The Evaporation of Water in the West

Samuel Taylor Coleridge's renowned lines recount the voyage of a thirsty sailor stranded at sea: “Water, water everywhere, nor any drop to drink.” Today, more than two centuries later, water woes continue. The challenge of quenching the thirst of the ever-expanding American West is not of saline seawater, however, but of changing climate patterns and an increasing demand on freshwater supply. It’s a predicament perhaps not so bleak but seemingly as dire.

The source of seven major rivers and an average of 4 trillion gallons of fresh water, the Greater Yellowstone region has been referred to as the Headwaters of the West for its abundance and significant role in meeting the country’s water demands. And yet, in drought-prone and developing cities like Bozeman, which on average receives just 16 inches of precipitation each year, the talk of the town is not if taps will run dry, but when.

Jessica Ahlstrom studies the water stakes and knows the pressures the growing city of Bozeman faces, but its newly enacted water conservation plan has her optimistic. She spent the past eight years dedicating her energy to water conservation data and outreach as one of Bozeman’s first water technicians and now serves as the manager of Bozeman’s Water Conservation Program.

On October 25, Ahlstrom presented a robust water conservation plan to city commissioners, who voted unanimously to adopt it. With full support from the city, the 2023 Water Conservation and Efficiency Plan became the first of its kind in Montana, offering a roadmap in hopes that other cities in Greater Yellowstone will follow suit.

“There's no cavalry coming to the rescue," City Commissioner Terry Cunningham pronounced before the vote. "We are the cavalry. We are at the mercy of the snowpack, and that is a fickle thing according to all projections, so we take this seriously—we as a city need to be leading the way."

The water conservation outline expands upon Bozeman’s 2013 Integrated Water Resources Plan, an effort to predict the city's gap between water supply and demand, and one that recommends water conservation measures reduce that gap by 50 percent by 2062, the equivalent of 10,100 acre-feet of water. One acre-foot, for reference, equals 325,851 gallons of water.

The newly adopted plan focuses on specific, attainable measures to make water use more efficient and ensure that Bozeman's growth considers its reliable water supply. If implemented as recommended, it will effectively push back by four to nine years the day Bozeman's water demand outstrips its supply.

Where that day falls within the given range depends on climate trends. The city used two possible climate scenarios to predict the date: a worst-case scenario that assumes Bozeman will experience significant decreases in precipitation and significant increases in temperature on an annual basis, and another that assumes a one-in-50-year drought will occur every year. The correlating water supply projections are based on numbers from a statistical analysis conducted by the city’s engineering team using streamflow data and advanced hydrologic modeling.

Bozeman contracted Maddaus Water Management, an engineering consultant firm specializing in water conservation program planning, to analyze the current water use and build projections based on achievable savings by implementing various water conservation measures.

"We are making all these assumptions about growth and demand and what our reliable yield will be, but we don't want to assume that what we've had is what we're going to get," Ahlstrom told Mountain Journal. “Using worst-case scenarios from climate change, we are saying that if this is all [the water] we get, and we grow at a rate of 4 percent annually, we expect demand to exceed supply between 2027 and 2033. That would be the year we ‘run out of water.’”

Ahlstrom notes that this doesn’t necessarily mean our taps will run dry. “We’re not going to turn on the sink and not have water; it means that we will have to implement more frequent mandatory restrictions on water use, like outdoor landscaping, even if it’s not a very hot or dry year.”

With a booming population upwards of 57,000, one that’s grown more than 8 percent since the last census in 2020, Bozeman sits along the northern edge of the Greater Yellowstone Ecosystem at the top of the drainage of the Missouri River Basin. With no upstream source to find additional water nor surface water rights available to acquire, planning for the city’s future water needs is vital to meeting the demands of this headwaters community.

Three main sources supply the municipality—Hyalite Reservoir, Sourdough Creek and Lyman Spring—all of which rely on snowpack from the Gallatin and Bridger mountain ranges to replenish their flows, sustain aquatic life, and quell the thirst of an insatiable and growing city. Bozeman and its life-supporting mountains are not alone in experiencing the pressures of population growth and a changing climate—the entire ecosystem is feeling the heat.

According to an ongoing analysis in the Greater Yellowstone Climate Assessment, models using climate scenarios developed for the Intergovernmental Panel on Climate Change show the total annual water supply in the region remaining steady, if not increasing through 2100. That’s the good news. However, projections also show the majority of that precipitation will occur earlier each year—in the form of rain, not snow—leaving summers hotter and drier on average than ever before.

“Looking toward the future in the Greater Yellowstone Ecosystem, the biggest challenge in terms of water supply is less about volume and more about timing,” explained John Lunzer, a hydrologist with Montana’s Department of Natural Resources and Conservation. “The trend likely to continue will be more water running off early in the season and less later in the season. So, despite an overall increase in annual water supply, conditions in late [summer] are drier than normal while the spring is wetter than normal."

Lunzer and Ahlstrom agree that to combat the limited late-season water supply issue, communities need to look closely at how water is used and identify where changes can be made to conserve it effectively.

“I'm glad to see something like this being done,” Lunzer said. “We need to start looking at our use behavior and focus on consistently conserving water as a long-term adaptation rather than as a response to an event like a drought. Drought plans and the new water conservation plan implemented by Bozeman are becoming necessary for municipalities to continue to grow while fighting those challenges.”

Grassroots efforts elsewhere in Montana, such as in the Big Hole and Blackfoot watersheds, are already tackling the issue of reduced late-season water levels. Both communities have enacted watershed drought plans to combat the problem. "While the genesis of each of these plans has their own roots and drivers, the overall goal is to increase streamflows during times of low flow," Lunzer said. "This is done through a variety of voluntary actions taken by irrigators and other water users in the watershed."

In Greater Yellowstone, the Upper Yellowstone Watershed Group is comprised of diverse stakeholders, including ranchers, irrigators, small parcel owners, business owners, outfitters, regional conservation groups, nonprofit organizations, and state environmental agencies. The group is developing its own drought plan with voluntary action, which has garnered growing interest from folks in Livingston, Montana, 26 miles east of Bozeman.

Shannon Holmes, Livingston’s Public Works Director, is a member of the watershed group’s coalition on drought management. “As the largest water user in Park County, I feel it is important to participate as a stakeholder and understand the demand on the watershed as a whole,” he said. “Livingston needs to do its part to be a good stakeholder in the watershed.” 

Holmes added that while each city is different with respect to its growth and water demand, water sources, availability and capacity, Bozeman’s new water conservation plan can benefit other municipalities. “Bozeman’s growth rate is substantially higher than most communities in Montana, and their water resources are scarcer than other communities I am aware of. Each community could use it as a template that fits their own needs.”

From a legal standpoint, Ahlstrom explains that Bozeman’s municipal water supply does not affect people downstream because the city owns the water rights.

“However,” she said, “if you take out that legal element and look at where Bozeman is situated geographically, we’re at the headwaters, so we have a lot of downstream users that rely on us to be good stewards. From that standpoint, I’d say yes, we have an impact on the surrounding areas. By having a drought management plan and now a conservation program, we are putting in growth policies to ensure that new development is more efficient—by being good stewards of our water supply, we will help the whole region.”

Patrick Byorth, an environmental attorney who is director of the Montana Water Program at Trout Unlimited and a former fisheries biologist for Montana Fish, Wildlife and Parks, is encouraged that Bozeman is prioritizing a plan for its ongoing and unbridled growth. Still, he's not as optimistic that it will be a long-term fix to increasing water demands. He would like to see the city help develop a water market where community members and entities can sell their water rights, and developers can buy them. “I think that would be the best chance of having our cake and eating it too,” Byorth said. “It would bring high-quality water to the growing population without depleting streamflows.”

At the end of the day, Byorth says the essential question for Bozeman is how much of its surface water it’s willing to sacrifice for continued development. “Some believe we should develop to be as big as we can get, but surface water limitations make that unrealistic; I worry that conservation alone won’t necessarily meet the needs of that kind of growth.”

Bozeman’s 2023 Water Conservation and Efficiency Plan outlines three potential paths forward. Of those programs, the city is moving ahead with Program B, which will serve as a flexible roadmap through 2040, recommending 18 measures and ordinances that sitting city commissioners will decide whether or not to adopt. It assesses existing program measures, identifies cost-effective actions for future consideration, sets measurable targets for existing and future initiatives, and provides an implementation and monitoring schedule.

"Nearly everything in this plan is making sure that as we grow, we are more efficient," Ahlstrom said. "We will likely see increased water rates as time goes on, but most of the new measures will apply to future developments."

One example is the recommendation to mandate net-zero impact for new construction. Currently, developers in Bozeman are required to either bring water rights to the table that will cover the project's demands, or pay cash-in-lieu. The new plan recommends that the city remove this cash-in-lieu option and require developers to either optimize efficiency in their project or elsewhere within city limits to the extent that they create water savings equal to the amount of water demand their development will generate.

While this type of mandate could be substantial as the city grows, Ahlstrom says it's important to note that residents are already relieving some of the stress on water supply simply by conserving where they can, updating appliances, and using drought-minded landscaping practices.

An analysis of Bozeman's current water usage shows that 50 percent of the city's water use goes to lawns and landscapes. "Growth and development of the city aside, there are a lot of opportunities for existing homeowners to reduce their water use, and it really makes a big difference,” Ahlstrom said.

From the start of the 2013 Integrated Water Resources Plan through today, Bozeman has reduced water use on average by 13 gallons per person per day, and that's merely due to community members doing their part.

“That's just the tip of the iceberg of what we can save assuming the implementation of this new conservation plan,” Ahlstrom said. “And everything outlined in the new plan is best in class, proactive and aggressive water conservation, and that makes me very optimistic.”

Lunzer identified funding and staff capacity as potential barriers for other communities tackling the same challenges as Gallatin Valley. But as the first city with a water conservation plan in the state, Bozeman could make waves, or at least ripples, in the right direction, creating a foundation for other communities in the region to do the same.

“So much time, money and work goes into a plan like this,” Lunzer said. "Once these drought or conservation plans are implemented, other places will see them, learn from them, and use them as examples in their watersheds. I'm hoping that's what this turns into.”

With alternatives like increased storage not necessarily feasible, Lunzer added, conserving water is the most effective tool we have to combat future conditions. “For growth to be sustained, water must be conserved,” he said. “That is the reality of living in a headwaters state in the West.”