Suspected development runoff causes siltation event in Woolgoolga Lake

Run-off from nearby developments thought to be the cause, prompting one person to question ‘how much more will this poor little lake be able to take?’

Karen Dallas and the Woolgoolga Lake Working Group are concerned at how a significant amount of silt runoff was able to flow into Woolgoolga Lake, turning it brown in July 2021.

On Thursday morning Karen Dallas’ day began with some shocking news, Woolgoolga Lake had turned an ugly shade of brown as run-off and siltation inundated the waterway.

It wasn’t long before the secretary of the Woolgoolga Lake Working Group began hitting the phones with urgency, calling key stakeholders and urging them to take action.

“(I said) something has gone terribly wrong … and we need action taken straight away before it completely destroys the lake,” she said.

Ms Dallas said the suspended sediment can have a severe impact on the health of the lake, clogging fish gills and reducing their resistance to disease. It can also absorb heat from the sun and increase the temperature of the lake, causing further problems.

To their credit, Ms Dallas said all the organisations, including Council, had responded to their complaints “extremely quickly” and were working together to find a solution.

However, she added it was after the fact and “the damage is done”.

Silt-filled water from higher up in the catchment flows downstream to Woolgoolga Lake.

The siltation event is believed to have been caused by run-off from nearby developments though it is unclear exactly which ones.

There were initial concerns it may have come from Coffs Harbour City Council’s Wiigulga Sports Complex development, which is located nearby, or an agricultural development also in proximity.

A Council spokesperson said they did not suspect the Wiigulga Sports Complex was the “primary site of concern”.

Council officers are investigating if sediment associated with works at the agricultural site near the Wiigulga Sports Complex had contributed to the run-off.

“(Council) will take appropriate compliance action to ensure the right controls are in place (at the agricultural site),” the spokesperson said.

“The contractor working on the Wiigulga Sports Complex has also been made aware and reviewed all their controls and increased the levels on the perimeter silt drains and sediment control measures as additional precautions.”

Ms Dallas said not only was it yet another reminder of the importance of developers to ensure they have adequate erosion and sediment control plans, it served as a reminder to the community that their actions in the catchment can have severe consequences for the area’s waterways.

In May 2019 the lake was turned orange after a nearby resident cleaned their roof and the run-off flowed straight into the catchment.

In 2019 Woolgoolga Lake was coloured orange after a roof cleaning exercise in Tomkins Avenue went horribly wrong. The water ran straight off the roof and into the waterway, though at the time Council believed the run-off did not pose a risk to aquatic life.

“You expect dirty water after a rain event – that's normal,” she said.

“But when you can see the lighter colour – which is newly cleared land – running in, that’s when it is devastating,” Ms Dallas said.

“Because you know that dirt and silt is going to stay suspended in the water and eventually sink to the bottom and suffocate the aquatic life.

“We just throw our hands up and think ‘how much more will this poor little lake be able to take?”