The rivers of the northern Murray-Darling Basin (MDB) experienced high levels of flooding and hydrological connection during 2022 and early 2023. However, low rainfall and hot conditions from the end of summer 2022-23 resulted in rivers drying back, some quite quickly. This caused poor water quality, increased algal blooms and fish death events in the Baawan-Baaka (Barwon-Darling) River, and other rivers. Continuing warm, dry conditions are forecast through 2023, with a return to El Niño conditions.
Warm, low-flow conditions increase the risk of further algal blooms, reductions in water quality and potential fish deaths. The Commonwealth Environmental Water Holder (CEWH) identified the need to use small volumes of water for the environment through autumn 2023 to maintain river flows into the cooler months and mitigate the effects of these conditions on native fish and other species. The CEWH delivered the Northern Refresh Flow into the Baawan-Baaka (Barwon-Darling) system using water entitlements held in storages in the Gwydir and Namoi rivers. This water was combined with water for the environment released to support native fish in the Macquarie River and was timed to supplement a natural flow pulse resulting from rainfall in the northern catchments in April 2023. This flow pulse and associated deliveries, along with amounts protected by the use of CEWH Barwon-Darling unregulated licences, were protected from extraction through active management in the Baawan-Baaka (BarwonDarling) River system and were observed as far downstream as Wilcannia.