The Gillilands have never seen the creek dry up before, Siri said, but after fighting the city over water rights in court for years, she worries it is on course to dewater the stream. That could trigger significant ecological consequences, she said.

The city argues that when it comes to Bozeman’s water supply, Lyman Creek is and will continue to be a critical asset as the area develops. Officials insist that they have no plans of increasing the amount of water they withdraw from the creek, and they intend to use the water responsibly to benefit a growing community.

Lyman Creek is “the City’s highest quality water source and our community’s least expensive to operate,” a city spokesperson wrote in an email. “The City intends to continue providing Lyman water to its residents and businesses at amounts it is legally entitled to.”

The Gillilands’ legal battle with the city has dragged on for five years, and so far, the couple’s case has been rejected in the state’s district and supreme courts. The parties have also failed to settle the dispute.

Now the couple said they are in Montana Water Court, and they’ve decided to launch a public awareness campaign called Save Lyman Creek. It includes television, digital and social media components. The goal, said Siri, is to see what Bozeman residents think about the issue.

“We’re not trying to prevent them from taking the water. We’re just trying to get them to be reasonable and leave enough water in there to maintain an ecosystem,” Siri said. “With climate change and a growing population, it becomes ever more important to preserve those things. I’m baffled that they won’t do it. I really am.”

The Gillilands bought Lyman Creek Ranch near the foothills of the Bridger Mountains in 2014, and the property came with water rights to the stream that were junior to the city’s. Around that time, a consultant flagged some issues with the city’s diversion upstream, Siri said.

“We looked into it a little further and realized they put in what we consider to be an illegal diversion in 2008,” she said.

The Gillilands are arguing that at the time, the city had already reduced instream flows to the creek, which adversely affected their water rights. While the couple admits that the city’s water rights are senior, they believe those rights were not perfected.

The Gillilands approached the city about the diversion, and Siri said officials claimed to be entitled to a volume of about 5.95 cubic feet per second of water, which was more than she believed the small stream could support.

“We asked, ‘Can we do something about this? Can we get you guys to agree to let water flow year round? Because if you take all that you think you’re entitled to, it will dry up. We don’t think you’re entitled to it. You historically have never taken it,’” Siri said.

In an email, a city spokesperson wrote that it denies the accusation that an un-permitted diversion was installed along Lyman Creek, and it disputes the allegation that it is diverting water from the stream at higher rates than are authorized by its water rights.

“This is an issue in the current litigation and the City will not litigate issues in the media that will be addressed through the courts,” the spokesperson wrote.

The city did not comply with the Gillilands’ request, and it argues that as junior water users, they do not have the right to interfere in its water rights. The couple filed a lawsuit, lost in district court, then appealed the case to the Montana Supreme Court.

In October of 2019, the state Supreme Court dismissed the Gillilands’ case, noting in an opinion that as private landowners, the couple did not have standing to sue the city of Bozeman over alleged Montana Water Use Act violations.

Now the Gillilands have returned to the drawing board. They still want to resolve the issue through a settlement, and they’re asking the city to agree to maintain a minimum instream flow of 1 to 2 cubic feet per second in the stream, depending on whether trout are spawning.

A press release from the Gillilands notes that “the city would have been the big winner." Lyman Creek Ranch would get the preservation of a minimal instream flow to support trout spawning and wildlife habitat. The city “would get to perfect its water rights to Lyman Creek and receive more water than they currently have rights to.”

Byorth of Trout Unlimited said the creek doesn’t “get the icing issues that tend to limit reproductive success,” and as one of about a dozen spring creeks that are scattered around the valley, it’s likely one of the area’s most important spawning tributaries.

When streams are dewatered, trout eggs in the gravel dry out and die, and there aren’t any younger fish to replace the aging population, he said. There are also significant impacts on all invertebrate life, and the riparian habitat that a stream provides can become unspooled.

“(The city) has established water rights that they have operated on for more than 100 years, but they have never maximized or taken every drop of the creek like they claim that they can,” he said. “It’s a nuance of water law, but historic use sets the level of an existing water right.”

In an internal memo sent in May of 2017, Bozeman water conservation specialist Lain Leoniak wrote that in accordance with an Integrated Water Resources Plan, the city sought to increase the efficiency of diversions from Lyman Creek several years ago.

A few years prior, “a couple from Houston, Texas by the name of Mr. and Mrs. Lance Gilliland purchased several large parcels of land in the Lyman Creek Watershed for a vacation home,” Leoniak wrote. “Mr. Gilliland and his wife are now looking to stop the City’s Lyman Creek Efficiency Project.”

The memo said that after attempting unsuccessfully to stop the project through legal counsel, the Gillilands solicited the “misguided involvement” of groups including Trout Unlimited. Leoniak added that the city “is on solid legal footing regarding its use of the Lyman Creek water right.”

The city’s Lyman Creek diversion system “has at all times been constructed with adequate capacity and has been used historically to divert water at the full rate allowed under its claims,” Leoniak wrote.

She added in the memo that the optimization project was designed to improve the efficiency and performance of the collection and diversion system — “not to increase the overall system capacity as the Gillilands and TU incorrectly assert.”

A city spokesperson wrote in an email to the Chronicle that the city’s approach to resolving disputes is to remain open to settling issues before and during litigation. Over the past 30 years, the vast majority of water needed to serve population growth in Bozeman has come through the city’s conservation efforts. They have included minimal increases in annual diverted volumes from Sourdough, Hyalite and Lyman creeks.

Bozeman City Manager Jeff Mihelich spoke about the Gillilands’ public awareness campaign during a city commission meeting on Tuesday. He emphasized that the city has no plans to dewater Lyman Creek, and it does not take any additional water from the creek than it has the right to.

“We have also consistently used this water to support our water system,” he said. “We haven’t been fluctuating and we certainly haven’t been drawing for that more and more over the past several years. That is simply not true.”

Byorth said that there’s an amazing ecosystem right on the edge of town, and if the city is sincere and has no intention of drying up the creek, it can resolve this conflict easily.

“Why do we care about this little creek? In this rapidly-changing climate, it’s the little creeks that really mean a lot for resilience. When we lose these, the system comes unspooled. And we see that time and time again across the West,” he said.