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Highlights in this update

  • Total rainfall improved across much of the Murray–Darling Basin with some areas breaking daily rainfall records
  • Water storages in the Basin continue to fill with some dams reaching capacity
  • The Bureau of Meteorology raises its ENSO status to La Niña ALERT
  • Spotlight story: Water flows into the Great Darling Anabranch
Rainfall deficiency for the Murray-Darling Basin, 48 months to August 2021


Water storages in the Murray–Darling Basin continued to fill during September. As of 29 September 2021, the Hume Dam was sitting at 97% capacity while some smaller storages in the northern Basin were above 100% capacity.

Multi-year rainfall deficiencies, which originated during the 2017–2019 drought remain over parts of the Basin, particularly in the northern Basin and western catchments.

The 2020–21 La Niña saw improvement in conditions over parts of the Basin and a negative Indian Ocean Dipole event also led to above-average rainfall during June and July 2021. During September, much of New South Wales and north east Victoria also experienced wetter than average conditions.

Despite this, the Bureau of Meteorology maintains that further periods of above-average rainfall are needed to continue towards recovery, especially in South Australia, the far west of New South Wales, and southern Queensland.

Rainfall totals for the Murray-Darling Basin - September 2021


September proved to be a wetter month than August 2021 with much of the Murray–Darling Basin receiving above-average rainfall.

Central parts of the Basin received the most rainfall, averaging above-average to very much above-average. Meanwhile, outlying areas of the northern and southern Basin averaged below average-to-average rainfall.

Western catchments received 5–50 mm of rainfall during September, while falls in the eastern ranges were slightly better with catchments receiving 25–200 mm. This is similar to June and July 2021 when rainfall totals were higher due to a negative Indian Ocean Dipole (IOD) event.

Although the negative IOD event has weakened it is still impacting the Basin’s rainfall. In the northern Basin, above-average rainfall was experienced in the New South Wales towns of Bourke (60.8 mm), Walgett (77 mm), and Moree (78.2 mm). On 30 September, Walgett and Moree experienced their highest September daily rainfall on record recording 60 mm and 58.8 mm.

In the southern Basin, some rainfall totals were lower in September with the New South Wales towns of Broken Hill receiving 4 mm and Wilcannia 14.2 mm. Meanwhile, the Victorian towns of Shepparton (52.8 mm) and Bendigo (71.6 mm) received high rainfall, while Cobram and Yarrawonga received their highest September daily rainfall on record at 40 mm and 42 mm.

Summary of water in storage as at 29 September 2021

Water storages and streamflow

Public water storages across the Murray–Darling Basin continued to increase across September and were holding 19,497 GL (88%) as of 29 September 2021. This was an increase from 83% as of 1 September 2021.

Public storages in the northern Basin increased slightly and were holding 3,868 GL (82%). This was a 1% increase from 1 September 2021 when the northern Basin was holding 3,812 GL (81%).

Several public storages in the northern Basin were still at 100% capacity or more as of 29 September 2021. In the Border Rivers catchment, Pindari Lake was at 100% capacity while Lake Coolmunda reduced from 101% to 98%. In the Macquarie catchment, Lake Burrendong was at 101%, while in the Namoi catchment, Chaffey Dam was at 102%. With several of these dams exceeding 100% they are now above their capacity and surcharging (storing water above capacity.

Meanwhile, storages in the southern Basin have continued to steadily increase. As of 29 September 2021, southern Basin storages were holding 14,426 GL (89%). This is a 6% increase from 1 September when storages in the southern Basin were 13,538% (83%) and an increase from August 2021 when storages were 12,640 GL (78%).

Persistent rainfall across September saw the storage volume at Hume Dam continue to increase, rising to 97% as of 29 September 2021. Meanwhile, Menindee Lakes exceeded its capacity, increasing to 111%. Water is now making its way from Menindee Lakes down the Great Anabranch for the first time since 2017.

Climate outlook – The Bureau of Meteorology raises its ENSO status to La Niña ALERT

The Murray–Darling Basin is likely to experience wetter than average conditions between October and December 2021.

Continued cooling in the tropical Pacific Ocean and an increase in the number of climate models showing sustained La Niña conditions over summer has raised the chance of La Niña thresholds being met for 2021. The Bureau of Meteorology’s

El Niño–Southern Oscillation (ENSO) Outlook has been raised to La Niña ALERT. There is now a 70% chance of a La Niña event developing, which is triple the normal likelihood. A La Niña event will increase the chances of above average rainfall for the Basin during spring and summer.

A weak negative Indian Ocean Dipole (IOD) event is likely to continue through to late spring with levels then returning to neutral. Although weak, the negative IOD event is still likely to increase the chances of above-average spring rainfall across much of the Basin.

As a result, October to December is likely to be wetter than average for the Basin, with above-average rainfall expected. Near median to high stream flows are also expected leading up to November. Further rainfall is likely to increase the risk of flooding, particularly downstream of Hume Dam.

From October to December, nights are likely to be warmer than average across the Basin while days are expected to range from average to below average.

Please note that the ENSO Outlook was raised to La Niña ALERT after publication of the Climate and Water Outlook video from the Bureau of Meteorology.

Water quality

Water quality issues continue to be assessed, with an overall lower risk in line with seasonal expectations.

The MDBA and state authorities continue to monitor water quality across the Basin. For more information on water quality, and a map of threats, see the water quality page of our website.

Summary of key water quality issues

  • Blue-green algae: Many locations throughout the Basin are at risk of algal blooms. Conditions have the potential to change rapidly. For the latest information on blue-green algae alerts, contact the relevant state government contacts via the Getting information about current algal blooms page of our website.
  • Bushfire contamination remains a possible threat in the upper Murrumbidgee, upper Murray and Ovens catchments following rainfall. This risk will reduce as areas recover from bushfire damage.

Spotlight: Fresh flows revive ancestral path of Darling (Baaka)

Video: Water being released from Menindee Lakes is flowing into the Great Darling Anabranch, through Redbank Creek and Tandou Creek. (Sources: Video - Commonwealth Environmental Water Office, Audio - Ethereal by Alexander Nakarada ( Licensed under Creative Commons BY Attribution 4.0 License)

For the first time since 2017, water is flowing from Menindee Lakes down the Great Darling Anabranch.

Following much needed rain and high flows in parts of the northern Basin, the Menindee Lakes are now full and overflowing. The flows down the anabranch are a combination of releases to manage the high storage levels of the lakes and water for the environment.

The flows being released from Menindee Lakes will help golden perch migrate down to the River Murray and create additional feeding grounds for waterbirds. It is expected to take more than 8 weeks for this water to flow down the anabranch and into the River Murray.

On Friday 24 September Water NSW started releasing additional water from Menindee Lakes. Initially 1,000 megalitres of water per day was released from Lake Cawndilla. This was increased to 1,500 megalitres per day and then reduced to 1,000 megalitres per day on Thursday 14 October. As of 11 October 2021, Menindee Lakes was at 114% capacity.

The high levels in Menindee Lakes are also being used to ensure elevated and relatively stable flows are being delivered down the Lower Darling (Baaka) River.

These flows will support Murray cod breeding by inundating fish breeding habitat.

Golden perch don’t spawn every year and often need a fast-flowing pulse to cue their spawning. It is likely to have been several years since golden perch have spawned successfully in the Lower Darling (Baaka).

Towards the end of spring and into summer, there is potential for a pulse of water to be released from the Menindee Lakes down the Lower Darling (Baaka) River using water for the environment and/or operational releases.

Water managers will continue to consult with stakeholders throughout spring about the potential to release a pulse to cue golden perch spawning.

These flows are the result of cooperation between water managers from New South Wales, along with the Commonwealth Environmental Water Office, The Living Murray program, local scientists and community members.

For more information about the 2021 Lower Darling-Baaka and Great Darling Anabranch spring fish flows see the Commonwealth Environmental Water Office.

For more information about the Darling (Baaka) River: