Auckland Council is advising people not to swim in the quarry lake at the end of Wilson Road in Warkworth because of an algae bloom.
The lake – which has changed to an orangey colour as a result of the bloom – has had elevated E. coli and algal levels in the past month. While the lake’s E. coli levels dropped to an acceptable level last week, the algae bloom is still of concern.
Auckland Council staff put up warning signs at the lake on November 9 advising people not to swim in it. These will remain in place until further notice.
The council’s environmental health team is investigating the cause of the elevated E. coli and algal levels. It is also continuing to monitor the lake to determine what level of risk the water poses.
The origin of the E. coli could be attributed to several sources, including animals such as birds, dogs or livestock, or humans. Further investigation is required to determine whether the elevated E. coli earlier this month was due to an isolated incident.
It is unknown when the lake will return to its normal colour, as this will depend on several factors including weather conditions, nutrient levels in the water, the types of algae present and the water chemistry of the lake.
