Preliminary estimates from Utah’s Division of Water Rights show that the Spanish Valley Watershed, which includes Moab, can safely withdraw 50-100% more water than it currently uses each year.
The range of uncertainty in part has to do with the difficulties that come with accounting for groundwater and in part from the range of possibilities in how much climate change affects water availability in the valley.
State Engineer Teresa Wilhelmsen praised research by the U.S. Geological Survey that she said “provides a wealth of information on movement of water between the various components of the aquifer system” in Moab.
“We believe from that the valley aquifer system has a long-term annual recharge value between 4,500 and 7,800 acre-feet,” Wilhelmsen said. “This value can be refined with additional research.”
Wilhelmsen oversees the Division of Water Rights, which is tasked with determining how much water Utah communities can safely pull from their aquifers, has been studying that question in Moab since around 2014.
The 4,500 to 7,800 acre-feet estimates what is called the safe yield and typically is imposed on communities to reduce their water usage but in Moab is serving a different purpose: setting a ceiling on use that the valley has not yet reached.
Ongoing work encouraged
Beyond USGS studies published in 2019 and 2020, a 1976 study, ongoing work by the division on water rights adjudication in the valley, data on consumption in public water systems, and more are also adding to the picture.
According to Wilhemlsen, there are some particular areas of research she wants to see completed as the process moves forward, and she said, “The State Engineer always encourages the collection of more data and is willing to cooperate on additional data collection and study in the coming years.”
Detraction from conservationists
Marc Stilson, an engineer with the Division of Water Rights, discussed the estimates during a March 17 meeting of the Moab Area Watershed Partnership, a coalition of stakeholders from the federal to local level, each interested in protecting Moab’s watershed. He came under scrutiny from a conservationist on the call, Dave Earley of Castle Valley, for the implications of the division’s findings.
“Marc [Stilson] throws up, ‘Well, we’re only using 2,700 acre-feet of water; what’s the problem?’” Earley said, referring to part of an estimate of total water consumption in the valley. “Well, I guarantee there’s a problem and we’re going to know it in five or 10 years, so we need to get tough now — quick.”
Stilson responded, saying that he agreed with Earley that conservation, paired with other water management strategies, would be beneficial and ensure that Moab does not surpass the safe yield that his agency is calculating.
“There’s a lot of citizens in Moab that are using groundwater — pristine, treated drinking water — to water their lawns,” Stilson said. “Conservation is an important part of it; I agree with Dave on that. The low hanging fruit … is to get citizens in Moab to stop using their drinking water for watering their lawns, and there’s some strategies for doing that.”
Using the Colorado River
One of the strategies is pulling water out of the Colorado River for irrigators and others to use in lieu of treated drinking water, an idea that city officials are already investigating for feasibility, according to Moab City Engineer Chuck Williams.
“Part of water management is not just determining how much we have but wisest ways to use it,” Williams said.
The City of Moab currently does not use any Colorado River water for any consumptive purposes. Rather, its culinary water system derives its water from the aquifer below Moab, which is recharged by precipitation in the valley and, particularly, in the La Sal Mountains.
The idea, Williams said, would be to remove some of the strain on the city’s public drinking water supply by taking irrigation and related uses off the culinary system and supply those users instead with water from the Colorado River.
Although the valley’s aquifer is not fully tapped, the supply is limited, particularly when compared to the availability of water in the Colorado River.
Where capacities are available
The valley’s water users share between 4,500 and 7,800 acre-feet of groundwater per year and currently only use a portion of that, according to the Division of Water Rights’ preliminary estimates.
By comparison, state and federal agreements entitle the State of Utah to 23% of the supply of water in the Colorado River’s upper basin, which in recent years has been roughly 1.7 million acre-feet. The state currently consumes 1 million acre-feet of river water and, to account for climate change, it plans to develop only 400,000 additional acre-feet in coming years.
The plan has its detractors, including John Weisheit, conservation director of Colorado River advocate Living Rivers, who says that amount of water is not, in reality, available to the state for use. Weisheit’s organization is a nonprofit seeking “ecological restoration, balanced with human needs” in the Colorado River basin.
“The reservoirs of the Colorado River are going to dry up, and for decades,” Weisheit said. “No hydropower. Economic systems and ecosystems will malfunction. It won’t be pretty.”
The larger picture: Managing Moab’s supply
As the Division of Water Rights narrows its estimate of the valley’s groundwater safe yield, it and the many locals participating in the process are also hoping to devise a water management plan for Moab.
Climate scientists, including those on whose work the Division of Water Rights is relying in determining Moab’s groundwater safe yield, do anticipate increases in average temperatures to cause more evaporation of water from streams. However, the exact degree of the effect is uncertain and contingent.
In the meantime, officials are already implementing conservation rules, most notably on new lodging developments, and building Moab’s drought resilience, including by drafting a water management plan.
The plan concerns not just the use of groundwater but surface water as well, be it from Mill Creek, Pack Creek, or the Colorado River. According to Stilson, the division will not complete its safe yield calculations until the valley settles on the water management plan currently in the works.