Two Wyo rivers under restrictions due to low snowpack, drought


WYOMING -- April is typically when thousands of irrigators on the North Platte River — particularly along its tributaries — begin to divert spring runoff onto hayfields and crops, kicking off what they hope will be a productive growing season. Today, however, those with junior water rights are under new orders to curtail those critical early springtime diversions — a rare scenario that could prove costly for many farmers and ranchers in the state.  

“When the water is coming, you’ve got one shot at it,” Upper North Platte Water Users Association Chairman Chris Williams said. Watching spring runoff flow downstream without tapping it is counterintuitive and frustrating for any ag producer, he added. “It has the potential to dry acres up.”

The “call,” or order, to restrict water diversions among North Platte River users with junior rights was initiated by the U.S. Bureau of Reclamation during the first week of April. The order, which is enforced by the Wyoming State Engineer’s Office, is set to expire at the end of the month. Water rights are prioritized based on a “first in time, first in right” doctrine. Those who gain rights to use water first have “senior” rights over those who gain water rights after them.

It’s unlikely the BOR will recommend extending the call, even if hydrological conditions and forecasts for the seven-reservoir North Platte River water storage system do not improve, according to Lyle Myler, acting manager for the Wyoming Area Office of the Bureau of Reclamation.

“Our hope is that the curtailment of [junior] water rights will allow us to receive our share that’s allotted to us under our 1904 water rights, or as much as we can get,” Myler said.

Water users with junior rights on the Tongue River and its tributaries in northeast Wyoming are also on notice for similar, legally enforceable water conservation measures, following a call from Montana. Though no actual water diversion curtailment orders have resulted so far, those users will remain on notice until Montana officials remove the call, according to the Wyoming State Engineer’s Office.

A call on a river or drainage system is a legal mechanism to order water conservation actions to help ensure minimum, legally required flows to users with senior rights to divert water — typically for irrigation. It can also apply to groundwater wells that pump from a drainage for municipal or industrial uses. In the event of a potential water shortage, those with junior rights can be ordered to forgo diverting water to help ensure that senior-rights holders downstream get their full allotment.

The BOR and water management authorities in Wyoming and Montana all cited low snowpack, persistent drought conditions and forecasts for lower-than-average precipitation for initiating the water conservation measures and notices.

“The Tongue River Basin has been experiencing drought conditions over the past year with below average winter snowpack and streamflow conditions,” according to an April 7 statement from the Wyoming SEO. “The North Platte River system has experienced multiple years of drought resulting in low reservoir storage carryover.”

The conditions are consistent with climate trends that have pushed the statewide annual mean temperature upward by 2.2 degrees Fahrenheit from 1920 to 2020, according to National Oceanic and Atmospheric Administration data. The climate trend is also altering hydrological conditions in the state, such as lower snowpack and an earlier spring runoff season.

Despite current conditions and forecasts for lower-than-normal precipitation, however, it’s too early to know what spring may have in store, Wyoming State Engineer Brandon Gebhart said. If heavy spring snow and rain events do materialize, it could negate the need to curtail water diversions, he added.

The climate conditions contributing to the calls in Wyoming are likely to continue to force water managers to cooperate on conservation measures throughout the West, according to Utah Rivers Council Executive Director Zachary Frankel.

“As our precipitation shifts from snow to rain, it is causing havoc on our water supplies, and that’s going to continue in coming years and decades,” Frankel said. “Although some climate model runs show increased precipitation — meaning more rain — it’s not likely to increase our total water supplies because of additional challenges from decreased soil moisture and a range of other challenges on the water demand side.”

The BOR initiated the call on the North Platte River during the first week of April based on measurements and forecasts that indicate the seven-reservoir storage system might fill to only 950,000 acre-feet of water during this year’s “water season.” That’s below the Modified North Platte Decree’s call-triggering minimum of 1.1 million acre feet. The order applies to those with post 1904 water rights from the Wyoming-Colorado border to Guernsey Reservoir.

In a separate action, the Montana Department of Natural Resources and Conservation issued a call on the Tongue River and its tributaries in Wyoming on April 1. The call is necessary to ensure that the Tongue River Reservoir in Montana fills this summer, and to otherwise hold Wyoming to account for legal obligations under the Yellowstone River Compact, according to Montana NRC Commissioner Anna Pakenham Stevenson.

Gebhart responded by notifying those with post-1950 water rights — junior rights — on the Tongue River and its tributaries that they may be ordered to curtail diversions at some point this summer. However, Gebhart and the agency’s Division II management that oversees the Tongue River drainage took issue with Montana’s initial assertions regarding forecasts for flows in the Tongue River.

Although both states acknowledged critical “data gaps,” the water storage and snowpack assessments initially cited by Montana should never have resulted in a call on the Tongue River, according to Gebhart. At the time, snowpack measurements for the drainage area measured more than 90 percent of the annual average. On April 19, it increased to 99 percent, according to a Natural Resources Conservation Service report. 

Montana issued similar calls on the Tongue River in 2015 and 2016 based on more dire assessments than those cited this year, Gebhart said. But no orders to limit water diversions were necessary in response to either of those calls.

For now, both Wyoming and Montana continue to measure snowpack, water volumes and forecasts in the Tongue and greater Yellowstone River systems — hopeful that it might not be necessary to order irrigators to curtail normal irrigation practices, Gebhart said.

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

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