Murray-Darling is the longest river system of Australia but it has had problems to reach the sea. Some of the causes are over exploitation and pollution, directly related to the agriculture activity in the region representing 40% of the total in the country, another one is global warming. The region has been afflicted by El Niño phenomena, drying the area causing depletion not only in the groundwater but also in the soil conditions. As a consequence the agriculture there is at risk. Many crops have failed already because of the lack of water. Biodiversity have been hurt in this process too. The number of endemic fish has decreased. The government proposed investing in more efficient irrigation and water trading rights.
For more information go to http://www.mdbc.gov.au/nrm/water_issues/surface_water, http://www.cana.net.au/water/changes/index.html.
The economist April 28th 2007. Briefing Australia's water shortage.