The Macquarie–Castlereagh catchment covers more than 75,000 square kilometres in the State’s central west. It extends from the Blue Mountains to the Barwon River plains, with major tributaries including the Cudgegong, Talbragar and Bell rivers.
The catchment is home to the iconic Macquarie Marshes – one of the largest semi-permanent wetland systems and colonial waterbird breeding sites in inland Australia.
The catchment supports important cultural values for Wiradjuri and Ngemba-Wayilwan people.
Water for rivers and wetlands
Increased rainfall and river flows since January 2020 have supported the recovery from the 2017–2019 drought.
Both planned and held accounts will be at 100% from 1 July 2022, with 334 gigalitres (GL) of the Department of Planning and Environment (the department) and Commonwealth Environmental Water Holder carryover available for the 2022–23 water year. Further rainfall could lead to the possibility of additional allocations early in the water year.
In 2022–23, water managers will target ongoing drought recovery outcomes for native fish, wetland vegetation, waterbirds and flow connection to the Barwon River.
Subject to regulated Water Sharing Plan amendment, a discretionary Environmental Water Allowance may be created in the regulated Cudgegong River in late 2022. This water has been managed to date as a rules-based translucent dam release. Water managers will plan the management of this allowance later in the year.
Weather and water forecast
The El Niño–Southern Oscillation (ENSO) outlook remains at La Nina, with a return to neutral ENSO during winter, meaning average or wetter conditions are likely. Further, the Bureau of Meteorology has forecast average temperatures in the Macquarie catchment.
Water managers have prepared watering plans that consider a range of weather and water availability scenarios. As at April 2022, conditions in the Macquarie– Castlereagh catchment are ‘wet’.
1. ENSO: The interaction between the sea surface and atmosphere over the Pacific Ocean which results in dryer or wetter conditions (El Nino or La Nina).
Resource availability scenario
Main aim: Protect
Avoid critical loss
Main aim: Maintain
Maintain river functioning
Main aim: Recover
Improve ecological health and resilience
Wet to very wet
Main aim: Enhance
Restore key floodplain and wetland linkages
Key planned actions for 2022–23
An inundation event in the Macquarie Marshes during spring 2022 will provide habitat for waterbirds, including first-year birds from colonies in the Macquarie Marshes and wider Basin.
Water managers will use water for the environment to target native fish populations in the mid Macquarie Wambuul River.
The fish species targeted will depend upon conditions over spring. Flow generalists like Murray cod and eel-tailed catfish will be targeted if other river flows are relatively stable, while flow specialists including golden perch will be supported if conditions remain wet with variable flows.
Water managers will deliver environmental flows during spring 2022 to support drought recovery for a third year. These flows will target the inundation of the inner 9,000 to 19,000 hectares of the Macquarie Marshes at a minimum.
Some riparian vegetation along the mid and lower Macquarie Wambuul River will be supported where flows are present. These flows will also recharge shallow groundwater systems and sustain vegetation that rely on this water source.
Connectivity to the Barwon has been consistent through 2021 and 2022. With a wetted Macquarie Marshes, it is expected spring flows in 2022 will provide extended flow connection along the lower Macquarie River to the Barwon River.
Figure 1 Map of proposed annual priority targets in the Macquarie–Castlereagh Water Resource Plan area 2022–23.