The Barwon–Darling watercourse connects the river systems of the northern Murray–Darling Basin with those of the south. Major river systems that flow into the Barwon–Darling include the Macintyre, Moonie, Gwydir, Namoi, Macquarie, Culgoa, Bogan, Warrego and Paroo.
The 2020–21 water year delivered a range of extremes from cease-to-flow conditions to overbank flows in some areas.
Drought conditions began to ease in early 2020 with upstream rainfall providing localised replenishment of the system as the 2020–21 water year began. However, in late 2020, cease-to-flow conditions returned to much of the Barwon–Darling system before significant flows commenced in late December, peaked in March–April and continued through to the end of the water year.
Environmental flows delivered from tributary catchments supported localised replenishment in the Barwon River until rainfall provided sustained relief from cease-to-flow conditions and an improved environmental outlook for the 2021–22 water year. For example:
- In late winter and spring, environmental flows from the Macquarie River replenished a small section of the Darling River downstream to Brewarrina.
- In summer, water for the environment from the Pindari Dam was used to provide a replenishment flow in the Barwon River downstream of Mungindi.
- Additional Commonwealth Environmental Water Holder water was delivered to the Barwon River from the Gwydir via the Carole/Gil Gil system to coincide with the delivery of water from the Border Rivers.
Natural flows occurred from January 2021 until the end of the water year. This helped meet key environmental needs identified in the Barwon–Darling rivers: Annual environmental watering priorities for the 2020–21 water year. Environmental water flowing into the Barwon–Darling from the tributaries was protected from extraction under active management rules. The Commonwealth Environmental Water Holder used its Barwon–Darling licenses to protect over 66 gigalitres between January and the end of the water year.
- protection of ecological assets and functionality
- support for native fish habitat
- bankfull flows at sites including Bourke and Wilcannia and overbank flows at Collarenebri
- inundation and connection of in-channel and off-stream habitats, triggering and enabling fish movement.