Aurora, continuing a varied approach to supplying water to the rapidly growing city, recently deployed its checkbook to acquire thousands of acre-feet from the expanse of the South Platte River basin in northeast Colorado. The move has stirred concern that thirsty Front Range municipalities will damage the state’s agriculture industry as they hunt for more water.
Aurora Water, the agency that manages water supplies in the booming Denver suburb, insists that no such harm will result from its purchase of nearly 1,700 acre-feet in the farm-heavy watershed. “We’re not trying to remove agriculture from the region,” Greg Baker, a spokesperson for the bureau, said, adding that Aurora Water buys only from willing farm sellers. “Agriculture is a phenomenally tough business,” he said. “There’s folks who just can’t afford to stay in it. It becomes a natural outlet for sale of these rights.”
The Aurora transactions closed in July. They involve 1,052 acre-feet obtained through acquisition of the Tetsel Ditch Co., an irrigation supplier in Washington County, and an additional 1,629 acre feet from the Whitney Ditch near Windsor. The Whitney Ditch carries water from the Cache la Poudre River and has one of the highest priorities for diversions. It was built in 1862.
One acre-foot of water is enough to cover one acre of land to a depth of one foot. Based on average household use of 45,000 gallons per year, the deal promises to provide for thousands of additional homes. For Dawn Jewell, a water resources supervisor planner for Aurora, that need means her city had no alternative but to jump at the opportunity for access to that much water in one fell swoop. “Most water rights acquisitions that take place are a hundred to a couple hundred acre-feet at a time,” she said. “It is very unusual to have purchases in the 1,000 acre-foot range.”
Overall, Aurora now uses about 50,000 acre-feet every year. “That’s actually been holding very consistently for the past decade even though we’ve seen substantial increase in population,” Baker said. By mid-century, though, a dramatic increase in the city’s water use is likely unavoidable. According to the 2015 Colorado Water Plan, the population will nearly double in the South Platte River Basin. In Aurora and other Front Range cities, the continued influx of people will mean that annual water use will explode. “We’ll need well over two times that amount of water,” Baker said.
In Colorado, the drive to accommodate the demand has traditionally been the province of local governments. Because of the vagaries of the state’s prior appropriation-based water code, developers often find it difficult to obtain the water needed to support their building projects. “It’s very difficult for a developer to purchase surface water rights in a location that is accessible to us and that have seniority that meets our needs,” Baker explained. “Rather than saying, ‘developers, you bring in the water,’ here it just becomes so complicated that we say, ‘you pay us, and we will acquire the water for future growth.’”
For Aurora and other Denver-area communities, providing for growth has historically meant moving water from the Western Slope. Half of Aurora’s water, even today, comes from the Colorado River Basin and the Arkansas River Basin. Starting in the first half of last century a vast network of canals, pipelines, reservoirs, transmission lines, and tunnels. For all Front Range cities, it’s unlikely that growth in historical reliance on the rivers flowing to the Pacific Ocean is realistic. “The practice of bringing water from the Western Slope to the Front Range is not as practical, for several reasons,” Kevin Rein, Colorado’s state engineer and director of the Colorado Division of Water Resources, said. These include the difficulty and expense of developing the necessary infrastructure.
For that reason and others, including drought, cities began early in the last decade to look elsewhere for water. The South Platte, wellspring to more than 80% of the state’s farming sector, has proven to be an attractive target. “We’re seeing more and more, especially on the Front Range and in the South Platte Basin, there are no other options or few other options for these cities to find water to fund growth,” Joe Frank, general manager of the Lower South Platte Water Conservancy District in Sterling, said.
Farmers find that trend both alarming and welcome. Frank explained that, without water, agriculture’s role in local economies teeters. “Small rural communities rely on that water as an economic base,” he said. While it is not surprising that Aurora and other municipal hunters of water have turned to the South Platte, he said, it’s vital that a continuation of “buy and dry” be avoided. Shorthand for a practice that involves fallowing of agriculture land and repurposing the attached water rights, Frank argued that it’s become common enough to be a significant concern to eastern Colorado communities. 
Jewell pointed out that 1,629 acre-feet obtained via the contracts that were approved by Aurora’s city council this summer are associated with land formerly owned by Eastman Kodak since the 1960s and are already available for municipal use. As for the other 1,052 acre-feet, she said Aurora may use alternative transfer mechanisms to minimize adverse impact on farmers. These so-called ATMs allow for “flexible” plans, Jewell said, which can make the acquisition “more beneficial to numerous parties.”
Baker emphasized that Aurora’s precedent-setting effort to reuse water on a large scale would also assure that the city’s purchases of South Platte water rights would lead to the maximum possible benefit for that city. The Prairie Waters project, opened in 2010, allows Aurora to reuse 10-12 million gallons of water per day and assures that 95 percent of its water is reclaimable. “Aurora is the only municipal system in Colorado right now that has a potable reuse system,” he said. “All of this water that Dawn is buying, whether it’s from agriculture or from trans-basin diversions, is fully reusable.”
Aurora Water has also turned to a historically untapped source: mines. In 2018 the city paid $34 million for 1,400 acre feet of water trapped in an inactive gold mine in Park County. The water will need to be pumped to a tunnel, carried to South Mosquito Creek, then into the South Platte River and Spinney Reservoir.
It has also aggressively implemented conservation measures, which Baker said is saving the city several hundred acre-feet per year. “We treat our conservation program as a water requisition program,” he explained. “Most of the time we are trying to reduce the outdoor use of water because, when you use water outdoors, it evaporates and is lost to the system forever.” Aurora’s commitment to reducing the use of water to provide landscaping was evident as early as 1968, when the city began to reuse water to irrigate golf courses and parks, and has expanded today to include a program that provides rebates to city businesses and residents who xeriscape.
The city, which has more land area than Denver and which now has an estimated population of nearly 380,000, also continues to seek ways to take advantage of water available on the western side of the Rocky Mountains. Those efforts include a proposal, along with Colorado Springs, to build a new storage project called Whitney Reservoir on the edge of the Holy Cross Wilderness that would divert as much as 33,000 acre feet of water. The idea, if it reaches fruition, would damage sensitive 10,000-year-old fens. For Western Slope leaders like Sen. Kerry Donovan, D-Vail, that impact alone is enough to reject it. “Those aren’t a dime a dozen and are important to the overall health of the river system,” she said. Construction of Whitney Reservoir would require trimming about 500 acres from the 122,000-acre preserve. Rep. Dylan Roberts, D-Avon, emphasized that Western Slope residents are unlikely to look kindly on the plan. “Our natural environment and habitats are something that we value immensely,” he said. “Any project that would destroy what’s naturally there would be incredibly concerning.” Baker explained that, while Aurora is aware of Whitney Reservoir skeptics’ concerns, the city remains committed to a principle of shifting dependence away from groundwater first made by its city council during the 1950s. “It’s becoming more challenging,” he admitted.
As for when the water obtained from the Whitney Ditch and the Tetsel Ditch will be used, or how it will be transported to Aurora, Jewell does not yet have answers. She explained that Aurora will need to ask a state water court to authorize a change of use location for the Whitney Ditch water and a change of use for the Tetsel Ditch water. Infrastructure investments will be figured out in the future. “When somebody has water for sale, you might not have all the exact answers on how you’re going to use that water,” Jewell said. “But you try not to pass up opportunities for those purchases when there’s a logical way of using that water. In these cases, the logical way is an exchange up the river and possible pipelines to those locations.”
More generally, Baker said, Aurora does not consider that water is likely to soon be a constraint on its persistent growth and will continue to compete around the state for the resource wherever doing so is a feasible choice for the city. “Water’s probably always available,” he said. “It’s a question of how much you want to pay for it.”