Abstract
The Koekemoerspruit is a possible pollution source of the Middle Vaal River, an important drinking water source in South Africa. This case study aimed to establish the water quality of the Koekemoerspruit, to evaluate the impact of the Koekemoerspruit on the Vaal River, and to use this information to identify shortcomings in the monitoring program. Monthly and weekly samples from both the Vaal River and the Koekemoerspruit were analyzed at an accredited testing laboratory based on ISO 17025 for 20 chemical methods. A dataset from 2002 to 2015 was statistically analyzed by means of Statistica software, the Mann-Kendall test and the Sens’s slope to determine descriptive statistics and significant trends respectively. The sites’ water quality was evaluated by comparison with both national drinking water standards and environmental target water quality objectives. Results indicated that the target water quality objectives for orthophosphate, nitrate and nitrite, and ammonia concentrations were considerably exceeded in the Koekemoerspruit. The drinking water quality of the Koekemoerspruit and the Middle Vaal was noncompliant with South African standards. Color, electrical conductivity, turbidity, sulfate, recoverable cyanide and arsenic at one site posed aesthetic, operational, acute and chronic health risks. Color, mean ammonia and total chlorophyll concentrations displayed significant trends of increase over time and increased drastically after 2012 at the site where water enters the Middle Vaal River. However, the Koekemoerspruit did not seem to have a significant impact on the overall water quality of the Middle Vaal River, except for total chlorophyll concentrations. Moreover, the review and recommendations for optimizing the water quality monitoring program proved that original monitoring objectives have been achieved. The reviewed monitoring program has consequently been adopted in the water safety plan to address the shortcomings that were identified during this case study.
Highlights
A healthy river ecosystem is an essential resource for surrounding communities in terms of drinking water, agriculture, and industries
Seeing that the target water quality objectives are in many instances stricter than the drinking water limits
The electrical conductivity, an indicator of salinization, did not comply with limits set for these sites, and the sulfate concentration of site 5 failed to comply with the set limit as well
Summary
A healthy river ecosystem is an essential resource for surrounding communities in terms of drinking water, agriculture, and industries. IWRM has to take into account both economic benefits and ecological concerns [2]. In this respect, IWRM succeeds in satisfying present needs and usually does not consider future changes. Environmental monitoring is essential for detecting water quality and land use changes as well as associated pollution sources and other stressors, such as climate change. During this study we used Midvaal Water Company in South Africa (a water treatment plant that supplies bulk potable water from the Middle Vaal River to 501 500 consumers), as a case study to show how changes in surface water stressors due to changes in land use and socio-economic issues can impact on the challenge of providing safe drinking water
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