Gwydir 2020-21 Annual Report Appendix G Low Flow WQ

The four years preceding December 2020 were the driest on record. Despite rain in early 2020, much of the northern Murray-Darling Basin remained in drought conditions with parts of the Barwon River ceasing to flow with large stretches drying back to disconnected waterholes. During disconnected stages these waterholes provide critical refuge habitat for aquatic organisms such as fish and invertebrates including mussels and crustaceans (Figure 1). However, as climatic conditions continued to bring hot and dry weather throughout the summer months, there was community concern that the water and habitat quality of these refugia were deteriorating quickly putting native aquatic organisms at risk. In response, the Commonwealth Environmental Water Office (CEWO) delivered water for the environment in December 2020 and January 2021. The objectives of these flows were to ‘help native fish survival by improving water quality in drying waterholes’ in both the Carole/Gil Gil and Barwon River systems.