Denver is planning to nearly triple the size of Gross Reservoir in southern Boulder County.

The city of Denver wants to build a bigger dam in southern Boulder County, nearly tripling the size of its reservoir.

And environmentalists have something to say about it: They want to know if Denver would mind making that dam even a little bit bigger.

It’s an odd request from a group like Trout Unlimited, which has partnered with the cities of Boulder and Lafayette to try and negotiate the bigger dam, but it actually represents a calculated effort to make the best out of a bad situation.

Denver — thirstier now than ever – is trying to push through a plan to expand Gross Reservoir by 72,000 acre feet, which would require making the current dam 125 feet taller. The water to fill the new reservoir would be pumped from the other side of the continental divide, sucking more water out of the tributaries that feed the now-not-so-mighty Colorado River.

The Colorado office of Trout Unlimited, based in Boulder, thinks this is a terrible idea, but they’ve come to accept the reality — there may be no stopping the project. But there may still be an opportunity for a small victory to be had in the Gross Reservoir expansion.

Environmentalists are asking Denver to consider adding an extra 5,000 acre feet of water to the reservoir, creating a bank of water that could be used to guarantee that South Boulder Creek, which flows from the dam at Gross Reservoir through the stunning cliffs in Eldorado Canyon State Park.

Most winters,  South Boulder Creek completely dries up as Denver draws down the water in the reservoir, causing devastating fish kills and compromising the stream’s ecological integrity.

Read more about this project in a story by Boulder Daily Camera reporter Laura Snider after the jump, or check out a story from the Denver Post that details this new trend here.

Cities, environmentalists to help South Boulder Creek

Gross Reservoir expansion could restore stream flows

Laura Snider, Daily Camera: Sunday, August 9, 2009

South Boulder Creek used to be a vibrant stream, swelling and shrinking with the sun and the snowmelt. 

Now, the stream’s flow is controlled by the dam that creates Gross Reservoir, and in the winter, it’s not uncommon to see South Boulder Creek dry up completely — and quickly — sometimes scattering the stream bed with the bodies of dead fish.

For more than a decade, water lawyers, conservationists and anglers have been wading through the complex maze of Colorado’s water rights system, trying to figure out how to restore the ecological health of South Boulder Creek, which flows through both Walker Ranch open space and Eldorado State Park.

And they may have finally found an answer, one that could make South Boulder Creek the silver lining of another river’s plight.

“It’s a stream that needs help,” said Drew Peternell, a water lawyer working on the Colorado Water Project for Trout Unlimited, a national conservation organization. “For a long time Trout Unlimited has been trying to restore flows in South Boulder Creek.”

Gross Reservoir is filled largely with water that was pulled from the Fraser River — a tributary to the Colorado — and then pumped through Moffat Tunnel to quench Denver’s thirst. As the city has grown, so has its demand for water, and now Denver has asked for permission to nearly triple the size of Gross Reservoir, pumping even more water from the Fraser.

Trout Unlimited opposes the expansion, arguing that the project would further drain the already over-taxed Colorado River. But if the project goes through — and most people expect it will — Trout Unlimited wants to see some victory for the fish.

Both Boulder and Lafayette have also joined with Trout Unlimited in the negotiations over the expansion, asking Denver Water to add another 5,000 acre-feet to the planned 72,000-acre-foot expansion of Gross Reservoir. The idea would be to release the extra water into South Boulder Creek in the winter, ensuring that the stream never dries up.

“This is something that is under serious consideration,” said David Little, Denver Water’s director of planning. “But as you might imagine, money is an issue.”

Adding the extra volume in the reservoir could cost about $8 million, and while Denver, Boulder and Lafayette have all said they’re willing to throw some money into the pot, Denver Water is still looking at a shortfall.

“We’re all very excited about the possibility,” Little said. “We hope that this money thing doesn’t get in the way.”

Denver Water expects to release a draft environmental impact statement on the Gross Reservoir expansion this fall, when the public will be invited to comment on the project.