No end in sight for Willwood Dam silt


Public meeting touts new technology and research, but may never solve problem with current system

Much has changed since a massive release of sediment from the Willwood Dam last year. But according to David Waterstreet, watershed protection program manager for the Wyoming Department of Environmental Quality, sediment is still building up behind the dam.

“We’ve got to recognize the fact that we have an annual load of sediment that makes it to the Willwood Dam regardless of what we do,” Waterstreet said, adding, “For many decades past, basically, Willwood Dam has been capturing a good portion of sediment that would have naturally flowed all the way down [river]. We’re still at a point that we have a heavy buildup of sediment.”

Waterstreet emceed a Tuesday public meeting organized by the Willwood Dam Advisory Committee. It was an effort to keep the public up to date on the goals of three working groups set up to study and make recommendations on how to deal with the hundreds of thousands of cubic yards of sediment that pass through the dam each year.

There has been progress: Equipment that measures turbidity (the cloudiness or haziness of the river caused by large numbers of individual particles in the water) and conditions at the dam have been installed on both sides of the structure.

Roger Smith, chairman of the board of the Willwood Irrigation District, is thankful for the new technology. Prior to the installation, “the only way we knew what was going on at the dam was to drive up and physically observe what was happening,” Smith said. “That left an opening for problems to happen. If we weren’t up there every hour or two, something could happen and we wouldn’t know about it.”

The automated system now in place “allows us to see what level the pool is at, where the gates are at and if there’s a fault in the actuators. It can be seen in the office or on a smart phone,” Smith said. “We know instantly when there’s a problem.”

One of the working groups is studying ways to keep sediment from running off into the river. One of the largest problems in the silt equation is erosion from the McCullough Peaks. The group has already made some recommendations, resulting in the construction of runoff channels and ponds to catch sediment.

But the problem is not going away. Jason Burckhardt, Wyoming Game and Fish Department fisheries biologist, shared data from studies showing the Shoshone River’s “Blue Ribbon” fishery stops at the Willwood Dam.

The department halved its stocking programs east of the dam in 2010. Fish population surveys conducted by the department on that side of the structure showed the number of fish falls below the standard for Blue Ribbon fisheries. A very small amount of the fish were wild and very few of the stocked fish were making it through the winter.

“It doesn’t make sense to stock fish in a habitat that can’t sustain them,” Burckhardt said after the conclusion of the meeting.

The possibility of dramatically altering the way that water is provided to Willwood area irrigators was raised at Tuesday’s meeting.

“All of our efforts have looked at how can we change the operation of a system that we know over the years has continually created problems; over the years we’ve had multiple releases and multiple fish kills,” said Dave Sweet of Cody. “I wonder if this group is willing to look at a longer term solution — which is changing the point of diversion.”

Sweet, who’s a member of the local Trout Unlimited chapter but spoke as a private citizen, suggested moving the diversion point or bypassing it by creating water sharing agreements with other area canals.

“That may be where we end up landing, because we have too much sediment load and no matter how we turn the knobs and dials, we can’t bring the sediment level down,” Waterstreet said. “But we definitely don’t want to jump into that.”

The working groups have discussed the possibility that the system, built in the 1930s, will never allow them to meet their goals. But mechanically removing the sediment or changing the point of diversion — such as by moving the dam or getting water from the Corbett Dam, for example — are time consuming and very expensive. “I don’t want to push that to the front until we have a better understanding of the problem,” Waterstreet said.

The committee plans to continue studying the issue in hopes of finding an option that solves the sediment issue without spending the millions of dollars it would take to change the current system.

Repairs to one of the gates on the dam last year necessitated lowering the pool, which caused the release of sediment and led to a grayish-colored river and public outcry. Two of the three gates now work, but according to Smith, there’s not a repair that can be made to stop the build-up of sediment behind the dam. The gates must be closed when the water is diverted for irrigation and that’s when the sediment builds. Restrictions on the amount of sediment that can be released when the gates can be open ties their hands.

“For 50 years we haven’t been able to pass that sediment,” Smith said.