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Colorado: Snowmaking impacts Snake River flows

Massive Snake River snowmaking diversions means tough times for trout after drought summer

This year’s snowpack is well below average and tracking just barely above last year’s.

By Bob Berwyn

SUMMIT COUNTY — The most recent snowstorm helped boost the overall Colorado snowpack just a bit, bringing it on par with last year’s level at this time, which is still well below average for mid-November. Statewide, the snowpack was at 57 percent of average, as of Nov. 15, with most West Slope basins between 50 and 60 percent of average. Even the North Platte drainage, which has seen some significant snows in the Never Summer Range, is only at 64 percent of average.

In Summit and Eagle counties, many streams are flowing at or below historic low levels, creating challenges for some ski areas that rely on direct stream diversions for snowmaking. Keystone, for example, has had to dial back its snow guns several times in the past week as the Snake River dropped to a flow of just six cubic feet per second, the minimum required under state regulations.

Earlier this week, automated gage readings posted online showed that the Snake flowed below that minimum for several hours. Last winter — during a wet year — Keystone’s snowmaking diversions caused the Snake River to drop below the required minimum stream flow between 15 and 20 times, according to officials with the Colorado Water Conservation Board.

“We’re aware of the situation at Keystone,” said Linda Bassi, section chief of the CWCB’s  Stream and Lake Protection Program. “We’ve talked about it with them in the past, and we’re asking them to refine their timing … It’s kind of a complicated situation.”

Part of the issue at Keystone is that there’s a lag between when the stream flow starts dropping close to the 6 cfs level and the response, which is to stop operating the pumps that suck water out of the Snake, she explained.

“They keep in pretty good communication with the water commissioner – we are going to try and We’re trying to head off having this many events this coming year,” she said. “We take all our instream flows seriously.”

Keystone apparently faces particular challenges when it comes to maintaining required minimum flows. Other streams that have similar limits also have gages which are connected to an alert system, but staffers with the CWCB instream flow program said they haven’t received alerts on any other streams in recent days.

When there is an alert, the CWCB tries to determine whether the low flows are a result of diversions, that must then be curtailed to restore the minimum flow, or whether the low flows are due to natural conditions, in which case not much can be done.

“I think it is a very significant issue,” said Blue River Basin water commissioner Troy Wineland, explaining that Keystone’s diversions are impacting the Snake River despite the resort’s agreement with Denver Water that enables snow makers to pump water out of the Roberts Tunnel to augment flows in the river.

“When Keystone’s diversions from the Snake River cause interference with instream flows, they can pump up to 1,500 acre feet from the Montezuma Shaft,” said Denver Water engineer Bob Peters. “They either use that water directly or let it flow back to the Snake River to augment the flows due to their usage. They can do this from September 1 through March 31,” he said.

This year, because of the extremely dry summer conditions, that water apparently isn’t making it from the Montezuma Shaft down to the Keystone’s diversion pumps, possible because the geomorphology of stream channel in the reach between the two points, Wineland said, adding that new beaver dams may also be a factor. Some of the water may simply be spreading into wetlands, recharging a water table that dropped dramatically during this summer’s drought, he said.

Under a special agreement, Keystone also has the ability to draw the Snake River down to two cfs — a mere trickle — if they invoke skier safety concerns and get special permission from the U.S. Forest Service.

That was done a couple of years ago, when White River Forest Supervisor Scott Fitzwilliams rubber-stamped the request without any public process and without consulting with field level biologists about potential impacts to aquatic resources. The Snake River may be the only stream that has two minimum stream flows, according to Colorado Parks and Wildlife aquatic biologist Jon Ewert, who monitors the trout population in the river on a regular basis.

“If they go below 2 cfs, any over-winter survival we get is a bonus,” Ewert said, adding that the native population of Snake River brook trout don’t need a huge amount of water to survive, but at some point, the pockets of habitat where they can ride out the winter simply freeze up if flows drop too low.

To mitigate impacts, Keystone has an agreement with the state wildlife agency to stock the river each year with catchable size rainbow trout, which helps create the illusion of a fishery, but is a far cry from a self-sustaining trout population.

Along with low early winter flows, the Snake is also heavily impacted by toxic heavy metals at concentrations that far exceed state and federal standards set to protect aquatic life. In some ways, it’s a small wonder that any trout manage to survive long term.

“They’re limping along but their numbers aren’t huge,” Ewert said, explaining that his annual surveys have only recently found over-winter survival.

“In the winter of 2009 to 2010 we had fish for the first time, fish that were 3 inches long … In 2011, those same fish were 4 inches larger, but we didn’t find any juvenile fish. This year, we still found some fish in the 7-inch range,” he said.

Former water commissioner Scott Hummer (now with the Colorado Water Trust) said he’s not surprised that Snake River flows dropped below the required minimum recently. During these early cold snaps, it’s hard to know exactly how the river will respond, even with the augmenting flows from the Roberts Tunnel.

The flow regime is inherently volatile, and this year’s dry conditions add another level of complexity.

“Its’ going to be an interesting winter … Keystone has refined its monitoring …  when they start to shut guns down, it’s not like going to your kitchen faucet and instantly turning it off. Over the years, Keystone has become much more cognizant and responsive to ensuring that the minimums streamflow is being met,” Hummer said.

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  1. [...] Colorado: Snowmaking impacts Snake River flows (summitcountyvoice.com) [...]

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