: News Article

Harvester brought in to free weirs

15/03/2004

Water Boy has called in the big guns to help him fight what’s been described as the worst outbreak of submerged and floating weed in recent memory.

A weed harvester has been bought in to provide mechanical help to manage the growth which blocks the passage of recreational vessels and presents a threat to fish stocks.

The problem is generic along Ross River but worst under Nathan Street Bridge where weed covers an estimated 70,000 square metres of Aplin Weir.

The failure of a big wet season flush allowed the weed to proliferate says NQ Water Environment Manager Rob Hunt.

“These weirs are among the most valued recreational assets in the area,” Mr Hunt says.

“There is no way a (rowing) skull would get through weed that dense. Fishers are also registering their frustration with lures and props becoming tangled, making a catch impossible.

“This volume of weed also has the potential to denude the weirs of oxygen, which could cause fish kills come the warmer weather.

“We’ve consulted with both Townsville and Thuringowa City Council and believe that the mechanical harvester is the best management method available.”

The $200,000 paddle wheel driven harvester is leased from the Burdekin Shire Council and has been used periodically on the river for the last two years.

The weed is cut about two metres underwater and packed into bags for recycling into compost.

Water Boy in the hunt for Cabomba

Water Boy says a constant vigil is needed to help keep weed growth in check and to ensure clean and safe waterways.

“The most subversive weed is ‘Cabomba’ (pro. CAB-BOMB-BAH),” says Water Boy.

“It completely dominates the native underwater vegetation and is our biggest weed concern,” he says.

“Cabomba can grow in water up to five metres deep and mass to a hundred tonnes per hectare. That’s about the same as sugar cane.

“The fronds can grow up to eleven metres long, which makes it dangerous for swimmers and boats. It also taints the water, which makes treatment more expensive, so we can never allow it into Ross River Dam.

“The harvester is my favourite weapon as testing has shown that Cabomba responds less and less after repeat harvesting.

The other type of weed in the weirs is the more familiar floating kind, like Water Hyacinth, Salvinia and Water Lettuce.

© 2004 NQ Water