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Kevin Moloney

Glen Canyon’s sandstone walls, bleached to Lake Powell’s high-water line, are telltale reminders of the reservoir’s shrunken bounty.

The Larger Basin

Bound for the delta, through seven states and Mexico By Jerd Smith

Each year, in an ancient ritual,

the Colorado River Basin’s mountain watersheds graciously give up their melting snows to the river as it winds some 1,450 miles from its headwaters in Rocky Mountain National Park to the Gulf of California. But while water managers along the river’s path consider increasing demands due to population growth, they’re also expecting the river’s bounty to shrink under the influence of prolonged drought and climate change. As states and various interest groups stake out their positions, the health of the river itself suffers. “The overarching issues of the main river are often neglected because people are so up in arms protecting their own private Edens,” says Jonathan Waterman, who has traveled the river from its headwaters to its delta and written about it extensively for the National Geographic Society. “Meanwhile, no one seems to put much stock in the fact that the river no longer reaches the sea and hasn’t for more than 12 years. “ Under the 1922 Colorado River Compact, the seven states that comprise the basin must share its water. At the time the compact was signed, the river’s average annual flow was thought to be 17.5 million acre feet (maf). The three lower basin states—Nevada, Arizona and California—were allotted 7.5 maf per year, and the four upper basin states—Wyoming, Utah, Colorado and New Mexico—expected to receive the same amount. The compact requires, however, that a flow condition be met at Lee Ferry in Arizona, the dividing line between the upper and lower basins—75 maf over a 10-year running average— resulting in the upper basin bearing the impact of shortage created under lower flow conditions. In addition, the lower basin states received the option to develop an additional 1 maf, apparently accounting for the Gila River’s flows in the lower basin. And Mexico, by a treaty in 1944, was awarded 1.5 maf annually, an obligation currently shared equally by the upper and lower basin states, but which raises significant legal issues that remain unsettled. 26

Any excess, historically, has been stored by the upper basin in Lake Powell and by the lower basin in Lake Mead. But over the last decade there has been little excess, in part because the lower basin is consistently overusing its share by 1.5 maf each year, but also because the original allocation of the river was based on a decade of exceptional moisture. In fact today, based on ancient tree-ring studies, modern water measurement techniques and sophisticated weather forecasting, the river is believed to produce no more than 14.7 maf on average. Thanks to drought and climate change, that figure may continue to shrink. The good news for Colorado, which, until recently, believed it had room under the compact to safely develop as much as a half million more acre feet, is that the harsh, exposed shorelines of Lake Powell and Lake Mead are forcing all seven famously combative states to try new arrangements. Some are starting to pay off. In 2002, California signed an historic quantification agreement that reduced its use of the river from 5.2 maf to 4.4 maf. For decades, thanks to surpluses in the river, few ever thought California would agree to such a reduction. But growth in the other lower basin states and painful droughts helped push the parties to finalize the agreement. Then, in 2007, with the help of the U.S. Bureau of Reclamation and the U.S. Department of the Interior, the basin states adopted a more flexible management regime for Powell and Mead, allowing the reservoirs to operate in tandem to ensure their storage levels are kept roughly equal. This reduces the likelihood of either basin hitting the low levels that could lead to a compact curtailment situation and allows the whole river system to both take advantage of good years and make water deliveries easier in dry years. Another important new agreement was triggered in the spring of 2010 by a major earthquake in Mexicali, Mexico. The quake damaged a critical irrigation system, causing physical shortages in Mexico. For the first time, rather than taking its full share of the river’s flows each

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Headwaters Summer 2011: The Mighty Colorado  

As the Colorado River flows through its seven-state, canyon carving traverse, it is tapped and retapped-- supporting acres of irrigated agri...

Headwaters Summer 2011: The Mighty Colorado  

As the Colorado River flows through its seven-state, canyon carving traverse, it is tapped and retapped-- supporting acres of irrigated agri...

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