Drought
Rainfall deficiencies and water availability

Short-term deficiencies emerge in south-east Australia

Rainfall for May 2021 was average to below average for most of mainland Australia with respect to the 1961–1990 standard averaging period. For Queensland's Capricornia, Wide Bay and Burnett districts, where serious or severe rainfall deficiencies have been present since 2020, May rainfall was generally below average. Below average May rainfall also contributed to an increase in short-term deficiencies in western Victoria into New South Wales and South Australia.

Rainfall deficiencies present since the drought of 2017-2019 remain over very large parts of the country and may persist for some time.

The Climate Outlook released 3 June 2021 indicates that June to August rainfall is likely to be above average for much of the eastern two-thirds of mainland Australia, while areas in the west of Western Australia and western Tasmania may experience below average rainfall. Winter is the dry season for northern Australia, therefore above average rainfall totals are unlikely to relieve any rainfall deficiencies.

4-month rainfall deficiencies

May 2021 rainfall was below average for large areas of western Victoria, south-west New South Wales, and central eastern South Australia which has led to the emergence of short-term (4-month) rainfall deficiencies in these regions. Serious and severe rainfall deficiencies for the period February 2021 to May 2021, compared to all years since national records began in 1900, have emerged in a large area covering western Victoria, southwestern New South Wales and central eastern South Australia. As we are coming into an important time of the year for agriculture in these regions, these deficiencies will be monitored closely.

14-month rainfall deficiencies

Rainfall for large parts of Queensland was below average during May 2021, adding to deficiencies present in two regions since April 2020. Serious or severe rainfall deficiencies for the period April 2020 to May 2021, compared to all years since national records began in 1900, persist in the Capricornia and Wide Bay and Burnett districts and extend west into the Central Highlands District in Queensland. Deficiencies have also increased in extent and severity in areas around Bundaberg and Boulia.

Extended dry conditions over eastern Australia

Multi-year rainfall deficiencies accumulated over the period 2017 – 2019 and their impact on the Murray–Darling Basin are discussed in Special Climate Statement 70. The strip along the west and south coasts of Western Australia was also affected by rainfall deficiencies over this period.

Steady recovery from the drought has occurred over parts of eastern Australia since La Niña started to develop in mid−2020, but further periods of above average rainfall are needed to continue the recovery, especially in parts of Queensland, coastal south-west Western Australia, parts of South Australia and far west New South Wales.

Rainfall in 2020 and in early 2021 saw improvement across many areas, though April and May were drier than average across much of mainland Australia, and particularly in the south-east. Many areas experiencing rainfall deficiencies for periods longer than 24 months have typically experienced below average rainfall between April and October.

The role of climate change in rainfall reduction over southern Australia and along the Great Dividing Range is discussed in State of the Climate 2020. Parts of south-west, south-east, and eastern Australia—including parts of south-east Queensland and southern and eastern New South Wales—have seen substantial declines in cool-season (April to October) rainfall in recent decades.

Soil moisture

Over the past month, root-zone soil moisture (soil moisture in the top 100 cm) has decreased for much of southern mainland Australia.

Soil moisture was below average for western Victoria, south-west New South Wales, and south-east South Australia, where below average May rainfall was recorded. Parts of Queensland have seen below average soil moisture continue.

• Rainfall deficiencies remain in Queensland at the 14-month timescale and are emerging in parts of south-east Australia
• Accumulated rainfall deficits at multi-year timescales remain significant in many parts of Australia, and may persist for some time
• Water storage levels continued to improve in the northern Murray–Darling Basin following record March rainfall
• Menindee Lakes water storage levels reached their highest level in four years
• South East Queensland storages remain low

Water storage levels continued to improve in the Murray–Darling Basin

Following rainfall in March and April, the northern Murray–Darling Basin soil moisture levels were above average in the east but below average in the west. In the southern Murray-Darling Basin, soil moisture was below average to very much below average due to average to below average rainfall in May. Where soils are wetter than average further rainfall can lead to larger increases in water storages than in drier than average areas.

The total water storage (accessible) in the Murray–Darling Basin increased in May to 59% of capacity at the end of the month, an increase of 3% of capacity since the last month. Compared to the same time last year, when the total storage volume was only 40%.

In the northern Basin the total water storage increased by 0.4% to 49.3% of capacity (2 288 GL) at the end of May, which is much higher than the same time last year when it was only 17.3%.

Although May rainfall was average to below average across most of the southern Basin except for a small area in the east, the total storage in the southern Basin increased in May by 3.7% to 61.3% (12 673 GL). This is significantly higher than the storage situation at the same time last year when it was only 44.8%.

Floodwaters from the end of March rainfall in the northern Murray-Darling Basin have continued to make their way to fill the Menindee Lakes system. The total storage volume has reached 51.9%, an increase of 21.2% since last month, and the highest level in four years. In response to the recent dry condition across the southern Basin, water is now being released from Menindee lakes into the lower Darling River.

Further detail on individual Murray–Darling Basin catchments can be found in the fortnightly Water Reporting Summaries for MDB Catchments.

South East Queensland storages remain low

In South East Queensland, the largest storage, Wivenhoe, which has experienced significant declines in water levels over the past three years, increased by 0.6% in May to reach to 41.9% of capacity. This is significantly lower than the 49.3% storage of the same time last year.