Drought
Rainfall deficiencies and water availability

Tenth-driest August on record for Australia

August rainfall was 49.5% below the 1961–1990 average for Australia, the tenth-driest August on record (since 1900). Rainfall in August was below to very much below average for the southern two-thirds of Queensland, most of New South Wales, Victoria and Tasmania, and large parts of South Australia, southern Northern Territory and south-west Western Australia. August rainfall was very much below average (in the driest 10% of historical observations) for most of the Darling Downs and Granite Belt extending into surrounding districts (Queensland), southern parts of New South Wales' Upper Western district, coastal parts of the Southern Agricultural Areas in South Australia, much of southern Victoria, and parts of the South West Land Division (Western Australia).

For Australia as a whole, winter rainfall was 4.3% below the 1961–1990 average. Winter rainfall was below average for much of southern Western Australia, parts of coastal South Australia, southern and eastern Victoria, eastern Tasmania, and eastern New South Wales extending into south-eastern Queensland.

Most areas of Australia that were already experiencing rainfall deficiencies received below average August rainfall, so areas of deficiency have generally expanded and become more severe. Additional areas have emerged in South Australia, Victoria, and Tasmania.

For the 4-month period starting May 2023, areas of severe rainfall deficiency (totals in the lowest 5% of periods since 1900) extend across large areas of south-west Western Australia, far-eastern Victoria, much of coastal New South Wales and an area in south-eastern Queensland. Areas of serious deficiency (totals in the lowest 10% of periods since 1900) extended further inland across the New South Wales North West Slopes and Plains, into south-eastern Queensland.

For the 9-month period starting December 2022, areas experiencing severe rainfall deficiencies intensified along the southern coast of Western Australia and increased in extent in south-eastern Queensland. Areas of serious deficiencies have generally expanded in eastern Australia, and pockets have emerged along south-eastern coastal areas in New South Wales, Victoria and Tasmania.

Longer-term deficiencies persist on the south-west coast of Tasmania and in small areas within south-west Western Australia. Rainfall deficiencies for the period since December 2021 are no longer actively monitored.

The long-range forecast released on 31 August 2023 indicates below median rainfall for September to November is likely to very likely (60% to greater than 80% chance) for southern Western Australia and most of the eastern two-thirds of Australia. Chances of below median rainfall increase to very likely (greater than 80% chance) for areas of southern Australia and eastern Queensland. Unusually low rainfall is at least twice as likely for much of southern Australia and broad areas of the Northern Territory and Queensland. Unusually low rainfall equates to the driest 20% of September to November periods from 1981 to 2018.

State of the Climate 2022 reported a shift towards drier conditions across the south-west and south-east of Australia, particularly during 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, cool season (April to October) rainfall in southern Australia has generally been lower than average.

Deficiencies for the 4 months since May 2023

For the 4-months since May 2023, areas of severe rainfall deficiency (totals in the lowest 5% of periods since 1900) extend across a large area of the south-west and Eucla District of Western Australia, as well as areas along the south-east coast of Australia from East Gippsland in Victoria to northern New South Wales, and in Wide Bay and Burnett and parts of adjoining districts in Queensland.

Areas of serious rainfall deficiencies (totals in the lowest 10% of periods since 1900) extend inland across the North West Slopes and Plains in New South Wales, and over the west of the Darling Downs and Granite Belt into the Maranoa and Warrego districts in Queensland. There are also isolated pockets of serious deficiencies in South Australia's Northern Agricultural Areas, south-east Tasmania and southern Victoria. From May to date, much of the Northern Territory's Top End has had a drier than usual dry season to date.

Since July, rainfall deficiencies have eased in the Western Australia's Goldfields District but they have extended further along the south-west coast of the state. Areas of rainfall deficiencies have expanded in far-eastern Victoria, New South Wales, particularly in the North West Slopes and Plains, and in areas of the south-eastern corner of Queensland. Deficiencies remain, but have eased, in some parts of the New South Wales Hunter District.

Deficiencies for the 9 months since December 2022

For the 9-month period starting December 2022, areas experiencing severe rainfall deficiencies (totals in the lowest 5% of periods since 1900) have intensified and expanded along the coast of Western Australia between Carnarvon and Busselton, and increased in extent in south-eastern Queensland. Areas of serious (totals in the lowest 10% of periods since 1900) to severe rainfall deficiencies have generally expanded in eastern Australia, and pockets of serious deficiencies have emerged along south-eastern coastal areas in New South Wales, Victoria and Tasmania.

Since July, areas with rainfall deficiencies have grown and become more intense. These include areas along the south-west coast of Western Australia with lowest on record rainfall (for the December to August period), areas in south-eastern Queensland, where deficiencies have grown in extent and severity, and pockets along coastal south-eastern New South Wales, Victoria and Tasmania.

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Soil moisture

August root-zone soil moisture (soil moisture in the top 100 cm) was below to very much below average (driest 30% of years since 1911) across large areas in the west of Western Australia; along much of coastal South Australia, eastern parts of Tasmania and Victoria, and much of New South Wales and southern Queensland. Pockets of lowest on record soil moisture have emerged in south-west Western Australia, far eastern Victoria, and coastal New South Wales.

Since July, soil moisture decreased along coastal South Australia, eastern parts of Tasmania and Victoria, and much of New South Wales and southern Queensland. In Western Australia, soil moisture deficiency increased in severity along parts of the west coast and part of the Goldfields District.

Evaporative stress

Evaporative stress for the 4 weeks ending 1 September 2023 is elevated (index is negative) in Western Australia, from the Pilbara into the Southern Interior and Eucla districts, west and Northern Agricultural Areas of South Australia, western Tasmania, south-eastern Victoria, most of coastal and northern inland New South Wales, and southern Queensland.

Since July, the evaporation stress index has increased in intensity to the north and west of Perth, along much of southern South Australia, western and northern Tasmania, and west of the Great Divide across much of inland New South Wales, southern Queensland and across to central Australia.

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

• For Australia as a whole, August rainfall was 49.5% below the 1961–1990 average, the tenth-driest August on record (since 1900). It was below or very much below average for the southern two-thirds of Queensland, most of New South Wales, Victoria and Tasmania, and large parts of South Australia.
• Since May 2023, areas of severe rainfall deficiency (totals in the lowest 5% of periods since 1900) have persisted in south-west. Western Australia, and expanded along eastern Australia, from far-eastern Victoria to much of coastal New South Wales and an area in south-eastern Queensland. Serious deficiencies (totals in the lowest 10% of periods since 1900) have expanded inland across north-eastern New South Wales into Queensland.
• August soil moisture was below average (in the lowest 30% of all years since 1911) across a wide band from south-west Western Australia into southern South Australia, south-central and eastern Victoria, eastern Tasmania, and New South Wales and southern Queensland, except in the west.
• Low streamflows were observed mostly at sites in the west of Western Australia, eastern New South Wales, south-eastern parts of Queensland, and across most of Victoria and Tasmania.
• Storage levels remain low in some parts of south and central Queensland, northern and eastern parts of New South Wales, central Tasmania, and urban areas of Perth.
• For September to November, below median rainfall is likely to very likely (60% to greater than 80% chance) for most of Australia.

Streamflows high in parts of the northern Australia; low in south eastern Australia and in the west of Western Australia

August streamflow conditions mostly followed rainfall patterns. Areas of average to below average rainfall and soil moisture, and subsequent low streamflow conditions, were largely concentrated in southern and south-eastern Australia, and in the west of Western Australia. Streamflow was average at 47% of the 558 sites across the country (based on records since 1975). Below to very much below average streamflow was observed at 37% of the 558 sites, mostly associated with below average rainfall and drier catchment conditions, particularly in the west of Western Australia, eastern New South Wales, south-east Queensland, scattered sites in Queensland's wet tropics, and most sites in Victoria and Tasmania.

In August, above to very much above average streamflow was observed at 16% of sites, mainly in northern Australia, including the Kimberley (Western Australia), Northern Territory and scattered sites in Queensland's wet tropics.

In early August, moderate to minor flood warnings were issued for parts of the Murray River in Victoria and New South Wales. Downstream movement of these floodwaters resulted in above average streamflows in rivers in these areas.

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

August had below to very much below average rainfall and soil moisture, particularly in the south-west of Western Australia; most of New South Wales, Victoria and Tasmania; the southern two-thirds of Queensland; and large parts of South Australia. Higher than average rainfall for parts of the Western Australia interior, Northern Territory and the east coast of the Cape York Peninsula, resulting in a slight increase in some storage levels from July. By the end of August, the total water storage level in Australia (across Australia's 306 public storages) was at 78.7% of capacity, slightly higher than the previous month, and higher than at the same time last year. Despite most of Australia's major storages being high, storage volumes remain low in several locations, particularly in south and central Queensland, northern and south-eastern parts of New South Wales, central Tasmania, and urban areas of Perth.

Despite lower than average rainfall and dry catchment conditions, combined storages in the Murray–Darling Basin were 93.0% full at the end of August, a slight increase, by 1.3%, from July, but a decrease of 1.7% from the same time last year.

Despite lower than average rainfall and dry catchment conditions in August for most of south-west Western Australia, except for the central west, there was a slight increase in some storage levels. Perth's surface water storages remained low (51.6% full) at the end of August, a 2.1% increase from July, and a 7.5% decrease from the same time last year (59.1%). Long-term declines in surface water inflows to Perth's storages means the city's water supply is generally more reliant on desalination and groundwater sources.

During August, Tasmania received lower than average rainfall overall, but small areas in the west received average rainfall, resulting in an increase in the volume of some storages. Storage volume in Tasmania was 60.4% full at the end of August, an increase, by 1.6%, from July, and higher than at the same time last year (52.8%).

Serious rainfall deficiencies since May, and dry catchment conditions across large parts of south-eastern Australia, including most of south-eastern Queensland, resulted in decreased volumes for many storages from last month. Water levels in the Beardmore storage remain low, slightly decreasing to 14.7% full by the end of August (a significant decrease from 101% at the same time last year). Water levels in the Nogoa Mackenzie system in central Queensland remain low, below half capacity (37.9% full) at the end of August, but up from 22% at the same time last year. Water storage in Wivenhoe was slightly decreased to 68.9% full by the end of August, a decrease from same time last year (90.3%). In central Queensland, water storage in Fairbairn was below half capacity at the end of August, at 37.4%, although it was an increase from same time last year (20.9%).