Denver Water increases reservoir outflows to Blue River

Over Memorial Day weekend, Denver Water increased the outflow from Dillon Reservoir to the lower Blue River.

The utility raised outflows below Dillon Dam from about 900 cubic feet per second on Friday, May 22, to roughly 1,500 cfs by Monday in hopes of creating more space in the reservoir ahead of this year’s peak runoff.

Denver Water spokesman Travis Thompson said the utility is not legally allowed to take more water under the Continental Divide through the Roberts Tunnel than is needed by Front Range and Eastern Slope customers. Because of high flows in the South Platte River and low customer water use, Denver Water doesn’t expect to take water through the tunnel until mid-July or later.

On Tuesday, Thompson said, Dillon Reservoir is 92-percent full, which is typical for this time of year.

Though the reservoir’s current inflow is much lower than it was in 2014, water managers expect to see a dramatic increase in the coming weeks as snowpack above the reservoir is above-average and has surpassed even last year’s snowpack.

Every spring, Denver Water coordinates with local government officials, and water managers to try to prevent flooding in Silverthorne.

As a rule of thumb, 200 to 550 cfs on the Blue River below the dam is the ideal flow range for fishing, while 400 to 1,300 cfs is ideal for rafting.

At 1,500 cfs, flows start to create safety concerns for rafting, and, by 1,800 cfs, the Blue River’s banks can start to overflow.