Rainfall deficiencies and water availability
Australia's third-driest June on record increases rainfall deficiencies
Rainfall during June 2020 was below average for most of Australia, although large areas of the east and north had close to average rainfall. Nationally, June was the third-driest on record for the country as a whole, behind only June 2017 and June 1940. It was also Australia’s third-warmest June on record for mean maximum temperature.
This drier than average June has seen short-term rainfall deficiencies over the west of the country increase in both severity and spatial extent, and from this month the 3-month (April–June 2020) period will be included in the Drought Statement.
Rainfall deficiencies at the 27-month timescale (since April 2018) have also seen an increase in severity or extent over large areas this month.
The Bureau of Meteorology also monitors rainfall deficiencies, and impacts on water resources, on longer timescales such as the current severe multi-year drought affecting large parts of eastern Australia. This is discussed further below, and in more detail in our Special Climate Statements.
The Climate Outlook for August to October, to be issued 9 July, indicates an increased chance of wetter than average conditions across most of the eastern two thirds of Australia.
The Bureau will continue to closely watch and report on observed rainfall and seasonal outlooks over coming months. While the current state of climate drivers and antecedent conditions is quite different for much of the country than at the same point in 2019 or 2018, it remains important to monitor evolving conditions as the warmer months approach.
The role of climate change in rainfall reduction over southern Australia and along the Great Dividing Range is discussed in State of the Climate 2018 which shows that parts of southwest, southeast and eastern Australia, including parts of southeast Queensland and southern and eastern New South Wales, have seen substantial declines in cool-season rainfall in recent decades.
3-month rainfall deficiencies
April usually marks the start of the wetter cool season in the southern half of Western Australia, however this year April rainfall was below average over the west and south of Western Australia. May also brought below average rainfall over much of southern Western Australia, though the southern half of the South West Land Division saw mostly close to average rainfall. June rainfall was below average for most of Western Australia.
The southern wet season spans April to November; most of southern Australia receives the bulk of its annual rainfall during these cooler months. The poor start to the southern wet season is concerning in Western Australia, and follows very much below average rainfall over much of the south of the State during April–November 2019. Consecutive poor wet seasons in agricultural regions can amplify the impact of rainfall deficiencies on economic and social systems.
Serious or severe rainfall deficiencies for the 3-month period are in place in Western Australia across most of the southwestern half of the State. Areas of the northwestern Gascoyne and much of the southern half of the South West Land Division which are not experiencing serious rainfall deficiencies (i.e. rainfall in the lowest 10% of historical observations for the period) have received rainfall in the lowest 20% of historical observations for the period, and are just outside the threshold.
Serious rainfall deficiencies are also in place across parts of central southern and southeast Queensland, mostly as a result of below average rainfall during April and May. Other small areas are also experiencing serious rainfall deficiencies including the extreme south cost of New South Wales, the southwest of the Alice Springs District in the Northern Territory, and pockets of southwest and northern South Australia.
27-month rainfall deficiencies
Rainfall deficiencies at the 27-month timescale, from April 2018 to June 2020, have increased over the west of Western Australia, much of South Australia, northeastern New South Wales, and southeast Queensland following below average June rainfall over most of Australia.
Serious to severe rainfall deficiencies are in place for the 27-month period across the South West Land Division, much of the west of the Gascoyne and Pilbara, along the south coast of Western Australia, the northern tip of the Kimberley, the east of the Interior District, and pockets throughout the inland areas of the State. Deficiencies are also in place across much of the Northern Territory; nearly all of South Australia; the southeastern quarter of Queensland; much of New South Wales except areas of the northeast coast and central coast, and a broad band through the central west from around Griffith to the Queensland border north of Bourke; and across eastern Victoria and the northern border regions of that State.
The area of lowest on record rainfall for the 27-month period has increased month-on-month. These include areas on the south coast of Western Australia; along the border of New South Wales and South Australia, extending into parts of the Lake Eyre / Kati Thanda catchment; and parts of northeast New South Wales and greater southeastern Queensland.
Extended dry conditions over eastern Australia
Rainfall deficiencies have affected much of the southeastern quarter of Australia since early 2017. Rainfall deficiencies for the period starting January 2017 are most extreme in the northern and western Murray–Darling Basin, and across much of eastern and central Gippsland in Victoria. This long-running dry period has previously been discussed in the last update on the long-running dry and for 2019 in the Annual Climate Statement.
The size of the rainfall deficit accumulated over annual and longer timescales prior to 2020 remains very large over much of Australia. Despite above average rainfall during January to June 2020 for much of southeastern Australia and parts of the inland northwest and Northern Territory, serious or severe longer-term rainfall deficiencies persist over very large areas.
Additional widespread, above average rainfall is needed to lift areas out of deficiency at annual and longer timescales and provide relief from the impacts of this long period of low rainfall (such as renewing water storages). The impact of the longer dry on water resources is still evident, especially in northern parts of the Murray–Darling Basin where total storages are still low (see Water section of this Statement).
Water storages continue to fill in the southern Murray–Darling Basin but levels remain low in the north
Water storage levels increased slightly in most of the major storages in the Murray–Darling Basin since May. The total storage reached 43% at the end of June, an increase of 3% since last month and 7% compared to the same time last year.
Major storage levels remain low in the northern Murray–Darling Basin at only 17.9% (832 GL) of total capacity. Most of the northern storage levels had little change in June with Burrendong storage in the Macquarie Valley seeing the largest increase of 2%. Many of the northern Basin catchments have experienced prolonged dry conditions and significant follow-up rainfall is still needed to replenish these water storages.
The total storage in the southern Basin increased by 5% during June to 49.6% (10 248 GL), 7% higher than June 2019. All three of the very large storages in the southern Basin (Hume, Dartmouth, and Eildon) increased this month with Hume increasing by 12% to 38% full. Lake Victoria, on the Murray upstream of the South Australian border, increased by 34% to 86% in June. This is an encouraging start to the winter filling season given the past three filling seasons have had insufficient inflows to replenish the seasonal drawdown. The filling season in the southern Basin will generally continue until the end of September.
Rivers levels continue to drop in the northern Murray–Darling Basin
The monthly average river flows have now declined to below average across most of the northern and central Basin. The far northern rivers have now stopped flowing at most of the gauge locations and this will likely continue through the northern dry season.
The rivers further south in the Gwydir, Namoi, Castlereagh, and Macquarie catchments still contain some water but the levels are lower than average at several locations. Given the low water levels in the major storages in these river systems, there are unlikely to be major releases downstream and these rivers are likely to remain low until significant further rain.
Minor flows are being maintained down most of the Darling River, but the peak flows seen in early 2020 have now subsided. Some minor releases are still being made from the Menindee Lakes to the Lower Darling, maintaining connectivity with the Murray River.
The majority of the southern Basin rivers are running at near average flows for June. There are significant flows, up to 50 000 ML per day, in the Murray River main channel but this is near average for the southern winter period.
Of local significance, Peery Lake, a significant wetland near White Cliffs, filled with water this month. Peery Lake is in the Paroo River system in the largely dry, far western Murray–Darling Basin. It is not a heavily gauged environment, but it tends to fill with water once a decade. The water that reached the lake spent several months making its way across the flat landscape and through the braided river system of the Paroo River. The water will provide habitat for local and migratory wildlife as well as a welcome sight for local communities.
After a drier than average June across most of Australia, root-zone soil moisture (in the top 100 cm) has decreased across most of South Australia and the eastern States, compared to soil moisture for May.
Soils were drier than average for the month across the southwestern half of Western Australia; most of South Australia, the southern Northern Territory, Queensland's Channel Country and Central West District, and northwest New South Wales; much of the Top End; coastal southeast Queensland; and far eastern Victoria and far southwestern New South Wales.
Soil moisture was above average for June for much of the Kimberley and adjacent Victoria River District of the Northern Territory, across the base of the Cape York Peninsula in Queensland, and for parts of southeastern Australia, mostly west of the ranges in New South Wales and Victoria, but also in coastal southeast South Australia and northern Tasmania.
The influence of very low rainfall over longer timescales is still evident in the 12-month soil moisture for July 2019–June 2020, which was very much below average over very large areas of Australia.
Soil moisture returns to near average for much of the Murray–Darling Basin
Root-zone soil moisture in the Murray–Darling Basin has declined to near average across the Basin. Following significant rain in early 2020, soil moisture has generally declined in the east of the Basin since the end of April. This has resulted in the soil moisture dropping from very much above average across large areas in May, to be close to average for large areas in June, and below average in the west of the Basin.
The only areas to see a significant increase in soil moisture in June were the upland catchments of the Murrumbidgee and Murray River systems, east of Wagga Wagga and Albury, which contain several key water storage catchments for the southern Basin.
- June rainfall was the third-lowest on record for Australia as a whole, and below average for most of the country
- Both short- and longer-term rainfall deficiencies have increased this month
- Accumulated rainfall deficits at multi-year timescales are significant in many parts of Australia, and may persist for some time
- Root-zone soil moisture has decreased across most of South Australia and the eastern States, and remained below average for the southwestern half of Western Australia
- Water storage levels in the northern Murray–Darling Basin remain low; river levels continued to decrease in June, returning to below average flow
- Storages in the southern Murray–Darling Basin continue to fill, and the Murray River is receiving inflows from local and headwater catchments
Product code: IDCKGD0AR0
A very dry month for the southeastern mainland increases rainfall deficiencies
Soil moisture details are reported when there are periods of significant rainfall deficits.
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.
For the week to 4 August, rainfall was recorded in the South West Land Division in Western Australia, southern and eastern Victoria, western Tasmania, parts of the east coast of New South Wales and about the north tropical coast and far northern Cape York Peninsula. Little or no rainfall was recorded elsewhere.
At the start of the week, a low pressure system and surface trough slowly moved off the New South Wales coast, and widespread showers eased and contracted to the central to southeast coast of New South Wales, and light to moderate falls were recorded in parts of eastern Victoria.
In the south, a cold front embedded in a westerly airstream tracked over Tasmania, generating moderate falls in western Tasmania. A large high pressure system dominated much of the Australian continent in the middle of the week, with only a few coastal showers reported.
In the second part of the week, the high pressure system was located over the Tasman Sea, and extended a firm ridge along the east coast of Australia. Moist onshore flow produced showers and moderate falls in the north tropical coast and far northern Cape York Peninsula.
A cold front and trough tracked over far southeast Australia, and generated light to moderate falls over western Tasmania, and light falls across that state's north. A complex area of low pressure and cold front followed and tracked over western Tasmania and southern Victoria. Light to moderate falls were recorded in western Tasmania and along the south coast of Victoria.
At the end of the week, in the west, a low pressure system, cold front and pre-frontal trough moved over southwest and southern Western Australia. Widespread moderate falls were reported over large areas of the South West Land Division, with locally heavier falls reported in the South Coastal and South East Coastal districts in Western Australia.
Rainfall totals in excess of 100 mm were recorded along parts of the South Coastal District in Western Australia, including the highest weekly total of 122 mm at King River.
Rainfall totals in excess of 50 mm were recorded in the South Coastal and South East Coastal districts of Western Australia, an area in western Tasmania and the north tropical coast of Queensland.
Rainfall totals between 10 mm and 50 mm were recorded across large areas of the South West Land Division in Western Australia, western Tasmania, parts of southern and eastern Victoria, pockets of the Hunter District in New South Wales, and in the north tropical coast and far northern Cape York Peninsula of Queensland.
Rainfall totals of less than 10 mm were recorded across remaining parts of the South West Land Division in Western Australia, the eastern half of Tasmania, parts of eastern Victoria and east coast New South Wales, and in the far northeast coast of Queensland.
Impact of recent rainfall on deficits
Rainfall deficits over Australia for the 4-month (April–July 2020) and the 28-month (April 2018–July 2020) periods are discussed in the Drought Statement, to be issued on 6 August 2020.
Rainfall deficit maps are available for these periods as well as for standard periods. The maps below show the percentage of mean rainfall that has been received for the rainfall deficit period for the 4-month and 28-month periods, extended to the week ending 4 August 2020.
Rainfall for the period 1 April to 4 August 2020
Serious or severe rainfall deficiencies for the 4-month period are in place in Western Australia across most of the southwestern half of the State. Serious rainfall deficiencies are also in place across parts of central southern and southeast Queensland. Other small areas experiencing serious rainfall deficiencies include the extreme south coast of New South Wales, the southwest of the Alice Springs District in the Northern Territory, and pockets of southwest and northern South Australia.
Inland areas of Western Australia, southwest South Australia and parts of central Queensland received less than 40% their average for the period, while remaining areas have generally received less than 80 % to 40% of their average for the period.
Rainfall for the period 1 April 2018 to 4 August 2020
Serious to severe rainfall deficiencies are in place for the 27-month period across the South West Land Division, much of the west of the Gascoyne and Pilbara, along the south coast of Western Australia, the northern tip of the Kimberley, the east of the Interior District, and pockets throughout the inland areas of the State. Deficiencies are also in place across much of the Northern Territory, nearly all of South Australia, the southeastern quarter of Queensland, much of western and northern inland parts of New South Wales, and across eastern Victoria and the northern border regions of that state.
Affected areas through the interior of Australia into western New South Wales, southern inland Queensland, northeastern South Australia and the southern parts of the Northern Territory have generally received less than 50% of average rainfall for this period. Remaining areas have generally received between 80% and 50% of average rainfall.
Product code: IDCKGRWAR0