Proposed dam valve upgrade enabling Warren fish study

A first-time extensive fish population study is underway at Warren Reservoir, aiming to support SA Water’s proposed upgrade of the dam’s intake and scour valves next year.

Findings from the study will be used to inform how native fish species may be safely relocated to the nearby South Para Reservoir during the time Warren’s water level is temporarily lowered, a necessary method in order to perform an upgrade on the valves which ensure water can be transferred from the reservoir and supplied to customers.

Constructed in 1914, Warren Reservoir provides a direct supply of water for irrigation, as well as supplementing South Para Reservoir – where water flows to Barossa Reservoir for treatment before it’s supplied to around 85,000 customers in Adelaide’s northern suburbs and nearby townships.

SA Water’s General Manager of Sustainable Infrastructure, Amanda Lewry, said the fish study is an important part of planning for this project, which has been underway since 2016.

“Warren Reservoir Reserve in the Barossa Valley is one of several reservoir reserves that have been transformed into thriving recreational destinations supporting community wellbeing, with the reservoir particularly popular among anglers,” Ms Lewry said.

“To balance preserving the reservoir’s recreational role with our emphasis on dam safety, we’re partnering with RecFish SA and its members – the South Australian Research and Development Institute – and commercial fishers to monitor and then relocate, as much as possible, the valuable native fish including Murray cod, silver perch and golden perch, before we lower the reservoir to near zero capacity.

“As part of the monitoring stage of the study, we’re catching native fish using a combination of techniques – such as traditional rod and reel fishing as well as electrofishing technology, which is a safe method that briefly stuns the fish – to record their size and species, tag and then return them to the reservoir.

The size and species of native fish in Warren Reservoir are being caught, tagged and returned as part of a comprehensive fish study. Image: SA Water

“Our analysis will help build a picture of the fish population to understand how the changes in oxygen levels will influence our approach to lowering the water level, and at what point we should relocate fish, to minimise potential loss to the overall population.”

Ms Lewry said that during this time noxious fish species, including carp and redfin, will be removed from Warren and provided to fish markets or fertiliser suppliers.

“Subject to standard State Government development approvals for the overall project, at this stage, we are expecting to partially lower the reservoir and start relocating fish in March next year.

“Lowering the reservoir will enable the valve upgrade to be completed safely and efficiently, which ensures we can return it to full capacity as quickly as possible following the completion of works, with fish restocking likely to occur in September 2023.”

For the safety of crews and the community during the valve upgrade, Warren Reservoir will temporarily close to visitors for on-water access from February 2023, with a partial closure of the reserve’s western section from April 2023.

Ms Lewry said the valve upgrade is part of a long-term initiative to elevate dam safety at Warren, in line with refreshed national guidelines.

“Our dam safety upgrades ensure we remain in step with the water industry’s evolving design and safety standards, with eight of our dams already receiving major upgrades since 2002,” Ms Lewry said.

“While the reservoir’s water level is temporarily lowered, we’ll also be performing a detailed investigation of the structures that are normally underwater, to help inform our understanding of the dam as part of our long-term dam safety upgrade program.”

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