Denver: 2100 acre-feet for South Platte environmental flows

From The Denver Post (Bruce Finley):

The Denver Water and Colorado Parks and Wildlife officials said they’ve obtained 2,100 acre-feet of water that they will use strictly for environmental purposes…

“We’re trying to make the South Platte the best it can be for this city. … It’s not going to be like a Danube,” Denver Water manager Jim Lochhead said. “We can make it what it is, which is a plains river that creates an appreciation of the connection to water in this city. The city would not exist without that water supply.”

The idea is that putting more water into the Platte at the southwestern edge of metro Denver will mimic long-lost natural flows, to the extent possible given the channelization of the Platte after the 1965 flood that destroyed buildings in the floodplain. More water also would help a fish hatchery where state wildlife workers breed rainbow trout.

For more than two decades, Denver conservationists have worked at reviving the Platte corridor, building cycling-oriented pathways and riverside parks. It’s been complicated because metro Denver grew up around the river and, for more than a century, people exploited it as a sewer with industrial plants and discharge pipes draining into the water. Now as kayakers, surfers, skaters, waders and others flock to the river, city leaders face rising demands for more water, cleaner water and wildlife.
But just beyond Denver, farmers await every drop of the treated wastewater metro users put back in the Platte, water used to grow food. There’s so much demand for South Platte water across booming northeastern Colorado that parts of the river run dry.

By 2018, project leaders say, new environmental flows from Chatfield will keep that from happening — and create curves and pools favoring aquatic bugs and fish.

“Now we’ve got some water so that we can start to build the river back to being a natural-looking river. It is limited. The river won’t have access to the true floodplain. But we can build smaller floodplain ditches so that the river will look more like a sinuous river coming through Denver,” CPW senior aquatic biologist Ken Kehmeier said.

“The water will be used mostly during the low-flow times of the year,” the 65 or so days when water rights holders have the ability to dry up sections of the river, Kehmeier said.

“It will mean water stays in the river downstream of Chatfield, including the hatchery. That’s where the trout will come from. And brown trout in the river now, with this extra water, will be able to reproduce naturally.”

Lining up storage for the water proved crucial. Denver Water has committed to work with the Greenway Foundation to buy space for 500 acre-feet in an enlarged Chatfield Reservoir. This water adds to 1,600 acre-feet of water to be used only for environmental purposes that federal engineers required as “mitigation” for Colorado’s repurposing of the reservoir from flood control to water supply. The 500 acre-feet would be owned by the Central Colorado Water Conservancy District, a downstream agricultural entity, which agreed to pay annual operational and maintenance costs.

Storing water in Chatfield costs $7,500 an acre-foot, Denver Water officials said. They’ll spend $2 million to buy storage space, on the condition the Greenway Foundation does the same…

This push to put more clean water in the Platte through Denver coincides with broader environmental efforts. Federal, state and city engineers have been mulling possibilities for restoring other metro waterways, for which the U.S. Army Corps of Engineers has dangled possible funding.