Lake Benalla to be drawn down to control weed

Wednesday 16 December, 2020
The water level in Lake Benalla will start to be slowly drawn down from February 8 to control the aquatic weed cabomba.

Goulburn Broken Catchment Management Authority’s Jo Deretic said as well as smothering native aquatic vegetation that provided valuable habitat for animals, fish and waterbugs, cabomba also clogged pumps and filters.

“It also seriously compromises the aesthetic and recreational value of waterways and wetlands and poses a real water quality hazard to people and animals,” Ms Deretic said.

 “Lowering the lake for a couple of months will expose the weed to air and dry it out. This is the most effective and efficient way to manage cabomba. Lowering of the lake has been successful in the past and has reduced the weed population significantly.  Back in 2007 cabomba covered most of the lake, causing major issues for the town. Today it’s at a manageable level. Drying it can reduce this weed again.”

Goulburn Broken CMA and Benalla Rural City Council have been in contact with a range of groups and lake users to discuss timing of the drawdown. Australian Platypus Conservancy ecologists surveyed the lake’s platypus population late last year (December 12 and 13) and will carry out another survey after the drawdown. 

“A small channel of water – the original course of the Broken River before the lake was created - will remain, which will help native animals, fish and other creatures move to other sections of the river while the level is being lowered,” Ms Deretic said. “It will also be a good opportunity to remove any rubbish and debris that has been dumped or washed into the lake over the past few years.

“We are keen to control the weed to protect irrigators’ and lake users’ interests, which is why on-going diligence is required to prevent cabomba’s re-establishment.”

Cabomba is an introduced plant that is often used in aquariums. It has fan-shaped, brownish ferny leaves that sit mostly underwater, with a white flower floating on the surface.  To prevent further infestations, it is essential that aquarium plants be composted and not disposed of in or near waterways. 

Goulburn Broken CMA is working with Benalla Rural City Council and Goulburn-Murray Water on the project.

For more information phone 5822 7700.