Colorado: Dillon Reservoir close to filling

Peak runoff helps boost water storage across the state

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Snowpack across most of Colorado dropped to below average as temperatures warmed to above average in June.

FRISCO — After a big weather turnaround in April and May, Dillon Reservoir is well on its way to filling, with the water level reaching an elevation of just about 9,008 on June 13, just nine feet below capacity. The last time the water level was this high was July 26, 2012.

“We think it’s likely we’ll fill or at least get within a few feet of full elevation,” Denver Water spokesperson Stacy Chesney said.

Peak inflow into the reservoir was June 10, with the mainstem of the Blue River and the rest of the basin tributaries combining to deliver 1,754 cubic feet of water per second. The inflow hovered around that level early in the week, and started to drop a little bit by Thursday and Friday as the snowpack at higher elevations dwindled.

By June 14, most of the automated SNOTEL sites had melted out, making it more difficult to assess how much runoff is still to come.

The reservoir bottomed out April 27 at an elevation of 8,982 feet, about 35 feet below capacity, and has been rising steadily ever since, coming up 26 feet in just 48 days, at an average rate of about six inches per day. At times, the reservoir visibly refilled as water spilled from the main body into shallower ponds at edge separated by terrain features.

Chesney said Denver Water projects releasing between 50 and 100 cfs down the Lower Blue the next few months and will also divert water through the Roberts Tunnel to the South Platte, currently flowing at a rate of about 150 cfs.

Overall, Denver Water’s storage in the South Platte system is nearing capacity. Antero Reservoir just two feet below full and Eleven Mile Reservoir is at capacity, holding more than 98,000 acre feet.

On the West Slope, Williams Fork Reservoir, Denver Water’s other big bucket, is about five feet below full, holding 89,000 acre feet, with a capacity of 97,000 acre feet.

Green Mountain Reservoir, administered by the U.S. Bureau of Reclamation, has also bounced back from what looked like it was going to be a woeful summer. As of mid-June, Green Mountain was about 76 percent full and still rising, according to BuRec spokesperson Kara Lamb.

For now, releases from Green Mountain Reservoir are holding steady at around 70 cfs, but those flows will ramp up later in the summer as downstream users call for irrigation water, Lamb said.

Green Mountain Reservoir will have what’s called a “paper fill” this year, meaning that there’s enough water in storage in the Upper Colorado system to fulfill Green Mountain’s contractual obligations, even if it doesn’t physically fill.

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One Response

  1. […] per day. Denver Water now expects the reservoir to come very close to filling. More details in this Summit Voice story. Jenney Coberly documented the surging water level from the saddle of her bicycle, compiling this […]

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