From the Sky-Hi Daily News (Hank Shell):
Typically, reservoirs on the Front Range fill by May, which lowers Lake Granby enough to accept additional water during runoff season, said Kara Lamb with the U.S. Bureau of Reclamation. But flooding on the East Slope in September, coupled with additional precipitation and runoff, have kept Carter and Horsetooth reservoirs, the Colorado-Big Thompson Project’s main draw points for Front Range water users, too full to accept much water. Add above-average runoff on the Western Slope to the equation, and there is a fair amount of uncertainty whether the Alva B. Adams Tunnel will have anywhere to transport water if and when Lake Granby spills.
“There could be a little pumping to help with the spill situation,” said Brian Werner with Northern Water. “It’s dependent on this side of the mountains, and if there’s any room to put any water, so demands really haven’t started, and like I said, we’re full everywhere.”
There’s a possibility that pumping could be halted until Labor Day, Werner said.
For Grand Lake residents, pumping can mean the difference between pristine clarity and a cloudy lake. Last year, reduced pumping saw the clarity of natural Grand Lake increase, while the shallower Shadow Mountain Reservoir became more turbid…
As of July 3, Lake Granby was at 2.6 feet from capacity, with levels rising around a third of a foot per day. Werner, of Northern, said if the lake does spill, forecasters expect it to do so between July 10 and July 14.
“Our forecaster, who I just talked to, said we’re still 50-50 on whether we’re going to spill,” Werner said.
Spilling is not a very common occurrence for Lake Granby. The last time the lake spilled was in 2011, and before that it was in 2000. The large amount of snowpack has led to above-average flows this year, and reservoirs on the Front Range are already near capacity. Specifically, Carter Lake is at 99 percent full, while Horsetooth Reservoir is 99.2 percent full, according to the Bureau of Reclamation’s website.