The Gwydir Environmental Water Advisory Group met in Moree on 12 December 2024. High rainfall in late November and early December provided a wet base for delivering environmental water to the Mallowa, Lower Gwydir, and Gingham wetlands. One landholder noted, ‘Rainfall and runoff likely topped up fish holes in Carole Creek.’ Many landholders observed increased vegetation growth and bird activity, with continuous creek flows in the upper catchment. Although the Gwydir Wetlands State Conservation Area received less rainfall, it still had high diversity and moderate waterbird numbers.
Monitoring update
Vegetation
Surveys identified 90 plant species across the 35 sites monitored in March 2024 and 100 species in October 2024. The mix of aquatic and terrestrial vegetation was attributed to the drying conditions in the wetlands.
Waterbirds
Aerial and on-ground surveys conducted in November 2024 identified 131 bird species, including 47 waterbird species. Notable sightings included threatened and migratory species such as Latham's snipe and little bittern. Over 100 brolgas were observed in the Lower Gwydir.
Frogs
In September 2024, monitoring teams detected frog calls, indicating reproductive effort in response to inundation. However, November surveys found relatively few juvenile frogs, likely due to the short inundation event, which wasn't long enough for tadpoles to grow into mature frogs.
Fish
The fish community across the Gwydir is considered poor, with few species recruiting sufficiently to sustain a natural population. Murray cod are widely present, but abundance and biomass are declining. Freshwater catfish were found east of Moree and are present in lower abundance around Moree. Researchers believe there was a good recruitment event in 2022–23.
Golden perch are present but are not recruiting in the Gwydir.
Silver perch are below detectable limits. Silver perch are not spawning or recruiting in the Gwydir.
No purple-spotted gudgeon or olive perchlet were detected in the regulated Gwydir system during the recent round of surveys.
An upcoming sampling round by Department of Primary Industries Regional Development Fisheries researchers in the Gwydir River will compare results from the Severn and Gwydir Rivers as part of the Pindari Dam Cold-Water Pollution mitigation project. Researchers have also installed thermal monitoring equipment to measure the magnitude and extent of cold water pollution along the Gwydir.
Completed water deliveries
The early season stimulus flow was completed, using 8,024 megalitres (ML). Subsequently, a minimum flow target of 300 ML per day (ML/d) at Gravesend was briefly implemented, using 990 ML of environmental water before irrigation releases met and exceeded this target. In October, to prevent ecologically impactful reductions in flow rates due to changing irrigation requirements, 700 ML of environmental water was used. This process, known as 'pothole filling’, helped maintain stable flow rates.
Conditions and forecast
Rainfall forecasts of 100–200 millimetres for January to March 2025 are below the historical average. Temperatures are forecast to be above the historical minimum and maximum temperatures. The eastern Gingham, Lower Gwydir, and Mallowa regions are drier than the west. From August to December 2024, Tillaloo and Teralba flows remained below 200 ML/d, with Gingham Bridge peaking at 55 ML/d in late August. Ballin Boora Creek flowed briefly due to the late November and early December rainfall event. While recent rainfall inundated large areas, delivery of water for the environment will continue due to drying conditions. Planned environmental flows aim to meet the lifecycle needs of vegetation, frogs, and other fauna.
Determining flows for inundation
Data from the Bureau of Meteorology was presented to demonstrate how water managers calculate the necessary flows to maintain inundation in wetland areas. This process involves determining the required daily inflows while considering factors such as rainfall and evaporation. For example, a net loss of 114 ML/d was recorded in January. Typically, an inflow of 250 ML/d would be delivered; however, due to the wet conditions, this has been adjusted to 100 ML/d. Flow rates will be managed adaptively throughout the event and are likely to increase if conditions remain dry.
The Gwydir Raft
The Gwydir Raft was discussed, including the challenges it creates for delivering water for the environment to the Gingham Watercourse. The Environmental Water Advisory Group considered available actions to help restore flows to the watercourse, and flow rates are being managed to work with current conditions whenever possible.
What’s next
The Environmental Water Advisory Group will meet in April 2025 to discuss how environmental water has been used for the current water year and plan for the 2025–26 year.
