Just below the Eleven Mile Reservoir dam, the spawning rainbow trout pointed their noses upstream, intently focused on finding the perfect spot in the rocky river bed.
“They’re not interested in feeding, they’re not too spooked by us,” Colorado Division of Parks and Wildlife aquatic biologist Jeff Spohn said as a handful of trout spawned in the shallow water below. “They’ve got one thing on their mind.”
That one thing certainly wasn’t the goings-on 100 miles away at the Aurora Municipal Center or at Denver Water’s headquarters. But because of an agreement between the two water departments, state wildlife officials say the future of the rainbow trout population in that stretch of the South Platte — one of only two natural rainbow fisheries on the river — is much brighter than it was a few years ago.
Under the agreement between Parks and Wildlife, Aurora Water and Denver Water, the three agencies are working together to make sure stream flows in the Platte remain constant during the critical spring spawning season.
Regulating the flows in the canyon required Aurora’s and Denver’s help because flows there are largely determined by the water departments’ decisions upstream. Denver Water owns Eleven Mile Reservoir, which flows into the Platte, and Aurora owns Spinney Mountain Reservoir, which feeds Eleven Mile. Because it is a designated “drought reservoir,” the output from Eleven Mile into the Platte is based on what Aurora dumps from Spinney.
If Aurora dumps too much, the Platte moves too fast and the young trout are rushed downstream just as they emerge from the egg. If the water level drops too quickly, fertilized eggs could be exposed and dry up on the banks.
Spohn has been working on the canyon’s fishery for nine years, and in 2011 he noticed a troubling trend.
After the fry numbers peaked at 1,088 in 2004, they fell steadily for the next several years, first to 421 in 2005 before bottoming out at just 23 in 2008.
For years, wildlife biologists thought the fishery had rebounded from a rough few years in the 1990s because of a catch-and-release mandate instituted there in 2000. But Spohn said after studying a mountain of statistics about stream flows, water temperatures and other factors, he realized the regulation helped, but it wasn’t the biggest issue on the river.
“We really thought the special regulation was driving this fishery,” he said. “It’s not, it’s the stream-flow management.”
With a pile of numbers in hand, Spohn approached Aurora and Denver and asked them to maintain a steady flow during some crucial times. If the river could stay at about 75 cubic feet per second, it would be ideal for spawning, he said.
But job No. 1 for Aurora Water and Denver Water is making sure when someone turns on their tap or their sprinkler, a steady stream comes pouring out — regardless of what that means for trout in the canyon. Sometimes that means more than 75 CFS, often as much as 200 CFS.
“We can’t operate to the detriment of the citizens of Aurora,” said Brian Fitzpatrick, water resources manager for Aurora Water.
And while Spohn’s focus is on improving the trout fishery in Eleven Mile Canyon, he knows that’s not Aurora’s chief concern.
“Wildlife understands that Aurora’s job is to provide water to their customers in the city,” he said.
That’s where Denver Water comes in.
When Aurora slows the flow from Spinney — often to levels well below what the city needs — Denver Water steps in and loans Aurora some water from Strontia Springs Reservoir. As soon as flows can be bumped up again, Aurora pays back Denver with water from other storage.
So far, the agreement is helping the trout and providing ample water to the Front Range cities.
“We’re working together to try to do both,” Spohn said. “And it’s working.”
Last year, wildlife officials counted 299 “young of the year” rainbows in the upper canyon, up from just 70 in 2010 and the fourth-best year on record.
Dave Bennett, water resource project manager for Denver Water, said the agreement is working out well for all three agencies, and the fish, too.
“It’s really turning into a very special trout fishery,” he said.
Lisa Darling, Aurora Water’s program manager for the South Platte River Basin, said she was thrilled to see the plan working well and expected it to continue.
“I can’t see any reason why we can’t do programs like this in the future,” she said. “It’s a win-win for everyone, even the fish.”
Spohn said the trout population in Eleven Mile Canyon is particularly important because it is a natural rainbow fishery. Almost all of the rainbow trout pulled from the South Platte in other areas were put there by Parks and Wildlife’s stocking program.
Only this stretch below Eleven Mile and another stretch below Cheesman Reservoir are natural.
When Whirling Disease hit the Platte in the late 1990s, it decimated much of the rainbow population, killing off young fish throughout the river.
The disease hit in Eleven Mile Canyon, too, but Spohn said it didn’t have the devastating effects that it did elsewhere.
“It’s low enough that these fish can survive,” he said.
Having a natural trout population means Parks and Wildlife doesn’t have to undergo expensive stocking operations in the canyon the way they do elsewhere, he said.
“It’s a rare fishery for the Platte and the rainbow trout population is in decline. That’s the whole reason why we’re doing this,” he said.
The fishermen who make regular trips to Eleven Mile Canyon have a different reason for liking the natural trout population there.
“It’s a bigger challenge,” Bob Furman, 65, said as he cast a flashback pheasant tail fly into river. “I don’t want to catch stocked fish, I want to fool the smart ones. And they are smart here, believe me.”
Furman, of Tribes Hill, New York, said he averages about 25 fish per day when he visits the canyon. By mid-day on an overcast Thursday last month, he said he’d already hooked 16.
Hearing that the trout population had a bright future was welcome news to the fishermen who waded the frigid Platte that day.
Joe Garcia, 32, said he makes the drive from his home in Denver down to the canyon west of Colorado Springs once every few months.
It’s good to hear future years should have a sizeable trout population, he said. It’s also nice to hear government officials working together.
“Especially in this era, I think it’s great,” he said as he and his father cast their flies. “You don’t hear of that too often.”
For Spohn, getting the agreement in place wasn’t much of a challenge once Aurora and Denver officials understood how important the cities’ decisions were for the fish.
“It was never a pointing finger type of deal, we just never had the knowledge,” he said. “Now we have the knowledge.”
Reach reporter Brandon Johansson at 720-449-9040 or [email protected]
1. Water from Spinney Mountain Reservoir, which is owned by Aurora Water, flows into Dream Stream, typically at rates varying from less than 75 cubic feet per second, to well over 200 feet per second. Last year, at the request of the Colorado Division of Parks and Wildlife, Aurora kept those flows steady at about 75 feet per second during the critical spawning season.
2. Because Eleven Mile is a designated “drought reservoir,” Denver Water keeps its level steady unless a drought necessitates tapping the reservoir’s reserves. That means flows out of Eleven Mile into the South Platte river are based solely on what Aurora releases from Spinney.
3. Fluctuating flows from Spinney in the past made spawning difficult for rainbow trout in the Platte — heavy flows washed eggs down stream, weak flows left eggs to dry on the banks. Constant flows from Spinney last year lead to a 300 percent spike in young trout after several years of decline.