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Highlights in this update

  • Persistent rainfall has continued to benefit the Murray–Darling Basin, helping to ease deficiencies
  • Water storages across the Murray–Darling Basin remain – Menindee Lakes at 110% capacity
  • The 2021–22 La Niña event continues to weaken
  • Spotlight story: Basin storages at record highs during ongoing wet

Drought

Persistent rainfall across the past 6 months has continued to benefit the Murray–Darling Basin, further easing deficiencies.

As of 27 April 2022, whole of Basin water storages were sitting at 89%, a significant increase from the same time last year when storages were sitting at 54%. The northern Basin has particularly benefited from strong rainfall across the 6 months with almost all its water storages now above 90% capacity.

As shown in the graphic on the left, rainfall has also had positive results for soil moisture across the Murray–Darling Basin. Soil moisture in the Basin is now mostly average to above average, with small areas showing signs of below average and very much above average.

According to the Bureau of Meteorology, although the 2021–22 La Niña event is weakening atmospheric indicators remain above La Niña thresholds. This means that La Niña is likely to continue influencing rainfall in the Murray–Darling Basin as we enter winter.

Rainfall deciles for April 2022

Rainfall

April 2022 saw strong rainfall across much of the Murray–Darling Basin, with central parts of the Basin recording above average to very much above average rainfall.

As shown in the graphic on the left, parts of the southern and northern Basin recorded below average to above average rainfall. This is an improvement from March 2022 when most of the Basin received average rainfall.

The April 2022 rainfall has helped reduce serious to severe rainfall deficiencies across the Murray–Darling Basin for the period of December 2021 to April 2022. Good rainfall has also seen water storages in both the southern and northern Murray–Darling Basin remain at high levels with whole of Basin storages at 89% as of 27 April 2022.

In the northern Murray–Darling Basin, towns like Warwick and Toowoomba in Queensland continued to receive high rainfall similar to March 2022. Warwick received 94.6 mm – the town’s highest April rainfall since 2010, while Toowoomba received 39.2 mm. Warwick also recorded its highest daily rainfall total for April at 66.2 mm on 4 April 2022.

Meanwhile in the southern Murray–Darling Basin, rainfall mostly ranged from average to very much above average. Towns like Shepparton, Bendigo and Yarrawonga in Victoria all recorded high rainfall at 78.2 mm, 90.2 mm and 43.8 mm respectively.

Extreme April temperatures were also recorded in Victoria during April 2022. Mildura recorded the warmest days on average at 24.4 °C, while Mount Buller recorded the coldest day on 30 April at 2.2 °C.

Water storage levels across the Basin as at 27 April 2022

Water storages and streamflow

Public water storages across the Murray–Darling Basin remained steady across April and were holding 19,726 GL (89%) as of 27 April 2022.This is similar to 13 April 2022 when whole of Basin storages were at 19,705 GL (89%).

Public storages in the northern Basin decreased slightly from early April 2022 and were holding 4,477 GL (95%) as of 27 April 2022. Most public storages in the northern Basin were at 100% capacity or more as of 27 April 2022. In the Border Rivers catchment, Pindari Lake was at 100% while Lake Coolmunda dropped slightly from 100% to 99%. In the Macquarie catchment, Lake Burrendong was at 109%, while in the Condamine–Balonne catchment, Chinchilla Weir dropped from 130% capacity 13 April to 105% on 27 April.

Many northern Basin dams continue to exceed 100% of their capacity and are surcharging. WaterNSW is continuing to manage the risk of flooding. Split Rock Reservoir (72%) in the Namoi catchment and Lake Windamere (55%) in the Macquarie catchment remain the only 2 water storages in the northern Basin that are sitting below 80%.

Meanwhile, storages in the southern Basin have remained consistent at 14,080 GL (86%) as of 27 April 2022.

As of 27 April 2022, Hume Dam was sitting at 86% while Menindee Lakes was continuing to spill at 110%. The volume of water in Hume Dam has remained steady, with increased inflows and reduced releases due to continued reduction in downstream irrigation demands.

Water releases continue from Menindee Lakes to manage airspace. Upstream of Menindee Lakes, heavy rainfall over the past few months in southern Queensland and northern News South Wales has resulted in higher flows across the Barwon Darling River system. WaterNSW is forecasting a further 600 to 1,000 GL of inflow to the Menindee Lakes system by the end of June 2022.

Climate outlook – La Niña weakens

The Bureau of Meteorology’s latest outlook indicates that the 2021–22 La Niña is continuing to weaken. However, atmospheric indicators remain above La Niña thresholds, meaning La Niña’s influence continues with above average rainfall likely for parts of the Murray–Darling Basin.

Models indicate an increased chance of a negative Indian Ocean Dipole developing, which typically brings more rainfall to the southern Basin.

The current outlook indicates that above average rainfall is likely across most of the Murray–Darling Basin from May to July 2022. Much of the Basin is also likely to experience high streamflow and this combined with already wet soils means there is a chance for flooding in some parts of the southern Basin.

From May to July 2022, overnight temperatures are likely to be warmer than average, while daytime temperatures are likely to be cooler than average for most of the Basin.

Summary of threats to water quality in the Basin - May 2022

Water quality

Water quality issues continue to become less of a concern as we move out of the higher risk summer and early autumn period.

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. To report a water quality issue see the water quality contacts page of our website.

Summary of key water quality issues

  • Hypoxic blackwater: It has been several years since large flooding events last occurred in the Murray, Murrumbidgee and Edward–Wakool systems, with an anticipated high load of organic matter and carbon on the floodplains. Although storages and flows remain high and there are continuing La Niña conditions, cooler weather will reduce the risk of hypoxic blackwater events.
  • Low dissolved oxygen: With the onset of cooler weather, the risk of low dissolved oxygen conditions has reduced across the Basin.
  • 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 continues to lower as areas recover from bushfire damage.

Spotlight: Basin storages at record highs during ongoing wet

Image: Main Weir on the lower Darling (Baaka) River at Menindee passing around 3,000 ML/day. Credit: Craig Symonds


Did you know the amount of water in the Murray–Darling Basin’s storages is at the highest level since 1979, when Dartmouth Dam was built?

The prolonged period of above-average rainfall driven by the La Niña conditions has filled dams across the Basin keeping all river operators on high alert.

The sustained falls of recent weeks, particularly in the north, come even as the ongoing La Niña pattern weakens. And there is more on the way, with the intense rain forecast for northern Queensland this week moving south into parts of the Basin. With catchments already wet, there is potential for flash flooding, and large parts of Queensland remain on flood watch.

At Hume Dam upstream of Albury, the MDBA's river operations team has been actively managing the dam since August 2021. River operators have successfully managed airspace and inflows through the dam, mitigating the impacts on downstream communities while maximising water availability. It’s been a major juggling act that was assisted by the MDBA’s strong partnership with the BoM forecasters and WaterNSW. We have kept the community informed each step of the way.

The water that has flowed down from the northern Basin into Menindee Lakes has been keenly watched – it’s been the first big flush in a decade. As far as the MDBA is concerned, the amount of water in the Murray system means the MDBA is unlikely to need to draw water from Menindee Lakes any time soon. 

Going into winter with this much in storage means we’ll be keeping a careful watch on any need to make pre-emptive releases to create airspace and reduce the risk of flooding, while keeping local communities well informed. 

The BoM is recommending communities in flood warning areas stay up to date with warnings via the Bureau's website or Weather app and follow the advice of emergency services.