The Barmah-Millewa Forest covers 66,000 ha and spans the New South Wales (NSW)– Victoria border between Tocumwal, Deniliquin and Echuca (Figure 5.2.1). It is listed under the (Ramsar) Convention on Wetlands of International Importance (the Ramsar Convention), the Australian Directory of Important Wetlands and is one of six Living Murray icon sites. The forest’s Victorian components are the Barmah National Park and part of the River Murray Reserve, covering 28,500 ha of forest and wetlands that support a vast range of significant plant and animal species.
The wetlands throughout the forest continue to provide a constant source of nutritional foods and significant fibres for the Yorta Yorta People. It is also evident that the resources in the landscape were utilized to manufacture canoes, shields and carrying devices.
Flooding in the Barmah-Millewa Forest depends on flows in the Murray River. A natural narrowing of the river (known as the Barmah choke) restricts flow and causes overbank flooding when flows below Yarrawonga Weir exceed the channel’s capacity. This restriction influences both the operation of Yarrawonga Weir and the upper limit of environmental flows that can be delivered to the forests.
Prior to river regulation for water supply, flooding would have regularly occurred with high flows from rainfall in winter and spring – helping to shape a rich and productive forest environment. Today, flooding in the forest is also influenced by system operation for water supply for users downstream in the Murray River, which can cause damage to the forest and banks of the river depending on the timing and volume of the flows.
The delivery of irrigation water during summer/autumn is managed to minimise unseasonal flooding of the forest. Regulators along the banks of the Murray River that control flow between the river and the forest remain closed during summer and autumn to restrict flow through low-lying flood runners. The delivery of water to Barmah Forest is also limited by a flow constraint below Yarrawonga Weir to minimise impacts to adjacent farming operations in NSW. The current constraint limits releases to a maximum of 18,000 ML per day between July and September (with potentially-affected landholder support) and to 15,000 ML per day for the rest of the year. To overcome this constraint, most environmental flows are shared between Barmah and Millewa forests to deliver water to low-lying wetlands in each forest at least every second year. It is currently not possible to achieve the desired flood depth and duration for floodplain marsh vegetation in both forests at the same time without larger natural flooding.
Water management at Barmah–Millewa Forest seeks to build on natural flow and the delivery of consumptive and operational water en route to optimise environmental outcomes when possible. As Barmah-Millewa Forest is located towards the upper reaches of the regulated portion of the Murray River, water for the environment that passes through the forest can often be used at sites further downstream as part of multi-site watering events.