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Highlights in this update

  • The northern Murray–Darling Basin experienced above average rainfall across March 2021
  • Water storages improved in the northern Basin but decreased slightly in the southern Basin
  • El Niño–Southern Oscillation (ENSO) returns to a neutral state
  • Spotlight story: Flooding in the northern Basin
Mean temperature anomaly for March 2021

Drought

Above average rainfall in March has helped ease shorter-term deficiencies in the northern MurrayDarling Basin, increasing water storages in the north to 2,264 GL (48%).

However, water storage levels in south-Queensland remain low with the Bureau of Meteorology maintaining that more widespread, above-average rainfall is needed to lift some areas of the northern Basin out of deficiency. This demonstrates that consistent rainfall is still needed to end the long-term drought in the northern Basin.

In contrast to February 2021, much of the Basin experienced below average temperatures across March, with temperatures 1 to 3 degrees below average. Some areas of the northern Basin even recorded very much below average temperatures, while parts of the southern Basin in the Lower Murray region recorded average temperatures.

Rainfall totals for March 2021

Rainfall

In contrast to previous months, the northern Basin received above-average rainfall during March 2021, while in the southern Basin rainfall remained mostly average.

Across the northern Basin, rainfall deciles ranged from above average to highest on record. Areas such as Goondiwindi, Toowoomba, and Dalby in Queensland received very much above average to highest on record rainfall. Goondiwindi received 165.6 mm of rain during March, while Toowoomba received 179.2 mm, and Dalby 172.2 mm.

Meanwhile in the southern Basin, rainfall deciles were mostly average with areas such as the Mallee in north-west Victoria recording less than 10 mm for the month, while towns like Pinnaroo in South Australia recorded below-average rainfall. In contrast, Kyabram in northern Victoria received 76.8 mm of rain during March 2021, up from 30.1 mm in March 2020.

Summary of water in storage as at 31 March 2021

Water storages and streamflow

Public water storages across the Basin were holding 12,156 GL (55%) as at 31 March 2021. This was up from 50% in February 2021.

Public water storages in the northern Basin were holding 2,264 GL (48%). This is a significant increase from the start of March 2021 when northern Basin storages were holding 1,286 GL (27%).

Despite this, some public water storages in the northern Basin remained below 30% at 31 March 2021. In the Condamine–Balonne catchment, Coby Creek Reservoir was 19%, while Lake Leslie was 28%. In the Namoi catchment, Split Rock Creek Reservoir was 29%.

Meanwhile, storages in the southern Basin are slightly down from the start of March 2021. As at 31 March 2021, southern Basin storages were holding 9,033 GL (55%). This is a 1% decrease from 3 March 2021 when storages in the southern Basin were 9,110 GL (56%) and is also a decrease from the beginning of February 2021 when storages were 9,356 GL (57%).

In the southern Basin water quality is still being impacted by blue-green algae with the Murray and Lower Darling Regional Algal Coordinating Committee declaring several red and amber alerts. Red alert warnings are in place on the River Murray between the Darling River and Mount Dispersion. Amber alerts are in place at several sites on the River Murray and along the EdwardWakool River system. The locations of these sites are available on the WaterNSW website.

Climate outlook – La Niña weakens

 

The El Niño–Southern Oscillation (ENSO) has recently returned to neutral with La Niña coming to an end. As we head further into autumn ENSO neutral conditions will continue with little likelihood of a return to La Niña in the coming months.

According to the Bureau of Meteorology April is likely to be the wettest month, while rainfall for May to July is predicted to be below average for parts of the Murray–Darling Basin.

Rainfall in March was above average for the northern Basin allowing water storages to rise from 27% at the start of March to 48% as of 31 March.

Rainfall during April is likely to lead to wet catchments and high streamflow in the northern Basin, which could cause further flooding.

The Bureau of Meteorology also predicts that daytime temperatures from April to June are likely to be average to cooler than average for much of the Murray–Darling Basin. However, temperatures at night are likely to be warmer than average.

Summary of threats to water quality in the Basin - April 2021

Water quality

Water quality risks continue to be assessed. In line with seasonal expectations, the risk of hypoxic blackwater is now lowering and blue-green algae occurrences are gradually decreasing.

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 or join us for a webinar focused on Water quality in the Basin on Tuesday, 20 April.

Summary of key water quality issues

  • Blue-green algae: Many locations throughout the Basin are at risk of blue-green 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.
  • Blackwater threats are possible during warmer conditions in several southern Basin rivers, including the potential for hypoxic blackwater in the Murray, Murrumbidgee, Edward-Wakool and Lachlan Rivers. State governments and the MDBA are monitoring and considering these threats.
  • Low dissolved oxygen threat levels are lowering in line with seasonal conditions and improved flows through numerous catchments across the Northern Basin and Barwon–Darling Rivers.
  • Bushfire contamination remains a possible threat in the upper Murrumbidgee, upper Murray and Ovens catchments following rainfall. This risk will decrease as areas recover from bushfire damage.

Spotlight: Bushfires leave an unwanted legacy

Image slider (above): The flooding of the northern Basin between Goondiwindi and Mungindi is clear in this slider image that shows the area before the rain on 3 March 2021 and after the rain on 28 March 2021.


The northern Murray–Darling Basin received substantial rainfall starting in mid-March 2021 which resulted in flooding in some areas and additional flows down the Darling River.

The rain has been welcomed by some northern Basin communities who have endured years of drought but are now seeing rivers flowing again.

The flooding was caused by a surface trough which produced widespread rainfall across central and southern Queensland, and inland and northern parts of New South Wales.

The Macquarie–Castlereagh and Condamine–Balonne systems, both experienced rainfall of more than 150 mm across large areas between 17 and 24 March.

The Gwydir and Border Rivers systems also experienced heavy rainfall between 17 and 24 March, with both areas receiving more than 100 mm.

Significant rainfall resulted in Beardmore Dam in the Condamine–Balonne system increasing from 44% to 99% as of 24 March, while in the Border Rivers system, the Pindari Lake storage doubled from 13.3% on 17 March to 26.6% on 24 March.  

The Namoi, Paroo, and Warrego systems also experienced substantial rainfall, with water storages increasing in these catchments.

The southern Basin is also benefiting with the drought-stricken Lower Darling (Baaka) receiving flows from the Barwon–Darling tributaries.

These flows arrived at Wilcannia on 25 March, and at Menindee in late March, marking the biggest flows the Darling (Baaka) River has experienced since 2016.

Water NSW has estimated the inflows into the Menindee Lakes could reach a total of 450 – 650 GL. As of 31 March, Menindee Lakes storage was holding around 300 GL (17 %). When the volume in Menindee Lakes reaches 640 GL, the water becomes a shared resource with Victoria and is drawn on by the MDBA to fulfill downstream demands in the River Murray System.

While flowing rivers are welcome, multiple water quality risks arise when rivers receive flows after a long dry period. In this event, there are two risks that are being monitored:

Depending on the extent of the floods and the temperatures experienced across the northern catchments over the coming weeks, there may be a risk of hypoxic blackwater. It is possible that blackwater events will eventuate due to the initial poor water quality as flows return and channels and floodplains are flushed.