Despite climatic and operational challenges, the delivery of water for the environment in 2018–19 largely achieved planned outcomes.
The combined winter priming and spring flows to the south, north and eastern marshes inundated about 15,000 hectares of the targeted 21,000 hectares. The releases were made over 140 days between July and December and aimed to:
- inundate mixed marsh vegetation, including water couch and common reed
- reach inner areas of river red gum woodlands
- enable seed-setting in marsh vegetation.
Subsequent hot, dry conditions and the absence of follow-up rain-fed inflows over summer led to rapid drying of the areas inundated.
The combination of low rainfall in the marshes and less water available from the account (30% restriction) meant the area inundated was reduced.
Low levels of inundation in the eastern marshes were caused by:
- changed in-channel conditions (low water levels) in the Gum Cowal, which affected gauge accuracy and the rate at which water was delivered
- operational issues
- harsh climatic conditions, including record high temperatures and record high evaporation rates, which limited the spread of water and the duration of inundation.
Monitoring in the marshes, which was completed in spring, reported:
- widespread calling activity by flow-responsive frogs, such as the eastern sign-bearing froglet, spotted marsh frog and the barking marsh frog
- frog egg masses and tadpoles in the north and south marsh
- limited frog activity in the eastern marshes, therefore recruitment in this area was likely to be very limited.
Forty waterbird species, including a rare sighting of the nationally endangered Australasian bittern in the reedbeds in the northern nature reserve, migratory Latham’s snipe and a large flock (>40) of the NSW threatened brolga.
As well as delivery to the Macquarie Marshes, a small volume of water was used to support key refuge pools for native fish to allow them to move to better habitat with improved water quality.
- Nyngan lower town weir pool, which is the only recorded location of threatened olive perchlet in the catchment this year
- Methalibar Weir pool on the Ewenmar Creek, which supports the threatened eel-tailed catfish.