The Gwydir Environmental Water Advisory Group met in March to review its environmental water use strategy for the 2023–24 water year.
Colonial waterbird breeding summary
This summer, the colonial waterbird breeding event has been successful, with 55,000 nests counted across 17 colonies. A total of 16 species were detected across 2 sites in the lower Gwydir and 6 in the Gingham watercourse. Juveniles in some colonies were expected to be under parental care until March 2023.
This is Gwydir's fourth large-scale waterbird breeding event in the last 20 years, each occurring during large-scale natural flood events. Successful breeding events support recovery of colonial waterbird populations, which are in decline.
| Year | Number of nests recorded |
|---|---|
| 2004–05 | 22,500 |
| 2011–12 | 75,000 |
| 2021–22 | 45,000 |
| 2022–23 | 55,000 (current best estimate) |
Frog survey results summary
Frog surveys occurred at 9 sites in spring 2022 and 17 sites in summer 2022–23. Juvenile flow-dependent frogs were detected at most sites (15 sites), indicating another successful breeding season. All 6 expected flow-dependant species were detected. They are:
- spotted marsh frog
- barking marsh frog
- Peron's tree frog
- eastern sign-bearing froglet
- broad-palmed frog
- salmon-striped frog.
Frog breeding continued into February 2023 with widespread calling by the 6 flow-dependent species heard during the follow-up surveys.
Vegetation survey results summary
Surveys of plant communities were completed in early March 2023. Survey sites were dominated by aquatic vegetation species, including water couch. Water couch is a native aquatic species becoming more prevalent across some floodplain areas this year. Small patches of the persistent pest species, water hyacinth and lippia, were detected during the surveys.
Environmental water deliveries
The Gwydir regulated water sharing plan has a rule that requires the first 500 megalitres per day from Horton, Halls and Myall tributaries is to be delivered to the Gingham and Lower Gwydir watercourses. Locally this is known as the 3T rule. Following very wet periods, an option to divert or reduce 3T flows away from the Lower Gwydir and Gingham watercourses is available when 500,000 megalitres has flowed past Yarraman gauge station in the previous 6 months. This volume was reached on 10 October 2022. On 3 November 2022 the Environmental Water Advisory Group supported continuing to allow flows to pass to the wetlands due to the significant colonial waterbird breeding event.
By March 2023, much of the floodplain had significantly dried. The core wetland area was drying, and the waterbird breeding event was nearing completion. Furthermore, many floodplain inundation dependant plants and animals have completed or are nearing completion of their reproductive cycles. Considering the current conditions, the Environmental Water Advisory Group gave advice to divert 3T flows away from the wetlands at the end of March 2023.
Planning for the 2023–24 water year
Potential annual watering strategies for 2023–24 were presented to the Environmental Water Advisory Group for discussion and endorsement. The extended wet period has left the wetlands in good condition, negating the need for restoration flows that are generally provided to the core wetlands during extended dry phases. A strategy to support Mallowa and Ballin Bora creeks was proposed and accepted by the Environmental Water Advisory Group.
Environmental water managers will include the endorsed strategies in the 2023–24 Annual Environmental Watering Priority Statement and share it with Environmental Water Advisory Group for comment before approval and implementation.