Drought
Rainfall deficiencies and water availability

Rainfall deficiencies in Queensland, New South Wales and Western Australia

May rainfall was 72.8% below average for Australia, the second-lowest for May on record. Rainfall was in the lowest 10% of historical observations for May (compared with all Mays since observations began in 1900) for large parts of Western Australia, western South Australia and adjacent parts of the Northern Territory, New South Wales and pockets of eastern Queensland and eastern Tasmania. Western Australia had areas of lowest on record May rainfall in the south-west and interior.

May rainfall was above average for small areas in the east and south-east of Australia, including western Tasmania, where it eased local short-term rainfall deficiencies.

For the 6-month period starting December 2022, areas experiencing serious or severe rainfall deficiencies (totals in the lowest 10% since 1900) include the south-east quarter of Queensland, particularly from Wide Bay and Burnett, inland and through Maranoa and Warrego, the North West Slopes and Plains and pockets of coastal north-eastern New South Wales, a small area of coastal south-west Tasmania, and small areas mostly along the coast, of Western Australia, from Gascoyne to Eucla districts.

Above average rainfall in May led to a reduction in the area of short-term deficiencies in western Tasmania, compared to April. However, below average rainfall in May led to an increase in areas with deficiencies, compared to April, for New South Wales, and produced new areas of deficiency along the Western Australia coast.

For the 18-month period starting December 2021, deficiencies persist on the west coast of Tasmania and a small pocket of far south-west Western Australia where below average May rainfall has increased the area of severe deficiency.

The long-range forecast released on 1 June 2023 indicates that for June to August, below median rainfall is likely to very likely (60% to greater than 80% chance) for almost all of Australia. Unusually low rainfall is at least twice as likely for much of Australia with some parts of the south-west and south-east more than three times as likely to experience unusually low rainfall.

State of the Climate 2022 reported that there has been a shift towards drier conditions across the south-west and south-east Australia, especially for the cool season months of April to October. This is due to a combination of natural variability on decadal timescales and changes in large-scale circulation caused by an increase in greenhouse gas emissions. Since the 1990s, in the absence of strong 'wet' drivers, autumn rainfall in southern Australia has generally been lower than average.

Deficiencies for the 6 months since December 2022

For the 6-month period starting December 2022, areas experiencing serious or severe rainfall deficiencies (totals in the lowest 10% since 1900) include the south-east quarter of Queensland, particularly from Wide Bay and Burnett, inland and through Maranoa and Warrego, the North West Slopes and Plains and pockets of coastal north-eastern New South Wales, a small area of coastal south-west Tasmania, and small areas mostly along the coast, of Western Australia, from Gascoyne to Eucla districts.

Smaller patches of severe rainfall deficiencies (totals in the lowest 5% of historical observations) run along the Western Australian coast from Gascoyne to Eucla, and in Queensland a band of severe deficiency extends from the Wide Bay and Burnett coast inland to the region around Roma.

Deficiencies for the 18 months since December 2021

For the 18-month period starting December 2021, deficiencies persist on the west coast of Tasmania and a small pocket of far south-west Western Australia where below average May rainfall has increased the area of severe deficiency.

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Soil moisture

Root-zone soil moisture (soil moisture in the top 100 cm) was below average along the west and much of the south of Western Australia, across most of eastern Queensland, a large area of inland New South Wales, with patches also along the coast and in the Hunter region, in north-east Victoria, areas of western and eastern South Australia and much of Tasmania. There were pockets of very much below average soil moisture in Western Australia, South Australia, central New South Wales, Tasmania and the east coast of Queensland.

Soil moisture was above average in areas of northern and central Australia, the southern coastline and along the Great Dividing Range to Queensland. aSoil moisture was very much above average in areas of the Western Australia interior, the Northern Territory and South Australia.

Compared with last month, soil moisture decreased for most of the west and east of Australia.

Evaporative stress

Evaporative stress for the 4 weeks ending 31 May 2023 is elevated (index is negative) for parts of Tasmania, eastern WA and most of the north and east of Australia, except for the ranges in New South Wales, southern Victoria, Channel Country and parts of the Darling Downs and Granite Belt in Queensland.

Compared to last month, ESI has decreased in intensity through much of the interior of Western Australia, the inland west of the Northern Territory, and through the centre and south of South Australia.

See the journal publication for further details on calculation and use of evaporative stress index in drought monitoring.

• May rainfall was 72.8% below average for Australia, the second-lowest for May on record.
• Rainfall was in the lowest 10% of historical observations for May (compared with all Mays since observations began in 1900) in large parts of Western Australia, western South Australia and adjacent parts of the Northern Territory, New South Wales, pockets of eastern Queensland, and eastern Tasmania.
• Western Australia overall had its lowest May rainfall on record, and it was particularly dry in the south-west and interior.
• Small areas in the east and south-east of Australia had above average rainfall, including western Tasmania, where it eased local short-term rainfall deficiencies.
• For the period commencing December 2022, areas experiencing serious or severe rainfall deficiencies (totals in the lowest 10% of observations since 1900) include the south-east quarter of Queensland, areas in the north-eastern quarter of New South Wales, and areas along the coast from the Gascoyne to Eucla districts in Western Australia.
• Soil moisture was below average across much of the eastern half of Queensland, the Hunter District, coastal pockets, and inland New South Wales, north-west Victoria, parts of South Australia and Tasmania, and broad areas of the west and south of Western Australia.
• Low streamflows were observed mostly at sites in the south-west of Western Australia, in the north of the Murray–Darling Basin, south-east Queensland, the east coast of New South Wales and eastern Tasmania.
• Low storage levels continue in some parts of south and central Queensland, central Tasmania, some storages across parts of New South Wales and Victoria, and some urban storages for Perth and Adelaide.
• For June to August, below median rainfall is likely to very likely (60% to greater than 80% chance) for almost all of Australia.

Streamflows high in parts of the north and south-east Australia; low in parts of east coast Australia and south-west Western Australia

Average to lower-than-average May rainfall across Australia, and very much below average rainfall in south and central parts of the western Australia and central inland New South Wales, was reflected in the streamflow conditions of these regions. Streamflows were average at 42% of the 860 sites (based on records since 1975), spread across the country. Lower than average streamflows were observed at 17% of the sites, mostly associated with below average rainfall and drier catchment conditions in the south-west of Western Australia, north-west of the Murray–Darling Basin, south eastern New South Wales, eastern Queensland and eastern Tasmania.

In May, above to very much above average streamflows were observed at 41% of the sites, mainly in south eastern Australia, eastern areas of the Murray–Darling Basin, many sites across Victoria, the wet tropics in Queensland, the Northern Territory, scattered sites in South Australia, and some sites in north-west in Western Australia. In early May, moderate flood warnings were issued for Eyre Creek catchment in western Queensland and downstream movement of floodwater north-west Queensland resulted in higher-than-average streamflows in rivers in these areas.

Overall high storage levels across the country but low storage levels at several locations

In May, average to lower-than-average rainfall and soil moisture particularly in western Australia, south-eastern Queensland and eastern New South Wales resulted in a slight decrease in some storage levels from April. By the end of May, the total water storage volume in Australia (across Australia's 306 public storages) was 76.3% of full capacity; slightly lower than the previous month and higher than at the same time last year. Despite most of Australia's major storages being at high levels, there remain several locations with low storage volumes: particularly in south and central Queensland, central Tasmania, some storages across parts of New South Wales and Victoria, and some urban storages for Perth and Adelaide.

Despite below average rainfall in eastern coast to central inland regions of New South Wales, the combined storages in the Murray–Darling Basin were 88.9% full at the end of May which is 1.4% up from the same time last year.

In May across most of southern Western Australia received very much below average rainfall and dry catchment conditions resulted in a slight decrease in some storage levels. Perth's surface water storages were 45.8% full at the end of May which is slightly lower (1%) than last month and slightly down from 47.6% at the same time last 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.

During May, western and central Tasmania received average to above average rainfall resulted in a slight increase in some storages although eastern Tasmania received lower than average rainfall. Storages volume in Tasmania remains around half of full capacity (50.7%) at the end of May which is slightly higher (0.3%) than last month and higher than at the same time last year.

Average to below average rainfall across most of the Queensland during May resulted in decreased storage volumes. Water levels in the Beardmore storage remain low, decreasing to 17.6% by the end of May (lower from 100.7% at the same time last year). Water levels in the Nogoa Mackenzie system in central Queensland remain low, slightly decreasing to 42% by the end of May (up from 23.4% at the same time last year). In central Queensland, water storage in Fairbairn was below half capacity at the end of May at 41.3% (up from 22.2% at the same time last year).