An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management
| dc.contributor.advisor | Armitage, Neil | |
| dc.contributor.author | Harvey, Alice Lindiwe | |
| dc.date.accessioned | 2020-02-24T09:49:21Z | |
| dc.date.available | 2020-02-24T09:49:21Z | |
| dc.date.issued | 2019 | |
| dc.date.updated | 2020-02-24T09:49:00Z | |
| dc.description.abstract | The Knysna Estuary is ranked highest in South Africa for conservation importance and is a haven for endemic marine species. The ecosystem services provided by the estuary include significant biodiversity value and amenity value for residents and tourists. The economy of Knysna is reliant on tourism, which in turn is dependent on ecosystem services. The health of the Knysna Estuary is currently threatened by poor water quality. If the water pollution can be addressed, ecosystems can be protected and significant social and economic costs of environmental degradation can be avoided. The pollution contribution of runoff from catchments to the estuary is imperfectly understood. Mitigation measures designed based on imperfect knowledge may be inappropriate or fail to address the pollution concerns. A poor understanding of the world views of stakeholders could lead to the design of socially unacceptable solutions. This study aimed to improve knowledge of the catchments surrounding the estuary, and stakeholders within these areas, to inform solutions. Surface water sampling and testing and analysis of national and municipal databases were used to assess the pollutant contribution of catchment runoff. High nutrient concentrations were conducive to eutrophic or hypertrophic conditions at most sites. Total Inorganic Nitrogen (TIN) concentrations exceeded 5 mg/â„“ at 60% of the sites. Ammonium concentrations made up a disproportionate fraction of the TIN readings, with most fractions exceeding 20%, and many exceeding 70%. Student t tests indicated that TIN concentrations at the Bongani River were significantly higher than historical data. Total Suspended Solid (TSS) concentrations at some sites were lower than historical data. E. coli spikes of over 30,000 CFU/100 mâ„“ were measured at nine sites in October 2018. The Bongani River catchment was identified as a significant source of elevated nutrients and E. coli. Elevated nutrients and TSS were also recorded in the effluent from the Knysna Waste Water Treatment Works (WWTW) with mean values of 36 and 24 mg/â„“ for Total Ammonia Nitrogen (TAN) and TSS respectively. A Kendall correlation analysis indicated significant positive trends in TIN and TAN, and negative trends in Soluble Reactive Phosphorus. A hydrological model was built for the Bongani Catchment. Data input to the model was obtained from site visits, literature, and a desktop study of available catchment information. The model was calibrated against observed data at two water level monitoring points. The model was used to estimate pollutant loads for large storms, and can be used to inform possible pollution mitigation strategies. Further water management challenges and pollution sources were identified through stakeholder interviews. A decision support tool was used to understand how stakeholder world views and values can inform the selection of socially acceptable solutions. Stakeholder interviews identified sewage leaks as a water management concern. This corresponds well with the elevated nutrient and E. coli concentrations measured in many catchments. Other identified pollutants were litter and TSS. | |
| dc.identifier.apacitation | Harvey, A. L. (2019). <i>An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management</i>. (). ,Engineering and the Built Environment ,Department of Civil Engineering. Retrieved from http://hdl.handle.net/11427/31254 | en_ZA |
| dc.identifier.chicagocitation | Harvey, Alice Lindiwe. <i>"An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management."</i> ., ,Engineering and the Built Environment ,Department of Civil Engineering, 2019. http://hdl.handle.net/11427/31254 | en_ZA |
| dc.identifier.citation | Harvey, A. 2019. An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management. | en_ZA |
| dc.identifier.ris | TY - Thesis / Dissertation AU - Harvey, Alice Lindiwe AB - The Knysna Estuary is ranked highest in South Africa for conservation importance and is a haven for endemic marine species. The ecosystem services provided by the estuary include significant biodiversity value and amenity value for residents and tourists. The economy of Knysna is reliant on tourism, which in turn is dependent on ecosystem services. The health of the Knysna Estuary is currently threatened by poor water quality. If the water pollution can be addressed, ecosystems can be protected and significant social and economic costs of environmental degradation can be avoided. The pollution contribution of runoff from catchments to the estuary is imperfectly understood. Mitigation measures designed based on imperfect knowledge may be inappropriate or fail to address the pollution concerns. A poor understanding of the world views of stakeholders could lead to the design of socially unacceptable solutions. This study aimed to improve knowledge of the catchments surrounding the estuary, and stakeholders within these areas, to inform solutions. Surface water sampling and testing and analysis of national and municipal databases were used to assess the pollutant contribution of catchment runoff. High nutrient concentrations were conducive to eutrophic or hypertrophic conditions at most sites. Total Inorganic Nitrogen (TIN) concentrations exceeded 5 mg/â„“ at 60% of the sites. Ammonium concentrations made up a disproportionate fraction of the TIN readings, with most fractions exceeding 20%, and many exceeding 70%. Student t tests indicated that TIN concentrations at the Bongani River were significantly higher than historical data. Total Suspended Solid (TSS) concentrations at some sites were lower than historical data. E. coli spikes of over 30,000 CFU/100 mâ„“ were measured at nine sites in October 2018. The Bongani River catchment was identified as a significant source of elevated nutrients and E. coli. Elevated nutrients and TSS were also recorded in the effluent from the Knysna Waste Water Treatment Works (WWTW) with mean values of 36 and 24 mg/â„“ for Total Ammonia Nitrogen (TAN) and TSS respectively. A Kendall correlation analysis indicated significant positive trends in TIN and TAN, and negative trends in Soluble Reactive Phosphorus. A hydrological model was built for the Bongani Catchment. Data input to the model was obtained from site visits, literature, and a desktop study of available catchment information. The model was calibrated against observed data at two water level monitoring points. The model was used to estimate pollutant loads for large storms, and can be used to inform possible pollution mitigation strategies. Further water management challenges and pollution sources were identified through stakeholder interviews. A decision support tool was used to understand how stakeholder world views and values can inform the selection of socially acceptable solutions. Stakeholder interviews identified sewage leaks as a water management concern. This corresponds well with the elevated nutrient and E. coli concentrations measured in many catchments. Other identified pollutants were litter and TSS. DA - 2019 DB - OpenUCT DP - University of Cape Town KW - civil engineering LK - https://open.uct.ac.za PY - 2019 T1 - An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management TI - An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management UR - http://hdl.handle.net/11427/31254 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/31254 | |
| dc.identifier.vancouvercitation | Harvey AL. An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management. []. ,Engineering and the Built Environment ,Department of Civil Engineering, 2019 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/31254 | en_ZA |
| dc.language.rfc3066 | eng | |
| dc.publisher.department | Department of Civil Engineering | |
| dc.publisher.faculty | Faculty of Engineering and the Built Environment | |
| dc.subject | civil engineering | |
| dc.title | An investigation of the pollution contribution of catchments surrounding the Knysna Estuary, with implications for stormwater management | |
| dc.type | Master Thesis | |
| dc.type.qualificationlevel | Masters | |
| dc.type.qualificationname | MSc |