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Long-awaited decision released in Mont v Wyo case

by Wyoming Livestock Roundup

After seven years of litigation, Special Master Barton Thompson of Stanford, Calif., appointed by the U.S. Supreme Court, released his decision in the Montana versus Wyoming water case, and the Wyoming Attorney General noted in a press release that, “in nearly every important respect, the Special Master sided with Wyoming.”

Beginning in 2007, Montana alleged that Wyoming had violated the Yellowstone River Compact in both the Tongue and Powder River Basins nearly every year since 1950, when the Compact was ratified. 

Case history

After the case began, in 2011, Wyoming won what the Wyoming Attorney General’s Office called “the most important issues in the case” in the ruling that irrigators could improve their irrigation methods to increase crop uptake without violating the Compact. 

“The Supreme Court also found that no Wyoming water user with a water right predating the Compact can ever be required to curtail their diversions for the benefit of Montana,” the Wyoming Attorney General’s Office continued. “The vast majority of water rights in the Tongue and Powder River Basins predate 1950 and were, therefore, unaffected by this litigation.”

Montana later opted to voluntarily dismiss its claims related to the Tongue River, and the Special Master further noted that Montana must make an affirmative call for water before Wyoming has an obligation to act. 

“Montana lost or voluntarily withdrew the vast majority of its claims prior to trial,” said Wyoming Attorney General Peter Michael. 

The remainder of the case was tried over 25 days in late 2013 in Billings, Mont.

New decision

In his Dec. 29 decision, Thompson made five recommendations. 

First, he cited that the court should grant Wyoming summary judgment for 1982, 1985, 1992, 1994 and 1998. He also noted that Wyoming was not liable to Montana in 1981, 1987-89 and 2000-03. 

“The Court should find that Wyoming is liable to Montana in the amount of 1,300 acre-feet for 2004,” Thompson continued. “This represents the impact of Wyoming’s post-1950 uses and storage during the 2004 notice period on the flow of the Tongue River at the Stateline.”

Additionally, Thompson said Wyoming is liable for 56 acre-feet of water in 2006. 

“The Court should remand the case to determine damages and other appropriate relief,” he continued.

The total replacement value of this water for both years is approximately $14,000, cited the Wyoming Attorney General.

Other components

During the case, Wyoming admitted that it did not curtail several small divisions in response to Montana’s demands in 2004 and 2006.

“We took seriously their requests prior to my decisions in 2004 and 2006,” said Wyoming State Engineer Pat Tyrell of his decision to refuse Montana’s demands for water. “We felt confident that the minor amounts at issue were within our Compact allocation and that our interpretation was sound.”

He noted that while the Supreme Court disagreed with their Compact interpretation, it was positive to see that their estimates were correct.

“With a few minor adjustments in our regulatory response to Montana in future years, Wyoming should have no difficulty meeting its obligations under the compact,” Tyrell added.


Michael said, “What this case confirms is that the primary solution to water issues in Montana on the Tongue River can be found in Montana’s operation of the Tongue River Reservoir.”

He added, “Montana’s internal operational decisions have the biggest impact on its ability to cope with drought, and fortunately, over the course of this litigation Montana has taken that lesson to heart. Recent changes in reservoir operational practices in Montana have been much more conservative and responsible, and we anticipate fewer future disputes as a result.”

Governor Matt Mead also said, “I am very pleased with the outcome in this case to this point and proud of the outstanding work of the Attorney General and the State Engineer’s Office.”

Net steps

The Office of the Wyoming Attorney General stated, “While Wyoming is generally pleased with the specific ruling and the overall result, Wyoming is considering whether to ask the Supreme Court to review parts of the Special Master’s recommendations.”

Parties have an opportunity to ask the Supreme Court to reject or modify the Special Master’s recommendations. 

Michael added, “At this time, we are carefully evaluating the lengthy recommendations, and we do have some concern that the Special Master has not held Montana to the appropriate standard under the Compact.”

“Montana failed to use immense amounts of water during the drought years of the last decade, and Wyoming believes that the Compact requires more diligence from Montana before it can be heard to complain about uses in Wyoming,” Michael continued. 

Coal-bed methane and groundwater

An additional aspect of the Montana v. Wyoming case was related to coal-bed methane. 

“During the litigation, Montana also alleged that coal-bed methane production in Wyoming adversely affected the flow of water in the Tongue River,” said the Wyoming Attorney General’s Office. “However, the Special Master found that there was insufficient evidence that groundwater pumping associated with coal-bed methane production caused any reduction in flow of the Tongue River.”

Wyoming State Engineer Pat Tyrrell noted, “There was a significant amount of research and investigation into the effects of coal-bed methane production on the Tongue River, and all of the work done by both parties revealed that there was no discernible impact at the surface from these deep wells.”

“As a result, groundwater turned out to be an insignificant issue in the case,” Tyrrell added.

Saige Albert, managing editor of the Wyoming Livestock Roundup, compiled this article from the Special Master’s Decision and press releases from the Wyoming Attorney General’s Office. She can be reached at

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