Colorado-Big Thompson Project: The Upper Colorado River benefits from the seventh spill in Lake Granby history

A picture named granbyspill06222011

From the Sky-Hi Daily News (Tonya Bina). Click through for the cool video footage of the spill that Ms. Bina shot yesterday. Here’s an excerpt from the article:

This is the seventh year that water has gone over the Granby spillway because of abundant runoff, according to Dana Strongin, spokesperson for the Northern Colorado Water Conservancy District. The last time was 14 years ago. Before the dam spillway was built in 1965, water would cascade over the cliff rocks into the pool of Colorado River water below.

Although that stretch of the Colorado River directly below the Granby Dam may pose some flood risks, it is now receiving long-awaited flushing flows deemed necessary to river health. Flushing flows remove sediment and make it easier for fish to spawn. They also rejuvenate the riparian areas adjacent to the river. Such areas are important since 90 percent of Colorado’s wildlife live in or near water…

Silt had accumulated at the river bed to a point that made it difficult to even wade in it, [Jon Ewert, DOW aquatics biologist based in Hot Sulphur Springs] said. Such conditions can choke life in the river. “From what I’ve seen on that section of river before this flow, it had some of the most impaired habitat on the Colorado in Grand County,” he said.

That Upper Colorado section can go years with average flows around 150 cfs, according to the state Division of Water Resources website. From a prescription set by the U.S. Secretary of the Interior in 1961 having to do with the management of the Colorado-Big Thompson Project, flows on the Colorado River in that section from May to July must be at a minimum of 75 cfs, and in late summer a minimum of 40 cfs…

On Wednesday, June 22, flows at the gauge below Granby dam were at a healthy flushing rate of about 1,800 cfs, which included flows coming out from the bottom of the dam.

More Colorado-Big Thompson Project coverage here.

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