Colorado-Big Thompson Project update: 125 cfs in the Big Thompson River below Olympus Dam


From email from Reclamation (Kara Lamb):

As everyone has likely heard by now, we didn’t have much snow pack this year. As a result, I haven’t had much run-off information to share over the last several weeks. But, now that we are on the brink of summer, I thought a Memorial Weekend update on Colorado-Big Thompson Project reservoirs and operations might be helpful.

Over on the west side of the Continental Divide, we’ve seen a steady release from Green Mountain Reservoir to the Lower Blue River of about 75 cfs. That does not appear likely to change in the near future. The reservoir is currently at a water level elevation of about 7920 feet, that’s about 64% full. That is actually slightly above what we might normally see in late May. This is because run-off in the Blue River Basin started early this year and we began filling at Green Mountain on April 1.

Similarly, storage levels at Granby, Willow Creek and Shadow Mountain reservoirs–where we collect the water that will be diverted to the East Slope–are also slightly higher than is typical for this time of year. Like Green Mountain, that is because we saw run-off start and peak early on the upper reaches of the Colorado River. Currently, Granby has a water level elevation of about 8263 feet, around 79% full, and is releasing about 53 cfs to the Colorado River at the Y gage. In a more normal snow pack year, we’d be releasing 75 cfs at the Y gage.

Willow Creek Reservoir, whose water is pumped up to Granby is about 82% full and Shadow Mountain Reservoir is around 96% full–it usually is.

Following the project over to the East Slope, we have seen fairly typical water elevations in Lake Estes for most of the spring. Releases from the reservoir through Olympus Dam to the Big Thompson River have not fluctuated much, averaging around 120 cfs for the past several weeks. Currently, releases to the Big T are closer to 125 cfs.

Pinewood and Flatiron water levels fluctuate fairly often. Water elevations rise and fall daily, depending on power generation at the Flatiron Power Plant. Over the last couple of weeks, Pinewood’s elevation declined, but we are steadily bringing it back up again. Next week, visitors to both reservoirs might notice some surveying going on. Reclamation employees will be out at the reservoirs looking at sediment.

The pump is on to Carter Lake and its water level elevation continues to rise. It’s currently at an elevation of 5735 feet, about 77% full. While it will go up in elevation a little more, how high it gets now depends on downstream demands. Demands will come up with hot and dry weather.

Horsetooth is in a similar situation. The reservoir saw its highest water level elevation (about 5424) for the summer season at the end of April/early May. It has been slowly dropping this month and is currently around 5419 feet–that’s roughly 87% full. Like Carter, summer water levels at Horsetooth depend largely on downstream demands, which depend largely on weather. We’ll see how hot and dry it gets.

If you plan to visit one of our reservoirs over the holiday weekend, check out its current operations via our Colorado Lakes and Reservoir website. We have up-to-date information posted there.

More Colorado-Big Thompson Project coverage here.

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