The partnership solved a tricky balancing act of bringing water to the metro area in a way that benefits fish in the canyon, a popular fly-fishing destination along the South Platte River in Park County.
“We started coordinating water system operations with Aurora between Spinney Mountain and Eleven Mile reservoirs in 2011 and since then, the rainbow trout population has really taken off,” said Dave Bennett, water resource program manager.
Here’s how the partnership works:
When Aurora needs water, their water department releases it from Spinney Mountain Reservoir and sends it down the South Platte through Denver Water’s Eleven Mile Reservoir. During the spring runoff, when rainbow trout spawn, high river flows can sweep away the eggs and young fish. To help the trout during spawning season, Aurora can hold some of its water back in Spinney.
“This sends nice moderate flows through Eleven Mile so the young rainbows and eggs can survive,” Bennett said.
If Aurora still needs water to meet its customer demand, Denver Water is able to loan the city water from its downstream reservoirs.
Once the runoff ends and the young rainbow have had a chance to grow, Aurora pays back Denver by releasing water saved up in Spinney.
The lower flows through Eleven Mile Canyon typically begin in late-April and last until late-June once the fish have hatched and are strong enough to survive.
“Having relatively stable river flows from spawning to a few weeks after the young fish emerge really benefits the fishery,” said Jeff Spohn, Colorado Parks and Wildlife aquatic biologist.
Aurora has not had to borrow water so far in 2016 and in 2015, the water was too high for the sharing plan to work effectively. The effort has been successful in past years with average runoff and will continue each year as needed.
“When we bring water into the city, we’re always looking to provide additional benefits along the way, such as helping trout fisheries and recreation,” Bennett said. “We strive to get multiple uses from every drop released from our reservoirs.”
The operation is one of the success stories of the South Platte Protection Plan, which is an agreement among utilities, landowners, recreationists, environmental groups and local governments to protect the health of the river.
“We have always believed that regional solutions benefit everyone, and we’re thrilled that in this case, it even helps the fish,” said Lisa Darling, Aurora Water’s South Platte River program manager.
“As Colorado’s population increases, demands on our aquatic resources and water supply systems will increase,” Spohn said. “In the future, we need to continue working collaboratively with each other so everyone can enjoy what our rivers have to offer.”