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Water pollution- is it safe to swim?
janinerSun, 03/01/2021 - 8:46pm
We have had a lot of rain in the past two weeks and the Cove waters are a muddy brown colour. The colour is caused by both silt and tannins (from the breakdown of vegetation), and it is an indicator that the water may be polluted. One measure of pollution is the bacterial content in faecal coliforms. If the level exceeds 150 faecal coliforms per 100ml the water is unsafe for swimming.
There is a long history of water testing in the Cove for the oyster industry. After heavy rain, it takes about 6 days for the bacterial levels in the water to return to levels that are safe for swimming. However, this is variable and dependent on the amount of sunlight, temperature, the size of the tides and the amount of rainfall in the last few months.
So what does this all mean for swimming and other recreational activities? I think the best advice is to be cautious and follow Beachwatch recommendations of not swimming for 3 days after heavy rainfall, if the water is discoloured or if there is debris in the water. If the water is still brown after three days, it would be wise to wait another couple of days.
Another way you can check the water quality is to go to the Food Authority website. https://www.foodauthority.nsw.gov.au/industry/shellfish/status
This website lists the oyster harvest conditions for the Bundabah harvest area (basically the Cove waters). Oysters cannot be harvested for at least two weeks after heavy rain has stopped as they are filter feeders and concentrate any contaminants in the water. The Cove waters have been closed for harvest since the 22nd December, 2020 and are still closed at the time of writing this article on 3rd January, 2021. The rainfall has continued off and on since the harvest closure with the last significant rain on 2nd January. You can probably swim before the oyster harvest restrictions are lifted but you should not eat any wild oysters collected from rocks or posts until the water quality improves.