Innovative Conservation

Good For Fish, Good For Farms

By Susan Hess, 2-07-06

	Julie Davies O'Shea and Les Perkins, Farmers Conservation Alliance staff, look over the small version of the fish screen. This one is a 2 cfs of water. The full-size screen, the one you see on the webcam, is an 85 cfs.

 "If it's good for fish, it's good for farms. If it's good for farms, it's good for fish," says Julie Davies O'Shea, director of Farmers Conservation Alliance.

After the 1996 flood hit Hood River County, it washed away Farmers Irrigation District's debris screens. The district's staff and community came together to design a new type of screen.
 
"The screen design they produced and patented, they then licensed to the non-profit Farmers Conservation Alliance to ensure all screen profits went to the common good," says O'Shea. The new screen goes on sale this month.
 
Irrigation ditches carry water to orchards, hay fields and vegetable crops. Water flows into the ditches from rivers and creeks. And those rivers carry not only water but also leaves, branches, sediment, rocks, and fish. When farmers divert river water into their ditches, all that comes along, everything from leaves to fish, and clogs irrigation channels, pipes and sprinkler heads. To solve the problem, farmers install either a small vertical screens or a rotary drum, called debris screens. While that keeps debris out, the debris still piles up behind the screen, clogging the system. During irrigation season, maintenance is a time-consuming chore and expense.
 
"It's like Christmas lights. When one stops working, it makes the whole string goes out. You have to figure out which one," says O'Shea.
 
Irrigation ditches without debris screens can block the upstream passage of salmon, steelhead and trout, and sometimes kill them. While the vertical screens and drums allowed the passage of fish, often they clogged and fish got caught in them. No one wanted that, especially the State of Oregon. In the mid-1980s, the state passed a law that said diversion structures must not kill one single fish. At all. Nada.
 
Farmers Irrigation District had lots of debris screens and two hydroelectric plants. The 1996 flood washed away the screens. Instead of looking around for someone else to solve the problem, the district staff designed a horizontal screen, and installed a prototype on their Hood River diversion. Tests proved that fish passed over the screen with zero mortality. No dead salmon, steelhead, trout. Not even a scale damaged.
 
And the screen blocked debris, while providing water for farms.
 
It doesn't seem like a screen laid flat would screen air, much less branches and salmon. The idea seems almost magic until you see all the calculus and hydrologic equations used to figure out how to make it work, which then makes it seem scientific, friendly scientific.
 
Here's how it works: A concrete trough set in the ground is divided lengthwise. On one side a metal plate perforated by thousands of minute holes is set horizontally. You can see it yourself on their webcam. As water runs over the plate, some seeps down through the holes and is shunted off to the other half of the trough.  Sediment drops out there and the water flows on into an irrigation canal.
 
Water flowing over the screen speeds up due to a wall that tapers sharply at the downstream end — keeping the screen virtually debris-free. If you put your finger almost covering a hose nozzle, you get the same effect. Water shoots out the nozzle faster. The design also maintains a uniform water depth, as a result enough water stays atop the plate for fish to swim on through; they're carried into a stream, which links back into the river. Water with fish, branches, and leaves go one way and irrigation waters the other.
 
The result is that Hood River has the nation's first NOAA Fisheries-approved horizontal fish screen.
 
The significance is that according to the state of Oregon, there are 55,000 diversions around the state that need screening, 3,200 of them high priority.
 
"It's a big market — 75 to 90 percent of them are five cubic feet per second (cfs) or less," says O'Shea. The Alliance plans to focus on that segment. "Our aim is to put 24 screens in the ground this year."
 
She says it cost the average farmer $1,500 to $5,000 a year to keep their current screens clean. She figures the new screens will provide a three to five year payback for the $16,000 to $20,000 screen cost, because farmers can use a state tax credit and other funding.
 
Says O'Shea, "These screens benefit fish, farms and families. It saves farmers money and protects fish, equally."

Susan Hess is an award-winning freelance writer and columnist. She lives in Hood River and contributes regularly to New West Columbia Gorge. She can be reached at cgi@gorge.net.

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