporating uncertainty into the hydrologic estimation tools used in southern Africa entails rethinking the way the uncertain results can be used in further analysis and how they will be interpreted by stakeholders. An uncertainty framework is proposed. The framework is made up of a number of components related to the estimation of the prior distribution of the parameters, used to generate output ensembles which are then assessed and constrained using regionalised indices of basin behavioural responses. This is premised on such indices being based on the best available knowledge covering different regions. This framework is flexible enough to be used with any model structure to ensure consistent and comparable results. While the aim is to eventually apply the uncertainty framework in the southern African region, this study reports on the preliminary work on the development and testing of the framework components based on South African basins. This is necessitated by the variations in the availability and quality of the data across the region. Uncertainty in the parameter estimation process was incorporated by assuming uncertainty in the physical and hydro-meteorological data used to directly quantify the parameter. This uncertainty was represented by the range of variability of these basin characteristics and probability distribution functions were developed to account for this uncertainty and propagate it through the estimation process to generate posterior distributions for the parameters. The results show that the framework has a great deal of potential but can still be improved. In general, the estimated uncertain parameters managed to produce hydrologically realistic model outputs capturing the expected regimes across the different hydro-climatic and geo-physical gradients examined. The regional relationships for the three indices developed and tested in this study were in general agreement with existing knowledge and managed to successfully provide a multi-criteria conditioning of the model output ensembles. The feedback loop included in the framework enabled a systematic re-examination of the estimation procedures for both the parameters and the indices when inconsistencies in the results were identified. This improved results. However, there is need to carefully examine the issues and problems that may arise within other basins outside South Africa and develop guidelines for the use of the framework. , iText 1.4.6 (by lowagie.com)
- Full Text:
- Date Issued: 2011
- Authors: Kapangaziwiri, Evison
- Date: 2011
- Subjects: Water supply -- Africa, Southern Water supply -- Measurement -- Africa, Southern Hydrology -- Mathematical models -- Africa, Southern Hydrologic models Rain and rainfall -- Mathematical models -- Africa, Southern Runoff -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6037 , http://hdl.handle.net/10962/d1006178
- Description: Climate change and a growing demand for freshwater resources due to population increases and socio-economic changes will make water a limiting factor (in terms of both quantity and quality) in development. The need for reliable quantitative estimates of water availability cannot be over-emphasised. However, there is frequently a paucity of the data required for this quantification as many basins, especially in the developing world, are inadequately equipped with monitoring networks. Existing networks are also shrinking due mainly to shortages in human and financial resources. Over the past few decades mathematical models have been used to bridge the data gap by generating datasets for use in management and policy making. In southern Africa, the Pitman monthly rainfall-runoff model has enjoyed relatively popular use as a water resources estimation tool. However, it is acknowledged that models are abstractions of reality and the data used to drive them is imperfect, making the model outputs uncertain. While there is acknowledgement of the limitations of modelled data in the southern African region among water practitioners, there has been little effort to explicitly quantify and account for this uncertainty in water resources estimation tools and explore how it affects the decision making process. Uncertainty manifests itself in three major areas of the modelling chain; the input data used to force the model, the parameter estimation process and the model structural errors. A previous study concluded that the parameter estimation process for the Pitman model contributed more to the global uncertainty of the model than other sources. While the literature abounds with uncertainty estimation techniques, many of these are dependent on observations and are therefore unlikely to be easily applicable to the southern African region where there is an acute shortage of such data. This study focuses on two aspects of making hydrologic predictions in ungauged basins. Firstly, the study advocates the development of an a priori parameter estimation process for the Pitman model and secondly, uses indices of hydrological functional behaviour to condition and reduce predictive uncertainty in both gauged and ungauged basins. In this approach all the basins are treated as ungauged, while the historical records in the gauged basins are used to develop regional indices of expected hydrological behaviour and assess the applicability of these methods. Incorporating uncertainty into the hydrologic estimation tools used in southern Africa entails rethinking the way the uncertain results can be used in further analysis and how they will be interpreted by stakeholders. An uncertainty framework is proposed. The framework is made up of a number of components related to the estimation of the prior distribution of the parameters, used to generate output ensembles which are then assessed and constrained using regionalised indices of basin behavioural responses. This is premised on such indices being based on the best available knowledge covering different regions. This framework is flexible enough to be used with any model structure to ensure consistent and comparable results. While the aim is to eventually apply the uncertainty framework in the southern African region, this study reports on the preliminary work on the development and testing of the framework components based on South African basins. This is necessitated by the variations in the availability and quality of the data across the region. Uncertainty in the parameter estimation process was incorporated by assuming uncertainty in the physical and hydro-meteorological data used to directly quantify the parameter. This uncertainty was represented by the range of variability of these basin characteristics and probability distribution functions were developed to account for this uncertainty and propagate it through the estimation process to generate posterior distributions for the parameters. The results show that the framework has a great deal of potential but can still be improved. In general, the estimated uncertain parameters managed to produce hydrologically realistic model outputs capturing the expected regimes across the different hydro-climatic and geo-physical gradients examined. The regional relationships for the three indices developed and tested in this study were in general agreement with existing knowledge and managed to successfully provide a multi-criteria conditioning of the model output ensembles. The feedback loop included in the framework enabled a systematic re-examination of the estimation procedures for both the parameters and the indices when inconsistencies in the results were identified. This improved results. However, there is need to carefully examine the issues and problems that may arise within other basins outside South Africa and develop guidelines for the use of the framework. , iText 1.4.6 (by lowagie.com)
- Full Text:
- Date Issued: 2011
Mining, agriculture and wetland ecological infrastructure in the Upper Komati catchment (South Africa): contestations in a complex social-ecological system
- Authors: Keighley, Tia-Kristi
- Date: 2018
- Subjects: Wetland ecology -- Komati River Watershed , Coal mines and mining -- Environmental aspects -- Komati River Watershed , Agriculture -- Environmental aspects -- Komati River Watershed , Acid mine drainage -- Komati River Watershed , Water quality -- Physiological effect -- Komati River Watershed , Wetland conservation -- Komati River Watershed , National Freshwater Ecosystem Priority Areas (NFEPAs)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63810 , vital:28491
- Description: Wetlands provide a wide variety of natural benefits (ecosystem services) from the natural environment to human populations, making them key examples of ecological infrastructure. However, the use of wetlands and their associated catchments is often contested by different users, making them nodes of conflict. Thus, there is a range of pressures on many wetlands which can ultimately lead to degradation or destruction. This study investigated the X11B quaternary catchment in the Upper Inkomati basin, Mpumalanga, South Africa. This catchment is characterised by a network of wetlands and streams that provide catchment residents with water. The sub-catchment is heavily used, dominated by the agricultural sector and coal mining. To understand the contestation, a contextual analysis was carried out. Selected wetland conditions and ecosystem services, along with user perceptions and the value of wetland-use, were assessed. Wetlands were observably in a relatively healthy condition. The resilience of wetlands and the efficiency of the ecosystem services they offer, especially in mediating water quality, were clear. The early results indicated a healthy landscape despite multiple-user impact from human activity. The health scores and provision of ecosystem services, along with the identified National Freshwater Ecosystem Priority Areas (NFEPAs) and red-listed fauna and flora, provide a substantial grounding for advocating the conservation of the wetlands of the contested X11B catchment. When water quality measures were added to the wetland health and ecosystem service assessment, low pH levels and high electrical conductivity were recorded. Both measures indicate coal mining impacts, more specifically Acid Mine Drainage (AMD) impacts, since AMD typically has sulphate as the dominant salt ion, and high concentrations of trace elements and metal ions. Concentrations breaching the recommended resource quality objectives (RQOs) of trace elements and ions, found in fertilizers and pesticides, were recorded in most sites, suggesting agricultural impacts on the landscape’s hydrology. Further, these agricultural impacts would add to the compromising effect of the wetlands’ capacity to remove pollutants from the water body. Livestock farming on all sites were also near wetlands which may have limited the vegetation cover of grazed land, so increasing runoff and the volume of water entering wetlands and compromising their ecosystem services. Poor water quality has implications for biophysical processes, which play an important role in the functioning of wetlands, for the benefit of users. Without the water quality measures, ecosystem health and ecosystem service methodology used suggested a healthy catchment. However, simple field water quality measures indicated past and present mining impacts. Therefore, the mandatory use of water chemistry is recommended in the assessment of wetlands in catchments with past and present mining activity taking place. Without this, repercussions would include wetland loss, and a more thorough investigation into the water quality and its effects on the wetland ecosystems is suggested. Further ecological investigation of water chemistry (heavy metals, ions, nutrients and trace elements) and macroinvertebrate assemblages identified links to water chemistry impacts on macroinvertebrate abundance and diversity. Abundance results based on the presence, absence and abundance of macroinvertebrates at the different sites did not reveal any clear patterns associated with different landscape users. Diversity, on the other hand, was related to land-use, where sites with high mining use had lower macroinvertebrate diversity than other sites. Related, concurrent, hydro-pedology research produced a more comprehensive understanding of the impact of mining on hydro-connectivity that clearly indicates mining as the cause of long-term deterioration of functional wetland health in a way that is practically impossible to restore. This study suggests that wetlands provide a strong ecosystem service of intermittent resetting of the wetland sediment adsorptive capacity for toxic metal and other salt ions. The hypothesis arising from the work is that, in the case of another heavy rainfall event, the town of Carolina risks another AMD crisis. As sediments are likely to be accumulating and saturated with toxic metal ions. Further AMD-related changes in acidity will increase the mobilisation of adsorbed ions. Future flooding and flushing of wetlands will therefore once again move toxic metal ions through the system, and possibly re-contaminate the Boesmanspruit dam. The value of the study is in delivering specific evidence on the impacts of mining (and to a lesser extent agriculture) on wetland quality. Overall, this study, combined with additional research, indicates that in the X11B catchment, mining impacts are long-term and more serious than agriculture. In terms of contestation the research indicates that reliance on bio-physical data and knowledge is inadequate in resolving conflict between coal mining and other land- and water-users. The study demonstrates the necessity of insight into the social system and the value of a transdisciplinary approach in addressing land-use conflicts and wetland protection.
- Full Text:
- Date Issued: 2018
- Authors: Keighley, Tia-Kristi
- Date: 2018
- Subjects: Wetland ecology -- Komati River Watershed , Coal mines and mining -- Environmental aspects -- Komati River Watershed , Agriculture -- Environmental aspects -- Komati River Watershed , Acid mine drainage -- Komati River Watershed , Water quality -- Physiological effect -- Komati River Watershed , Wetland conservation -- Komati River Watershed , National Freshwater Ecosystem Priority Areas (NFEPAs)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63810 , vital:28491
- Description: Wetlands provide a wide variety of natural benefits (ecosystem services) from the natural environment to human populations, making them key examples of ecological infrastructure. However, the use of wetlands and their associated catchments is often contested by different users, making them nodes of conflict. Thus, there is a range of pressures on many wetlands which can ultimately lead to degradation or destruction. This study investigated the X11B quaternary catchment in the Upper Inkomati basin, Mpumalanga, South Africa. This catchment is characterised by a network of wetlands and streams that provide catchment residents with water. The sub-catchment is heavily used, dominated by the agricultural sector and coal mining. To understand the contestation, a contextual analysis was carried out. Selected wetland conditions and ecosystem services, along with user perceptions and the value of wetland-use, were assessed. Wetlands were observably in a relatively healthy condition. The resilience of wetlands and the efficiency of the ecosystem services they offer, especially in mediating water quality, were clear. The early results indicated a healthy landscape despite multiple-user impact from human activity. The health scores and provision of ecosystem services, along with the identified National Freshwater Ecosystem Priority Areas (NFEPAs) and red-listed fauna and flora, provide a substantial grounding for advocating the conservation of the wetlands of the contested X11B catchment. When water quality measures were added to the wetland health and ecosystem service assessment, low pH levels and high electrical conductivity were recorded. Both measures indicate coal mining impacts, more specifically Acid Mine Drainage (AMD) impacts, since AMD typically has sulphate as the dominant salt ion, and high concentrations of trace elements and metal ions. Concentrations breaching the recommended resource quality objectives (RQOs) of trace elements and ions, found in fertilizers and pesticides, were recorded in most sites, suggesting agricultural impacts on the landscape’s hydrology. Further, these agricultural impacts would add to the compromising effect of the wetlands’ capacity to remove pollutants from the water body. Livestock farming on all sites were also near wetlands which may have limited the vegetation cover of grazed land, so increasing runoff and the volume of water entering wetlands and compromising their ecosystem services. Poor water quality has implications for biophysical processes, which play an important role in the functioning of wetlands, for the benefit of users. Without the water quality measures, ecosystem health and ecosystem service methodology used suggested a healthy catchment. However, simple field water quality measures indicated past and present mining impacts. Therefore, the mandatory use of water chemistry is recommended in the assessment of wetlands in catchments with past and present mining activity taking place. Without this, repercussions would include wetland loss, and a more thorough investigation into the water quality and its effects on the wetland ecosystems is suggested. Further ecological investigation of water chemistry (heavy metals, ions, nutrients and trace elements) and macroinvertebrate assemblages identified links to water chemistry impacts on macroinvertebrate abundance and diversity. Abundance results based on the presence, absence and abundance of macroinvertebrates at the different sites did not reveal any clear patterns associated with different landscape users. Diversity, on the other hand, was related to land-use, where sites with high mining use had lower macroinvertebrate diversity than other sites. Related, concurrent, hydro-pedology research produced a more comprehensive understanding of the impact of mining on hydro-connectivity that clearly indicates mining as the cause of long-term deterioration of functional wetland health in a way that is practically impossible to restore. This study suggests that wetlands provide a strong ecosystem service of intermittent resetting of the wetland sediment adsorptive capacity for toxic metal and other salt ions. The hypothesis arising from the work is that, in the case of another heavy rainfall event, the town of Carolina risks another AMD crisis. As sediments are likely to be accumulating and saturated with toxic metal ions. Further AMD-related changes in acidity will increase the mobilisation of adsorbed ions. Future flooding and flushing of wetlands will therefore once again move toxic metal ions through the system, and possibly re-contaminate the Boesmanspruit dam. The value of the study is in delivering specific evidence on the impacts of mining (and to a lesser extent agriculture) on wetland quality. Overall, this study, combined with additional research, indicates that in the X11B catchment, mining impacts are long-term and more serious than agriculture. In terms of contestation the research indicates that reliance on bio-physical data and knowledge is inadequate in resolving conflict between coal mining and other land- and water-users. The study demonstrates the necessity of insight into the social system and the value of a transdisciplinary approach in addressing land-use conflicts and wetland protection.
- Full Text:
- Date Issued: 2018