Keeping weeds at bay
ACTION must be taken before the freshwater reaches of the Ross River are again taken over by aquatic weeds, a water quality and urban ecosystem academic has warned.
Townsville’s floods this year have all but flushed out the weirs of its aquatic weeds, most notably the water hyacinth.
The infestation of the noxious plant got so severe that major events including rowing regattas were cancelled last year, but recreational users are enjoying a clear waterway because of the clean-out that came as a result the floods.
Dr Nathan Waltham from JCU’S TROPWATER centre said despite the weirs’ current condition, it was inevitable water hyacinth would return without a proactive approach.
“It now needs to be managed long term,” he said.
“They (aquatic weeds) need sediment and nutrients, and it is inevitable that with a buildup of nutrients and sediment it will grow back.
“In the urban context a lot of nutrients get washed off, for example from people’s front lawns.
“It may take a bit of time for nutrients and sediment to accumulate, and if there’s rain in the next few years it can slow the process down. But having a long-term management plan is the key to stopping it from spreading to excessive levels.”
Water hyacinth is native to South America and was released into Australian ponds and lagoons in the early 1900s as an ornamental feature.
It’s now rated as one of the world’s most toxic weeds and chokes ways.
Riverside Tavern venue manager Linda Moyle said patrons of the Douglas establishment – which overlooks Black Weir – were relishing the clear waterway.
“It’s pretty much 100 per cent better than what it was,” Ms Moyle said. “It looked like a turf farm, and people who dine wetlands and waterhere on our deck overlooking the water have seen a remarkable difference compared to what it was before the floods.
“Now that it’s been cleaned I think there should be a plan put in place to prevent it from spreading like that again.”
Townsville Water Ski club president Gary Pollack, whose club hosts regular major meets, said conditions for water skiers and boat users in the river were as good as any seen in years.
“It’s a huge improvement, I think the general health of the river has improved,” he said.
“Our slalom course is anchored at the bottom of the river at three parts and it relies on tension of stainless steel wires, and the aquatic weed was a real hazard. Not having that hazard is amazing.”
Townsville Local Recovery and Resilience Group chair Cr Les Walker said the council had plans in place to manage the aquatic weed problem.
“Following the cleanout, council has been given a rare opportunity to suppress the formation of floating weeds along the river through the eradication program,” he said.
“Council crews will continue to collect rubbish from the water and water’s edge while using an environmentally friendly spray to kill weeds throughout the river.
“This schedule will be staggered along the river to ensure that all of the weeds are targeted by crews carrying out the spraying.”
Cr Walker said the council would also begin clearing any weeds under the surface regularly with a weed harvester.