by Jack Rosebro
|Mountain snowpack in the Great basin and major water supply basins for California. Source: USDA. Click to enlarge.|
Faced with three straight years of drought and an uncertain agricultural water supply, California Governor Arnold Schwarzenegger declared a state of emergency Friday, announcing that statewide water rationing could be instituted as early as the end of next month. “Despite the recent rain and snow,” the governor’s office warned, “cumulative water deficit is so large that there is only a 15% chance that California will replenish its water supply this year.”
Just 2.47 million acre-feet (MAF) of natural inflows are projected to reach the state’s Shasta Reservoir in 2009, less than half the 6.1 MAF average of the past half century (1956-2005). Major reservoirs such as Oroville, Folsom, and San Luis, as well as Shasta, are already two-thirds or more below capacity.
If dry conditions persist through the spring, California will be facing its worst drought ever recorded. This week’s forecasts for projected runoff suggest tough times ahead.—Donald Glaser, regional director for US Bureau of Reclamation (BOM) Mid-Pacific Region
Last week, the BOM announced that diminished natural inflows of water in California had triggered predetermined “shortage criteria” which may leave some of the state’s major water users, including as much as two-thirds of farms in California’s Central Valley, with little to no federal water allotments for 2009. Many farms south of the Sacramento Delta are expected to receive no federal water at all unless precipitation increases dramatically over the next two months. Urban areas of the state will also see their water allotments reduced.
More than a million acres (4,000 square kilometers) of farmland may be idled as a result of the restrictions, and UC Davis economist Richard Howitt has estimated that the San Joaquin Valley alone will suffer a loss of approximately 70,000 jobs and US$2 billion in economic activity this year as a result of restrictions on agricultural water. The governor’s office projects the overall loss of statewide economic activity at US $3 billion.
“It’s grim news,” remarked Tim Quinn, executive director of the Association of California Water Agencies (ACWA), whose members represent more than nine-tenths of water delivered in the state. “If this isn’t the bottom, I don't want to be around for the bottom.” Although the Bureau of Reclamation forecast does not include runoff from storms since 1 February, that runoff is not expected to significantly alter its forecast, which the BOM has projected with a 90% confidence rate.
“We Have Never Squarely Faced The Future”
In an opinion published this week in the Los Angeles Times, oceanography research scientist William Patzert of Jet Propulsion Laboratories and Los Angeles Metropolitan Water District (LA-MWD) Chairman of the Board Timothy E. Brick declared “...the way Californians have been using water is simply not sustainable. We have no choice but to use less and to pay more for it.”
Last year, LA-MWD depleted its reserves at a rate of more than half a billion gallons of water per day to meet customer demand. “That can’t go on indefinitely,” wrote Patzert and Brick. “We have never squarely faced the future. Water projects built Southern California. Now we need water stewardship to sustain it.” The Metropolitan Water District gains about 200,000 new customers per year.
Commenting on the Patzert-Brick opinion, Lucinda Sue Crosby of the Indian Wells Valley Water District warned that “decades-long droughts are the tip of the iceberg. Ancient bristlecone pines tell a story through dendrochronlogy about droughts over the past 11,000 years in California and Arizona... Droughts of 30-60 years are not unusual and those of 150 years are not uncommon.”
Earlier this month, Energy Secretary Stephen Chu also expressed concern (earlier post) that California’s agriculture industry would not survive a loss of up to nine-tenths of the state’s Sierra Nevada snowpack, coupled with business-as-usual warming, as projected by the end of this century.
A study completed last year by research marine physicist Tim Barnett and climate scientist David Pierce of the Scripps Institute of Oceanography, found a 50% chance that Lake Mead, a key source of water for millions of people in the southwestern United States, will be unable to produce hydropower at Hoover Dam by 2017, and be dry by 2021, if climate changes as projected and future water usage is not sharply reduced.
“We were stunned at the magnitude of the problem and how fast it was coming at us,” said Barnett. “Make no mistake, this water problem is not a scientific abstraction, but rather one that will impact each and every one of us that live in the Southwest.” Barnett and Pierce used what they consider conservative metrics, assuming that the effects of climate change on the Colorado Basin began in 2007, and using only the last 100 years of riverflow. The average annual flow into what is now Lake Mead, taken over the last 500 years, is even lower.
Last week’s actions taken by the Bureau of Reclamation parallel policy decisions that the Australian government have made in the past regarding its Murray-Darling Basin, a region almost twice as large as California, which provides water for more than 40% of Australia’s agriculture. Farmers served by the MDB saw 2007 water allocations cut by 50 to 100% as a result of extended drought, which the government now regards as semi-permanent.
Barnett, T. P., and D. W. Pierce (2008), When will Lake Mead go dry?, Water Resour. Res., doi: 10.1029/2007WR006704