In Southwestern Australia, drought is the new norm. Rainfall there has been below average since 2012 and yearly averages have been dropping since 1970. Researchers from the National Oceanic and Atmospheric Administration (NOAA), using a new and improved climate model to simulate regional-scale precipitation, predict 40 percent less rainfall in the austral autumn and winter (rainy season) for Southwestern Australia through the end of the twenty-first century. The modeling study, reported on June 13, 2014 in Nature Geoscience, found that the declining rainfall is caused by changes in atmospheric circulation and pressure in the region as a result of increased greenhouse-gas emissions and thinning of stratospheric ozone (ozone hole) over Antarctica. Such projections are important for drying regions because in the march toward desertification, historical rainfall records may no longer be useful guides for water resource managers and hydrologists. See also: Air pressure; Atmospheric general circulation; Australia; Climate modeling; Climatology; Desertification; Drought; Ecohydrology; Greenhouse effect; Hydrological consequences of global warming; Hydrology; Precipitation (meteorology); Stratospheric ozone; Water resources

Perth, a city of about 2 million people and the capital of Western Australia, is a representative example of a metropolitan area with a drying climate. According to the Australian Government Bureau of Meteorology, the rainfall totals for Perth in June 2014 were 20–50 percent below average. Less rainfall means less runoff, and on July 17, 2014 only 11 gigaliters (GL; one billion liters) had flowed this year into Perth’s reservoirs, which were at 29.7 percent of capacity. From 1911 to 1974, streamflow to Perth’s reservoirs averaged 338 GL. For the period 2006–2013 the average streamflow was 65.8 GL—a serious decline. See also: Climate modification; Global climate change; Reservoir

As its reservoir levels decline, Perth has been coping with its water-supply deficit through seawater desalinization and by drawing on its groundwater (aquifers). Desalinization is expensive, however, and groundwater extraction is not sustainable. To adapt to the growing difference between water supply and demand, Perth has implemented, or plans to implement, conservation measures, wastewater reuse (recycling), stormwater runoff management, and groundwater management, including recharge. In June 2016, Perth will begin injecting treated wastewater into its aquifers, with the intention of eventually supplying 20–25 percent of its drinking water by this method. For a sustainable groundwater supply, water resource managers are proposing limiting groundwater extraction during wetter periods and allowing some aquifers to be overdrawn during extremely dry spells. By 2060, however, the Water Corporation of Western Australia estimates that Perth will need an additional 365 GL of water to meet its demands. See also: Aquifer; Groundwater hydrology; Seawater; Sewage treatment; Sewage water reclamation; Streamgaging; Wastewater reuse; Water conservation; Water desalination; Water supply engineering; Water table