Evolving Historic Australian Drought

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Fig. 1: Water storage levels are well below normal for most of the northern Murray-Darling Basin located on Southeast Australia.

Australian water supply below levels previously seen at end of 2010 Millennium Drought (text from Australia Meteorology Bureau): The dry soils have absorbed most of the rain that has fallen across the Murray–Darling Basin (Fig. 1) resulting in limited runoff and inflows to the major storages.

The winter “filling” season in the Southern Basin has been below average for the third year in a row while water storages of the Northern Murray–Darling Basin are extremely low or close to empty with no meaningful inflows. The major storages of the Northern Basin have now dropped well below those seen at the end of the Millennium Drought in 2010.

The large storages of the Southern Basin, including Dartmouth, Hume, and Eildon, all remain above 43% which brings the total storage of the Basin to 41% at the end of August, up only 2.8% from last month.

The Indian Ocean Dipole: Cooling of the ocean surface west and northwest of Australia lower a key moisture source for Australian storms during winter and spring forcing storms approaching Australia from the west to have limited moisture and/or deflect to the south of the continent. The result is increased risk of drought. The condition described represents the positive phase of the Indian Ocean Dipole (+IOD). Last week the strongest +IOD on record was recorded. The Australian Bureau of Meteorology maintains an intense +IOD through quarter 4 of 2019. Historic drought conditions continue to worsen across much of Australia.

Fig. 2: A record +IOD and leading indicator of worsening Australian drought.