Denver Water trying to balance storage across its system
By Bob Berwyn
SUMMIT COUNTY — Slowly but surely, Dillon Reservoir is starting to inch upward again, as Denver Water seeks to maximize storage in all its reservoirs during what looks to be a meager peak runoff.
Since hitting a low on May 5, the elevation of the reservoir climbed by almost six inches, to 9,012.67 feet on May 15. After a small drop, it’s been holding steady since then.
“Today we cut back on the Roberts Tunnel a little bit,” said Bob Steger, manager of raw water resources for Denver Water. “We’re trying to fill the South Platte system and Dillon at about the same rate. We saw that Cheesman Reservoir was filling a little quicker, so we cut back,” Steger said.
Currently, Denver is diverting about 250 cubic feet per second through the Roberts Tunnel under the Continental Divide to the South Platte drainage. Another 53 cfs is flowing out of the reservoir into the Lower Blue — just above a 50 cfs minimum stream flow set to protect aquatic life, for a total of about 300 cfs coming out of the reservoir daily.
The total combined inflow from the Snake and Blue rivers, as well as Tenmile Creek, has varied between 301 cfs on May 13 to as high as 394 cfs on May 11, Steger said, adding that, since overnight lows in the high country are still dropping below freezing, the runoff hasn’t quite peaked yet.
But based on the most recent outlook for reservoir operation, Dillon may not get much higher than it is right now. So far, May precipitation in the Blue River basin is lagging behind average, Steger said.
In a drier-than-normal scenario, Denver Water’s figures show that the end-of-month level may actually be two feet lower than it is right now, then drop another four feet by the end of June. With average precipitation, the reservoir level should hold steady about where it is right now.