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www.thevillagenews.co.za
15 May 2019
Water quality of Onrus lagoon under the spotlight Writer & Photographer Hedda Mittner
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recent report on the water quality of the Onrus lagoon has elicited much debate on social media especially relating to sampling procedures, the monitoring of those results and the prime indicators used to determine the perceived health risks to recreational users of the Onrus lagoon. Pivotal to the report entitled Recreational water quality in the Onrus River Estuary: Issues and Appropriate Indicators by the chair of the Onrus River Estuary Forum (OREF), Dr Peter van Niekerk, is the issue of whether the guidelines pertaining to “coastal, marine waters” should be applied to the Onrus River Estuary – or whether it should rather be defined as “freshwater”. Based on several research studies, Van Niekerk is recommending that, due to its physical characteristics, the estuary should be regarded as a “freshwater-dominated system” as it is mainly supratidal (the sandbar is higher than the tidal reach) with an average salinity that is drastically lower than that of seawater. This would mean that a different bacteria indicator count is used to determine water quality, which results in more positive readings that classify the water quality as generally acceptable for full-contact recreation. While this might sound like good news to some, others have levelled severe criticisms against the report, with OREF, and Van Niekerk in particular, being accused of wanting to “lower standards” and “smoothing over the real issues”. However, Van Niekerk stresses that his report does not minimise the issues or suggest there will be no risks. “The report is clear that this is not the case; it is an honest attempt to ensure that the most appropriate quality standard is applied and that we thereby have greater clarity regarding the health risks to bathers.”
Van Niekerk says the report was submitted to the Overberg District Municipality (ODM), as the responsible authority, to consider for implementation. So what exactly are the conclusions and recommendations of the report? Background In his report, Van Niekerk points out that Onrus River has been a sought-after family holiday destination for more than a century. Both holidaymakers and permanent residents are attracted to the area because of its natural beauty, with the Onrus beach and ‘lagoon’ (as it is commonly known) at the mouth of the Onrus River Estuary being a prime attraction. “In recent years the quality of its water and doubts about its suitability for full contact recreation… received the greatest publicity and caused the greatest public concern, as the lagoon is especially popular with younger children due to its warmer and placid waters,” reads Van Niekerk’s report. “Warning signs, erected by the authorities, discouraged people from using it as a bathing area with consequent detrimental implications for the well-being of the users of the lagoon and the community at large.”
Although it is unfortunate that the appeal of Onrus as well as its local economy have been negatively impacted by these warnings, Van Niekerk says concerns about the water quality at the estuary mouth were not unfounded. Several studies have been undertaken over the years, including the Onrus Estuarine Management Plan, Situation Assessment Report, prepared for the Overstrand Municipality and the Lagoon Preservation Trust by Anchor Environmental Consultants (Pty) Ltd in 2016. In this report, it is noted that, “Sewage contamination in the Onrus Estuary has been a long-standing concern. Sewage spills have occurred
The scenic beauty of the Onrus Estuary is an important drawcard for holiday makers. However, the quality and safety of the water remains a concern – and a hotly-debated topic.
on occasion, and bacterial counts (indicators for faecal contamination) are frequently high. For example, in December 1999 only two pump stations were in working order and could not cope with the flows during the peak holiday season and the estuary has had to be closed to swimming at times, often during the peak summer season.” The report also refers to a monitoring study conducted in 2007 – 2008 by Dr Vic Hamilton-Attwell at five sites on the Onrus River downstream of De Bos Dam, which “showed that faecal bacteria levels were relatively low at the dam outfall and Camphill, and increased towards the estuary. Since December 2010, the Breede-Gouritz Catchment Management Agency has been testing water quality at the estuary mouth, which shows that E. coli and Enterococci levels are very high with >185 and >500 organisms
per 100 ml respectively.” Van Niekerk says the continuous faecal contamination of the estuary has been ascribed to two sources: the Kidbrooke sewer pipeline, which was constructed in and close to the riverbed in 1996 and is in a poor condition; and leaking conservancy tanks, being earlier septic tanks reconfigured to link to a small-bore sewer system installed in the early 1990s. Both these issues were identified in a report by V3 Consulting Engineers in 2000 as having “the potential to pollute the estuary, particularly during rain events”. According to Van Niekerk, water quality monitoring of the Onrus River and estuary is continuing; the Breede-Gouritz Catchment Management Agency (BGCMA) conducts bacteriological testing on a two-weekly basis and this is increased to weekly
during the peak holiday periods. In addition, the Overberg District Municipality (ODM) in recent years also conducted its own weekly monitoring during these peak times. The BGCMA also conducts a monthly chemical analysis of the waters of the Onrus River and its estuary. This includes physical parameters such as pH and EC. Actions taken by OREF In 2015 the Overstrand Municipality (OM) initiated the development of a management plan through a public participation process in accordance with the National Environmental Management: Integrated Coastal Management Act. Van Niekerk says the purpose of the Estuary Management Plan (EMP) is, “by means of a step-wise set of actions, to improve the estuary’s health, enhance its recreational utility and retain its sense of place”. Continues on P 4
