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TRANSBOUNDARY WATER MANAGEMENTSharing water in Australia:a collaborative endeavourJames Cameron, CEO, National Water Commission, AustraliaSharing water between competing users continues to beone of the world’s hallmark challenges of the twenty-firstcentury. This is no less true in Australia, the driest inhabitedcontinent on Earth.Australia has a challenging hydrology. Highly variable and oftenirregular rainfall and high rates of evaporation result in the lowestrun-off of inhabited continents. About 65 per cent of Australia’srun-off is in the three drainage divisions located in the sparselypopulatedtropical north. Irrigated agriculture is concentrated inthe Murray-Darling Basin to the south-east where only 6.1 per centof national run-off occurs. The basin comprises about 14 per centof Australia’s land area, accounts for 65 per cent of Australia’s totalirrigated land and provides 39 per cent of the total Australian valueof agricultural commodities. 1Most inland Australian rivers are naturally intermittentand are unreliable water sources. The ratio betweenthe maximum and minimum annual flows in Australianrivers is much higher than most major rivers across theworld. For the Yangtze in China, that ratio is two. Forthe Darling River in Australia, the ratio is almost 5,000.Groundwater usage also varies from region to region,on average supplying around 30 per cent of total wateruse in Australia. Consequently, Australia depends onwater storage more than any other developed countryand stores more water per head of population thananywhere else in the world. Yet Australia has relativelyfew sites for efficient dams. The Australian continent ischaracterized by a lack of high mountains, and manywater storages are inefficient, shallow and wide.Image: courtesy of the Murray-Darling Basin AuthorityIrrigation of the Murray River[ 61 ]