Assessment of water quality status of the Woestalleen wetland before and after rehabilitation
Date
2022
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Abstract
The key objective was to assess the water quality status of the Woestalleen wetland before and after rehabilitation using water quality data from five monitoring points, two upstream (KFBM1 and Dam), one within the wetland (KFBM2) and two downstream (KFBM3 and KFBM4) and to determine if the ecological status of Woestalleen wetland class has been upgraded from a Class D to a Class C or higher.
The channelled valley bottom wetland conditions for the post rehabilitation activities of the Roodepoort Colliery were found to be badly altered (Category E). Changes to the wetland and the subsequent consequence on the condition of the wetlands is mainly linked to the widespread alien invasive vegetation, erosion, damming and current mining activities from the Colliery adjacent to the wetland area. Monitoring data during study period 1, before rehabilitation (July 2018 to July 2019), study period 2, during rehabilitation (August 2019-January 2020) and study period 3, after rehabilitation (February 2020-June 2020) indicated higher values of electrical conductivity, turbidity, suspended solids, total alkalinity, chloride, sulphate, ortho phosphate, and sodium at the upstream site KFBM1 which were not compliant to the provided water quality limits on the WUL. Therefore, there are water contamination issues that emanated from upstream of the mining area. Higher values of TSS, EC, turbidity, and sulphate during study period 1 at downstream sites than upstream sites were also observed, this implies that the mine may have contributed to the water contamination of Woestalleen Spruit.
Most of the water quality variables such as electrical conductivity, turbidity, suspended solids, total alkalinity, sulphate, ortho phosphate, and sodium were found to be noncompliant to the WUL both at upstream sites and downstream sites during study periods 1, 2 and 3. Significantly higher concentrations of variables such as hydrogen ions, sodium, chloride and sulphates were observed at downstream sites, KFBM2, KFBM3 and KFBM4 as compared to upstream sites, KFBM1 and Dam before, during and after rehabilitation. Therefore, mining activities may have contributed to acid mine drainage leading to these changes, even though the upstream water quality arriving at the mining area was already non-compliant and lastly the Woestalleen wetland rehabilitation has not yet improved water quality downstream. The PES of Woestalleen wetland further degraded from class D to E.
Description
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, University of the Witwatersrand, Johannesburg, 2022
Keywords
Water quality, Woestalleen wetland