<strong>The</strong> Big Picturethe water cycle in AustraliaTropicalFigure 1. <strong>The</strong> major climate zones across Australia<strong>The</strong> Australian continent features a wide range of climatic zonesdispersed within three broad regions: the topical regions of thenorth, the arid expanses of the inland, and the temperate regionsof the east and south.Source: National Land and Water Resources Audit, Australiancatchment, river and estuary assessment, NLWRA, Canberra, 2002,vol.1, p. 57.TransitionalSubtropical dryTropical/warmtemperateWarm-temperateREFERENCEs1. Australian Bureau of Statistics, Year book, Australia,2005, ABS, Canberra, 2005, pp. 16–19.2.ibid., p.16.Some other useful sources• M White, Running down: Water in a changing land,Kangaroo Press, Sydney, Australia, 2000.• Australian Bureau of Statistics, Year book, Australia,2005, ABS, Canberra, 2005, pp. 668–77.18 <strong>Victorian</strong> Women’s <strong>Trust</strong> - Our Water Mark
<strong>The</strong> Big PicturevariabilityOur rainfall and stream flows arehighly variable. This variability will increasewith predicted climate change …This climatic unpredictability is somethingthat no-one can change and with which wemust learn to co-operate. To have any hopeof succeeding we have to have a wide vision,see the ‘big picture’ and understand theco-evolution of this continent, its waterresources and its biota through geological time.Mary White, Running down: Water in a changing land,Kangaroo Press, Australia, 2000, p. 1.<strong>The</strong> best-laid plans …Australia has the greatest rainfall variability of any countryin the world. We are captive to this variability. IndigenousAustralians have known for thousands of years thatAustralia’s rainfall is highly variable. Yet from Europeansettlement onwards, this variability has confronted andbewildered us. Understanding this variability is the key tounderstanding how we have managed our water resources.Australia’s climatic variability is captured in its extremes: frommonsoonal patterns in its tropical north to desert areas w<strong>here</strong>no real rain falls for years (and yet w<strong>here</strong> flash floods periodicallyIn 1931–32, the NSW Government funded the construction of a new crossing over the SnowyRiver at McKellar Crossing. <strong>The</strong> concrete-and-steel bridge was 50 m high and 250 m long. Justa few days before the official opening, a major storm, accompanied by a cloudburst, occurredin the upper catchment. This is how the impact was captured:‘<strong>The</strong> ensuing flash flood, thick with uprooted trees and rocks, swept out of the tributary justabove the new bridge, shot across the Snowy River and smashed against the far bank, then swungdownstream. <strong>The</strong> water level was 4 m higher than any flood previously recorded. <strong>The</strong> force torethe bridge’s steel trusses from its pylons. <strong>The</strong> tangled wreckage came to rest a few hundred metresdownstream. <strong>The</strong> construction foreman, Edward ‘Ted’ Kay, contacted Orbost on his short-wave radioto advise that the opening should be cancelled.’ 3occur, miraculously bringing these arid areas to life). T<strong>here</strong> areplaces in our warm-temperate zone w<strong>here</strong> summer temperaturessoar over 40°C, while winter temperatures fall below freezing.Early European settlers were struck by the variability of ourrainfall. Australian rivers and streams could be raging torrentsbursting their banks in the spring yet slow to a trickle by summer.<strong>The</strong> iconic Murray River is a good illustration of this naturalvariability in flow. <strong>The</strong> long-term, average runoff reaching theriver is 11 259 GL (gigalitres*), but this can vary from 1670 GLin a very dry year to 30 000 GL in one very wet year. 1 <strong>The</strong> OrdRiver in Western Australia has a long-term average flowof 3980 GL. This can be as low as 1000 GL and as high as12 000 GL. 2<strong>The</strong>se kinds of extremes are in stark contrast to riverssuch as the Thames, the Nile, the Mississippi and theDanube, which have appreciable flow throughout the<strong>entire</strong> year.This high variability defies prediction. Yet it’s important for usto understand the ways in which this climatic variability bothdominates and constrains our use of land and water. It has playeda huge role in the past and will continue to do so into the future.*A gigalitre is a thousand megalitres or one billion litres. <strong>The</strong>volume of water in Sydney Harbour is approximately 500 gigalitres.<strong>Victorian</strong> Women’s <strong>Trust</strong> - Our Water Mark 19
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