From Grist (Nathanael Johnson):

For the first time in history, low water levels on the Colorado River have forced Arizona, Nevada, and Mexico to cut back the amount of water they use. It’s the latest example of climate change affecting daily life, but also an encouraging sign that people can handle a world with less: These orderly cutbacks are only happening because seven U.S. states and Mexico had agreed to abide by conservation rules when flows subside, rather than fight for the last drops.

“It is a new era of limits,” said Kevin Moran, who directs the Environmental Defense Fund’s Colorado River efforts…

A Bureau of Reclamation study of Colorado River levels, released Thursday, triggered the cutbacks. The Rocky Mountains finally turned white with heavy snow last winter, but despite a galloping spring runoff, drought persists and bathtub-ringed reservoirs in the Grand Canyon are low. In its study, the Bureau highlighted the unique circumstances: “This 20-year period is also one of the driest in the 1,200-year paleo record.”

Rising temperatures brought on by rising carbon emissions are partly to blame. “Approximately one‐third of the [Colorado River] flow loss is due to high temperatures now common in the basin, a result of human caused climate change,” wrote scientists Brad Udall and Jonathan Overpeck in a study published in 2017 that anticipated water will only become scarcer in the future.

But these water-use reductions are also an example of people binding themselves to rules to deal with scarce resources, rather than going to court, or war. The cutbacks come from an agreement hammered out by the Southwestern states and Mexico to impose limits on themselves.

“It’s not necessarily well known or talked about, but this collaboration between the states and Mexico is one of the most successful cross-border water management stories in the world,” Moran said.

From the Associated Press (Felicia Fonseca) via The Las Vegas Sun:

Arizona and Nevada are faced with the first-ever cuts to their Colorado River water supply in 2020.

But the cuts aren’t expected to be overly burdensome for either state because they’ve been conserving and storing water for years…

Arizona will leave 7% of its allocation in Lake Mead under a drought plan approved earlier this year by several states that rely on the river. Nevada will leave 3%.

Mexico also gives up 3% under a separate accord.

The states and Mexico can recover the water if Lake Mead rises to a certain level.

From The Nevada Independent (Daniel Rothberg):

The decision to implement those cuts came on Thursday after federal water managers released a study that serves as a key benchmark for Southwest states. That forecast predicted that Lake Mead would start 2020 at 1089.4 feet above sea level, below the 1090-foot trigger for the cuts.

By forgoing water in dry years, the states store more water in Lake Mead, a reservoir that has decreased over the past two decades because of overuse, drought and climate change. If the reservoir drops further, states would be required to take more cuts to their allotment. When reservoir levels rise, the states are allowed to access the stored water for future use.

In practice, the cuts will have no effect on Nevada’s short-term water security or water management. The Southern Nevada Water Authority is expected to voluntarily conserve about nine times more water this year than the required cuts under the drought plan in 2020. Since 2003, Nevada has used less water than what the state is allowed to take under the river’s interstate compact.

In 2017, the state used about 80 percent of its allotment, largely in part because of indoor water recycling and conservation programs that incentivize removing grass. This year the water authority is on track to use even less. That means Nevada is likely to leave substantially more water in the reservoir this year — as much as 75,000 acre-feet — than what is required by the cuts — about 8,000 acre-feet — next year. (An acre-foot is an agricultural term for the amount of water that can fill an acre to a depth of one foot. Nevada’s allocation is 300,000 acre-feet).

Bronson Mack, a water authority spokesman, said that the agency has cut its Colorado River water use by 25 percent since 2002, even as Las Vegas’ population has grown by 40 percent…

But the cuts are still significant, said John Fleck, a University of New Mexico professor who has a forthcoming book, “Science Be Dammed,” that looks at the history, politics and hydrology of the river. They mark the first time the states have been required to use less than their allocation…

It is also a recognition of a future where there is expected to be less — not more — water to go around. Even though above-average levels of snow fell across much of the West this year, the long-term trend in the Colorado River is toward declining streamflow. Research has found that high temperatures have made runoff less efficient. Scientists say that climate change could further reduce the river’s flow and make managing it more difficult, even as demands grow.

Heavy precipitation made a difference this year. When the U.S. Bureau of Reclamation released its 2019 forecast last year, the study predicted an official shortage in 2020. Water users avoided that declaration, although the federal water agency warned that they are not out of the clear.

From The Colorado Sun (Jason Blevins):

“This is a big deal for everybody on the Colorado River system,” said Jim Pokrandt, the head of community affairs for the Glenwood Springs-based Colorado River Water District.

The study won’t have much of an impact on Colorado, where the Upper Basin Drought Contingency Plan has water users hammering out the details of “demand management.” Those details include asking for temporary, voluntary and compensated curtailment of water rights to build a bank of Colorado water in Lake Powell before mandatory cuts are imposed by the federal government.

Pokrandt said the dawning of mandatory cuts in the Lower Basin increases the urgency of demand-management talks in Colorado. Without a demand-management plan encouraging water users to volunteer their water rights in Colorado, the state could see mandatory cuts, where “nobody gets paid,” he said.

“The news from the Lower Basin is a reminder that 2019’s snowpack cannot give us a false sense of security,” Pokrandt said, recalling that Colorado’s super-snowy 2011 was followed by an exceptionally dry 2012. “This is a reminder of the importance of what the Upper Basin states have to do for their own Drought Contingency Plan.”

[…]

hat’s called demand management. Across Colorado, water districts and water users are studying whether demand management will work.

“Nobody knows if it will be feasible,” said Pokrandt, whose 15-county district spans the Western Slope, noting that the Colorado Water Conservation Board just launched its Demand Management Workshop to educate the state’s water users on the idea of temporarily suspending water rights for cash in order to build a bank of Colorado water in Lake Powell. “Determining feasibility will be a long process.”

Lake Powell will enter 2020 in the “Intentionally Created Surplus Condition,” which allows for the release of the usual 8.23 million acre-feet of water in 2020 to fill Lake Mead. It also means the Upper Basin states will increase their own banked storage in the reservoir, enabling them to better weather low-snow years with a protected cache of extra water.

Total storage in both reservoirs is 55% of capacity, compared with 49% at this time last year.