Lake Wyangan fish kill linked to inflows by council

Fish kill at Griffith's Lake Wyangan likely due to inflows disturbing sediment

News
An investigation into a fish kill event at Lake Wyangan, north of Griffith, found the likely cause was the disturbance of sediments by recent inflows into the lake. One of the inflows was carried out by Griffith City Council who manage the lake. PHOTO: Declan Rurenga

An investigation into a fish kill event at Lake Wyangan, north of Griffith, found the likely cause was the disturbance of sediments by recent inflows into the lake. One of the inflows was carried out by Griffith City Council who manage the lake. PHOTO: Declan Rurenga

Aa

Investigation into fish kill near Griffith finds likely cause disturbance of sediments.

Aa

An investigation into a fish kill at Lake Wyangan, north of Griffith, has found there is a strong possibility that the cause of the event was the disturbance of sulfidic sediments by recent inflows into the lake.

Ironically, one of the inflows identified as contributing to the May event was 242 megalitres piped into the lake over six days by Griffith City Council to increase water levels and avoid future fish kills.

The other was an earlier inflow of several hundred ML of storm water, with a peak flow of 40ML/day, which entered the lake from April 29 to May 9.

Thousands of native fish died in the event including Bony Bream, Golden Perch, Murray Cod and Silver Perch.

Griffith City Council mayor John Dal Broi said the investigation, which was led by the NSW Environment Protection Authority (EPA), showed the fish kill was due to a culmination of issues, which technically were out of council's control.

"The inquiry into the fish death does not lay any blame on council," Cr Dal Broi said.

"We were putting water in to try and bring the level of the lake up but this is what happened.

"We also put in 900 megalitres in January because some of the fisherman approached us and were concerned after the fish deaths in Lake Menindee. We had no fish deaths then (in January).

"The only factor which changed during the May event was the water temperature - during January the temperature stayed high given it was summer, however following the storm event in April a cold snap dropped the water temperature over a period of 2-3 days significantly."

Cr Dal Broi said the drop in temperature when combined with other factors outlined in the report, including the disturbance of sediment, created an environment which led to the fish kill.

Lake Wyangan was on amber alert for blue-green algae at the time of the fish kill.

Lake Wyangan was on amber alert for blue-green algae at the time of the fish kill.

Blue-green algae an ongoing issue for Lake Wyangan

Lake Wyangan has been plagued by water quality issues in recent years, with blue-green algae a common occurrence.

The Lake was on a red alert for blue-green algae over the summer and was on amber alert at the time of the fish kill.

In 2018 Griffith City Council employed aquatic researcher, Tom Ryan, in a three year contract as a Lake Wyangan and Catchment Management Project Officer to help control the lake's blue-green algae problem.

However, Cr Dal Broi said Mr Ryan left the position prior to May inflows and fish kill event.

He said council is currently advertising for the position to be filled.

Griffith City Council has also committed $2 million to building sediment ponds and wetlands to improve water quality. Mr Dal Broi said the project is expected to be completed in May next year.

"The sediment build up is because the lake is a closed system, water's not flowing in one end and out the other," Cr Dal Broi explained.

"Over the 60 odd years that water's been flowing in there, there's been a build up of nutrients on the floor of the lake."

"Should never of happened" - Murray MP

Cr Dal Broi said the local state member, Helen Dalton, had made unsubstantiated allegations of mismanagement early in the investigation and the independent analysis demonstrated "her comments were unfounded."

However, Murray MP Helen Dalton said she still believes the fish kill "should never of happened."

"They (Griffith City Council) sit around the table and talk amongst themselves, but how about we talk to someone who might know something," Mrs Dalton said.

She said Griffith City Council should have sought advice from Griffith local and world-renowned fresh water ecologist, Geoff Sainty.

"Even though it's a closed system it can operate as a healthy system, it can be done," Mrs Dalton said.

Have you signed up to The Land's free daily newsletter? Register below to make sure you are up to date with everything that's important to NSW agriculture.

Aa

From the front page

Sponsored by