Issued 7 July 2016
A wet June further eases rainfall deficiencies
June 2016 was Australia's second-wettest June on record. Every State and Territory recorded above-average June rainfall. New daily and monthly rainfall records were set in several locations across the country. Significantly, highest on record rainfall was recorded in some of the areas where deficiencies were reported in the previous drought statement, most notably central Queensland. The June rainfall has led to either the removal, or reduction in extent and severity of some deficiencies for the period starting in May 2015.
While rainfall in June was average to above average over much of the country, there were a few areas with below average rainfall. Most notable was the lower southwest of Western Australia, where deficiencies at various timescales already existed. June rainfall was also mostly below average in a band from the northwest of the Kimberley to the tip of the Cape York Peninsula.
In many parts of the country, rainfall has been below average for much of the last four years, and in some areas for most of the last sixteen years or more. The accumulated rainfall deficits in these areas are very large, and their removal will require above average rainfall over a sustained period.
14-month rainfall deficiencies
Very high rainfall in June has removed or significantly reduced deficiencies in several areas. However, there has been a worsening of rainfall deficiencies over the lower southwest of Western Australia following a relatively dry June.
Queensland's Central West has seen a marked improvement at this time scale with much of the area of deficiency now removed and only small, isolated pockets of serious deficiency remaining. The area of deficiency in Tasmania has also been almost entirely removed.
Areas of serious to locally severe rainfall deficiency remain in parts of southeast South Australia along with western and southern Victoria. Deficiencies have eased and reduced in extent in the Upper and Lower South East districts of South Australia; and the Wimmera, Mallee and West Gippsland districts of Victoria.
Deficiencies have eased around southwestern coastal parts of the Kimberley, along coastal parts of the Gulf of Carpentaria and southern Cape York Peninsula. Whilst some of the area of severe deficiency in the Top End has reduced, areas of deficiency have slightly worsened around the northern Kimberley coast and at the tip of Cape York Peninsula.
Longer-term deficits in many parts of the country
Since the most recent La Niña concluded in autumn 2012, rainfall has generally been below average over large parts of Queensland and into northern New South Wales, and also over western Victoria, Tasmania and southwest Western Australia. The 2015–16 wet season provided rain to some, though not all, parts of the affected areas of Queensland, and was followed by a wet June. There was also significant rain during late autumn and early winter in Victoria and Tasmania.
However, the accumulated rainfall deficits over the past four years in these areas are very large, and will require a great deal more rain to remove them. Rainfall analyses for standard periods out to 36 months are available on our website.
Very long-term deficits in southern and eastern Australia
Rainfall in much of southern and eastern Australia has been generally below the long-term average since at least the beginning of this century. The period from January 2000 has been the driest such period on record in large parts of southwest Western Australia, and very much below average over much of southeast South Australia, Victoria, Tasmania, southern New South Wales and southeast Queensland. It has also been the warmest such period on record in these areas. Conversely, rainfall in northwestern Australia has been very much above average during the same period.
Southern Australia typically gets significant rainfall from autumn through spring from cold fronts and low pressure systems. However, this activity has substantially decreased in Australia over recent decades, as high pressure systems have become more dominant. This suggests the tendency for recurrent dry conditions is less related to natural climate drivers such as El Niño, and increasingly due to changes in the climate. Research suggests that long-term drying trends over southern Australia cannot be explained by natural variability alone. Comprehensive reports on changes in Australia's climate are available at the Climate Change in Australia website.
These very long-term deficiencies are most significant for slow processes such as the recharge of surface and groundwater storages, and the drying of forests and other parts of the landscape. When rainfall deficiencies are seen over such long timescales they are usually associated with marked impacts on water availability. A near-average season may provide enough rainfall for some agricultural applications but would not be enough to relieve the impacts of these long-term deficiencies on water supplies.
Well above average rainfall in June affected much of the country and has increased the relative amount of available soil moisture in the lower layer (from 10 to 100 cm deep) in several areas. Soil moisture is now above average in much of eastern Australia. The main exception is the southeastern interior of Queensland where soil moisture remains below average with isolated pockets that are well below average.
June's rainfall in Tasmania has resulted in well above average soil moisture for most of the State. Very much above average soil moisture is also evident in Australia's central interior near the borders of Western Australia, the Northern Territory and South Australia; in the Pilbara and Kimberley; in Queensland's Central West and southern parts of Cape York Peninsula; and in much of New South Wales. There are isolated pockets of record-high June soil moisture in some areas. Soil moisture was above average along the Esperance and Eucla Coasts of Western Australia.
Below-average soil moisture is apparent in parts of Western Australia's Central Wheat Belt and near the Gascoyne Coast. Soil moisture was below average near the tip of the Cape York Peninsula and in the Northern Territory's interior, whilst below to very much below average soil moisture is evident in parts of the Top End.
Soil moisture information presented here is from the Bureau's operational Australian Water Resources Assessment Landscape (AWRA-L) model.