An environmental watering event is planned for the Lachlan River system to support extensive areas of high-quality floodplain and wetland habitat from late winter through to summer.
Up to 80,000 megalitres (ML) of environmental water will be delivered, targeting the Lachlan Swamp wetland system and the Greater Cumbung region below Whealbah to Oxley. The flow is being coordinated and delivered together by New South Wales and the Commonwealth Environmental Water Holder.
Peak flows will average 1,600 ML/day at the Whealbah gauge for up to 44 days. Water will move through the Lachlan River and Torriganny Creek and across diverse floodplain vegetation types characterised by braided channels, swamps and deep, open water lakes.
Water will be supplied from Wyangala Dam with releases commencing in mid-June. It is estimated that the flows will reach Willandra Weir by 2 July and Whealbah by 10 July.
To achieve targeted flow rates at Whealbah gauge, releases from Wyangala Dam will largely be at rates higher than typical winter river flows, ranging from about 2,000 ML/day to 3,000 ML/day.
Senior Environmental Water Management Officer with the NSW Department of Climate Change, Energy, the Environment and Water, Dr Jo Lenehan, said the timing is important for the Lachlan Swamp.
‘Parts of these water dependent ecosystems have been without water for close to 2 years. This flow will provide the water they need while they can still respond and recover,’ Dr Lenehan said.
The flows are expected to inundate more than 25,000 hectares of wetland and floodplain, along with large sections of the Lachlan River channel downstream of Lake Brewster. The flows will deliver broad environmental benefits.
‘We expect strong outcomes for waterbirds, native vegetation and species like the southern bell frog that rely on these flows to breed,’ she said.
The watering will support river red gum forests, river cooba, black box woodlands and lignum shrublands, which depend on regular flooding to remain healthy.
It will also create feeding and nesting habitat for waterbirds, including threatened species such as the Australasian bittern, freckled duck and blue-billed duck.
‘Events like this can create tens of thousands of hectares of feeding habitat for waterbirds during peak movement and breeding seasons, when their energy needs are high,’ Dr Lenehan said.
The environmental flow is designed to build ecosystem resilience after the wetter years between 2021 and 2024. Research shows key floodplain species, such as river red gums, should ideally not be dry for more than 3 years if they are to remain healthy and recover from drought stress.
Follow-up watering is important to support the natural regeneration and recruitment of a range of flood-dependent species after the recent major flood events, and the long-term sustainability of vegetation communities at catchment scale.
With forecasts pointing to drier conditions, Dr Lenehan said acting now is important.
‘We’re using available water to maintain the improvements made during the recent wetter years and give these ecosystems the best chance to cope with what comes next.’
A bulk delivery in winter to early spring is also more efficient due to lower evaporation and seepage within the river channel as it moves to its target location. It also aligns with low irrigation demand.
The department has worked closely with landholders and stakeholders to provide clear information about how the flows will move through the system and spread onto the target floodplain.
A monitoring program will track outcomes, including surveys of waterbirds, vegetation, frogs and fish, supported by real-time sensors and on-ground observations.
‘This is one of the largest environmental watering actions planned for the Lachlan system in 2026. It will support the long-term health of nationally significant wetlands and the hundreds of species that rely on them,’ Dr Lenehan said.
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