5A1: Investigating Australia’s Physical Environments

Droughts

Drought is an ‘acute water shortage’ that results from a reduction in precipitation (e.g. a lack of rain, hail, snow) over an extended period of time.
Although it would be useful to define drought in purely meteorological terms it is not a simple matter. We might for example consider drought to have occurred in Alice Springs when annual rainfall falls below say 150 mm, but at Mount Hagen in the wet tropics of New Guinea, just a few weeks without rain might be regarded locally as a drought event. The occurrence and characteristics of drought vary from one region to another and have different impacts on the environment and human activities within each region.

Figure 1:  Soil that hasn’t seen rain in so long and has formed deep cracks (Source: Australian Bureau of Meteorology)

The 1982-83 drought

The El Niño episode of 1982-83 overlapped with a drought that may have been one of the worst for 100 years in Victoria, New South Wales and southern Queensland.  During this event;

  • The 1982 winter rains (June -September) failed over the south-eastern grain and pasture areas of Australia; and
  • In northern New South Wales and southern Queensland, the summer rains (December 1982 to February 1983) also failed.

During the 1982-83 El Niño episode virtually all of Victoria and southern New South Wales, and much of the settled areas of South Australia had record low rainfall for the period of April 1982-February 1983.  It is generally agreed that the widespread bushfires that ended in the enormous infernos of Ash Wednesday on 16 February 1983 were a direct result of the drought conditions brought about by the El Niño event.

Other major events that occurred during this period were: 

  • The drought increased the erosion of land throughout VIC, NSW and QLD;
  • Soils that were dry and powder-like blew away in the wind;
  • A dust storm on Feb 8-9 1983 blew away an estimated 150,000 tons of soil from farms in north-west Victoria;
  • More than 11,000 tons of dust landed on Melbourne (see the photo below); some was blown as far as New Zealand;
  • Bush fires killed 72 people and left 8,000 homeless and property damage estimated at A$400 million;
  • When the rains finally came, the burned areas were severely eroded, some having lost as much as 43 tons of soil per hectare;
  • Wildlife losses were not well documented but estimates suggests that up to 70% of the kangaroo population in commercial shootings zones died between November 1982-1983;
  • The total cost of the 1982-83 El Niño in Australia was estimated at more than US$2,500 million.

In the autumn (March to May) of 1983 the drought was broken by very heavy rains in eastern Australia.  Sheep that had been weakened by the drought suffered severely and many were drowned or starved, and foot-rot caused more death.  Total losses from this El Niño episode were estimated in excess of $3 billion which is substantial considering this was 1982-83.


Australian Curriculum links
 

The distribution and characteristics of biomes as regions with distinctive climates, soils, vegetation and productivity (ACHGK060)

The challenges to food production, including land and water degradation, shortage of fresh water, competing land uses, and climate change, for Australia and other areas of the world  (ACHGK063)

(ACHGK064) The capacity of the world’s environments to sustainably feed the projected future population to achieve food security for Australia and the world

Year 10

(ACHGK073) The application of human-environment systems thinking to understanding the causes and likely consequences of the environmental change being investigated

(ACHGK074) The application of geographical concepts and methods to the management of the environmental change being investigated