Blue River running high through Silverthorne
FRISCO — Flows in the Lower Blue River, below Dillon Dam, are going up again.
With snowmelt speeding up under warm and sunny skies, Denver is boosting the outflow to 1,800 cfs to avoid a scenario where Dillon Reservoir spills at a level that causes outflows to go over that level.
That’s exactly what could happen without upping controlled releases now, Denver Water spokesman Matt Wittern said via email.
“Our experts predict that, if we maintained 1,700 cfs outflow and inflows remain around 2,400, Dillon Reservoir would be full and spilling within a week,” Wittern said. That could bring excessive flows and the potential for flooding below Dillon Reservoir.
Wittern said Denver Water is estimating the remaining snowpack in the Blue River as equivalent to between five and seven inches of water near Hoosier and Fremont passes.
That snow is melting fast, with no letup in sight. Inflows from runoff into Dillon Reservoir averaged 2,467 cfs Tuesday, which was well above current and planned outflows. And those inflows aren’t expected to drop below 1,700 cfs in the next seven days, which means Dillon Reservoir will continue to fill quickly, at the rate of about six inches per day. As of Wednesday, the reservoir was 3.25 feet below capacity.
Wittern also explained that Denver Water can’t legally divert water through the Roberts Tunnel if it’s not needed.
“Right now water levels are very high on the South PIatte River, eliminating this action as an option,” he said.
Troy Wineland, state water commissioner for the Blue River, said property owners in the Lower Blue who face flooding risks can prepare by perusing Summit County’s High Water Preparedness” manual which includes instructions on sandbag preparation and placement, as well as free sand / bag supply locations.