Extensive effort since the early 1990s has developed environmental water requirements (EWRs) for Australian river ecosystems. Site watering plans have been prepared and annual priorities for environmental watering are determined in the Murray-Darling Basin.
Are the EWRs being met? Success stories include coordinated flows across multiple catchments that provide environmental benefits along river systems and capture return flows for use downstream. Key habitats which have benefited from coordinated flows include the Gwydir and Macquarie Rivers, Barmah-MIllewa forest, Pericoota-Gunbower forest, Hattah Lakes, the Lower Murray and the Coorong.
However, the focus of water delivery is still on selected sites and reaches, with whole sections of floodplains missing out. Walker and Thoms (1993) predicted that Murray floodplains would be reduced to one-third of their natural areas under projected flows. Sadly, this seems to be coming true in the Lower Murray.
No water has reached the outer floodplain communities in the Lower Murray since the 1970s. Monitoring results from 30 watered sites at 9 locations suggest that there has not been enough environmental water to meet EWRs.
We know what is needed for healthy floodplains. However, bureaucratic processes are limiting the effectiveness of environmental water. Once there is an approved process for annual prioritisation for sites with watering plans, water should be allocated to regions for local management, with sufficient volumes to ensure minimum water requirements are met.
In 2020, river red gums and black box on the Lower Murray floodplain are in their fifth year without over-bank flooding, a known critical trigger for stress in river red gums. Mature trees have gone into physiological hibernation, conserving water resources and reducing crop cycles and volumes. It is likely that almost all sites will need watering in 2021-22, which will severely test environmental water delivery capacity, not to mention the approvals process!