Lachlan Environmental Water Advisory Group communique

20 January 2023

On Friday 20 January 2023, the Lachlan Environmental Water Advisory Group (EWAG) met in Hay, New South Wales, to discuss the use of water for the environment in 2022–23.

Operations update

Almost record-breaking rainfall totals of 200–400 mm were recorded across the Lachlan Valley from October to December 2022. However, La Nina climate drivers are predicted to weaken and approach neutral by February 2023.

The Lachlan Airspace Reference Panel last met on 9 December 2022, agreeing to target 98% capacity in Wyangala Dam by the end of December 2022. The storage will then be managed as per normal demand-based operations if there are no further significant inflows.

Summary of waterbird breeding colonies

The annual waterbird monitoring program has been limited to mostly aerial flight and drone surveys since October 2022 due to flooding. However, the aerial flights and local landholder information confirmed 11 active colonies in the lower Lachlan. On-ground waterbird surveys will begin at the end of January 2023 as access opens and will be complemented by frog surveys.

Lachlan waterbird satellite tracking update (CSIRO)

In November 2022, 9 transmitters were fitted to straw-necked ibis and royal spoonbill in the Lachlan to learn more about their foraging and roosting habits. CSIRO project lead, Dr Heather McGinness, said the highly mobile Lachlan birds are moving between the Lowbidgee and Lachlan as if one expansive foraging area, highlighting the importance of inter-valley and Basin Scale management. Others headed north, with one straw-necked ibis foraging back and forth up to 60 km between Booligal and Willandra Creek. Computer models are investigating if birds are responding to weather conditions, inundation, and landscape disturbance, which will inform environmental water management in the future.

Environmental Water Advisory Group flight over the Lower Lachlan

Environmental Water Advisory Group members experienced a bird's eye view of the lower Lachlan's expansive floodplain ecosystems from Booligal to Hay, including Booligal Wetlands, Lachlan Swamps, Merrowie – Box Creek, and Great Cumbung Swamp region.

Members commented that 'there is no other way to achieve that whole of catchment perspective' and that the flight was a 'real education' on the scale and diversity of flooded habitats. The flights, organised by the department's Lachlan environmental water managers, were also used to survey waterbird breeding events and verify floodplain inundation extent, which will help strengthen the modelling currently being developed.

Recent watering events and outcomes

A total of 1,995 megalitres (ML) of New South Wales and Commonwealth environmental water was delivered over 57 days (August to October 2022) for floodplain and wetland inundation outcomes in the lower Merrimajeel Creek and Dry Lake. Outcomes for waterbirds, terrestrial productivity and native vegetation will be discussed at the next Environmental Water Advisory Group meeting.

The only other use of environmental water was 5,000 megalitres (ML) of Water Quality Allowance (WQA) released from Wyangala Dam. Water Quality Allowance is Planned Environmental Water (PEW) available to mitigate risks associated with water quality issues.

In this case, the issue was localised fish deaths, hypoxic conditions (I.e. low dissolved oxygen levels) and associated blue-green algal loading in Jemalong Creek. The arriving high oxygenated water from Wyangala diluted and flushed the poor-quality water from Jemalong Creek to reduce risks to native fish up and downstream of Jemalong Weir.

Future watering actions

There were no planned watering actions for the remainder of the 2022–23 water year. However, the Environmental Water Advisory Group's advice was sought on potential requirements to support colonial waterbird breeding, and maintain connectivity, hydrological variability and replenish refuges if system baseflows become low for extended periods. All unused general security licensed water will be carried over in accounts into 2023–24.