People are gathered around a waterfall and swimming hole at Mill Creek.
Mill Creek Canyon. Credit: Courtesy photo

The Grand County Commission hosted a water workshop ahead of its regular meeting on Aug. 2. Marc Stilson, regional engineer for the Utah Division of Water Rights, and Chris Wilkowske, supervisory hydrologist for the Moab Field office of the United States Geological Survey, presented information on Moab’s surface water resources. Director of the Utah Division of Water Resources Candace Hasenyager, who is also on the board of the recently-created Utah Colorado River Authority, also attended to explain the work of the Authority and give an overview of the state of the Colorado River.

Mill Creek

Stilson gave summaries of three main surface water sources in the Moab area: Mill Creek, Pack Creek, and the Colorado River. He reviewed how much water each channel has historically carried, how much it’s supplied recently, and how much is allocated from each through water rights.

Mill Creek’s ten-year average flow is about 8,000 acre-feet, with a maximum flow of 14,769 acre-feet in 1993 and a minimum flow of 3,424 acre-feet in 2002. Mill Creek water rights owned by several entities add up to 11,595 acre-feet.

“Our average year, there’s more water rights than there is supply,” Stilson said. Asked how often the flow was above average, Stilson replied “Not very often. Once in a while.”

Water rights are prioritized based on seniority: the oldest water rights on Mill Creek go back to 1890, and are held by the Moab Irrigation Company and the Grand Water and Sewer Service Agency. Dana Van Horn, manager of GWSSA, noted that the agency only takes its share of water if a certain threshold of flow is met.

Pack Creek

There is less information available on the flow of Pack Creek because until this summer, there wasn’t a gage on it.

“We’re really excited that the USGS has a new gage on Pack Creek,” Stilson said, thanking the county for supporting the gage and helping to fund it. “That’s a very important, I think, part of the water resource plan down here for Moab and Spanish Valley.”

Stilson looked at data from the 1950s, the last time there was a gage on Pack Creek. In 1957, Pack Creek supplied 3,316 acre-feet; the following year, it supplied 3,649 acre-feet, and in 1958 it dropped dramatically to 634 acre-feet, for a three-year average of 2,533 acre-feet. The rights on Pack Creek water add up to 839 acre-feet.

“There’s more water that comes down Pack Creek, usually, than there is water rights established to capture,” Stilson said, pointing out that it’s in the opposite circumstance to that of Mill Creek.

“Here’s the second piece of that puzzle,” Stilson went on. “Most all of that water is going into the ground. What’s not being captured by these water rights is being recharged into the Valley Fill Aquifer and being used as groundwater, or just making its way through the groundwater system. So Pack Creek is a great stream. And it has a way bigger influence on the groundwater resource than anybody thought until the USGS 2019 study brought that out.”

Stilson is interested to find out how data collected from the new gage compares to the 1950s data points.

“You talk to some of the old-timers, and they say Pack Creek used to water a thousand acres. That’s hard to believe, but that’s what they say. Now it’s probably watering less that 150 acres,” he said.

Both Pack and Mill creeks have flooded after heavy rain storms this week with dramatic spikes in flow. Commissioner Kevin Walker asked Stilson if water from such events is usable, or if it should be taken out of consideration when discussing available water. Stilson said that no, flash flood surges are not currently usable—managers would have to build new infrastructure to capture water from such events.

“That’s a new dynamic that we’re facing: we’re seeing less snowpack and heavier precipitation events,” Stilson said. “It would be nice if it came in a gentle rain, but we’re seeing these big flash floods—big, extreme precipitation events that carry a lot of rock, a lot of sediment, a lot of mud, a lot of trees and debris.”

Stilson presented that as a planning question for the county: should they pursue infrastructure that could capture floodwaters?

“It’s possible, but it’s a different engineering question,” Stilson said. “But that’s something that probably we need to study out and learn how to do. Because we still need the water.”

Colorado River

Panic regarding the Colorado River crisis has been in national news outlets for months. The river supplies water and power to millions of people in the U.S. and Mexico. Its allocation is governed by a complex set of agreements established in 1922 among seven states in the river basin, as well as Mexico, called the Colorado River Compact or the Law of the River.

Utah’s share of the Colorado is 23% of the amount allotted to the Upper Basin states (Utah, Colorado, New Mexico and Wyoming). The actual volume fluctuates according to supply. Four Native American tribes are within the Colorado River system in Utah; 26% of Utah’s agricultural land is in the Colorado River Basin. The river provides water to over 1.5 million people in the state and represents a third of Utah’s water supply.

Stilson displayed data on the river: the 103-year average, as measured by a gage near Cisco, is 5,073,746 acre-feet. The 10-year average is 3,730,600 acre-feet.

“That tells you the story, right there, of what’s happening in the Colorado River Basin,” Stilson said. “We’re seeing a huge decrease in the amount of water that the basin is producing.”

Moab-area entities hold 11,847 acre-feet of water rights to the Colorado; notably, the San Juan Spanish Valley Special Service District, which will serve community expansion planned for Spanish Valley, holds 5,000 acre-feet. However, that right only goes back to 2017. In the event of a “call” on the river—which would be an interstate issue, not a local one—the latest water right holders would be the first to have to cede their shares.

“Locally, we’ll never cut anybody back on the Green or the Colorado River on local water right distribution,” Stilson explained. “If anybody ever gets cut back, it’s because of a call between the states on the Colorado River compact.” Rights that predate the 1922 compact are the best protected; later rights could be subject to curtailment in future management decisions. All of the Colorado River water rights owned by Grand County-area entities are post-1922. Stilson advised the county to try to acquire pre-1922 rights whenever possible.

Utah Colorado River Authority

Hasenyager is on the board of the Utah Colorado River Authority, which was established by the state legislature in 2021 to “protect, conserve, use and develop Utah’s share of the Colorado River system.” Protecting Utah’s share of the water means both managing its water use efficiently, but also protecting Utah’s status in the tense and complex political framework surrounding the Colorado River.

The Authority has a three-part management plan that includes monitoring and measurement of the river; hydrology and operations, which Hasenyager said involves forecasting future supply; and using and developing Utah’s share of the river.

“This year was a roller coaster as far as the hydrology,” Hasenyager said. Water levels in reservoirs across the state dropped to alaming lows in 2021; winter storms brought them up again quickly, but they just as quickly dropped.

“It ended up that we received much less water than we had hoped for during those high snow times,” she said.

She reminded commissioners that the Bureau of Reclamation is releasing 500,000 acre-feet of water from Flaming Gorge Reservoir between May of this year and April of 2023 to help boost water levels in Lake Powell; lower basin states agreed to hold back 480,000 feet of water in Lake Powell that they would normally deliver to downstream users.

The Authority has drafted a five-year management plan stating that Utah must improve the certainty of the state’s Colorado River use; develop tools to facilitate longterm understanding of the water supply; optimize water use; strengthen relationships with other members of the Colorado River Compact; and “provide resources.”

The Utah Division of Water Rights and the Utah Division of Water Resources are collaborating to produce regular drought updates for the state. They can be found at The latest, from July 29, notes about 83% of the state is in extreme or exceptional drought, the most severe categories. Because of prolonged drought, reservoir storage across Utah is at 54%. (Ken’s Lake, however, is currently doing well: Commissioner Trisha Hedin reported that it’s at 2,300 acre-feet. Last year at this time, the lake was at 753 acre-feet.)

Water managers are responding with increasing alarm to conditions across the West. In June, Bureau of Reclamation Commissioner Camille Touton gave upper basin states two months to come up with a plan to reduce their water use by 2-4 million acre-feet in the next year, or the bureau would start making cuts for them. The states came up with a proposal to reduce water use, though the proposal didn’t identify any specific mandatory cuts.

Both the politics and hydrology of water in the West are tangled and complicated. The Grand County Commission plans to hold regular water workshops to promote understanding of crucial water issues.