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Highlights in this update

  • Much of the Murray–Darling Basin experienced above average temperatures in January
  • Water storage levels across the Basin remained steady in January
  • Cool and wet conditions are likely into early autumn thanks to La Niña
  • Spotlight story: Algal danger in bloom – blue-green algae red alerts
Temperature deciles for November 2020 to January 2021

Drought

La Niña has so far not delivered consistent rain to the northern Basin.

The northern Basin continues to swelter through a hot summer while some areas of Victoria and New South Wales in the southern Basin received record-high January daily rainfall in the first days of the new year.

Although La Niña has brought higher than average rainfall for much of the Basin, temperatures have remained high, with most temperatures across the Basin average to above average.

From January 23 to 26 the entire Basin experienced a heatwave with the Lower Darling, Lower Murray, and Paroo catchments reaching temperatures of more than 40 °C.

Rainfall totals for January 2021

Rainfall

January 2020 was warmer and wetter than average, with the BoM reporting that rainfall across the Murray–Darling Basin was 3% above the long-term January average of 57.9 mm.

Rainfall was widespread across the Basin at the end of January with Mount Buffalo and Falls Creek in the Victorian Alps recording 141 mm and 135 mm respectively. Meanwhile, Condobolin in New South Wales recorded 144 mm.

In the northern Basin, rainfall deciles were around average while in the southern Basin, rainfall deciles were mostly above average for January.   

The Bureau of Meteorology continues to advise that widespread and persistent rainfall is needed to lift areas out of deficiency, especially the northern Basin where total water storage levels remain low at 28%.

Water storage levels across the Basin for January 2021

Water storages and streamflow

Public water storages across the Basin were holding 11,398 GL (51%) as at 3 February 2021. This was down from 54% in December 2020 but 32% more than the same time last year. Public storages in the northern Basin were holding 1,316 GL (28%). This was a 1% increase from December 2020 when northern Basin storages were holding 1,281 GL (27%).

Many public storages in the northern Basin are now sitting above 30% with the exceptions of storages in the Border Rivers (Pindari Lake at 12%, Glenlyon Lake at 14%, Lake Coolmunda at 19%), and Gwydir (Lake Copeton at 20%).

As at 3 February 2021, southern Basin storages were holding 9,356 GL (57%). This is a decrease from the beginning of December 2020 when storages in the southern Basin were at 10,049 GL (62%).

In the northern Basin, summer rainfall allowed the Northern Waterhole Top-up to extend past its original target range. From December 2020 to January 2021, water was released from Pindari and Copeton Dams. By late January the flow extended from just downstream of Bourke to just upstream of Collarenebri, 3 times the distance of river it was originally expected to cover. A small portion of this water is expected to reach Menindee.

Climate outlook – La Niña conditions continue

The BoM forecasts that cool and wet conditions due to La Niña are likely to continue into early autumn.

So far summer rainfall has been mostly above average across the Basin – except the northern Basin where drought continues to persist.

Despite this, water storages in the Murray–Darling Basin have improved from last summer and are now sitting at 55%, compared to 32% in 2020.

La Niña is likely to break down during autumn with a return to neutral conditions by winter. Rainfall will begin to reduce in April, which is consistent with the decay of La Niña. However, from February to April, it is likely to be wetter than average across much of the Basin, including the northern Basin.

During February to April days are likely to be warmer than average for parts of the southern Basin, while nights are also likely to be warmer than average across the entire Basin.

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

Water quality

Water quality issues continue to be assessed, with some risk of hypoxic blackwater due to an ongoing forecast for wet conditions in the southern Basin and an increase in blue-green algae occurrence 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.
  • Blackwater threats are possible in several southern Basin rivers, including the potential for hypoxic blackwater in the Murray, Murrumbidgee and Lachlan Rivers. State governments and the MDBA are monitoring and considering these threats.
  • Low dissolved oxygen threat levels range from possible to likely for several locations in the Basin, including the Lachlan and Barwon–Darling Rivers, and the lower Darling around Menindee.
  • Bushfire contamination remains a possible threat in the upper Murrumbidgee, upper Murray and Ovens catchments following rainfall. This risk will lower as areas recover from bushfire damage.

Spotlight: Algal danger in bloom

It has been a summer of high-level algal warnings with toxic levels of blue-green algae being detected in several parts of the Murray–Darling Basin.

Red alerts remain in place for areas such as Copeton Dam near Inverell, the lower Murray River from Colignan to Merbein, and the lower Darling River below Menindee Lakes and downstream to Burtundy.

A red alert warning indicates that people should not undertake recreational activities like swimming and boating where they may come into direct contact with the water. Contact with the water can cause skin irritation and gastroenteritis, if consumed. The water can also pose a threat to livestock, wildlife and pets.

Algal blooms usually start as small green floating dots and develop into a thick scum on the water surface. They are often green, but can also be white, brown, blue, yellow or red. Potentially harmful blue-green algal blooms tend to occur when there are warm water temperatures and sunny days, low turbidity, and calm water conditions where water may stratify. It is not possible to predict how long the algae will remain at high levels.

Earlier this year, high-level red alerts were issued for Chaffey Dam near Tamworth, the lower Murray River downstream from Merbein to Lock 9, and upstream at Mount Dispersion. Some of these red alerts were recently cleared after ongoing monitoring indicated a decline in concentrations of blue-green algae. However, conditions can change rapidly, and it is not unusual for red alerts to be put back in place.

People who believe they may have been affected by blue-green algae are advised to seek medical advice. If you think you have seen blue-green algae, report it to your local council or water supplier.

The latest information on blue-green algae alerts is available from the relevant state government contacts via the Getting information about current algal blooms page on our website.


Image: Example of an algal bloom from the Loddon River (2010)