Swimmers in Nelson are being warned to stay away from rivers that could be contaminated from storm water runoff.
With more rain forecast for the region, Nelson City Council is urging the public to stay clear of rivers for at least 36 hours after rainfall.
"The risk of catching a disease from swimming in clear, clean water is usually low, however when contamination levels are high following heavy rainfall there is an increased chance that you may catch a gut, ear, skin or respiratory infection," said the council's monitoring and research manager Martin Workman.
"Our monitoring this summer has indicated that bathing sites in Nelson have maintained their 'fair' to 'good' bathing water quality. Sites categorised as 'fair' and 'good' are satisfactory for swimming in most of the time, except during or following periods of rainfall," he said.
However, health warnings are still in place for the lower Maitai River, below Collingwood Street Bridge and the Paremata Flats Reserve at Wakapuaka River, which have been rated as "very poor" due to high levels of contamination and bacteria from livestock and birds.
A full list of water quality ratings can be found on the Nelson Council's website.