Otago swimmers are urged to check the latest water quality results before taking the plunge this summer.
Photo: 123RF
Otago Regional Council has kicked off its summer monitoring programme, testing water quality at 29 of the region's most popular swimming sites.
Usually the council puts up temporary warning signs each time bacteria levels rise.
This year, the council said each site had a permanent sign reminding users to check the latest results online first.
New testing results are posted on the Land Air Water Aotearoa website weekly between December and March.
Council water scientist Rachel Ozanne said the water quality was generally good but that could be affected by wet and windy weather.
"Every Monday our team wades out to take water samples in every corner of Otago, then sends them up to a laboratory in Christchurch to be analysed for nasties like E coli, with those results automatically posted onto the LAWA website usually by Wednesday afternoon," Ozanne said.
"Unfortunately for the first week of testing, it was right after the heavy rain we experienced over the weekend - demonstrating how rain can affect water quality.
"When rain falls, it falls on our rooftops, on our roads, into our gutters; the rain and all the contaminants it brings with it eventually enter waterways.
"That's why it's best to stay out of the water 48 hours after rainfall. If you're in doubt - if the water looks a bit murky or smelly - choose another spot to swim."
One of the sites that would feature a permanent sign was Ōtokia Creek, a popular swimming spot near Dunedin.
More than a quarter of samples taken from Ōtokia Creek last summer had high bacteria concentrations requiring caution from swimmers.
According to the Land Air Water Aotearoa website, the creek is currently deemed unsuitable for swimming with testing results from last week identifying bacteria from ducks, sheep or cows and humans.
"The avian and ruminant sources are not surprising as there is a significant wetland upstream teeming with birdlife and further upstream there is also extensive farming activity," LAWA said.
"However, the source of human bacteria has not yet been identified and further investigation will be carried out this summer when the human elevations have been occurring."
Otago Regional Council said it would keep a close eye on bacteria levels at the creek.
The creek flowed into Brighton Beach, but the council said it was excluded from any warnings at Ōtokia Creek.
It undertook testing at Brighton Beach at the same time Ōtokia Creek was sampled last season.
All samples taken from Brighton Beach were well within the safe limits for swimming, indicating the issue was upstream.