Wednesday, December 21, 2011

The Coming Mega Drought

Australia experienced the worst and most consistent dry period in its recorded history over much of the past decade. The Murray River failed to reach the sea for the first time ever in 2002. Fires swept much of the country, and dust storms blanketed major cities for days. Australia’s sheep population dropped by 50 percent, and rice and cotton production collapsed in some years. Tens of thousands of farm families gave up their livelihoods. The drought ended in 2010 with torrential rains and flooding.

Australia’s Millennium Drought is a wake-up call for residents of the drought-plagued southwestern U.S. and for all of us. What happened in Australia could happen in the U.S., with devastating consequences to the region and to the nation. We can avert the worst, however, if we pay attention to Australia’s experience and learn the right lessons.

The southwestern U.S. bears some resemblance to parts of Australia before the drought. Both include arid regions where thirsty cities and irrigated agriculture are straining water supplies and damaging ecosystems. The Colorado River no longer flows to the sea in most years. Water levels in major reservoirs have steadily declined over the past decade; some analysts project that the largest may never refill. The U.S. and Australia also share a changing global climate that is increasing the risk of drought.

Evidence is mounting that climate change is playing a role in Australia’s water woes. Since 1950 average rainfall has decreased 15 percent, and researchers found average temperatures over southeastern Australia from 1995 to 2006 were 0.3 to 0.6 degree Celsius higher than the long-term average. The combination of higher evaporation and lower precipitation depletes soil moisture and reduces runoff, making droughts more intense and more frequent. Australian scientists forecast a 35 to 50 percent decline in water availability in the Murray-Darling river basin and a drop in flows near the mouth of the Murray by up to 70 percent by 2030.  More