Drought
Rainfall deficiencies and water availability

Below average rainfall in the south and parts of Queensland

Rainfall was below average to very much below average (in the lowest 10% of Augusts since 1900) for:

• most of the South West Land Division in Western Australia agricultural regions in South Australia
• northern Victoria and parts of southern and inland New South Wales
• large areas of central and eastern Queensland.

Rainfall was above average to very much above average (in the highest 10% of Augusts since 1900) for:

• most of Tasmania
• the Northern Territory, and northern and central Western Australia
• parts of the Cape York Peninsula in Queensland
• north-eastern New South Wales.

Long-range forecast

The long-range forecast released on 3 October 2024 for October to December shows:

• Above average rainfall is likely across much of the western half of Australia.
• Rainfall is likely to be within the typical seasonal range for much of eastern Australia.
• Warmer than average days and nights are likely to very likely across most of Australia.

October is the start of the northern wet season. Conditions across most of northern Australia are expected to shift from dry to wet.

Long-term trends

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 16% in April to October rainfall in the south-west of Australia between 1970 and 2023, and around 9% in the south-east since the late 1990s. 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.

Deficiencies for the 8 months since February 2024

For the 8-month period since February 2024, severe or serious rainfall deficiencies (rainfall totals in the lowest 5% or 10% of periods, respectively, since 1900) extend along:

• small areas along the south coast of Western Australia
• agricultural regions of South Australia into western Victoria
• coastal South Gippsland in Victoria and the north-eastern ranges into southern New South Wales
• coastal north-west Tasmania and Bass Strait islands.

Areas with lowest on record rainfall include parts of the Eyre Peninsula, York Peninsula and the agricultural regions of South Australia, into the western edge of Victoria and the Otway region.

Compared to August, in western Tasmania rainfall deficiency regions have reduced in size and severity. In the south-eastern mainland, deficiencies generally increased in extent and severity, particularly in Victoria. However in far south-east South Australia and bordering areas of Victoria rainfall deficiencies have eased from lowest on record to severe.

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Deficiencies for the 14 months since August 2023

For the 14-month period since September 2023, areas with severe or serious rainfall deficiencies (rainfall totals in the lowest 5% or 10% of periods, respectively, since 1900) extend along:

• small areas in the north-west of Western Australia and extending inland along the south-west coast
• agricultural regions of South Australia
• south-west and the far north-east of Victoria
• coastal fringes around Tasmania and Bass Strait islands.

Areas with lowest on record rainfall include the south-east coast of South Australia, south-west Victoria, and small pockets in south-west Western Australia.

Compared with August, in Western Australia rainfall deficiencies increased in severity and extent in the south-west. For south-eastern Australia, rainfall deficiency areas expanded further inland in South Australia and western and north-eastern Victoria. Rainfall deficiency areas have reduced in size in Tasmania.

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Below average soil moisture in the southern mainland

September soil moisture deficiencies continue in the southern mainland, with below to very much below average soil moisture in:

• most of Victoria into southern New South Wales
• southern South Australia
• scattered areas in the south of Western Australia
• parts of western and central Queensland and small parts of the Northern Territory.

Above average September rainfall across the north-west of Western Australia and western and central Tasmania eased soil moisture deficiencies in those areas.

However, rainfall was below to very much below average in September in the southern mainland and central Queensland, intensifying soil moisture deficiencies in Victoria and the south of South Australia. Soil moisture deficiencies have also developed in much of central Queensland.

Agriculture in southern Australia relies on higher cool season soil moisture. Low soil moisture for long periods of time affects crop growth and is an indicator of agricultural drought

Severe evaporative stress in large areas of southern Australia

Evaporative stress for the 4 weeks ending 30 September 2024 was elevated (negative Evaporative Stress Index (ESI)) in:

• most of central and southern Queensland
• parts of southern and eastern Northern Territory
• most of New South Wales
• most of western and northern Victoria
• most of South Australia
• much of south and parts of north-west Western Australia.

While vegetation moisture stress decreased in Top End of Northern Territory and western Tasmania in September compared with August, significantly elevated ESI values (less than −2) persisted and expanded over larger areas of the south of Western Australia, southern South Australia and northern and western Victoria into south New South Wales.

The ESI represents the influence of a combination of meteorological and land factors on drought conditions. A negative ESI indicates vegetation moisture stress linked to agricultural and ecological drought.

See this journal publication for further details on calculation and use of the ESI in drought monitoring.

Rainfall deficiencies and water shortage at the end of September

• September rainfall was below average for south-west Western Australia, agricultural regions in South Australia, northern Victoria and parts of southern and central New South Wales and large areas of central and eastern Queensland.
• Recent rainfall deficiency areas expanded in September in south-west Western Australia, the agricultural regions in South Australia, and across much of Victoria into southern New South Wales.
• Longer-term rainfall deficiencies persist and have expanded in September along areas of the mainland south coast.
• Soil moisture remains below average in southern Australia and deficiencies have developed in central Queensland, but deficiencies have eased in the north-west of Western Australia and central Tasmania.
• Streamflow was low at a large proportion of sites in Victoria, the southern Murray–Darling Basin, South Australia and south-west of Western Australia.
• Some water storage levels were low in the west of Western Australia and in central Queensland. Many storages in south-eastern states were 10 to 50% lower than the same time last year.

Low streamflow in the Victoria and south-east Murray–Darling Basin

In September, higher than average (based on records since 1975) streamflow was observed at 23% of the 887 sites with available data. These were mostly in northern and eastern Australia, but also in northern Tasmania where soil moisture was high following heavy rainfall and flooding in late August. Very much above average streamflow (highest 10% of years since 1975) was observed at 7% of sites, including 2% of sites with highest on record, mainly in the Northern Territory, Queensland, some sites in north-east coast of New South Wales and northern Tasmania.

Lower than average streamflow was observed in September at 29% of sites. These were mostly associated with below average rainfall and dry catchment conditions. These were observed in:

• Victoria
• South Australia
• the Murray–Darling Basin, particularly southern Basin
• scattered sites in Queensland
• many sites in the south-west of Western Australia.

Very much below average streamflow (lowest 10% of years since 1975) was observed at 7% of sites, mainly in western Victoria, South Australia, the southern Murray–Darling Basin, scattered sites in north Queensland and the south-west of Western Australia.

September streamflow was average at 48% of sites, spread across Australia.

Very much below average streamflow (lowest 10% of years since 1975) was observed at 10% of sites, including 2% of sites with lowest on record, mainly in Victoria, southern Murray–Darling Basin, scattered sites in north Queensland and south-west of Western Australia.

Streamflow was average at 38% of sites, across Australia.

Low storage levels in the west of Western Australia, southern Australia and central Queensland

By the end of September, the total water storage in Australia (across 306 public storages) was at 75.7% of capacity, slightly higher (by 0.2%) than the previous month, and 2.0% lower than at the same time last year . Despite Australia's overall high storage, volumes decreased in September for 179 public storages. Some storages were relatively low in several regions including:

• central Queensland
• the northern and southern Murray–Darling Basin
• western Victoria
• South Australian Gulf drainage division
• central Tasmania
• urban areas of Perth and in the Pilbara–Gascoyne in Western Australia.

The decrease in storage volumes were generally in regions that had below average rainfall and dry catchment conditions during September.

Combined storages in the Murray–Darling Basin were 79.7% full at the end of September, a 2.7% decrease from August and a 11.6% decrease from the same time last year. Menindee Lakes, in the west of New South Wales, was 56.5% full at the end of September, a slight decrease (3.3%) from August and a 20.2% decrease from the same time last year. The combined storage in the Wimmera–Mallee system of Victoria was just above half full (55.2% of its capacity) at the end of September, also a 20.2% decrease from the same time last year, mainly due to the below average rainfall during March to June and August to September periods.

Due to above average rainfall and soil moisture in August, Perth's surface water storages were 47.8% full at the end of September. This is a 3.1% increase from August, although still 5.3% lower than the same time last year. Long-term declines in surface water inflows to Perth's storages mean the city's water supply is reliant on desalination and groundwater sources.

The Harding storage in the Pilbara–Gascoyne drainage division was at 25.8% of capacity at the end of September, a 2.0% decrease from August and a 28.2% decrease from the same time last year.

In central Queensland, water storage in Fairbairn was at 32.1% of capacity, a 2.6% decrease from August and a 1.7% decrease from the same time last year. Water levels in the Lake Awoonga in south-eastern Queensland remain low (40.2% full) at the end of September, a 1.0% decrease from August and a 7.6% decrease from the same time last year.

Above average September rainfall and wet catchments across western Tasmania resulted in increased storage in the region. Water storage in Great Lake in central-northern Tasmania, the second largest by capacity in the state, was 32.5% full at the end of the month, a 4.1% increase from August, although still 5.4% lower than the same time last year.