Fish stocks at risk through inter-valley trading of water

GETTING IN A SPOT OF FISHING… Young Charlie Threlfall along with his grandfather, Steve Threlfall, owner of Trelly’s Outdoor and his mother, Jaclyn Threlfall try their hand at catching some fish in the Goulburn River. Photo: Steve Hutcheson

THE recent shutdown of recreational fishing due to the Coronavirus has given a welcome respite to fish stocks in the Victorian rivers yet other factors that contribute to their decline are ongoing.

Inter-valley trade (IVT) of water rights from Victorian sources to other parts further along the Murray system have over the years been contributing towards the decline due to the high flows in late spring and through summer reducing the survival, growth and recruitment of both wild and stocked juvenile Murray cod and other native threatened fish species.

The Department of Environment, Land, Water and Planning (DELWP) is currently seeking submissions (closing on 1 June) to help understand  how operational rules set by environmental thresholds interact with possible changes to trade rules and consider the potential implications of these changes for how water trade occurs in the future.

The Victorian Fishing Authority (VFA) currently in the early stages of constructing a fish hatchery in Kialla has expressed concerns that recent unpublished modelling by the Arthur Rylah Institute suggest a doubling of summer flows (above a baseline of 1000ML per day) down the lower Goulburn river and is likely to decrease Murray Cod  recruitment by up to 30% per annum.

According to the VFA submission ten years ago , base summer flows in the lower Goulburn River ranged from 250ML to 350ML per day. Since then, environmental flows have been added to this flow and its delivery has been designed to emulate natural flows at or less than 1000ML per day over this period (around 30 gigalitres per month). Over the last few years, primarily as a result of inter-valley transfers, Goulburn River summer flows have increased from peak flows of up to 1000ML per day, up to 3000ML per day.

Not only is this increased flow damaging fish stock due to the unseasonably high flow, it has contributed towards severe degradation to the river in the region of the Barmah choke.

The IVT flows affect not only the river health and fish stock, they are also instrumental in the elevated pricing and lack of availability of irrigation waters for local agricultural production along the waterways.

Recently the Victorian Government announced IVT deliveries would be limited to 50GL a month from December to April to help reduce environmental damage to the lower Goulburn River caused by high IVT deliveries during 2017-18 and 2018-19.

The Murray Darling Basin Authority (MDBA) has placed an order for 50GL to be delivered from the Goulburn.  The MDBA order will see flows in Goulburn River increase from the current IVT rate of 1300ML per day to an average of 1700ML per day.

Goulburn Broken Catchment Management Authority (CMA) has asked the IVT flows are delivered at a variable rate to limit environmental damage to the Goulburn River.

“We’d prefer to maintain the flow around 1000ML per day to give bank vegetation a chance to grow and spread and provide valuable habitat for bugs and small fish,” Goulburn Broken CMA CEO, Chris Norman said.