Rainfall deficiencies and water availability

Deficiencies ease in many affected areas following March rainfall

Above average rainfall for March 2021 resulted in a substantial lessening of deficiencies across much of Western Australia, and the southeast quarter of Queensland. However some pockets of rainfall deficiencies remain in southwest Western Australia and in some coastal areas in southern Queensland.

Rainfall in the past month has contributed further to gradual recovery from longer term multi-year rainfall deficits in parts of Western Australia, while in Queensland, shorter term deficits have eased but multi-year rainfall deficits persist. 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 8 April, indicates rainfall during May to July is likely to be below average across parts of northern Australia, though we are coming into the drier time of the year in that region. Some parts of the eastern Australia quarter are showing increased liklihood of below average rainfall.

12-month rainfall deficiencies

In Western Australia, areas of rainfall deficiencies have substantially reduced to small pockets compared to last month's Drought Statement following above average March rainfall. Serious or severe rainfall deficiencies for the 12-month period April 2020 to March 2021 remain in pockets of the Central West, Great Southern and Goldfields districts.

In Queensland, following above average March rainfall in the state's south, the areas and intensity of rainfall deficiencies have also lessened substantially. Deficiencies still remain in the Capricornia and Wide Bay and Burnett districts.

Extended dry conditions over eastern Australia

Australia has experienced a prolonged period of below average rainfall spanning several years.

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, though rainfall in 2020and in early 2021 has seen improvement across many areas. Above-average February and March rainfall has eased longer-term deficiencies in the inland west of Western Australia. In Queensland and New South Wales into South Australia the severity of multi-year rainfall deficiencies has also eased with March rainfall easing shorter term deficiencies in northern parts of the Murray–Darling Basin and providing increases to water storages in that region, though storage levels in south-east Queensland remain low.

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 further renewing water storages). Recent improvement to water storages in northern parts of the Murray–Darling Basin, have provided some recovery. With saturated catchments further rainfall will continue to assist in replenishing water storages.

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 across south much of Victoria, southern parts of South Australia, the Cape York Peninsula in Queensland, the Top End in the Northern Territory, and the Pilbara and Gascoyne districts in Western Australia.

Soil moisture was below average for part of eastern Queensland extending from around Mackay into the Wide Bay and Burnett region. Below average soil moisture emerged in western Victoria. 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 parts of west and east of Western Australia.

The influence of very low rainfall over longer timescales is still evident in the 18-month soil moisture for October 2019 to March 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. In areas

  • Rainfall deficiencies have eased in Queensland, and are now confined to coastal areas of the south
  • Deficiencies have also eased further in parts of south-western to central regions of Western Australia, with only small pockets remaining
  • 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 increased significantly while in northern Australia they reached above 80% of accessible capacity
  • South-east Queensland storages remain low while Sydney's major storage spills following March rainfall

Storage levels in the northern Murray–Darling Basin increased significantly

Significant amounts of rainfall which occurred in the second half of March have greatly increased soil moisture levels to very much above to above average in most of the Murray–Darling Basin, especially in the north. This has brought relief to drought affected catchments including the Border Rivers, Namoi and Gwydir in New South Wales. Saturated soil moisture conditions facilitated runoff and inflows to the northern storages.

The total water storage in the Murray–Darling Basin increased in March to 57% of capacity at the end of the month, an increase of 3.8% of capacity since last month. Compared to the same time last year, when capacity was only 33%, the total storage volume remains in a significantly better position.

During March, the highest and third highest daily increases in combined storage volumes were experienced in the northern Basin since 1993. Total water storage in the northern Basin increased significantly by 21% to 47.1% of capacity (2,179 GL) at the end of March, which is much higher than the same time last year when it was only 13.6%. In response to the above to very much above average rainfall occurring over much of the northern Basin in March, all the storages increased. The greatest increase was for Chinchilla which had fallen to zero accessible storage and rose to 91% of accessible storage. Coolmunda (+84%) and Lake Kajarabie (Beardmore Dam) (+51%) have reached their full accessible capacity. Other storages observing significant increases in volume are Pindari (+36%), Glenlyon (+35%), Keepit (+23%), Copeton (+22%), Leslie (+17%), Burrendong (+16%), Split Rock (+15%), and Chaffey (+15%).

Despite above to very much above average rainfall across the New South Wales part of the southern Basin, the total storage in the southern Basin remains almost the same as last month; at 59% (12,149 GL) of capacity which is still significantly higher than March 2020 when it was only 37.1%. The highest percentage increase in the volumes of the major storages in March were for Burrinjuck (19%), and Wyangala (10%).

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 continued to increase significantly and reached above 80% of accessible capacity

The northern Australian monsoon season commenced in December and since then above average rainfall has occurred. In response, the volume of water in two of the major water storages in northern Australia has increased significantly. Water levels in Lake Argyle, the largest water supply storage in Australia (10,400 GL) increased significantly this year after the past three failed wet seasons. This year's monsoon started to bring relief and the gradual wet season filling escalated in March to increase Lake Argyle's storage volume by 26.6% to reach 82.1% of accessible capacity. In a similar way, the Darwin River storage increased by 10.4% in March to reach 90.5% of its capacity.

South East Queensland storages remain low

Despite good rainfall across most of the continent, the storages in south eastern Queensland did not benefit from the rainfall in March. The volume of water in the largest storage in the area, Wivenhoe, had a very minor increase to reach 36.9% of capacity at the end of the month. This is the opposite to Sydney where storage volumes reached close to full capacity with the major storage for the city - Warragamba Dam - spilling for a few days.

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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