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Wyoming v. Montana water case heads to trial

by Wyoming Livestock Roundup

Billings, Mont. – On Oct. 16, the longstanding battle over water rights in the Tongue River began its final stages in the Supreme Court.

“The trial is scheduled to go to early December, with a break during the first week of November,” says Wyoming State Engineer Pat Tyrrell. 

As the case moves forward, Tyrrell says the first part will consist of Montana calling their primary witnesses and setting up their case.

“They will make their case for how the effects Wyoming’s operations have affected Montana’s water over the years,” says Tyrrell. “Wyoming will present our defense case starting in very late October or early November.”

Looking back

The case dates back to 2007, when Montana filed suit against Wyoming for violating the 1950 Yellowstone River Compact. 

“It stems from two letters that Montana sent in 2004 and 2006 essentially asking that we regulate and release stored water for their benefit,” explains Tyrrell. “In both of those years, we were down to our very early senior water rights, and I didn’t believe that we had water that was improperly stored.”

He further notes that the drought during those years further exacerbated water concerns. 

“My reply to Montana’s letters was, ‘This drought is painful for both of us,’” he says. 

“Wyoming and Montana have worked together off and on for a long time to mesh pre-compact and post-compact rights into a system, especially in dry years,” says Tyrrell. “The work never bore any fruit.”

Because Montana is a downstream state, he notes that the argument is similar to many other compact battles.

“We tend to hear things like, ‘The upstream state must be doing something wrong, and, ‘There must be something that can be done, so we can get more water,’” Tyrrell explains. 


Tyrrell notes that allegations against Wyoming include a number of aspects.

The Montana Law Review states, “Montana alleged that Wyoming was appropriating more water than it had in 1950 and that that water was being utilized for new uses, including ‘irrigating new acreage, building new storage facilities, conducting new groundwater pumping and increasing consumption on existing acreages.’”

“Allegations are that we can’t use any water with post-compact right if pre-compact rights are short, and we shouldn’t store if their pre-compact storage is short,” he says. “The other allegation is our coalbed methane pumping has been impacting water.”

Essentially, Montana claimed that Wyoming has improperly depleted water levels in the Tongue and Powder Rivers before entering the state.


While the last part of the case is going to trial now, Tyrrell also notes that Wyoming has seen several wins to this point.

“We have won two parts so far,” he says. “The Powder River has been dropped from the case, so we are only arguing about the Tongue River.”

An additional aspect of the case looked at irrigation practices.

“There was an argument a couple years ago that additional consumption resulted because irrigators have gone to sprinklers,” he explains. “The Supreme Court found in our favor and said that we can irrigate however we want.”

In addition, the Supreme Court found that Montana must make attempts to address water shortages with intrastate solutions before looking to Wyoming for breach of the compact.

“In the United States’ view, a decision that did not require Montana to apply intrastate measures would ultimately harm innocent Wyoming water users who had nothing to do with the water shortages of their downstream neighbors,” adds a Cornell Law Review of the case.

Moving forward

At the completion of the case, a ruling will come from the Special Master, explains Tyrrell, and Wyoming can either agree or take exception with that ruling. The U.S. Supreme Court appointed Stanford Law School professor Barton Thompson, Jr. to oversee the case.

However, he adds, “There will be several months of deliberation, so this is just the beginning of this case.”

During the next several weeks, Tyrrell also notes that he will be sitting in on the trial in Billings, Mont. to watch, learn and assist in any way he can.

“So far, we have won cases in Wyoming’s favor,” Tyrrell comments. “We’ll have to see how this turns out.”

Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to

Yellowstone River Compact

Beginning in 1950, the Yellowstone River Compact was negotiated by the Yellowstone River Compact Commission to apportion the waters of the Yellowstone River system, states a Cornell Law review.

In 1951, when Congress approved the agreement, a three-tiered framework was adopted.

“The first tier adopts the doctrine of ‘prior appropriation,’” reads the review, “which generally holds that the first people to put water to a beneficial use retain a continuing right to use the water.”

Water used prior to Jan. 1, 1950 was granted pre-compact rights, and users would retain their water rights following the agreement.

The second tier of the agreement notes that “unused and unapportioned” water is permitted to be diverted to supplement those rights granted under the first tier, adds Cornell.

“Finally the third tier of the compact gives each state a specified percentage of any remaining ‘unused and unapportioned’ water,” says the review, also noting that the percentages are to be calculated annually.


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