Victoria is working with other Murray-Darling Basin states (Glossary) on projects that involve changing the way river systems operate. These are known as operational rule changes.
Five Operational Rule Change projects are part of Victoria’s package of 22 projects to achieve the Basin Plan’s environmental targets without the need for further Commonwealth water buy-backs. These are joint projects with NSW. The projects involve changes to river operation rules to improve flexibility and control over delivering environmental water to the Murray River.
Complementary to the constraints projects, Victoria, New South Wales and South Australia are also working on an Enhanced Environmental Water Delivery project.
The Barmah-Millewa Forest is the largest river red gum forest in Australia and is listed under the Ramsar International Convention on Wetlands [link] as a significant breeding site for waterbirds.
This project involves changing the rules associated with the water set aside by Victoria and NSW in an environmental account (the Barmah-Millewa Forest Environmental Watering Allocation or BMFEWA). The BMFEWA was established by Victoria and NSW in the late 1990s. Since then, many more environmental water entitlements have been created.
The proposed operating rule change will improve the coordination of the BMFEWA with the environmental water recovered under the Basin Plan, leading to better environmental outcomes. It will enable BMFEWA to be used more effectively and improve the number of successful environmental events that can be delivered within the same volume of allocated water.
Hume Dam is the major operating storage on the Murray River system. The Hume Dam releases irrigation, domestic and stock, urban and environmental water to Victoria and New South Wales, and provides about one-third of South Australia's (SA) entitlement.
Hume Dam also affects the delivery of water to many important environmental assets. Currently, Hume Dam’s operators are not permitted to allow the flow rate below the dam to fall more than 150 mm a day (six inches – ‘the six-inch rule’) at Doctors Point. This rule was made to minimise risk of river bank slumping.
The rule has been reviewed by the Murray-Darling Basin Authority who found it was too conservative and could be relaxed without an unacceptable increase in slumping risk. ‘The six-inch rule’ uses more water than if the flow rate was allowed to drop more quickly. It also contributes to unseasonal flooding of Barmah-Millewa Forest — an adverse environmental impact — because dam releases cannot be quickly scaled back when rainfall means that irrigators no longer need water they have ordered.
This project will save water as well as reducing flooding risks to Barmah-Millewa Forest.
The volume of water held in Hume Dam is managed mainly to protect the storage and reliability of water supply, with some flood mitigation benefit to downstream communities. This is done by calculating a target volume that takes into account the total capacity of Hume, as well as forecast inflows, and irrigator demands – but not environmental demands.
The proposed operating rule change will enable environmental water demands to be considered when calculating requirements for space (‘airspace’) in the reservoir. This will reduce the need for the dam operators to pre-release water in spring to create additional airspace in the storage in advance of potential inflows, resulting in more water being available in Lake Hume for allocation against entitlements to meet irrigation and environmental demands.
A key decision in operating the River Murray system is determining how much water to release from storage each day to meet all commitments. Operators do not have perfect knowledge of river conditions and make conservative assumptions, releasing more water than is required. This excess water is the operational loss.
Leading up to and following the millennium drought, there has been significant water reform and a shift in operational practice. Operators are now making decisions informed by more accurate and plentiful data on river conditions. This results in lower operational losses, with more water being available for allocation to environmental and consumptive demands. This project proposed to recognise this as an enduring improvement in operational efficiency as a permanent change.
The “Improved regulation of the River Murray” project is included in the package of notified supply measures, but offsets associated with the project were not included in the 605 GL offset determination in 2017. The project has been retained in the package as a notified project to enable governments to consider the project again in the future.
This project involves changes to rules about flows from the Snowy Hydro scheme to the Murray River.
In 2002, Victoria, NSW and the Commonwealth agreed to fund water efficiency and water entitlement purchases in the Murrumbidgee and Goulburn river systems. The water recovered allows up to an additional 70 gigalitres (GL) and 212GL each year to be released to the Murray and Snowy rivers respectively for environmental purposes.
Formerly, the release of that water was at the discretion of the electricity generator Snowy Hydro. It was generally at times suited to Snowy Hydro’s commercial outcomes, which limited the environmental benefits.
In 2011, changes were made to the Snowy Hydro licence and to the release rules for this water (called ‘River Murray Increased Flows’ or RMIF). As a result, the Victorian and New South Wales governments now hold that water and order its release for environmental outcomes in the Murray River downstream of Lake Hume. This proposal will provide a means to control the timing of RMIF water releases from the Snowy Scheme, allowing more flexibility to achieve environmental outcomes targeted in the Murray River below Hume Dam.
This project looks at ways to operate the river to combine held environmental water with natural flows to optimise the use of environmental water to keep our floodplains and wetlands healthy and provide environmental benefits for the whole system.
The project will respect the independent decision making of environmental water holders, Catchment Management Authorities and Water Corporations and engage local communities.
The project will take several years to develop, then test and review before it is put into action.
This project is also sometimes referred to as “Hydro-cues”.