High cyanobacteria levels in Lake Clearwater

The Canterbury District Health Board has issued a health warning for Lake Clearwater after testing found the presence of high concentrations of potentially toxic cyanobacteria.

Temporary signage is being installed around the lake to alert people of the need to avoid contact with the water.

Water quality sampling at lake Camp and Clearwater

Environment Canterbury conducts summer water quality sampling at two LAWA-monitored swim sites in the area – lakes Camp and Clearwater – to monitor suitability for recreation.

Both lakes show low E. coli levels. However, recent samples from Lake Clearwater reflect the trend of deteriorating water quality with nutrient-enriched algal growth and high levels of chlorophyll-a. This is consistent with observations of discolouration of water in the lake.

Further test results revealed that an additional sample contained high levels of cyanobacteria.

Environment Canterbury will now begin weekly sampling for cyanobacteria at Lake Clearwater alongside routine E. coli sampling. Updated advice will be available on the LAWA website.

Testing for cyanobacteria will also be undertaken at Lake Camp this week. However, this site has low levels of E. coli and lower levels of algal growth than Lake Clearwater. At this time Lake Camp is rated suitable for swimming.

Find out more about current health warnings and what to look out for this summer.

Lake water quality a concern for some time

The detection of potentially toxic cyanobacteria in early summer season water sampling in Lake Clearwater is a further sign of degradation in lake water quality.

An Environment Canterbury report into high-country lake water quality published earlier this year found that Lake Clearwater underwent a period of sustained nutrient enrichment between 2005 and 2011, and it has since failed to achieve water quality objectives set out in the Land and Water Regional Plan.

Factors potentially contributing to a decline in water quality in the lake include surrounding land use, septic tank leakage from the Clearwater Huts village and groundwater infiltration into the lake.

Environment Canterbury has also recently installed two monitoring stations in Lake Camp and Lake Emma. These stations measure water temperature and level, and will assist with our overall understanding of the ecology of these high-country lakes.

Joint efforts to improve water quality in Ashburton lakes

Concerns relating to the water quality in the Ashburton Lakes resulted in the formation of a cross-sector working group in 2019 initiated at the request of rūnanga. This group is comprised of the statutory agencies with responsibilities for resource use in the area (Environment Canterbury, DoC, LINZ, Ashburton District Council and Fish & Game) working with local landowners.

Environment Canterbury staff recently reported back to the Ashburton Water Zone Committee regarding the working group’s progress over the past 12 months. Work has increased knowledge about water and nutrient flows into the lakes, allowing for an improved assessment of potential actions or mitigations. Further research is undergoing review and will be released next year.