Drought

Rainfall deficiencies persist over large parts of southeastern and northeastern Australia

July rainfall was below average across much of southern Australia, excluding some areas of western Victoria and Tasmania. Rainfall was very much below average over most of the Eyre Peninsula and southern pastoral districts in South Australia, and parts of the southern half of Western Australia, along with eastern inland New South Wales into southern Queensland. This has continued or added to long-term rainfall deficiencies in these regions.

For the year to date (January–July), rainfall has been below to very much below average over much of Australia, as is reflected in the 7-month rainfall deficiencies. It has been the fifth-driest start to the year on record for Australia and the driest since 1970. It has been an especially dry start to the year over the southern half of Australia, the driest on record for January to July for the region (January to July 1902 is the second driest).

Whilst the Bureau of Meteorology's monthly Drought Statement focuses on rainfall deficiencies for periods up to two years duration, we monitor rainfall deficiencies and impacts on water resources on longer timescales such as the current severe multi-year drought affecting large parts of eastern Australia. This is discussed further below, and we have special climate statements on this long-term drought, the drought and its impact on water resources and a July webinar where we explore this current drought more deeply, we will continue to monitor this situation.

The role of climate change in rainfall reduction over southern Australia is further discussed in State of the Climate 2018.

The Climate Outlook for August to October indicates a drier than average three months is likely for large parts of the country, including most of the eastern mainland and large areas of southwest Western Australia, where the chance of exceeding median rainfall is less than 40%.

7-month rainfall deficiencies

Below average rainfall for July has increased rainfall deficiencies for the year to date in northeastern New South Wales and southeastern Queensland, and southwestern Western Australia.

In New South Wales, serious to severe rainfall deficiencies extend across most of the North West Slopes and Northern Tablelands, along with coastal areas from the Hunter northwards. In Queensland, serious to severe rainfall deficiencies cover most of the southeast and extend into the eastern Maranoa and Capricornia Districts. Areas of record low rainfall cover an area extending from the central Northern Tablelands into the Southern Downs in Queensland.

Serious to severe rainfall deficiencies are also evident across a large area of the western and central interior, covering most of the western half of the central and southern Northern Territory, most of the pastoral districts of South Australia (extending to far western border areas of New South Wales and the northern Mallee in Victoria), and most of interior Western Australia, extending south to the Nullarbor. A number of areas within this region have had their driest January to July on record, particularly in the Northern Territory. Serious to severe rainfall deficiencies also exist in much of the Southwest Land Division in Western Australia, and in parts of the Kimberley. Smaller pockets of serious to severe rainfall deficiencies also exist in southern agricultural regions of South Australia, the Central District and West and South Gippsland in Victoria, and across eastern Tasmania.

16-month rainfall deficiencies

July rainfall has increased or maintained deficiencies for the period starting in April 2018 in the southwest of Western Australia, while in the southeast below average rainfall for the month has generally seen an increase in rainfall deficiencies across New South Wales, adjacent parts of Victoria, and parts of southern Queensland.

Serious to severe rainfall deficiencies are in place for the 16-month period from April 2018 to July 2019 across most of the northeastern quarter of Western Australia, except parts of the inland Kimberley, extending into the far northeastern Gascoyne and western Pilbara, and are also present in parts of the western Pilbara, along parts of the west coast, and across much of the southwest and south coast regions. Rainfall deficiencies also affect most of the Northern Territory away from the Top End and eastern border regions; most of central and eastern South Australia, away from the far northeast and far southeast; most of southern and southeastern Queensland, extending across much of the Central Highlands and Capricornia districts; much of New South Wales and parts of the central and southeast coast; northwestern Victoria and along the Murray in the Northern Country District, and also parts of the Northeast, Central, and West and South Gippsland districts; and in parts of Tasmania's east coast. Much of the northeast inland of New South Wales has had record low rainfall, as have smaller areas in other states.

Extended drought over eastern Australia and impact on water resources

Rainfall

Rainfall deficiencies have affected most of the New South Wales, Queensland and South Australian parts of the Murray-Darling Basin since the start of 2017. These longer-term deficiencies extend to parts of the New South Wales coast, particularly in the Hunter and Illawarra districts, and to much of the eastern half of South Australia from Adelaide northwards. The deficiencies have been most extreme in the northern Murray-Darling Basin, especially in the northern half of New South Wales, where areas of lowest on record rainfall extend from the Great Dividing Range west as far as Dubbo and Walgett. Some of the largest rainfall deficiencies have occurred in the upper catchments of some of the major tributaries of the Darling, including the Macquarie, the Namoi-Peel and the Border Rivers.

The 31 months from January 2017 to July 2019 has been the driest on record averaged over the Murray-Darling Basin (32% below the 1961-1990 average), as well as over the northern Murray-Darling Basin (38% below average) and for the state of New South Wales (33% below average). All three regions rank second-driest on record, for the 25 months from July 2017 to July 2019, and the 19 months from January 2018 to July 2019; only the 1900-02 peak of the Federation Drought has been drier. The last 31 months have also been the driest on record averaged over the Macquarie-Bogan, Namoi, Gwydir and Castlereagh catchments, with the last three also driest on record for the last 19 months.

The dry conditions of the last three years have been particularly acute during the cool season, which is important in many regions for generating runoff. Rainfall for the period from April to September was less than 50% of average in both 2017 and 2018 in 14 of the 30 rainfall districts of New South Wales. In 13 of these 14 districts, rainfall from April 2019 to date is also less than 50% of average. The Central Western Plains (North), which encompasses Nyngan, Trangie, Gilgandra and Coonamble, has had less than one-third of its average cool-season rainfall in all three years.

Another area of longer-term rainfall deficiencies affects Gippsland, in eastern Victoria, and the east coast of Tasmania. Both the West Gippsland and East Gippsland districts have had their driest 31 months on record, with a substantial area of record low rainfall in central Gippsland centred on Sale and Bairnsdale.

Soil Moisture

It has now been an extended period of very dry soils in the Murray-Darling Basin. The rootzone soil moisture in the northern basin (the Darling River and its tributary catchments) began to severely dry out in June 2017. Since then there has been little relief. The 26-month period to July 2019 represents one of the driest on record for large areas in central and northern New South Wales and southeast Queensland (figure 1). Rootzone soil moisture is also very much below average across the southern Basin (the Murray River and its tributary catchment excluding the Darling River) for this time of year, including in several upper catchment areas that are relied on for contributing winter runoff to the system.

Figure 1 shows the map of soil moisture deciles for the past 26 months in the root zone (top 100 cm of the soil profile) in the Murray–Darling Basin. The data is from AWRA-L version 6 model.

Water availability in the Murray-Darling Basin

The water storages of the southern Murray-Darling Basin saw minor increases from 46.2% to 49.5% of total capacity in July 2019 but this is still down significantly on the same time last year (figure 2).Water storage levels in the northern Murray-Darling Basin have significantly decreased since July last year reaching a low of just 6.7% of capacity at the end of June and holding steady at this level through July, as demand is low during winter (figure 2).

Winter and spring is traditionally a filling period for the storages of the southern Murray-Darling Basin. The filling this season is similar to the previous two years, which were both well below the draw down during the high-demand warm seasons.

The storage levels represent the balance between inflows and outflows. One of the major sources of inflow to storages is runoff from the landscape. Given the limited rainfall and the very low soil moisture it is not surprising that there has been very limited runoff in the northern Basin (figure 3). The runoff that did occur in the northern basin, produced by ex-Tropical Cyclone Trevor in March and subsequent rain in mid-April, was limited to the flat Warrego and Paroo systems, which have very limited connectivity to the Darling River. Subsequently, benefits were largely contained to those catchments. More information on this event can be found in the Water Focus Report.

Runoff in the southern basin has also been consistently below average but the shortfall has not been as severe as in the north.

Figure 2 shows the total storage volumes in the northern and southern Murray–Darling Basin at end of July 2019.

Figure 3 shows the modelled runoff for the northern Basin (the Darling River and its tributary catchments) and the southern Basin (the Murray River and its tributary catchments excluding the Darling River). The data is from AWRA-L version 6 model.

Soil moisture

July saw a decrease in lower-layer soil moisture (from 10 to 100 cm deep) across much of Australia, particularly in northern and western South Australia, much of New South Wales, southern and southeastern Queensland, the north of both the Northern Territory and Western Australia, and the south of Western Australia.

Soil moisture for July was below average for most of central to eastern New South Wales and across the greater southeast of Queensland, extending into the Capricornia District; along the western border of New South Wales, extending across northeastern South Australia; across most of the north of Western Australia, much of the north of north of the Northern Territory except the coastal Top End, and parts of Queensland's Gulf Country; across the southern coast and adjacent hinterland in southern Western Australia, extending into the Goldfields District and southwest South Australia; and for much of eastern Tasmania.

The relatively dry soils seen during July extends the run of dry months this year. Average soil moisture for soil moisture for January–July 2019 was very much below average over very large areas of Australia.

• July rainfall was below average over much of the southern mainland
• Rainfall deficiencies have generally persisted across New South Wales and southeastern Queensland at each monitored timescale
• Long-term rainfall deficiencies, record-low for some periods, have severely impacted on water resources across the Murray–Darling Basin
• Lower-level soil moisture below average for July across large parts of the country
• Warmer than average July across much of Australia continues to add to moisture stress