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University of the Western Cape (2017)

An investigation of water quality regulation by the Karsriviervlei, Bredasdorp

Munnik, Magen C.

Titre : An investigation of water quality regulation by the Karsriviervlei, Bredasdorp

Auteur : Munnik, Magen C.

Université de soutenance : University of the Western Cape

Grade : Magister Scientiae - MSc (Earth Science) 2017

Résumé
Studies have shown that ecosystem services that are provided by wetlands are beneficial to the improvement of water quality regulation. Some of these ecosystem services may include sequestration of sediment, toxicants and nutrients by wetlands, which contributes to the quality of water in rivers downstream and thereby, the health and well-being of humanity and the environment. However, studies have also shown that there has been insufficient research done on how natural wetlands regulate water quality. Therefore, this study investigated the regulation of water quality by a wetland located in an agricultural setting in the Western Cape. This type of research was essential to South Africa as the country is experiencing a great loss and degradation of wetlands, even though national policies and legislation are geared towards their protection and rehabilitation. The study was aimed at evaluating the assumption that wetlands improve the quality of water in river systems, using the Karsriviervlei as a case study and by invoking two objectives. The first objective was to investigate the spatial and temporal variation in selected water quality variables upstream, through the wetland and downstream. The second objective was to investigate the hydrogeomorphic characteristics and processes of the Karsriviervlei that determined the effectiveness of wetlands, in regulating water quality. Furthermore, the study also consisted of two methods that provided an understanding of how natural wetlands regulate water quality. These methods were namely the WET-EcoServices Assessment as well as fieldwork & laboratory analysis. The WETEcoServices method is a rapid assessment tool that was based on document analysis and observation. However, the fieldwork & laboratory analysis were based on observation as well as the collection of water samples - that were tested in laboratories - and field measurements using specific equipment. The results showed that the Karsriviervlei is influencing and to some extent improving the quality of water, through fluctuations and decreases in certain physico-chemical parameters. An essential decrease in specific parameters from the river inlet to the outlet downstream included nitrate, nitrite, turbidity and conductivity ; which decreased from 1.25mg/l to 0.4mg/l, 9.5mg/l to 6.5mg/l, 34.45NTU to 14.95NTU and 4439µs/cm to 2794.5µs/cm respectively. Additional findings included the presence of the pathogen indicator – Escherichia coli - and the possibility of the wetland indicating a ‘Severely Impacted Ecological Category’. The category is based on the values of nutrients as compared to previous research done on water quality boundary values (delimiting of Ecological Categories). Even though this was anticipated because modification to the Karsriviervlei is evident (i.e. implementation of agricultural drainage system), more research is required.

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Page publiée le 17 mars 2019