Environmental water helped maintain connectivity, improve water quality and support river communities across the Barwon-Darling during summer 2025-26.
The Commonwealth and New South Wales governments delivered more than 37 gigalitres (GL) of environmental water from the Border Rivers and Gwydir River systems over the dry summer of 2025-26. The water:
- helped maintain river connectivity
- improved water quality and
- supported native fish and sustained ecological resilience through the Barwon-Darling.
Flows reached Wilcannia and added environmental water to Menindee Lakes.
The purpose of the summer refresh
The summer refresh is to maintain river connectivity, improve water quality and avoid ecological decline during summer drying.
Conditions across the northern Murray-Darling Basin became much drier from October 2025. River flows fell quickly and the risk of poor water quality, blue-green algae and disconnected waterholes increased. The Barwon River ceased flowing at Mungindi twice, once in late December and again in early January, underlining the seriousness of the situation.
Environmental water delivered from December 2025 to March 2026
Three regulated environmental water deliveries were released from Glenlyon Dam (Border Rivers) and Copeton Dam (Gwydir) to maintain river flows at Mungindi, Mogil Mogil and Collarenebri. A total of 37.14 GL was delivered to the Barwon-Darling under this coordinated watering action, including 4.96 GL from Border Rivers plus 32.18 GL from Gwydir system via the Mehi River and Carole-Gil Gil Creek (26.68 GL Commonwealth and 5.5 GL NSW).
Water released from Glenlyon and Copeton dams on 24 December travelled nearly 2000km downstream. The flows reached Wilcannia 48 days later (see Figure 1 and Table 1).
Figure 1: Map showing sources of water, flow path and timeline for flows reaching various locations along the Barwon-Darling River
| Location | Delivery date |
|---|---|
| Glenlyon Dam and Copeton Dam | Released from storages on 24 December 2025 |
| Mogil Mogil | 6 January 2026 |
| Collarenebri | 7 January 2026 |
| Walgett | 10 January 2026 |
| Mungindi | 11 January 2026 |
| Geera | 17 January 2026 |
| Brewarrina | 20 January 2026 |
| Bourke | 24 January 2026 |
| Louth | 29 January 2026 |
| Tilpa | 3 February 2026 |
| Wilcannia | 10 February 2026 |
Key outcomes
Connectivity
Environmental water kept the river connected during the dry summer. About 13.6 GL reached Wilcannia and 8.8 GL protected to Menindee Lakes.
Figure 2: Barwon-Darling River flows (ML/day) at Collarenebri and active environmental water (AEW) being protected, 1 January to 30 April 2026
About the data
At Collarenebri, the Summer Refresh Flow maintained the target baseflow of 280 megalitres (ML) per day between January and March. These flows helped support other ecological outcomes, including native fish movement between habitats.
Figure 3: Barwon-Darling River flows (ML/day) at Wilcannia and active environmental water (AEW) being protected, 1 January to 30 April 2026
About the data
Less environmental water reaches Wilcannia because some of the water is lost to evaporation and seepage as it travels downstream.
The higher flows at Wilcannia from mid-February was due to local rainfall and other Commonwealth environmental watering actions between March and June 2026 (see Table 2).
| Source of environmental water | Volume (ML) | % of Total | Contribution to Wilcannia AEW | Contribution to Lake Wetherell AEW |
|---|---|---|---|---|
| Barwon-Darling summer refresh delivery | 37,140 | 59 | 13,610 | 8,832 |
| Mehi 50 ML baseflow | 6,308.9 | 10 | 2,312 | 1,500 |
| Namoi | 11,071 | 18 | 4,057 | 2,633 |
| Intersecting streams | 6,375 | 10 | 2,336 | 1,516 |
| Barwon-Darling licenses | 1,707 | 3 | 626 | 406 |
| Total | 62,602 | 100 | 22,940 | 14,887 |
Water quality
Additional flows improved water quality. They increased dissolved oxygen levels, reduced periods of low flow and lowered the risk of algal blooms, and fish deaths.
Figure 4: River flow (ML/d) vs Dissolved Oxygen (mg/L) at Mungindi, 25 Dec 2025 to 31 Mar 2026
About the data
The graph shows that dissolved oxygen increased as river flows increased. Better oxygen levels support native fish and other aquatic animals.
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Native fish
Flows maintained habitat, connected refuge pools and created opportunities for native fish movement and spawning.
Waterbird and river ecosystem
Field observations recorded increased waterbird activity and improved habitat conditions across the river corridor.
Benefits for communities
Local communities reported improved river conditions, with better opportunities for fishing, swimming and recreation over summer.
Important Country for First Nations
The Barwon-Darling River flows through the Country of many First Nations, including the Barkandji, Murrawarri, Ngemba, Ngiyampaa, Yuwaalaraay and Gomeroi peoples. For thousands of years, these nations have maintained a deep and enduring connection with the river. The Brewarrina Fish Traps on the Barwon River are one of the world’s oldest human-made structures. We pay our respects to the First Nations along the Barwon-Darling and their elders: past, present and emerging.
Looking ahead
Lessons from the Summer Refresh Flow will help guide future environmental watering actions and preparedness for future dry conditions across the northern Murray-Darling Basin.
Working together
We acknowledge the members of the Northern Basin Environmental Watering Group who supported the Summer Refresh. Managing water for the environment is a collaborative effort, working in partnership with communities, Traditional Owners, scientists and government agencies including:
- NSW Department of Climate Change, Energy, Environment and Water (DCCEEW)
- NSW Fisheries
- WaterNSW
- Qld Department of Local Government, Water and Volunteers (DLGWV)
- Murray-Darling Basin Authority (MDBA).
These contributions are gratefully acknowledged.
