Rainfall deficiencies and water availability

Little change to rainfall deficiencies in Queensland; April rainfall low for south-east Australia

Rainfall for April 2021 was below average for most of mainland Australia, and for New South Wales it was the equal-eighth-driest April on record and for South Australia it was the seventh-driest April on record. Rainfall for the month was above average for Queensland's Cape York Peninsula and adjacent northern Queensland, and around most of the west and north-west coast of Western Australia. For the areas of Queensland's Capricornia and Wide Bay and Burnett districts, where serious or severe rainfall deficiencies exist, April rainfall was mostly close to average resulting in little change in existing deficiencies.

Deficiencies for the periods January 2017 to present and January 2018 to present still exist over very large parts of the country. More rainfall is needed over an extended period to continue the recovery from the extended dry conditions of 2017 to 2019.

The Climate Outlook, issued 6 May 2021, indicates that June to August rainfall is likely to be above average for much of the eastern two-thirds of mainland Australia. Areas in the west, north and far south-east of Australia have roughly equal chances of above or below average rainfall. Winter is generally a drier time of the year for northern Australia.

At the 3-month timescale, February–April 2021 rainfall was below average for large areas of western Victoria, south-west New South Wales, and south-east South Australia although, as mentioned, these months typically see low rainfall totals in areas such as Victoria's Mallee and South Australia's Mid North.

The Bureau will continue to monitor rainfall over the coming month and season, particularly in parts of south-east Australia which typically see their transition from the climatologically driest part of the year during January to April to wetter conditions in the cool season, from May.

13-month rainfall deficiencies

Serious or severe rainfall deficiencies for the 13-month period April 2020 to April 2021 persist in the Capricornia and Wide Bay and Burnett districts in Queensland. While areas further north largely received above average rainfall for the month, for areas of Queensland with serious or severe rainfall deficiencies, rainfall was mostly close to average. Compared to the previous Drought Statement, deficiencies have increased in the south of the region, extend further inland in the north, and have lessened around the south-west of the Capricornia District.

Extended dry conditions over eastern Australia

Australia has experienced a prolonged period of below average rainfall spanning several years. Persistent, widespread, above average rainfall is needed to further lift areas out of deficiency at the multi-year timescales and provide relief from the impacts of this long period of low rainfall, such as by further recharging water storages.

Rainfall deficiencies have affected much of Australia since January 2017. Multi-year rainfall deficiencies and their impact on the Murray–Darling Basin are discussed in Special Climate Statement 70 and the dry conditions over Eastern Australia for the period commencing January 2018 are described in Special Climate Statement 66. The strip along the west and south coasts of Western Australia has also been affected by rainfall deficiencies for the periods commencing January 2017 and January 2018.

For periods longer than 24 months, the greatest impact of the prolonged below average rainfall has been in the cooler months of April to October. Rainfall in 2020 and in early 2021 saw improvement across many areas, though April was drier than average across much of mainland Australia and particularly the south-east.

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 rainfall in recent decades.

Soil moisture

Compared to last month, root-zone 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, and for a large area stretching from south-east Western Australia into the interior of that state.

Soils were wetter than average for the month across much of New South Wales except in the south-west, southern parts of Queensland, the northern parts of South Australia, the south and west of the Northern Territory, and the Kimberley and parts of the west coast of Western Australia.

The influence of very low rainfall over longer timescales is still evident in the 19-month soil moisture for October 2019 to April 2021, which was very much below average over large areas, predominantly in the southern half of Western Australia, but also in parts of Queensland extending from the east coast through central and northern Queensland to the Northern Territory border, and in western Victoria.

  • Rainfall deficiencies in Queensland similar to those for the period to March 2021
  • Accumulated rainfall deficits at multi-year timescales remain significant in many parts of Australia, and may persist for some time
  • Water storage levels in the northern Murray–Darling Basin continued to increase during April
  • Northern Australia water storage levels remained above 80% of accessible capacity during April
  • South East Queensland water storage levels remain low
  • Groundwater levels have improved in the Murray–Darling Basin and northern Australia

Storage levels in the northern Murray–Darling Basin continued to increase

In response to heavy rainfall that fell over the northern Murray–Darling Basin during the second half of March, soil moisture levels remain above average to very much above average in April. This has brought great relief to the drought affected areas in the New South Wales Border Rivers, Namoi and Gwydir catchments. In contrast, soil moisture levels were below average to very much below average in the southern Murray–Darling Basin due to the below average to very much below average rainfall in April.

The total water storage in the Murray–Darling Basin decreased slightly in April. Total storage was 56% of capacity at the end of the month, a decrease of 1% of capacity since the last month. Compared to the same time last year when the total storage volume was only 35%, the water storages are in a significantly better position.

Total water storage in the northern Basin increased by 1.5% to 48.9% of capacity (2, 271 GL) at the end of April, which is much higher than the same time last year when it was only 16.7%. The greatest increase was for Chinchilla which reached 99% of accessible capacity. Coolmunda and Lake Kajarabie (Beardmore Dam) remained close to their full accessible capacities at the end of April. Other storages observing increases in volume are Glenlyon (+5%) and Keepit (+5%). Despite the general increase, some storages like Split Rock, Windamere, Leslie and Cooby Creek were less than 35% full and other storage such as Copeton and Pindari are less than 50%.

Although above to very much above average rainfall fell across the New South Wales part of the southern Basin in late March, the total storage in the southern Basin (where the major storages are located) dropped by 1.2% to 57.6% of capacity at the end of April. This is, however, significantly higher than the storage situation at the same time last year when it was only 39.8%. The highest percentage decrease in the storage volumes in April were for Lake Buffalo (−9%), Upper Coliban (−9%), Burrinjuck (−8%), Hume (−6%), Lake Nillahcootie (−6%) and Lake Eildon (−4%). However, despite the overall decline, some individual storages like Bendora, Googong, Corin and Cotter, were close to their full capacities.

Floodwaters from record rainfall in the northern Murray–Darling Basin at the end of March have started to reach the Menindee Lakes and the storage volume has increased by 13.5% to 30.7% of capacity at the end of April. Significant increases in storage volumes were also observed in Lake Wetherell (+40%) and Lake Pamamaroo (+28%).

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

Major storage levels in the Murray-Darling Basin
Major storage levels in the Murray–Darling Basin
MDB south storage levels
MDB south storage levels
MDB north storage levels
MDB north storage levels

Northern Australia water storage levels recovered during the wet season and remained above 80% of accessible capacity in April

The northern Australian monsoon season commenced in December and officially finished in April bringing above average rainfall in northern parts of Northern Territory and northeastern Western Australia. In response, the volume of water in two of the major water storages in northern Australia has increased significantly during this wet season.

Water levels in Lake Argyle, the largest water supply storage in Australia (10,400 GL) had been decreasing since September 2017 as the past three wet seasons had not delivered significant inflows to the storage. Lake Argyle was at 25% of accessible capacity by the end of November 2020, the lowest level in almost 30 years. This year's monsoon brought relief and the Lake Argyle's storage volume reached 82.1% of accessible capacity by the end of March. Total water storage in the Lake Argyle decreased by 1.6% to 80.5% of capacity (8,398 GL) at the end of April, but is still 37.1% of capacity higher than the same time last year.

The normal filling and spilling of the Darwin River storage did not occur for the past two wet seasons (2018–19 and 2019–20). The accessible volume dropped to 50 per cent of capacity in December 2020, the lowest level in more than 10 years. Due to above average rainfall during the wet season the storage volume reached 94.3% of capacity at the end of March and remains at 93.5% at the end of April. This is significantly higher than the storage situation same time last year when it was only 72%.

South East Queensland storages remain low

In South East Queensland, the largest storage, Wivenhoe, which has decreased significantly in the past three years, increased by 4.4% in April to reach to 41.3% of capacity, but is significantly lower than the same time last year when it was 51.2%.

Groundwater levels are showing signs of recovery in the Murray–Darling Basin and have recovered in northern Australia

The drought in the Murray–Darling Basin (MDB) since 2017 resulted in widespread declines in groundwater levels in the MDB due to increased pumping and reduced or no recharge. In 2020–21 groundwater levels started to show signs of the usual annual recovery, although the response is still mixed. However, the full impact of the floods on groundwater levels the northern part of the Basin (e.g. Lower Namoi bore) will not be fully observed for a while due to the delayed response of groundwater.

In contrast, groundwater levels in the more responsive limestone aquifers in northern Australia have recovered due to the increased recharge during this wet season. Groundwater levels in the Tindall Limestone aquifer near Katherine peaked in late-February 2021 (increased by 5 metres) and again in March 2021 following very high rainfall during those months, before starting to drop in April. Prior to the 2020–21 wet season, groundwater levels were the lowest in more than 20 years as almost no recharge occurred during the 2018–19 and 2019–20 wet seasons due to the low rainfall received.

Product code: IDCKGD0AR0

A very dry month for the southeastern mainland increases rainfall deficiencies
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Soil moisture data is from the Bureau's Australian Water Resources Assessment Landscape (AWRA-L) model, developed through the Water Information Research and Development Alliance between the Bureau and CSIRO.
See: Australian Landscape Water Balance.

This section displays rainfall maps. Current drought status is described in the previous section. For historical drought status statements, go to archive of drought statements

Also available at Maps – recent conditions

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