#ColoradoRiver: The entire basin is pretty much in #drought #COriver #aridification

Credit: Wikipedia.org

From Water Deeply (Matt Weiser):

The river’s Upper Basin – generally north of Lake Powell – has been largely insulated from the 19-year drought afflicting the giant watershed, thanks to the region’s relatively small water demand and heavy snows that bury Colorado’s 14,000ft peaks each winter. But this year, there was no salvation in the snowpack.

Several major Colorado River tributaries – the Dolores, San Juan and Gunnison rivers – saw record-low snowpack this winter. Others, including the Yampa River and the headwaters of the Colorado itself, did not break records but saw snowpack shrink to 70 percent or less of average.

As a result, many reservoirs on the west slope of the Rocky Mountains have shrunk to mud puddles. In August, the resort city of Aspen, Colorado, imposed mandatory watering restrictions on its residents and visitors for the first time in its history. And in another first, the state of Colorado curtailed water rights on the Yampa River – which flows through Steamboat Springs – forcing some water users to stop extracting water to protect higher-priority users and aquatic life in the river.

In the Colorado River’s more arid Lower Basin, the chronic drought has received plenty of attention due to the dramatic shrinkage of Lake Mead and the likelihood of water shortages for Arizona, Nevada and California in 2020. But drought in the Upper Basin has gone relatively unnoticed, and in many ways it will be a much tougher problem to solve.

“This is the first time we’ve had to wake up in the morning and say, ‘Oh my gosh, our lives have changed,’” says Doug Monger, a county commissioner in Routt County, Colorado, home to Steamboat Springs. “It’s scary as hell.”

Mead and Powell are the largest and second-largest reservoirs in the nation, respectively. They’re linked by the Grand Canyon, one of the planet’s most iconic geologic features. Yet while everyone has watched epic drought paint a giant bathtub ring around Lake Mead, Lake Powell has been shrinking, too.

The water elevation at Powell has sunk 94ft since 2000. A big reason is that Lake Powell has been used to keep Lake Mead from sinking to an elevation of 1,075ft, the point at which the federal government must declare a water shortage under a 2007 agreement. This would cause mandatory water delivery cuts to the Lower Basin states, triggering widespread water rationing.

A new report by a team of science and policy experts, known as the Colorado River Research Group, notes that continuing this practice will bring harm to Lake Powell. If the lake shrinks, it could compromise hydropower generation at Glen Canyon Dam and prevent Lake Powell from continuing to backfill Lake Mead.

It could also touch off an ugly dispute between the two basins. To reach agreement on the 1922 Colorado River Compact, Upper Basin states committed to send the Lower Basin states a certain amount of water. As measured at Lee’s Ferry, just below Lake Powell, those water deliveries must achieve a 10-year running average of 75 million acre-feet. If not, the Lower Basin states can declare a “compact call,” triggering negotiations that could subject the Upper Basin states to water rationing.

That prospect, long considered remote, may now be looming.

“The lower Lake Powell gets, the higher the probability that’s going to happen,” says Douglas Kenney, a member of the research group and director of the Western Water Policy Program at University of Colorado Law School. “A compact call would be devastating in the Upper Basin. It would be total chaos.”

That’s because there are no hard and fast rules to govern a compact call. There is no clear trigger for the process, unlike the elevation triggers at Lake Mead. And there is no clear process that follows declaration of a compact call, nor any rules about who should cut their water use.

If the Lower Basin declares a compact call, Kenney says, it would surely be contested by Upper Basin water users.

“Some of that could be Supreme Court-type litigation that could come into play,” he says. “If you get to that point, all you’re doing is saying there’s not going to be enough water for everybody, so let’s decide who’s going to get the short end of the stick. You never solve problems when you get to that situation.”

Powell has continued shrinking not just because of drought in the Upper Basin, but because the Lower Basin has benefited from surplus water passed through Glen Canyon Dam – beyond requirements of the 1922 agreement. Through interim rules adopted in 2007, surplus flows in the Upper Basin have been passed along to Lake Mead to keep the latter from falling into shortage. This water would have otherwise stayed in Lake Powell and avoided the decline in water elevation there.

This has amounted to an 11 million acre-feet bonus for Lake Mead since the surplus water began flowing, Kenney’s group found in the new report. And Lake Powell is likely to go on shrinking as long as these water releases continue.

In addition to the threat of a compact call, Colorado now has its own water shortages to worry about from drought and climate change. A new study, for instance, blames 53 percent of the decline in water flows in the Colorado River on warmer temperatures, not just less precipitation. This is likely to continue as temperatures warm, a worrisome trend since the Upper Basin delivers about 90 percent of all the flow in the Colorado River.

West Drought Monitor September 11, 2018.

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