Annual environmental water priorities in the Lachlan catchment 2024–25

Water that is allocated and managed specifically to improve the health of rivers, wetlands and floodplains is known as water for the environment.

Our environmental water management teams work with local community advisory groups including landholders, Aboriginal stakeholders, partner agencies and other interested community members to develop detailed annual plans for the use of water for the environment in each catchment, including how its use is prioritised.

Water for rivers and wetlands

The Lachlan catchment experienced increasingly wet conditions from 2021 to 2023, with major flooding following a record release of 230,000 megalitres in one day from Wyangala Dam in November 2022.

Throughout the 2023–24 water year, water managers used water for the environment to support the only significant pelican breeding event in the Murray–Darling Basin at Lake Brewster. Refuge and recovery flows were delivered throughout summer and autumn after blue-green algal issues arose in the lower Lachlan River, including a large whole-of-system fresh from Wyangala Dam.

In planning for 2024–25, water managers have applied:

• a set of principles and triggers to guide the watering of key water-dependent biodiversity assets
• an adaptive approach to support native fish and downstream ecological connectivity.

Measures are in place to provide water for any unforeseen water demands, such as waterbird nesting and water quality issues.

The Department of Climate Change, Energy, the Environment and Water (the department) may also set aside water for use in future years to support the longer-term resilience of the catchment through drier times.

Partnering with Aboriginal peoples

Water for Country is environmental water use planned by the department and Aboriginal people to achieve shared benefits for the environment and cultural places, values and/or interests.

In 2024–25 we will partner with Aboriginal peoples and organisations in the Lachlan. This includes new and existing programs to consider Aboriginal rights and values in environmental water planning, delivery and monitoring. For example:

• the review and update of the Lachlan Long-Term Water Plan draws on local, traditional and scientific knowledge
• the Lachlan Regional Aboriginal Water Committee
• working with Canberra University on the Flow-MER 2.0 long-term monitoring program to strengthen Aboriginal peoples’ role in monitoring on-Country outcomes
• continuing to work with the Ngiyampaa Nation to support important cultural sites and lands where there is a connection to place
• Nation planning with the Condobolin Wiradjuri community for Murie Creek
• Nation planning with Wiradjuri, Mutthi Mutthi, Yita Yita and Nari Nari in the Great Cumbung regional water management plan.

Weather and water forecast

As of June 2024, the El Niño–Southern Oscillation outlook is neutral. That is, neither La Niña nor El Niño conditions are favoured as oceanic and atmospheric indicators have returned to neutral levels. International climate models suggest neutral El Niño–Southern Oscillation conditions will persist through the southern winter, but there are some signs that La Niña conditions could form later in the 2024–25 water year.

Wyangala Dam storage capacity is expected to remain high (>85%) at the start of the water year, leading into the winter storage inflow and low irrigation demand period. Environmental water accounts remain full. If La Niña conditions occur in winter, translucent and airspace or flood management releases at Wyangala Dam are anticipated. La Niña can be a very short, marginal spring event, often followed by a very hot and dry summer.

Water managers have prepared watering plans that consider a range of weather and water availability scenarios. This is known as resource availability scenario planning.

Resource availability scenario

This table provides details about how we plan for different resource availability scenarios. Wet to very wet conditions are forecast for the Lachlan catchment in 2024–25, which means water availability planning will follow the ‘wet to very wet’ scenario.

Key planned actions for 2024–25

Native fish

Up to 20 gigalitres (GL) in flows are planned to provide suitable nesting conditions for Murray cod in the Lachlan River. Two GL of these flows will be used to maintain permanent refugia for the newly discovered (in April 2023), Booligal population of the threatened olive perchlet in Merrowie Creek. Delivering flow pulses or ‘freshes’ will provide food, habitat, and refuge from poor water quality throughout the year.

Waterbirds

If needed, up to 10 GL will be managed through spring and autumn to provide core breeding, foraging and migratory wader habitats. Water managers will make up to 10 GL of additional water available to support bird breeding events, such as the pelicans at Lake Brewster.

Vegetation

Water managers will focus on successive waterings of floodplain vegetation to build on condition recovery and support recruitment of:

• lignum shrublands in Merrowie Creek, Box Creek and Willandra Creek (15 GL)
• phragmites, reed beds and river red gum woodland in the Great Cumbung Swamp (up to 15 GL).

Additional volumes of up to 8 GL will promote seed setting and establish inflow and outflow wetlands at Lake Brewster. These sites will contribute to waterbird and connectivity outcomes.

Connectivity

Water managers may use up to 60 GL across the catchment to provide connectivity by enhancing large natural overbank and wetland flows, including translucent flow releases and airspace management.

Map of proposed annual priority targets in the water resource plan area 2024–25