#Wyoming preps for less #water as #drought creeps up #ColoradoRiver — WyoFile.com #COriver #aridification

Photo credit: NPS

From Wyofile.com (Angus M. Thuermer Jr.):

As federal water managers declared the first-ever official Colorado River water shortage last week, a top official said he’s confident Wyoming will responsibly implement its plans to store and divert even more flows from the troubled waterway.

The Department of the Interior on Aug. 16 said it would reduce water diversions to Arizona, Nevada and Mexico in 2022 after a scheduled August review set the restrictive sideboards for releases next year.

Despite that curtailment, Wyoming plans to corral another 115,000 acre-feet annually by building and modifying dams and their operations to potentially allow more diversions.

At the same time, Wyoming is fleshing out its Drought Contingency Plan and a “demand management” program that could see voluntary reductions in diversions before users in the state might be cut off. Wyoming doesn’t expect curtailments to happen next year, unless drought, aridification and climate change unexpectedly exacerbate the decline in Lake Powell.

In a press call announcing the downstream diversion reductions, a regional Bureau of Reclamation director appeared unfazed by the potential impacts of Wyoming’s dam-building plans.

“Wyoming has exercised foresight in the work of their Wyoming Water Development Commission,” said Wayne Pullan, the BOR’s director for the Upper Colorado River Basin, “and with our long history with Wyoming we’re confident that they’ll pursue any future projects responsibly, fully aware of the context of the hydrology and the difficulties on the Colorado River.”

Wyoming’s representative to the Upper Colorado River Commission, which will decide how any curtailments in Wyoming, Utah, Colorado and New Mexico will be borne, said his cohorts are “very concerned about the hydrology this basin faces.” A Drought Contingency Plan that’s been adopted in skeleton form “does provide the tools to help manage what we’re seeing now, as troubling as that is,” commission member Pat Tyrrell said at the press call.

Wyo forges ahead with dams…

Pullan would not comment on specific ongoing Wyoming projects, at least five of which in the Green River and Little Snake River basins would collectively control an additional 115,000 acre-feet at an estimated cost of $123 million.

“It is worth noting that one of the purposes of the Colorado River storage project is to assist states, making use of their apportionment under the [1922 Colorado River] Compact,” Pullan said. Wyoming has not developed or appropriated its full share of the water entitled under that historic agreement, state officials have said.

Lake Powell end of month projections from August 2021 24-month Study. Credit: USBR

The compact and apportionment among the seven states and Mexico, however, is based on an annual supply of at least 15 million acre-feet, an amount experts say the river basin no longer produces. Further, Wyoming believes the lower basin’s Arizona, Nevada, California and Mexico have historically overused their share while upper division states have not exploited their full rights.

At least one group has called for a moratorium on new storage or diversion projects in the basin until the seven states and Mexico can address what’s widely seen as claims to flows that no longer exist. Wyoming still deserves its share, state officials believe.

“We aren’t obligated to sustain overuse anywhere else,” Tyrrell said in an interview, “to the detriment of our existing demands here in Wyoming.”

Tyrrell offered one scenario where an ongoing dam project could be immediately affected by less runoff. At the Big Sandy Dam in Sublette County, the Bureau of Reclamation is raising the structure to impound an additional 12,900 acre-feet for irrigation.

“That’ll come under a more recent priority date,” Tyrrell said, meaning the new storage area will be among the first to be cut off if lower-basin shortages creep upstream. The doctrine of prior appropriation that governs water use in Wyoming recognizes the first-in-time water appropriation to be first-in-right when shortages occur.

“If we are, for example, under any kind of curtailment,” Tyrrell said, Big Sandy “won’t be allowed to fill.

“It will put no more additional stress on the system if it’s not allowed to fill up,” he told WyoFile.

Other new dams, reservoir enlargements or operational changes that would give Wyoming access to more water would be subject to separate sideboards depending on whether they are built, what priority of appropriation they might impound, who owns them and other factors.

The amount of water involved in the Wyoming projects is “very small in comparison to Lake Powell,” Tyrrell said. Powell holds some 20 million acre-feet of what’s called active storage — the amount that can actually be used.

The downstream reductions — 18%, 7% and 5% of Arizona, Nevada and Mexico’s annual apportionments respectively — amount to 613,000 acre-feet. That’s about 3% of Powell’s storage or, seen another way, about 10% more than Wyoming’s average annual usage of basin flows.

The impact of any additional consumptive use in Wyoming — which could approach the 115,000 acre-feet contemplated in Wyoming’s dam plans — “is very, very small in comparison to what might be stored in Lake Powell,” Tyrrell said.

“I believe the environmental impact statement for Big Sandy found there would be no significant impact to reservoir elevations downstream by an enlargement,” he said.

Wyoming’s legal team stands behind water developers, assistant attorney general Chris Brown said as he echoed Tyrrell’s overview. “We are certainly not obligated to sustain overuse in other places in the basin on the backs of Wyoming water users, either current or future.”

Water developers, including Wyoming itself, understand the priority system and risks associated with constructing impoundments to hold back flows. In the face of dwindling supply, some wonder whether new structures might become stranded assets — facilities built under one scenario that can’t be used as intended in a new reality.

A professor of natural resources law at the University of Colorado Law School expressed skepticism about Wyoming’s basin-wide plans. “That seems like a bad investment,” Mark Squillace said in an interview.

… and plans for curtailments

Already the Bureau of Reclamation has activated provisions under its Drought Response Operations Agreement to release water from Flaming Gorge Reservoir in Wyoming and Utah. Pullan called the action a “small ‘e’” emergency release that will help keep the level at Powell high enough to continue generating valuable electricity.

The Flaming Gorge releases and others also help the four upper-basin states meet their water-flow obligations under the 1922 compact, Wyoming’s Tyrrell said. The dwindling flows, he said, “threaten to get worse.”

WyoFile is an independent nonprofit news organization focused on Wyoming people, places and policy.

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