Secular Regime Shifts,Global Warming and Sydney's Water Supply

Sydney's water crisis has been attributed to long-term drought, a population growing at >50 000 a year, the early impacts of global warming and the demands of a 4.2 million population leading a water-thirsty lifestyle. In this paper the drought is linked with a return to a drought-dominated flow regime in eastern New South Wales. This began in 1991 and is associated with a shift from flood to drought domination that occurs every 20 to 50 years. Its impacts will be further exaggerated by global warming. The reduction of runoff into Sydney's reservoirs is due primarily to regime shift, resulting in the diminution of inflows to about 25% of their levels in the 42 years before 1991. Possible ways of managing these dwindling water resources include building more reservoirs, exploiting largely unknown sources of groundwater, constructing a desalination plant, harvesting rainwater in the city, recycling used urban water and reducing individual water use. Despite arguments against the first three of these options, a desalination plant is currently under construction and investigations of deep groundwater proceed (shelved 18th June, 2008). Given that sources of water are distant and located in areas where rainfall reductions have been significant, greater efforts should be made to use water already in the city (rainfall and recycled water). Water restrictions and better domestic management of water are also areas where great savings can be and have been made.