Irrigation Canals Are Trapping Fish; Screens Could Prevent That

Oct 28, 2019

Throughout the West, water delivery systems have been developed for a number of purposes, including agriculture. But sometimes those solutions can lead to problems for fish. One Trout Unlimited chapter is dedicated to saving fish from getting stuck and dying in irrigation canals. 

On a warm Sunday morning in October, I trailed behind a man with a big, boxy-looking backpack on that turns out to be an electric shocker. Two women in front of me are holding nets larger than them. They are shocking fish in an irrigation canal, netting them and eventually releasing them back into the North Fork Shoshone River.

If you've never seen one, an irrigation canal is a big ditch that redirects water like a creek. 

The man with the electric shocker is Dave Sweet. He's been a member of the East Yellowstone Chapter of Trout Unlimited for over 20 years. As he shocks the water with his probe, fish stop moving and float up to the surface allowing the netters to swiftly scoop them in their nets.

"If we didn't get in here today, probably in another day or two this ditch would be dry," Sweet told me.  

Every year, the irrigation headwaters that lets water into these canals are shut down for the winter. When that happens up to tens of thousands of fish are trapped in the ditches and will die if not rescued. 

"Rescuing fish out of the irrigation diversion, that's a bandage, you know, we're just taking them out of the ditches," said Sweet. "Once they are trapped, the ultimate answer is to try to prevent them from being trapped [again] so you need fish-friendly screens.”"

Fish screens are basically what you are imagining. They are structures placed in irrigation canals that let's water go through but not debris or fish. They do a decent job, said Ryan Elliott, a Great West Engineering project manager and civil engineer.

Elliott said every screen has to be custom made in order to work for the specific conditions they are placed in. 

"They inherently are going to have maintenance needs, especially during high debris loading periods in the spring and then occasionally in the fall when you have leaf litter."

And it turns out, that the fish screen in the North Fork Valley Ditch malfunctioned because the solar powered panel didn’t supply enough energy for the screen to operate continuously over a 24 hour period. 

"Debris got washed down the ditch, jammed against the screen because it wasn't moving and as a result when it started up it tore lose the motor mounts on the motor that was turning it," explained Sweet.  

Trout Unlimited volunteers look at the fish screen in place at the North Fork Valley Ditch irrigation canal.
Credit Vanessa Hoene

The screen was difficult to replace because it cost around $25,000. The new plan is to use A-C power next year. They think that will finally address the problem.

But until then, they need to get the fish out of the canal and back into the river. Each time a bucket filled up, one volunteer carried the bucket to a water tank behind a truck and poured it out while counting and identifying the fish.

Rainbow trout and a hybrid between rainbows and cutthroats, known as cutbows, mainly populate these waters. 

Fisheries biologist Jason Burkhardt with Wyoming Game and Fish said these trout are of the greatest conservation need because they are migratory fish. They need to travel to different areas to spawn. He said it's similar to big game migration corridors. 

"Needing to access different portions of water bodies for different stages of life whether it's a trout trying to make it back to its spawning areas or running downstream into deeper water, there's a lot of fragmentation that has occurred in these irrigation canals," said Burkhardt.

In 2010, Governor Matt Mead introduced a program partly aimed at reducing the number of fish that are lost to irrigation canals. Because of the cost of fish screens, the department has been installing fish screens only in the highest priority waters. 

At the end of the day, the crew headed to a public access area of the North Fork Shoshone River. A truck backed up the tank filled with fish to the water’s edge.

Sweet explained what was going to happen, "All were going to do is open a pipe and they are going to fly out of here." Sweet opened the pipe and fish continuously flew into the river.

In one day the crew of volunteers saved 717 fish. And the chapter hopes there won't be any fish to save next year since the fish screen should work once more.

Have a question about this story? Contact the reporter, Kamila Kudelska, at kkudelsk@uwyo.edu.