Drought
Rainfall deficiencies and water availability

Rainfall deficiencies in south-east Queensland and south-west Tasmania

April rainfall was below average for scattered areas in the south-eastern quarter of Queensland and north-eastern New South Wales, parts of Western Australia's Pilbara, Gascoyne and Central West, and southern and parts of the west coast of Tasmania.

Rainfall was above average for most of Western Australia, the Northern Territory and South Australia, much of Queensland's Channel Country, far west and Cape York Peninsula, parts of southern New South Wales and most of central and western Victoria.

For the 5-month period starting December 2022, serious deficiencies (totals in the lowest 10% since 1900) are in place in south-east Queensland, pockets of the North West Slopes and Plains and coastal north-eastern New South Wales, and western Tasmania. Compared to March, April rain cleared short-term deficiencies in parts of coastal south-west Western Australia, while in western Tasmanian deficiencies for this period have increased in spatial extent, including areas of severe deficiency in the south-west.

For the 17-month period starting December 2021, deficiencies persist in a small pocket of far south-west Western Australia, as well as the west coast of Tasmania where below average April rainfall has increased the extent of severe deficiencies.

The long-range forecast released on 4 May 2023 indicates that for April to June, below median rainfall is likely (60 to 80% chance) for most of Australia away from the east coast, Far North Queensland, and southern Tasmania. Maximum temperatures are likely to be above average across much of the country.

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. Since the 1990s, in the absence of strong 'wet' drivers, autumn rainfall in southern Australia has generally been lower than average.

Deficiencies for the 5 months since December 2022

April rainfall was below average for scattered areas in the south-eastern quarter of Queensland and north-eastern New South Wales, parts of Western Australia's Pilbara, Gascoyne and Central West, and southern and parts of the west coast of Tasmania.

For the 5-month period starting December 2022, serious deficiencies (totals in the lowest 10% since 1900) are in place in south-east Queensland, pockets of the North West Slopes and Plains and coastal north-eastern New South Wales, and western Tasmania. Compared to March, April rain cleared short-term deficiencies in parts of coastal south-west Western Australia, while in western Tasmanian deficiencies for this period have increased in spatial extent, including areas of severe deficiency in the south-west.

In Queensland, a band of severe rainfall deficiencies (totals in the lowest 5% of historical observations) extends from the Wide Bay and Burnett coast inland to the region around Roma.

Deficiencies for the 17 months since December 2021

For the 17-month period starting December 2021, deficiencies persist in a small pocket of far south-west Western Australia, as well as the west coast of Tasmania where below average April rainfall has increased the extent of severe deficiencies.

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Soil moisture

Root-zone soil moisture (soil moisture in the top 100 cm) was below average across much of southern and south-eastern Queensland and pockets of the Cape York Peninsula, inland northern and coastal north-east New South Wales, south-west Tasmania, pockets of coastal Kimberley and Pilbara regions. Other very much below average areas included pockets of southern Queensland and on the Cape York Peninsula, and a small area of the Northern Rivers in New South Wales.

Soil moisture was above average in much of the rest of Australia. It was very much above average in some pockets on the western slopes of the Great Dividing Range in eastern Australia, in western Victoria, western Queensland, through the North West Pastoral and West Coast districts in South Australia, away from the Top End in Northern Territory, and in large areas of Western Australia where there were also highest on record areas in Goldfields, Southern Interior and Great Southern districts.

Compared with last month, soil moisture increased over most of Western Australia, South Australia, Victoria and southern New South Wales.

Evaporative stress

Evaporative stress for the 4 weeks ending 30 April 2023 is elevated (index is negative) for some areas of inland southern Queensland and the Channel Country, scattered areas through inland central to northern Queensland, much of inland northern and north-western New South Wales, adjacent north-eastern South Australia, the west coast of Western Australia, and the west coast of Tasmania. Areas of high ESI were also observed across the Nullarbor Desert in south-east Western Australia and adjacent parts of South Australia. Compared to last month, ESI has decreased in intensity through much of inland Western Australia, particularly the south-west, and also in parts of the Kimberley. It has also decreased in eastern Tasmania, Victoria, and eastern and southern New South Wales.

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

• April rainfall was below average for scattered areas in south-eastern Queensland and north-eastern New South Wales, parts of Western Australia's Pilbara, Gascoyne and Central West, and southern and south-western Tasmania.
• Above to very much above average April rainfall removed short-term deficiencies in coastal south-west Western Australia.
• For the period commencing December 2022, areas of serious or severe rainfall deficiencies (totals in the lowest 10% of observations since 1900) are in place in the south-east and the Darling Downs in Queensland, pockets in the north-eastern quarter of New South Wales, and along the west coast of Tasmania.
• Soil moisture was below average across much of southern Queensland and pockets of Cape York Peninsula, northern New South Wales and along the ranges, southern Tasmania, and pockets of the Gascoyne in Western Australia.
• Low streamflows were observed mostly at sites in the north of the Murray–Darling Basin and along parts of the east coast of Australia.
• Low storage levels continue in some parts of south and central Queensland, central and western Tasmania, south and north-east New South Wales, Victoria, South Australia and some urban storages for Perth in Western Australia.
• For May to July, below median rainfall is likely for most of Australia away from Cape York Peninsula, north-west Western Australia, southern Tasmania and much of coastal Victoria.

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

In April, average rainfall over the eastern half of Australia and some parts of the western Australia was reflected in the streamflow conditions of these regions. Streamflows were average at 38% of sites (based on records since 1975), spread across the country. Lower than average streamflows were observed at 15% of the 861 sites, mostly associated with below average rainfall and drier catchment conditions in the north of the Murray—Darling Basin and far south-east New South Wales, south-east Queensland and western Tasmania. Despite average to higher than average rainfall and soil moisture conditions across southern Western Australia, streamflows in the far south-west were average to below average.

In April, above to very much above average streamflows were observed at 47% of sites, mainly in south-eastern and eastern areas of the Murray—Darling Basin, western Victoria, the wet tropics in Queensland, the Northern Territory, scattered sites in South Australia, and some sites in northern and western sites in Western Australia. Following earlier March rainfall, flooding in north-west Queensland resulted in higher than average streamflows in rivers in these areas, and major or moderate flood warnings were issued for some catchments across western Queensland.

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

In April, areas in the western and southern Northern Territory, eastern to central Western Australia and some parts of southern mainland Australia received above average to very much above average rainfall. Soil moisture was average or very much above average in areas of the western Northern Territory, eastern to central Western Australia and some areas in South Australia. These resulted in a slight increase in some storage levels from March, particularly in south-eastern Australia. By the end of April, the total water storage volume in Australia (across Australia's 306 public storages) was 76.8% 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 and western Tasmania, southern and north-east New South Wales, across parts of Victoria, South Australia, and some urban storages for Perth.

In April north and north-east New South Wales received below average rainfall and dry catchment conditions resulted in a slight decrease in some storage levels in the Murray—Darling Basin. At the end of April, the combined storages in the Murray—Darling Basin were 86.8% full, 0.2% down from the same time last year.

Despite average to higher than average rainfall and soil moisture conditions across southern Western Australia, Perth's surface water storages were 46.8% full at the end of April (slightly down from 47.2% 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 April, much of Tasmania received average to below average rainfall and soil moisture conditions, storages volume in Tasmania remains around half of full capacity (50.4%) which is slightly lower (1.3%) than last month and higher than at the same time last year.

Average to below average rainfall across Queensland during April resulted in decreased storage volumes. Water levels in the Beardmore storage remain low, decreasing to 20.9% by the end of April (lower from 99.1% at the same time last year). Water levels in the Nogoa Mackenzie system in central Queensland remain low, slightly decreasing to 43.1% by the end of April (up from 19.7% at the same time last year). In central Queensland, water storage in Fairbairn was below half capacity at the end of April at 42.4% (up from 18.6% at the same time last year).