When Cheyenne’s municipal water board approved a deal in October to supply up to 14,500 acre-feet of water over 15 years for a proposed gold mine west of town, attorneys insisted on inserting a clause in the contract. It retained the right to cut water deliveries if the city itself has to curtail its water use due to the Colorado River crisis.
“The majority of our water comes from the Colorado River [basin] and if that call [requiring upstream users to cut consumption] comes in, we’re in big trouble,” Cheyenne Mayor Patrick Collins said.
About 70% of the city’s municipal water supply originates 150 miles west in the Little Snake River drainage, a part of the Colorado River Basin. A complex “trans-basin” system of pumps, tunnels and pipelines transports the water under the Continental Divide in the Medicine Bow Routt National Forest to the city.
Cheyenne’s legal claims to the Colorado River Basin water were appropriated from 1954 to 1982 — making it a relatively new user in the system. If there is a curtailment, it would be applied to the newest or most “junior” appropriations, then work back in time to the 1922 Colorado River Compact. That means, depending on how far back in time a curtailment extends, 70% of the city’s water supply could be shut off — an action that could come as soon as 2028 if hydrological conditions keep trending for the worse, according to the Wyoming State Engineer’s office.
“If we lose 100% of our Colorado River Compact water, we’re upside down,” Collins said, adding that about 80,000 people rely on the city’s municipal water system. “We wouldn’t have enough water to meet our current needs.”
For now, Cheyenne, Baggs, Rock Springs, Green River, Pinedale and a handful of other towns that depend on water from the Little Snake and Green River basins in Wyoming are assessing where they stand in the pecking order of appropriated water rights in the event of a curtailment. Although municipalities make up a small percentage of Wyoming water users under the Colorado River Compact and associated laws, their legal claims to the water are among the most vulnerable.
First in time, first in right
If the Upper Colorado River Basin Commission issues a curtailment for Wyoming, it would not necessarily force all water users subject to the compact to close their spigots completely.
For example, if the state had to curtail 100,000 acre-feet of water — approximately one-sixth of its annual Colorado River Basin consumptive water use — the state engineer would begin with the newest appropriations and work back in time until the 100,000 acre-feet of consumptive water use curtailment was met.
If, let’s say, that required turning off all Colorado River Basin water appropriations back to 1970, that would choke off all water appropriated since then — whether for industrial, municipal or agricultural use. The cities of Rock Springs and Green River, which share a municipal water system that serves some 39,000 residents, would lose access to 75% of their Green River water appropriation. The towns would still be allowed to tap the 4,343-acre-feet-per-year appropriation they secured in 1928 and the 2,895-acre-feet-per-year appropriation that predates the 1922 compact. The rest — 75% — was appropriated in 1971 and after.
This type of variable vulnerability applies to many Colorado River Basin water users with appropriated rights that were obtained at different times. The exact order for how a curtailment would be applied is well documented and under continual review, according to the state engineer’s office.
Small straw, big vulnerability
Agriculture accounts for 83.7% of Wyoming’s consumptive use of water in the Colorado River system, according to the SEO. Municipal water use accounts for about 2.8% — or 3.3% if you include rural domestic water use. Industry — trona facilities, coal power plants, oil and natural gas processing — make up most of the remaining 13%.
Approximately 70% of agricultural irrigation water rights in Wyoming were appropriated before 1922. Those pre-1922 appropriations are not subject to the Colorado River Compact and cannot be shut off under a curtailment. The pre-1922 protection applies to all Colorado River Basin water users.
A majority of Colorado River Basin water appropriations held by Wyoming municipal water authorities, however, are post-1922. That means some 125,000 urban Wyoming residents and businesses are vulnerable to a curtailment.
Given the curtailment clause in Cheyenne’s water contract, gold mine developer Gold King Corp. is shopping around to secure alternative water resources, according to Mayor Collins. The city of Cheyenne — as well as Green River, Rock Springs and others — are doing the same.
“There is the possibility that we would not be able to collect any water from the Little Snake System if [a] curtailment call goes below 1954,” Cheyenne Board of Public Utilities Administrator Brad Brooks told WyoFile. “We are looking for additional water to mitigate this possibility and planning for the worst case that our Little Snake water will not be available.”
Green River and Rock Springs are in the same boat. Their joint municipal water system collects 100% of its water from the Green River and its tributaries to serve some 39,000 residents in and around the two cities. Only 10% of their Colorado River Basin water appropriations pre-date the 1922 compact.
Although the cities don’t rely on the full volume of their legal claims to Colorado River Basin water, the time to plan for supplemental water sources is now; 2028, the year Wyoming might first see a curtailment, isn’t far away, Green River/Rock Springs Joint Powers Board General Manager Bryan Seppie said.
“Understand, [a curtailment] probably isn’t a one-year event,” Seppie told WyoFile, adding that much depends on what Mother Nature has in store. “We’ve got to secure other water resources to serve as replacement water if [a curtailment] were to happen. Conservation is a tool, but with these types of curtailments, conservation is not going to get you out of it.”
Part of the Gold King deal provides Cheyenne’s Board of Public Utilities approximately $5 million in fees that would help cover the cost to expand Cheyenne’s groundwater capacity. The city’s water board is also seeking up to $10.5 million in grants from the Wyoming Water Development Commission for its Borie wellfield expansion project. The expansion would add approximately 3,300 acre-feet of water per year to the city’s water portfolio, according to the board.
That would boost Cheyenne’s non-Colorado River Compact water source portfolio to 9,900 acre-feet per year. But the city would still be in trouble in the event of a curtailment because its average annual use is about 14,000 acre-feet.
“We are actively pursuing possibilities” for additional water resources, Brooks of the city’s BOPU said.
Expanding groundwater capacity, however, isn’t an affordable option for Rock Springs and Green River, according to Seppie. Instead, the cities are looking to those in the state with pre-1922 appropriations to share some water.
The federal System Conservation Program pays water users to curb consumption. Congress recently re-appropriated funding for the program, while the Inflation Reduction Act includes some $4 billion for efforts to modernize Colorado River Basin infrastructure and water management practices. Another $8.3 billion from the bipartisan Infrastructure law is available to address water and drought challenges throughout the U.S.
The SCP is an attractive option, Seppie said, for both ag irrigators and municipalities. Ag irrigators who volunteer for the program can use payments to upgrade their irrigation systems to waste less water.
“It’s a voluntary thing. It’s preemptive, and it’s benefiting the entire system,” Seppie said. “We haven’t gotten to a point where we’re having those discussions [with city officials]. But we have somewhat of a timeframe; 2028 is not all that far off.”