The Colorado River is starting to swell with spring runoff, but just a few months ago, Avi Stopper clocked a gap in the Western United States' most important water supply.
Stopper was driving back to Denver from an event in Carbondale. Heading east on Interstate 70 through Glenwood Canyon, he saw the Colorado River perform a curious trick.
“What I would consider the lower part of Glenwood Canyon had the Colorado River in its normal state: Raging amongst the stones and rapids and that sort of thing,” Stopper said. “And then as we drove a little farther east, all of a sudden, there was no river. There were some puddles, but it wasn't really even flowing.”
Stopper found the observation curious because he was traveling upriver. Even more curious, a mile or two later, the water was back. It wasn’t that the water had dried up. It’d just gone away for a minute.
“Maybe there's some sort of pipe or workaround or something like that,” Stopper theorized in his question to Colorado Wonders. “But something that consumes the entire river and then empties it out farther downstream? It's not something I've heard of.”
Stopper is onto something with his theory.
James Heath, division engineer for the Colorado River Basin for the Colorado Division of Water Resources, says Stopper most likely witnessed a roughly two-mile stretch where up to 1,400 cubic feet per second of water takes the scenic route through Xcel Energy’s Shoshone Hydro Electric Generating Plant. If that diversion is happening during high-water months like May, passersby would probably miss it entirely. But in the dead of winter, when river flows can be below 1,000 CFS, the difference can be seen by drivers heading east.
“At certain times of the year, the power plant can divert every single drop of water that's in the Colorado River and other times a year the stream flow is significant and it's hardly noticeable what the power plant's actually diverting off the stream system,” Heath said.
The water rights are considered “nonconsumptive,” which means there’s no water lost in the process. That’s also why the river disappeared and reappeared a short time later on Avi’s drive. Water leaves the river at a diversion dam near the Hanging Lake Tunnel and then reenters the river at the Shoshone plant. Heath said it’s about a 2-mile stretch and there’s little entering the stream during that period.
“There's a little bit of gate leakage there at the diversion dam. There are a couple small minor tributaries that come in between the diversion dam and the returns from the powerhouse, but it's a small trickle at times during the year,” Heath said.
It’s not the only place on the Colorado River where such a phenomenon can happen if the conditions are right. In Mesa County’s De Beque Canyon, there’s a point where water is diverted for irrigation and hydropower.
“During the summertime at the Roller Dam, they're diverting both for power and for irrigation operations. And the same thing can happen there. They can divert the entirety of the river,” Heath said.
The Shoshone plant is notable not only for the vanishing point it can create in Glenwood Canyon, but also for its importance in water conservation efforts. Its first turbines were installed in 1906, according to Xcel, and the water rights that feed the plant are among the oldest on the Colorado River. Because of that, a group of Western Slope entities have been working to purchase the water rights for close to $100 million in order to prevent them from possibly being bought up for diversion to the Front Range.
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