by Ker Than forÂ National Geographic
(As reported in National Geographic)Â Â
SALTON SEA – Standing atop a rocky outcrop on the southeastern edge of the Salton Sea in southern California, Bruce Wilcox pointed to the wooden ruins of a boat dock that dates back to the 1960s, when the region was a marina that attracted sport fishermen and celebrities.
On a sunny day last December, the dock sat hundreds of feet from the water, rendered obsolete by the shoreline’s steady withdrawal. No boats were visible anywhere on the shimmering blue water.
“The marina’s been dry for the last five or six years,” said Wilcox, 60, the environmental manager for the Imperial Irrigation District (IID), which manages water and energy in California’s Imperial Valley and has energy customers in the Eastern Coachella Valley.
Covering nearly 350 square miles (900 square kilometers), the Salton Sea is the largest lake in California. It was created in 1905 when heavy rain and snowmelt caused the Colorado River to swell and overtake headgates along the Alamo canal.
It was largely sustained by agricultural runoff from the Imperial Valley, but since the late 1990s the sea has been steadily shrinking, partly because the runoff has dwindled due to a combination of the ongoing California drought, more efficient irrigation methods, and changing crop patterns.
The sea’s decline will accelerate dramatically in 2018, when the IID must stop sending “mitigation water” to the lake as part of a pact known as the Quantification Settlement Agreement, or QSA.
Signed in 2003, the QSA was a deal between the U.S. Department of the Interior, California, and various water agencies in the state that placed California on a Colorado River water diet and transfers some of the river’s flow to San Diego and other cities, where water is scarce.
Under the terms of the QSA, 30 million acre-feet of water will be sent to San Diego County and Coachella Valley over a period of 75 years, making it the largest ever farm-to-city water transfer in U.S. history. One acre-foot is approximately 325,900 gallonsâ€”or enough to supply two single-family households of four for a year.
The QSA was designed to gradually wean California off its overdependence on water from the Colorado River.
According to a 1964 U.S. Supreme Court decree, California is entitled to 4.4 million acre-feet of waterâ€”or about 30 percent of the total allocationâ€”from the river annually, but the state regularly exceeded this amount in past years.
This wasn’t a problem as long as Arizona and Nevada didn’t use up their apportionments, but as the populations of those states grew, so too did their water needs.
Of California’s allotment, 2.6 million acre-feet is shunted to the Imperial Valley via an 82-mile (132-kilometer) canal, where it has been used to transform a sandy desert into a farming oasis.
The Imperial Valley thus uses 20 percent of the Colorado River’s total water allotment. With that water, farmers in the valley grow about 80 percent of the nation’s winter crops, including lettuce, broccoli, cauliflower, carrots, sweet corn, watermelons, cantaloupe, and onions.
Farmers also produce alfalfa and Bermuda grass hay, which is used as dairy feed in the U.S. and abroad.
The QSA has been in effect for more than a decade, but the deal’s long-term success could be threatened because two of its key requirements remain unmet, and observers say there is little hope of their being satisfied before a 2018 deadline.
Saving Water Down on the Farm
One of those requirements is the implementation of water-saving systems on farms. Under the terms of the QSA, the IID will deliver water to the San Diego County Water Authority and the Coachella Valley Water District for up to 75 years. The schedule calls for the amount of delivered water to increase by 20,000 acre-feet each year.
In 2013, about 100,000 acre-feet of water were delivered; by 2018, it will be 130,000 acre-feet per year, and by 2026, it will be 200,000 acre-feet per year, after which the volume will be capped.
The IID plans to meet its water obligations through a combination of efficiency improvements to its water delivery system and to on-farm water use.
As an example of the former, the IID is lining portions of its delivery canals with concrete to reduce seepage losses and is constructing regulatory reservoirs to better match farmers’ requests for water with actual supply.
Reducing on-farm water use has proven more difficult. The IID planned to meet this goal by enticing farmers to install advanced sprinkler systems and other improved irrigation techniques.
“If you used to use 200 acre-feet and now you’re using 160 acre-feet, we pay you for the 40 acre-feet that you saved,” explained David Bradshaw, IID assistant water manager for agriculture water management.