Lake Clearwater health warning lifted
The Canterbury District Health Board has removed a health warning for an algal bloom at Lake Clearwater, after testing found that the cyanobacteria present in the lake do not produce toxins.
Visitors to Lake Clearwater earlier this summer found significant discolouration in the lake due to algal growth, and early summer testing found the presence of planktonic cyanobacteria, and a warning was issued on 22 December.
Further testing early this year shows the type and concentration of cyanobacteria do not pose a threat to human or animal health.
Signage advising people to avoid contact with the water is being removed, but our monitoring of lake water quality will continue on a weekly basis.
Lake water quality issues continue
The removal of a health warning does not indicate an improvement in the water quality. Rather, it points to the particular cyanobacteria found in Lake Clearwater not being considered a risk to human health.
Cyanobacteria occur naturally in Canterbury lakes but their increase can be linked to a combination of nutrients in the water and warmer temperatures.
Monitoring at Lake Clearwater has shown high levels of cholrophyll-a, consistent with discolouration in the lake.
An Environment Canterbury report released in 2020 found that the lake underwent a period of sustained nutrient enrichment between 2005-2011, and has subsequently failed to achieve its objectives as outlined in the Land and Water Regional Plan.
Check before you swim
Sites are graded according to the suitability for contact recreation, but people are advised to avoid sites within 48 hours after heavy rain or if the water is discoloured with small globules suspended in it.