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Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison
Thesis (MSc)--Stellenbosch University, 2024.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613798221742080 |
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| access_status_str | Open Access |
| author | Welham, Angela Ruth |
| author2 | Roychoudhury, Alakendra |
| author_browse | Roychoudhury, Alakendra Welham, Angela Ruth |
| author_facet | Roychoudhury, Alakendra Welham, Angela Ruth |
| author_sort | Welham, Angela Ruth |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131969 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:41:51.674Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131969 Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison Welham, Angela Ruth Roychoudhury, Alakendra Chow, Reynold Van Rooyen, Jared Watson, Andrew Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Mediterranean climate -- South Africa -- Western Cape Wetland ecology -- South Africa -- Western Cape Wetlands -- Effect of drought on Sustainable agriculture -- Management Water chemistry Groundwater tracers -- South Africa -- Western Cape Hydrology Water -- Tritium content -- Measurement UCTD Thesis (MSc)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Wetlands in Mediterranean climates face threats to their water availability, quality, and hydrodynamics due to climate change and human activities. The Mediterranean climate of the Western Cape in South Africa, characterized by winter rainfall, plays a crucial role in recharging rivers and dams, which in turn sustains agricultural, urban, and ecological water demands (e.g., those of wetlands). The 2015 – 2018 drought has stressed surface waters, causing river flow modification as well as increased reliance on groundwater. Sustainable water management in water-scarce and disrupted hydrological systems necessitates understanding the system's baseline functioning and its response to above-average rainfall years after prolonged dry periods. Hydrological tracers are valuable methods to determine recharge, transport, and discharge dynamics. A tracer-based approach was applied to two contrasting data-poor catchments that host important estuaries in the Western Cape: the wetter, urban-modified Eerste River Catchment, and the drier, agricultural-dominated Verlorenvlei Catchment. Seasonal and spatial variations in the water sources supporting each wetland were investigated from five sample campaigns between March 2023 to January 2024, during dry and wet seasons. Water samples were analysed for δ18O, δ2H, 3H, and major ions, comprising of 26 rainwater, 2 wetland, 61 surface water, and 65 groundwater sites. Additionally, 35 groundwater tritium samples and 41 surface water O and H stable isotope samples from 2022 were included. The Eerste River Estuary is less vulnerable to evaporation (average δ2H = -11.1‰, average δ18O = -2.71‰) and maintains a steady water level predominantly due to perennial river inflow. However, streamflow is influenced by wastewater treatment facilities and storm runoff from informal settlements. Seasonal water transfer from the Kleinplaas holding dam (average δ2H = -10.3‰, average δ18O = -2.89‰) to Irrigation Boards changes the isotopic values of the Eerste River (average δ2H = -9.0‰, average δ18O =-2.73‰), due to surface runoff from irrigation. Conversely, water availability is of greater concern for the highly evaporative Verlorenvlei (average δ2H = 3.7‰, average δ18O = -0.22‰). The 2023 above-average rainfall year signalled a shift in the wetland groundwater support to primarily local sources. Additionally, the increase in river discharge highlights the importance of freshwater inflow into Verlorenvlei, to decrease salinity and balance acidity levels. Both catchments are sensitive to rainfall and recharge, with the degree of sensitivity dependent on the type and extent of catchment modification. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-05-02T12:52:55Z 2025-05-02T12:52:55Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131969 Stellenbosch University xv, 203 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Mediterranean climate -- South Africa -- Western Cape Wetland ecology -- South Africa -- Western Cape Wetlands -- Effect of drought on Sustainable agriculture -- Management Water chemistry Groundwater tracers -- South Africa -- Western Cape Hydrology Water -- Tritium content -- Measurement UCTD Welham, Angela Ruth Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison |
| title | Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison |
| title_full | Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison |
| title_fullStr | Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison |
| title_full_unstemmed | Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison |
| title_short | Evaluating the hydrological resilience of estuarine wetlands in the Western Cape using environmental tracers: an inter-catchment comparison |
| title_sort | evaluating the hydrological resilience of estuarine wetlands in the western cape using environmental tracers an inter catchment comparison |
| topic | Mediterranean climate -- South Africa -- Western Cape Wetland ecology -- South Africa -- Western Cape Wetlands -- Effect of drought on Sustainable agriculture -- Management Water chemistry Groundwater tracers -- South Africa -- Western Cape Hydrology Water -- Tritium content -- Measurement UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131969 |
| work_keys_str_mv | AT welhamangelaruth evaluatingthehydrologicalresilienceofestuarinewetlandsinthewesterncapeusingenvironmentaltracersanintercatchmentcomparison |