Colorado-Big Thompson Project update: 1400 cfs and rising in the Upper Colorado River below Lake Granby

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From email from Reclamation (Kara Lamb):

The gates at Granby Dam have been cracked open above the spillway so that water is pushing over the spillway. While the reservoir is still about 20 feet down from full, water is pushing over the spillway gates because the lip of those gates is also about 20 feet down from a full water elevation.

Consequently, we are seeing releases to the Colorado River below the dam steadily increase as run-off inflow increases. As the run-off inflow comes up, we are seeing the original plan we at Reclamation and Northern Water introduced back in April materialize.

We had originally forecasted that releases from Granby could get as high as 2500 cfs–and that is what we anticipate will happen come the top of next week, around Monday or Tuesday June 20 and 21. Today, releases from Granby Dam got upwards of 1400 cfs. They will continue to increase through the weekend.

Inflows to Shadow Mountain Reservoir, which releases to Granby, and other inflows to Granby, are on the rise. They bump up especially at night, when melted snow that has traveled down from high mountain elevations reaches the reservoirs. Today, Shadow Mountain was releasing about 2600 cfs.

Willow Creek Reservoir, whose drainage basin sits at a slightly lower elevation, has possibly seen its snow melt run-off peak (although I wouldn’t say that is certain). Inflow to the reservoir has dropped off since last week when it was as high as 1300 cfs. It is now steadily bypassing about 960 cfs of run-off inflows.

Next week, when Granby’s releases reach their high mark, the Colorado River below its junction with Willow Creek will likely have flows upwards of 3300 cfs.

From email from Reclamation (Kara Lamb):

Just a quick note that elevations are still on the rise for Horsetooth Reservoir, which will be above its average water level elevation for the coming Father’s Day weekend. And, Carter Lake remains full!

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