The Barwon–Darling watercourse connects the river systems of the northern Murray–Darling Basin with those of the south. Several major river systems flow into the Barwon–Darling including the Culgoa, Gwydir, Macintyre, Namoi, Macquarie, Bogan, Paroo and Warrego.
Severe drought conditions have been present in the region since mid-2017. Relief has been limited. The largest flows during this time occurred in early 2019 as a result of held water for the environment released from Glenlyon and Copeton dams. Late 2019 remained in drought with a wetter change observed in early 2020.
Prior to rainfall in early 2020 the Barwon–Darling watercourse experienced:
- less variability in flows
- an increase in the duration of cease-to-flow periods
- fewer and smaller pulses
- an overall reduction in the amount of water reaching the Lower Darling.
Rain provides relief
Rainfall has provided relief to diminishing water supplies and an improved environmental outlook, however more follow-up rainfall and flows are required to reverse drought impacts.
The focus of water managers in 2019–20 with an expected very dry resource availability scenario identified in the Barwon–Darling Rivers Annual Environmental Watering Priorities 2019–20, was to direct available resources to avoid unrecoverable loss of ecological assets and functionality, with a specific focus on supporting native fish habitat. This was true for 2019, but early 2020 was much wetter than expected with several environmental water requirements met along the river.
- protection of ecological assets and functionality
- support for native fish habitat
- several environmental water requirements were met, such as a small natural fresh at Mungindi, Bourke and Wilcannia, and a large natural fresh at Collarenebri, Walgett and Brewarrina – these were important for connecting habitats, triggering and enabling fish movement, and inundating benches for enhanced instream productivity
- the long-term water plan requirement of a maximum inter-event flow period not to exceed 2 years was not met in most sections of the river due to preceding drought conditions.