Rainfall deficiencies ease slightly across southern Australia at the 9-month timescale

Rainfall for August was above or very much above average for much of eastern Australia, across the central to southern Northern Territory, inland northern Western Australia, and across much of western and south coast Western Australia.

Rainfall was generally close to average along the coast of New South Wales, through much of eastern Queensland; parts of the coastal south-east in south-western Tasmania, around the Otways in Victoria, and in far south-east South Australia; across much of pastoral South Australia, the southern Northern Territory, south-west New South Wales, and the south-eastern quarter of Western Australia; far south-west and south coast Western Australia; and much of the northern tropics except the eastern Cape York Peninsula where rainfall was above average.

Rainfall averaged over the 9 months from December 2021 has been below average for areas of the west-facing coasts of south-eastern Australia and also in the south-west of Western Australia. Compared to last month, deficiencies have generally eased slightly across southern Australia. Serious or severe rainfall deficiencies persist in western Tasmania, across the base of the Top End and pockets of the central to south-eastern Top End in the Northern Territory, an isolated area of far south-east South Australia, and pockets of south-west Western Australia and the southern Goldfields District.

Evaporative stress remains high for the four-week window ending 30 August 2022 across south-western Tasmania, for areas around Port Augusta in South Australia, extending eastwards to far south-west New South Wales, and in parts of the eastern Top End and southern coast of the Gulf of Carpentaria in the Northern Territory. See the journal publication for further details on calculation and use of evaporative stress index in drought monitoring.

At shorter timescales, 3-month rainfall (for June to August) has been in the lowest 10% of historical observations since 1900 (serious or severe rainfall deficiencies) in parts of South Australia around the Flinders Ranges and between the Flinders Ranges and the border of New South Wales.

The Climate Outlook released on 1 September 2022 indicates rainfall for September to November is likely to be above median for the eastern two thirds of Australia, but below median for south-western Tasmania and south-west Western Australia.

Multi-year rainfall deficiencies, which originated during the 2017–2019 drought, continue to affect parts of the country. However, for recent seasons, conditions have improved over large areas, and water storages have increased across much of the country.

9-month rainfall deficiencies

Rainfall for August was above or very much above average for much of eastern Australia, across the central to southern Northern Territory, inland northern Western Australia, and across much of western and south coast Western Australia.

Rainfall was generally close to average along the coast of New South Wales, through much of eastern Queensland; parts of the coastal south-east in south-western Tasmania, around the Otways in Victoria, and in far south-east South Australia; across much of pastoral South Australia, the southern Northern Territory, south-west New South Wales, and the south-eastern quarter of Western Australia; far south-west and south coast Western Australia; and much of the northern tropics except the eastern Cape York Peninsula where rainfall was above average. Rainfall for August was below average for some small pockets on the east coast between the New South Wales Mid North Coast and Townsville in Queensland.

Serious and severe rainfall deficiencies (lowest 10% of historical observations) for the period December 2021 to August 2022, compared to all years since national records began in 1900, are in place across western Tasmania, across the base of the Top End and pockets of the central to south-eastern Top End in the Northern Territory, and small pockets of south-west Western Australia and the southern Goldfields District.

Compared to the 8-month period ending July 2022 the strength and spatial extent of rainfall deficiencies have generally eased slightly across southern Australia, with rainfall for the period now generally above the lowest 10% of historical observations for those areas of south-east South Australia shown in serious or severe deficiency last month.

In the Northern Territory deficiencies for the period since December 2021 remain similar to the previous Drought Statement. May to September is the northern Australian dry season. Tropical northern Australia typically has very low rainfall totals during this time (large areas typically see less than 25 mm for the dry season). While large areas of northern Australia have received unseasonal rainfall during the dry this year, it is likely there will not be significant change to rainfall deficiencies in the Northern Territory until the next wet season commences in the coming months.

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Soil moisture

Root-zone soil moisture (soil moisture in the top 100 cm) for August was above average across most of New South Wales away from the south and west, much of Queensland, and from the Barkly District to the south-west of the Top End in the Northern Territory, although compared to last month soil moisture had generally decreased across Queensland and the Northern Territory.

Following two periods of unusually heavy rain during the first half of August soil moisture increased along the west coast, and was above average for August along the coast of the South West Land Division and in the inland south-west in Western Australia. Soil moisture also increased across south-east Australia, with much of Tasmania showing above average soil moisture for the month.

In South Australia a drying has seen areas of below average soil moisture observed for August around the Flinders Ranges and between the Flinders Ranges and the South Australian border.

Elsewhere, root-zone soil moisture was near average for large parts of Australia, although there were areas of both above and below average scattered throughout.

In recent months, saturated soil conditions across eastern Australia have been a significant contributor to the severity of flooding and have also contributed to increased inflows into inland water storages.

  • August rainfall was above or very much above average for much of eastern Australia, across the central to southern Northern Territory, inland northern Western Australia, and across much of western and south coast Western Australia.
  • For the period starting December 2021, serious rainfall deficiencies (totals in the lowest 10% of historical observations since 1900) continue to affect western Tasmania, across the base of the Top End and parts of the central to south-eastern Top End in the Northern Territory, and small pockets of south-west Western Australia and the southern Goldfields District.
  • However, deficiencies across southern Australia have eased slightly since last month.
  • High streamflows were observed mostly along the south-west of Western Australia and in eastern Australia.
  • Flood warnings were issued for catchments across inland New South Wales, Gippsland in Victoria, and north-eastern and eastern Tasmania during August.
  • Moderate and major flood events continued in New South Wales and part of Victoria during August, with minor flooding also reported in the mid-west and Gascoyne regions of Western Australia.
  • At the end of August, Australia's total storage volume was 72.5% of full capacity.
  • Urban storages in all capital cities are above 88% of capacity, except for Adelaide and Perth.
  • The combined storages in the Murray–Darling Basin were 93% full; up from 82.5% at the same time last year.
  • Storages in Northern Australia remain above 65% capacity.
  • Low storage conditions continue in some parts of central Queensland, Western Tasmania, western Victoria and the Wimmera–Mallee region of the Murray–Darling Basin.

High streamflows in eastern Australia and the south-west of Western Australia

In August, high rainfall and wet soil conditions were observed over eastern Queensland, south-west Western Australia, Tasmania, and south-eastern areas of New South Wales. With these conditions streamflows were above to very much above average (based on records since 1975). Highest on record streamflows were observed at 5% of the 861 sites where streamflow is measured, mainly in the south-west of Western Australia, inland areas of New South Wales, and for some sites along the east coast of Australia. During August, higher than average streamflow was observed at 70% of sites.

During August, some parts of south-west Western Australia, coastal Queensland, western Victoria, and South Australia experienced streamflows that were average or below average (29% of sites).

Streamflow decile rankings across Australia
Streamflow decile rankings across Australia

Moderate to major flooding for parts of New South Wales and Queensland

In August, high rainfall occurred across large parts of New South Wales, Victoria, Tasmania, and Western Australia. Inland floodwaters continued to move through Queensland and New South Wales. Major Flood warnings were issued for parts of the Latrobe and Moe Rivers in Victoria, and parts of the Macquarie River in New South Wales. Moderate Flood warnings were issued for parts of the South Esk and Macquarie Rivers in Tasmania, parts of the Narran, Bogan, Culgoa, and Murrumbidgee rivers in New South Wales, and at Terrewah. Minor flooding was reported in the mid-west and Gascoyne regions of Western Australia.

Overall high storage levels across the country and most capital cities

By the end of August, the total water storage volume in Australia (across Australia's 306 large public storages) was 72.5% of full capacity; higher than the previous month and higher than at the same time last year. Despite most of the major storage levels being high, there are individual pockets of low storage volumes—particularly in western Victoria, central Queensland, central and western Tasmania, and some urban storages for Adelaide and Perth.

Major storage levels across Australia
Major storage levels across Australia

Above to very much above average rainfall and saturated soil conditions across much of eastern Australia have contributed to increased inflows into inland water storages. Storage volumes were above 88% full capacity for all capital cities except for Adelaide (67.9% full) and Perth (58.9% full). Average to above average rainfall in August for coastal south-east South Australia and flood waters from upstream rivers, contributed to a small increase in Adelaide's storages during August. In addition to surface water storages, Adelaide's water supply is met by water transfers from the River Murray, augmented by desalinated water and groundwater.

Perth's surface water storages were just above half capacity at the end of August at 58.9% (up from 56.6% at the same time the previous year). However, with the long-term decline of surface water inflows into storages, the city's water supply is generally more reliant on desalination and groundwater sources than surface water. Perth's water supply strategy involves 'banking' of groundwater and desalinated water in its surface water storages during low demand periods to buffer peak supply period requirements.

See storage graphs for other captial cities:

Northern Australia water storage levels are above 65% of accessible capacity

For most of the Northern Territory, August was typically dry with little or no rain recorded for the month. The storage volume in Lake Argyle decreased by 2.9% during August, which is lower than the same time last year. The storage volume in the Darwin River decreased by 3.3% from the previous month, although it remains close to full capacity.

Total storage volume in the Murray–Darling Basin remains high

During August, much of the Murray–Darling Basin received above average to very much above average rainfall. Due to and the wet catchment conditions, the total water storage in the Murray–Darling Basin reached at 93% of capacity at the end of August, higher than the previous month, and higher than the same time last year (82.5%).

The total storage in the northern Basin was 96.7% of capacity at the end of August, which is a slight increase (up by 1.4%) from July, and significantly higher than the same time last year.

The total storage in the southern Basin was 92.1% of capacity at the end of August, which is higher than the previous month. This is still considerably higher than the same time last year when it was 83% capacity. Most of the storages in the southern Basin are at or near full capacity.

The volume in the Menindee Lakes remains similar to the previous month at near full capacity (99.7% full). This is due to the flood waters from the New South Wales Border Rivers and Southern Queensland tributaries flowing down to the Lower Darling system.

In contrast, by the end of August, the combined storages in the Wimmera–Mallee region of the Murray–Darling Basin are only 33.6% full, mainly due to average to below average rainfall over autumn and winter.

Further detail on individual Murray–Darling Basin catchments can be found in the Murray–Darling Basin Water Information Portal.

Some central Queensland and Western Tasmanian water storages remain low

Water levels in the Nogoa Mackenzie system have been generally decreasing since March 2012. The storage volume decreased slightly from the previous month and reaching 22.1% by end of August. However, this is higher than same time in the previous year.

With serious rainfall deficiencies across parts of southern Australia in July and dry catchment conditions, storages volume in Tasmania and South East cost (Victoria) were about half full at the beginning of August. Despite average to above average rainfall in the August, storage volumes in Tasmania were at 52.7% full capacity at the end of August which is lower than the same time last year. Storage volumes in South East Coast (Victoria) were at 53.4% full capacity at the end of August.

Product code: IDCKGD0AR0

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.

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