Macquarie Cudgegong Environmental Water Advisory Group communique

On 2 and 3 May 2023, the Macquarie–Cudgegong Environmental Water Advisory Group (EWAG) met in Dubbo for a strategic planning session to determine annual environmental watering objectives and actions for the 2023–24 water year.

Strategic planning session

The Environmental Water Advisory Group was presented with historical and current flow information for the Macquarie and Cudgegong rivers. The analysis included environmental water use over time and how these activities have influenced environmental outcomes.

Multiple sources of information were presented to guide decision-making, including:

• the Bureau of Meteorology climate outlook
• Murray–Darling Basin Authority Basin annual environmental watering priorities
• dam storage levels
• environmental water demands
• water carry over strategy
• environmental water balances.

Water for the environment volumes for the 2023–24 water year are predicted to be approximately 400 gigalitres (GL) for the Macquarie catchment and 12–25 GL for the Cudgegong catchment.

Proposed Macquarie River actions 2023–24

The overarching objective for 2023–24 is to capitalise on previous natural flooding to improve the health of and build resilience in native fish populations and the Macquarie Marshes.

Two main actions are proposed:

1. Widespread inundation in the Macquarie Marshes from 2020–2023 provides a rare opportunity to use water for the environment to inundate the greater river red gum woodland area of the Marshes, which is between 20,000 and 50,000 hectares. This approach would require approximately 100–150 GL of water for the environment for the water year and improve the resilience of the river red gum woodland community over time.
2. Water managers will use environmental releases to smooth out large peaks and troughs in flows at Dubbo during the breeding season in spring and summer. This would specifically target freshwater catfish, which are declining in the basin, and also benefit Murray cod and several small-bodied native species.

This flow regime would also achieve several secondary benefits, including:

• supporting the health of vegetation in colonial waterbird breeding sites through the marshes
• supporting Australasian bittern breeding and habitat (the reedbeds)
• providing end-of-system flow connectivity to the Barwon River
• increasing river productivity and food web processes
• providing habitat for waterbirds and other wetland animals.

Proposed regulated Cudgegong River actions 2023–24

The 2023–24 water year will be the first time actively managed water for the environment has been available for use in the Cudgegong River.

The Environmental Water Advisory Group reviewed Cudgegong River Long Term Water Plan objectives and discussed potential outcomes for native fish, flow variability, river processes and platypus.

The Environmental Water Advisory Group recommended that water managers focus on delivering spring and summer flows to target the flow needs of Murray cod and freshwater catfish. This would also benefit a range of smaller-bodied native fish and river processes.

Monitoring plan 2023–24

The Environmental Water Advisory Group discussed the status of the current monitoring program, and noted the following proposed monitoring actions for 2023–24: