Lake Trevallyn algal bloom

Thursday, 25 January 2024

The bloom was detected in routine testing by the Tamar Estuary and Esk Rivers (TEER) Program, hosted by NRM North.

Following advice from the TEER Program, the West Tamar and Meander Valley Councils have closed Lake Trevallyn to recreational water users, in line with the National Health and Medical Research Council’s Guidelines for Managing Risks in Recreational Water.

The First Basin currently remains open to recreational water users, and the TEER Program team will continue to test water quality in the Cataract Gorge over coming weeks in consultation with the City of Launceston.

TasWater has put enhanced treatment measures in place as part of its operating procedures to ensure water drawn from Lake Trevallyn remains safe for consumption.

Blue-green algae, which are a type of photosynthesising bacteria, occur naturally in our waterways and are almost always present in low concentrations.

A bloom occurs when there is an environmental imbalance, causing algae to grow rapidly and accumulate into dense visible patches at the surface of the water.

At high concentrations, blue-green algae can impact public health and the environment. Algal blooms can make the water unsuitable for recreational activities such as boating, swimming, or fishing.

In very high concentrations, contact with blue-green algae can potentially be harmful and cause issues such as skin rashes, gastroenteritis and eye irritation.

The TEER Program has worked with a range of stakeholders to advise on the algal bloom, including Hydro Tasmania and TasWater, and the Meander Valley, City of Launceston and West Tamar Councils.

The first recorded bloom in Lake Trevallyn occurred in the summer of 2006-07 and persisted until the end of the following season.

NRM North Operations Manager Andrew Baldwin said the the Tamar Estuary and Esk Rivers (TEER) Program monitored water quality in Lake Trevallyn during the peak recreational use period between December and March.

“In response to data from recent sampling, the TEER Program team has initiated an expanded monitoring regime and has submitted water samples for laboratory testing to confirm algal count, species, and toxicity,” Mr Baldwin said.

“Noting that further laboratory testing is required to confirm initial assessments, the dominant blue-green algae species appears to be Dolichospermum planctonicum.

“The TEER Program will continue ongoing monitoring, in collaboration with the responsible agencies. This will allow the public to be informed as soon as possible when it is safe to recreate in the lake again.”

TasWater Head of Water and Environment Services Fran Smith said drinking water drawn from Lake Trevallyn remained safe for human consumption.

“The drinking water remains absolutely safe, and we are continuing to monitor the situation,” Ms Smith said.

“Our water treatment plant processes are designed to remove and eliminate any harmful compounds, including those from blue-green algae.”

Hydro Tasmania Head of Generation Operations Jack Penny said even with water flowing through the system from power station upstream, high water temperatures mean the conditions are perfect for algal blooms.

“We’ve been operating the power station upstream as normal, and water is cycling through the catchment,” Mr Penny said.

“Water will continue to flow from Poatina Power Station upstream and we are working with the experts about how we can best manage operations as part of a coordinated response to the bloom.”

More information on blue-green algae can be found here.