A very dry month for the southeastern mainland increases rainfall deficiencies
Soil moisture details are reported when there are periods of significant rainfall deficits.
Soil moisture data is from the Bureau's Australian Water Resources Assessment Landscape (AWRA-L) model, developed through the Water Information Research and Development Alliance between the Bureau and CSIRO.
See: Australian Landscape Water Balance.
Rainfall deficiencies continuefollowing drier than average October for southern Australia
October rainfall was below to very much below average across most of Australia, including nearly all of New South Wales, Victoria, South Australia, and Tasmania. For southern Australia (south of 26°S) it was the driest October on record.
For the year to date (January–October), rainfall has been below to very much below average over much of Australia, as is reflected in the 10-month rainfall deficiencies. For Australia as a whole, it was the second-driest January–October on record, coming in behind January–October 1902. It was the driest January–October on record for South Australia, and amongst the five driest on record for New South Wales, Western Australia, and the Northern Territory.
Widespread rain and scattered thunderstorms associated with a slow-moving trough and cold front in the first days of November brought some very welcome rainfall across large areas of eastern Australia which will be captured in the next Drought Statement at the start of December. Through some areas of inland Queensland and central to western New South Wales this event has brought the first significant rainfall since early May.
However, existing accumulated rainfall anomalies are very deep due to the prolonged nature of the current dry period, with below average rainfall over most months since early 2017. Consistent, widespread, above average rainfall over several months will be needed to See also comparison of rainfall anomalies over eastern Australia for the 18-month period ending October 2019, before and after early November rainfall.
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 period.
The role of climate change in rainfall reduction over southern Australia is discussed in State of the Climate 2018. Parts of southwest Australia, and large parts of southeast and eastern Australia including parts of southeast Queensland and southern and eastern New South Wales have seen substantial declines in cool season rainfall in recent decades.
The Climate Outlook for December to March, issued 7 November, indicates a drier than average end of the year is likely for most of Australia. The chance of exceeding median rainfall for December is less than 30% over large parts of southern and eastern Australia. The lower odds of receiving average or above average rainfall is likely being influenced by the positive Indian Ocean Dipole. The IOD typically wanes with the start of the northern monsoon, however, given the current positive IOD is so strong, it is likely to take several weeks to decline, and could persist well into mid-summer. It should also be noted that southern states are moving into their drier time of the year, with a typical, seasonal drop in water storages over summer months.
3-month rainfall deficiencies
Rainfall has continued to be below average over recent months, leading to the emergence of serious to severe rainfall deficiencies at shorter timescales over large areas of southern Australia.
Rainfall for the 3 months August to October 2019 has been record low over much of the northern half of New South Wales away from the coastal strip. Serious to severe rainfall deficiencies extend across the rest of New South Wales inland of the ranges; across northern Victoria and East Gippsland; across much of southern Queensland and parts of the central north of that State; northern Tasmania; large areas of western, northern, and eastern South Australia away from the northeast and the southeast; large areas of Western Australia between the southern Pilbara and Gascoyne, extending into the western Interior, as well as parts of the south and along the South Australian border; and for inland parts of the western Top End in the Northern Territory.
10-month rainfall deficiencies
Rainfall deficiencies for the year to date have increased slightly across the south of Western Australia and South Australia, southeastern New South Wales, and central and eastern Victoria.
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. Areas of deficiencies also exist across the southern coast of New South Wales, and between the New South Wales Tablelands and Central District in Victoria, as well as in inland to coastal central Gippsland. In Queensland, serious to severe rainfall deficiencies affect the greater southeast, the eastern Maranoa, and the Capricornia District. Areas of record low rainfall cover an area extending from the Southern Downs in Queensland to the New South Wales' central Northern Tablelands, Northwest Plains, and part of the Mid-North Coast district. In some areas, particularly in the Northern Tablelands and North West Slopes and Plains in New South Wales and the Southern Downs in Queensland, rainfall for January–October 2019 is more than 20% below previous record lows.
Serious to severe rainfall deficiencies are also evident across much of the central and southern Northern Territory away from the Queensland border; most of South Australia except parts of the southeast, western Eyre Peninsula, and far northeast; across western New South Wales and the Mallee in Victoria. In Western Australia serious to severe rainfall deficiencies affect most of the interior of that State, nearly all areas along the south coast and most of the Southwest Land Division, and parts of the Pilbara and Kimberley. A large area has observed lowest on record rainfall for January–September, particularly in the central Northern Territory, and around the Alice Springs District, pastoral South Australia, and central eastern Western Australia.
Deficiencies persist in eastern Tasmania, and have increased compared to last month, extending further around the northeast coast than previously. January to October 2019 rainfall has been the eighth-lowest on record for the East Coast District.
19-month rainfall deficiencies
Rainfall deficiencies for the period April 2018 to October 2019 remain generally similar to those for the period April 2018 to September 2019.
Serious to severe rainfall deficiencies are in place for the 19-month period from April 2018 to October 2019 across much of the northern half of Western Australia, except parts of the inland Kimberley, the central and southwestern Pilbara, and northeastern Gascoyne; across much of the South West Land Division in Western Australia; much of the Northern Territory except much of the Top End and eastern border; most of South Australia, except parts of the north, southwest, western Eyre Peninsula, and the southeastern tip; southern and southeastern Queensland, extending across much of the Central Highlands and Capricornia districts; most of New South Wales, except some pockets of the central coast, far southeast, and inland west; across northern Victoria and most of the eastern half of the State except parts of West and South Gippsland; and in Tasmania's east and north coast.
Much of the northeast inland of New South Wales has had record low rainfall, as have parts of adjacent southern Queensland, areas of western New South Wales to eastern South Australia, much of the Southeast Coastal District in Western Australia, and other smaller areas scattered elsewhere.
Extended dry conditions over eastern Australia
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 to southeastern 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 and adjacent southern Queensland, where areas of lowest on record rainfall extend across large parts of northeastern New South Wales inland of the Great Dividing Range to as far west as Dubbo and Walgett, as well as smaller areas on central and northwestern New South Wales and southern Queensland. 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.
When compared to other 34-month periods commencing in January, the 34 months from January 2017 to October 2019 has been the driest on record averaged over the Murray–Darling Basin (36% below the 1961–1990 average), as well as over the northern Murray–Darling Basin (40% below average) and for the state of New South Wales (35% below average). All three regions have also been the driest on record for the 22 months from January 2018 to October 2019, whilst for the 27 months from August 2017 to October 2019 rank second in all three regions; only the 1900–02 peak of the Federation Drought has been drier.
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 34 months on record. Rainfall for the period commencing January 2017 has been lowest on record for much of Gippsland, extending roughly from east of around Sale to around Point Hicks.
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 all three years in 12 of the 30 rainfall districts of New South Wales. The very much below average October rainfall over most of New South Wales and the Murray–Darling Basin as a whole has further exacerbated the effect of low inflows to date.
Limited inflows for major water storages in the Murray–Darling Basin
Dry soils absorbed most of the little rain that did fall across the Murray–Darling Basin during October, resulting in limited runoff and very low inflows to the major storages.
The storages in the northern Murray–Darling Basin remain extremely low, having received no significant inflows. Collectively, the major storages of the northern Basin are now at 7% of capacity, a decline of 1.5% from last month. Many towns in the region have raised their water restriction levels and are investigating alternative water sources, such as groundwater, to augment their water supply.
The volume of water in storage in the southern Murray–Darling Basin dropped in October for the first time since starting to fill in May 2019. This follows the start of irrigation seasons in August and reduced inflows to the major storages due to dry catchments and limited rain. The Hume dam, the third biggest storage in the Basin, has fallen to below 40% this month.
Continued low streamflows in the northern Murray–Darling Basin
Streamflow remains very much below average to lowest on record in many of the major rivers in the northern Murray–Daring Basin. Some of the rivers in the far northern Basin are actually dry but this is not unusual for October and therefore they display as average. Streamflow can be influenced by both water released from major storages and consumptive take from the rivers, in addition to natural runoff from rainfall. The very low soil moisture, storage levels and streamflow in the northern Murray–Darling Basin shows that there is very little water anywhere in the system. Streamflow in the southern Murray–Darling Basin ranges from average to very much below average, with the exception of the Darling River that is at lowest on record levels for October.
Urban water storages
Sydney's major water storage levels continue to fall
Lower than average rainfall combined with very dry soils has resulted in record low runoff from large areas of Sydney water storage catchments. Northern areas of Greater Sydney received average rainfall but the rain did not penetrate inland to the storage catchments. As a result, Sydney water storage levels continued to fall despite the desalination plant operating at full capacity and the implementation of Level 1 water restrictions in June. Total storage levels fell to 47.3% of capacity, a decline of 1.6% during October, continuing the consistent downwards trend in storage levels since June 2017.
Early November rainfall has limited impact on water storages
The widespread rainfall across eastern Australia in early November has led to some isolated increases in water resources but little has made it to the major storages of the Murray–Darling Basin. The recent rainfall has resulted in Darling River at Bourke flowing across the weir for the first time since August 2018. (see Water Data Online). Flows were also recorded in the Warrego river at Fords Bridge and Dicks Dam. Significant losses are expected to occur from these minor flows as the dry river bed wets, weir pools and waterholes fill and the water evaporates.
The soils in the major storage catchments, particularly in the northern Murray–Darling, were extremely dry prior to this rain event, meaning that the rain that did fall soaked into the soil and produced very little runoff. These catchments will require significant follow-up rainfall in the coming weeks and months to start to replenish the water storages.
October soil moisture in the root zone (from 0 to 100 cm deep) deciles remain similar to those for September. Soil moisture for October was below average for nearly all of New South Wales; southern Queensland and much of the Peninsula and Gulf Country, extending inland to around Longreach; much of Victoria away from the southwest, central southern, and South Gippsland regions; most of Tasmania; much of northern, southwestern, and eastern South Australia; most of western and southern Western Australia, and pockets of the Kimberley; and much of the northern half of the Northern Territory.
The relatively dry soils seen during October extends the run of dry months this year. Soil moisture for January–October 2019 was very much below average over very large areas of Australia.
Dry soils persist through October in the Murray–Darling Basin
Soil moisture remains very low across most of the Murray–Darling Basin. The catchments in the southern Basin that received near-average rainfall during late autumn to early winter are now drying out. In the upper reaches of the major water yielding catchments of the Goulbourn, Upper–Murray and Ovens rivers the available water content has dropped by more than 15% and now sits below to very much below average.
The soils of central and western NSW also continued drying throughout October bringing soil moisture down to very much below average across 72% of the State.
Rain at the end of October in the far northern Basin soaked in and brought soil moisture up to average in some areas north of Charleville.
Despite increases in soil moisture in some catchments, the northern catchments of the Namoi, Gwydir, Border and Macquarie–Bogan rivers and southern Basin catchment of the Lachlan River, all had their lowest October soil moisture levels on record.
Another dry month over the Murray–Darling Basin has set new long-term records for soil moisture for the past 34 months (January 2017 to October 2019) in ten of its 26 river catchments. Soil moisture levels for the past 34 months have been lowest on record for the Namoi, Gwydir, Moonie, Border Rivers, Castlereagh, Macquarie–Bogan, and Condamine–Culgoa catchments in the northern Basin and the Lake George, Lachlan, and Murrumbidgee catchments in the southern Basin.
Early November rainfall brings welcome increases in soil moisture
The widespread rain across eastern Australia over 1–5 November resulted in significant increases in surface soil moisture through large areas of central New South Wales. Increases in plant available water content greater then 15% were seen around Bourke, Griffith, and Wagga Wagga. These increases have at least temporarily brought moisture levels in the upper soil profile to average to above average through much of the western and southern Murray–Darling Basin. The soils in the higher water yielding areas in the north and east of the Basin remain very much below average.
Change in root-zone soil moisture from 1 to 5 November (left), and root-zone soil moisture daily decile for 6 November (right). Daily deciles produced based on a 30-day moving window (see FAQs on Australian Landscape Water Balance).
- October rainfall below to very much below average for most of Australia
- Driest October on record for southern Australia (south of the border between South Australian and the Northern Territory)
- Rainfall deficiencies persist in many areas, with slight increases across southern Australia
- Long-term rainfall deficiencies, record-low for some periods, continue to severely limit water resources across the Murray–Darling Basin
- Root-zone soil moisture was below average for October for most of Australia
- Inflows remain limited for major water storages in the Murray–Darling Basin
- Increases in soil moisture in the Murray–Darling Basin with recent rainfall in early November
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