Drought
Rainfall deficiencies and water availability

Very much below average rainfall in the south

Rainfall was below average for southern Australia and large areas of north-eastern Australia. Rainfall was below to very much below average (in the lowest 10% of Mays since 1900) for most of Tasmania and Victoria, southern South Australia extending into south-west Western Australia, scattered parts of the west coast and the Northern Territory's Top End, areas of inland southern Queensland and south-eastern New South Wales on and west of the Great Dividing Range.

In large areas of the agricultural regions in southern Western Australia, south-east South Australia and western Victoria, sufficient rainfall for the southern cool season 'autumn break' has fallen later than average or has not yet arrived. While daytime temperatures have been higher than average, potentially extending the growing season, clear skies have resulted in below average night-time temperatures in dry southern regions.

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. There has been a decline of around 15 per cent in April to October rainfall in the south-west of Australia since 1970. 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.

May was the first month of the dry season in northern Australia, and rainfall is usually low through to the start of the wet season in October.

Our rainfall deficiency monitoring from December 2022 has ended. Deficiencies monitored from May 2023 impact similar regions. A new period of rainfall deficiencies since February 2024 has been added, to document the extent and severity of recent significant dryness in parts of southern Australia.

The long-range forecast released on 6 June 2024, indicates that for July to September, Western Tasmania and the far south-eastern mainland are likely (60 to 70% chance) to receive below average rainfall, including areas that have had severe rainfall deficiencies since February (totals in the lowest 5% of all years since 1900).

Rainfall is likely (60 to 80%) to be above average for a wide area spanning Australia including some Western Australian areas that currently have long-term rainfall deficiencies.

Deficiencies for the 4 months since February 2024

For the 4-month period since February 2024, areas with lowest on record, severe or serious rainfall deficiencies (record low rainfall totals or in the lowest 5% or 10% of periods, respectively, since 1900) extend along:

• much of coastal south-west Western Australia and parts of the Pilbara-Gascoyne region;
• south-eastern and parts of southern South Australia;;
• western, and parts of eastern Victoria;
• most of Tasmania.

Deficiencies for the 10 months since August 2023

For the 10-month period since August 2023, areas with lowest on record, severe or serious rainfall deficiencies (record low rainfall totals or in the lowest 5% or 10% of periods, respectively, since 1900) extend along:

• much of the west coast of Western Australia extending into some inland areas, including large areas with lowest on record rainfall in the south-west;
• parts of coastal South Australia, south-west Victoria and much of Tasmania, including small areas with lowest on record rainfall.

These rainfall deficiency areas generally expanded further inland and increased in severity during May.

Deficiencies for the 13 months since May 2023

For the 13-month period since May 2023, areas with lowest on record, severe or serious rainfall deficiencies (record low rainfall totals or in the lowest 5% or 10% of periods, respectively, since 1900) extend across:

• much of the west of Western Australia, and along the Pilbara and south-west Kimberley coast. There were areas of lowest on record rainfall in the north-west of the Gascoyne district, areas north and inland from Perth, for much of the far south-west, and a small area inland from Esperance.
• In the east of the country, there are small areas of 13-month rainfall deficiency in southern South Australia, south-west Victoria, and northern and eastern Tasmania.

During May, the extent and severity of deficiency areas increased in each of these states.

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Lowest on record soil moisture in parts of the south

While May rainfall eased April root zone (0–1 m depth) soil moisture deficiencies in the far south-west, deficiencies persisted in parts of the west and most of the south-west of Western Australia in May. Compared with April, areas with very much below average soil moisture expanded and intensified across southern states and areas of lowest on record soil moisture for this time of year (based on all years since 1911) extend along much of the coast east of the Bight.

Large areas of southern Australian agriculture rely on autumn rainfall and soil moisture to support seed germination, pasture recovery, and crop growth. Prolonged low root zone soil moisture limits plant growth and is an indicator of agricultural drought.

Severe evaporative stress in large areas of southern Australia

Evaporative stress for the 4 weeks ending 31 May 2024 was elevated (negative Evaporative Stress Index (ESI)) in most of Western Australia, the southern states, central Queensland including central parts of its coast, and parts of northern and southern Northern Territory. Despite some easing from May rain in the far south-west of Western Australia, evaporative stress remained severely elevated along coastal fringes in parts of the south-west. Evaporative stress increased significantly across the south of South Australia, in western Victoria, the north-west of Tasmania, and along the ranges from north-eastern Victoria into southern New South Wales.

The ESI is the standardised anomaly of the ratio of actual evapotranspiration to potential evapotranspiration and represents the influence of a combination of meteorological and land factors on drought conditions. A negative ESI is an indicator of vegetation moisture stress associated with agricultural and ecological drought. See this journal publication for further details on calculation and use of the ESI in drought monitoring.

Water deficiencies at the end of May

• Rainfall was below average for southern Australia and areas of northern and eastern Australia.
• Recent rainfall deficiencies have been severe in south-west Western Australia, east of the Bight in southern South Australia and western and coastal Victoria and most of Tasmania. Longer-term deficiencies remain in much of the west of Western Australia, coastal fringes of south-eastern states and much of Tasmania.
• Soil moisture was lowest on record in large areas around the Bight and in north-western Tasmania, and below average across much of the southern states and Western Australia.
• Streamflow was low at a high proportion of sites in: south-west Western Australia; northern Tasmania; south-eastern South Australia; and southern Victoria.
• Most storage levels were low in the west of Western Australia, some large storages were low in Tasmania, and many storages were 10 to 50% lower than this time last year in south-eastern states.

Low streamflow in the west of Western Australia, South Australia, Tasmania and southern Victoria

Below average streamflow during May (based on records since 1975) was observed at 19% of the 655 sites with available data, including 5% of the sites with very much below average or lowest on record flows. Most of Western Australia had low streamflow, particularly in the south-west where most sites had very much below average or lowest on record flows. Most Tasmanian and South Australian sites also had very much below average, or lowest on record flows. Across southern Victoria, many sites had below to very much below average flows. Low streamflow was also observed in parts of the Top End of the Northern Territory and some Queensland sites.

Low storage levels in the west, the south-east and central Queensland

Storages data as processed 2 June 2024

At 2 June the total water storage in Australia (across 306 public storages) was at 74.8% of capacity, 3.8% lower than the previous month, and 1.5% lower than at the same time last year. Volumes decreased at 64% of public storages. Storages remained low across several regions, particularly in south-west Western Australia, and Tasmania where some large storages were low. South Australia, Victoria, New South Wales and central eastern Queensland also had some low storages.

Combined storages in the Murray–Darling Basin were 76.2% full at 2 June, a 1.3% decrease from April and a 13.1% decrease from the same time last year. Menindee Lakes, in the west of New South Wales were 57.0% full at 2 June, a decrease of 12.5% from April and a 22.0% decrease from the same time last year.

Perth's surface water storages were 36.1% full at 2 June, a 0.6% decrease from April and a 9.6% decrease from the same time last year. Long-term declines in surface water inflows to Perth's storages means the city's water supply is reliant on desalination and groundwater sources. Water storage in Pilbara–Gascoyne was at 31.0% of capacity at 2 June, a decrease of 2.6% from April and a considerable decrease of 33.6% from same time last year.

In central Queensland, water storage in Fairbairn was 37.0% full, a decrease of 1.8% from April and a 3.7% decrease from same time last year. Water levels in Lake Awoonga in the south-east of Queensland remained low at 45.1% full at 2 June, an 8.7% decrease from April and a 6.9% decrease from the same time last year.

Water storage in Great Lake in Tasmania decreased to 20.2% full at 2 June, a 1.8% decrease from April and a 7.4% decrease from the same time last year.