Encampment River decision highlights the impact of climate change on Wyoming water law

Climate change has Wyoming industry maneuvering to guarantee access to water during dry years. An order issued by Wyoming’s state engineer, and challenged by Encampment River irrigators in a recent appeal, foreshadows how water law will respond as the planet gets hotter and drier. 

The decision directly impacts the North Platte River basin but has statewide implications, particularly for the Green River and Little Snake River basins.

On Oct. 14, State Engineer Brandon Gephart approved the proposal of the Sinclair refinery near Rawlins to get water in very dry years from ranchland on the Grand Encampment River near the Colorado state line.

That new proposal is a response to climate change, which has had more drastic effects further west in the Colorado River Basin. Wyoming may have to reduce water consumption on the Green and Little Snake rivers to meet obligations to downstream Colorado River states. A trona company near Rock Springs has sent Gephart six requests like the proposal made by Sinclair.

The trona requests are on hold while awaiting Gephart’s decision in Carbon County. His decision there, with results on appeal, will set the guidelines for action on the trona proposals.

Sinclair bought an old ranch on the Encampment a couple of years ago and in 2023 filed its request to quit the ranch irrigation in very dry years and use the water at the refinery instead. 

In June 2024 a crowd assembled at a public meeting with Gephart. Irrigators on the Encampment vehemently opposed the plan. Carbon County and Rawlins officials backed Sinclair, championing the economic value of the refinery and its need for a secure water supply.

The Encampment River is a tributary to the North Platte River, on which the refinery sits some 100 miles north. As on many streams in the Little Snake and Green River basins, Encampment irrigators’ water use is interdependent. Neighbors have developed a pattern of water use that largely works for them all, and they don’t welcome the change or new state supervision.

Neighboring ranchers on the Encampment complained to Gephart that under Sinclair’s plan they could no longer rely every year on using water that replenished the river in late summer. That water has returned slowly to the stream late in summer from the irrigated fields of the upstream ranch Sinclair now owns. The lost timing of that “return flow” is what the neighbors lamented. 

Gephart’s decision makes it possible for that timing loss to occur only occasionally — in certain very dry years. If the oil company had simply sought to move the ranch water permanently to the refinery, the loss of “return flow” timing in late summer would have been permanent.

Starting 50 years ago, Wyoming water law has allowed permanent changes. An even older provision of state water law, encouraging “exchanges,” allows the refinery to use the Encampment ranch water in very dry years, Gephart ruled. That law requires the state engineer to avoid adverse effects on water users, harm to the public interest and exchanges too difficult to administer. 

Gephart found the Sinclair exchange creates none of those problems. Yet three irrigators on the Encampment and North Platte claimed in their appeal that adverse effects and tough administration abound .

In an unusual move, Gephart wrote a public letter to accompany his official order, to explain the considerations that underlie his decision.  

The very dry years he has defined as triggers for the Sinclair exchange have occurred in 20 percent of the years since 2002, he noted. In Wyoming’s “first in time, first in right” water right priority system, the refinery couldn’t use its own water rights in spring of those dry years and had to find older rights. The old water rights on the Encampment ranch that Sinclair bought now solve that problem and can serve the refinery in the very dry years under Gephart’s ruling, making refinery operations more secure. 

Now, in the key dry years the refinery can still take water from the North Platte. In return the company would not irrigate its Encampment ranch at all in spring or summer. Encampment River water unused at the ranch would flow down the North Platte as “makeup” water, as required by Wyoming’s water exchange law.

An important factor Gephart cites is the company’s calculation of how much irrigation water the ranch has genuinely used — how much it has consumed — in the past. That dictates how much water must flow unused downstream from the Encampment in exchange years. It also allows an estimate of how much water the ranch has not consumed annually out of all the water it typically diverted from the river. In exchange years, Gephart ordered, that amount of water must be left in the Encampment River to mimic return flow for neighbors to use. 

That does not fully address the neighbors’ complaints about losing the kind of return flows they have relied on. The water Gephart requires to remain in the Encampment River for neighbors approximates the amount of return flow water received in the past but does nothing for its timing. Most likely the volume he requires will be in the river in the early months of the irrigation season — but not late in the season.

The neighboring irrigators challenged the calculation of the amount of water that must remain in the river, and the failure to consider return flow timing. But the timing of return flows, and reliance on them, could be difficult to document, and Wyoming’s water statutes explicitly protect only the volume of return flows when water rights are changed. Nothing in water law says one neighbor can force another to continue irrigating.

Elsewhere in his order, Gephart required Sinclair to build specific infrastructure to ensure neighbors can get their water, regardless of activity on the Sinclair ranch. One neighbor (who has not joined the appeal) had complained that the company refused to commit to new infrastructure.

The appeal argues the Sinclair plan, analyzed as an unwelcome permanent change rather than an exchange, should go to the Board of Control. The board consists of the state engineer and the superintendents of Wyoming’s four geographic water divisions, people with considerable experience inspecting and assessing irrigation use. (The state engineer is recused from sitting on the board when a state engineer order is appealed, as in this case.) 

Gephart earlier required Sinclair to file water right “cleanup” proposals with the Board of Control. Cleanup includes proof of past water consumption on the ranch — including proof of adequate past consumption to serve the new exchange. Cleanups are standard in places like the Encampment River, since actual use of old water rights in Wyoming often changes over decades, as streams move a little and ditches fall into disuse. Old water rights often require some work to be properly identified and nailed down to the current use, before new plans can be implemented. 

Gephart provided that the Encampment cleanup must be done by fall 2029, and the exchange could be conditioned or revoked if past ranch water consumption is inadequate for the exchange.

Sinclair’s purchase of the old Encampment ranch and its exchange plan will, clearly, disturb familiar patterns of water use on the Encampment River. But it appears to avoid complete disruption of irrigation on the Encampment. Gephart apparently aimed to strike the right chord in the complicated balance between water users’ need for stable water access, and circumstances that demand change for the sake of all Wyoming’s society.

The irrigator appeal cast the exchange as major disruption and argued vehemently against the choice Gephart has made.

Wyoming water law has accommodated change over its 135 years as small cities and a significant minerals industry grew where irrigation once dominated water use. Refinery operations on the North Platte and irrigation on the tributary Encampment River have co-existed for some 100 years. Workers at the refinery include some from Encampment-area families.  

Now, the climate is changing, and the old accommodation is challenged. The problem of balancing water rights stability and changing circumstances has come home to people on the Encampment. Gephart’s decision sought to set some guidelines for proposals made to handle climate change. Once the appeal is addressed, whatever balance is ultimately struck on Sinclair will next ripple into the Green and the Little Snake.