Tens of thousands of trout were trapped in irrigation ditches that were shut off from the Boise River earlier this month.
Fish are left stranded each year in the 45 diversions that bring water to farms and homes and turn the Treasure Valley into a verdant, thriving community. They range from a few inches long to more than 16 inches. Several times over the years, fishing groups have worked with irrigation companies to salvage some of the fish before the waters dry up.
A state law stipulates that canal owners must have screens on the head gates to keep fish from entering, but its never really been enforced because officials know that if they did push it, powerful irrigation and farm interests would have Idaho lawmakers repeal it.
That lack of enforcement got a little trickier when Idaho salmon and steelhead were listed as threatened and endangered species a decade ago.
The threat of penalties along with millions of dollars in federal funding led the Idaho Department of Fish and Game to re-emphasize voluntary efforts by farmers and ranchers in the Lemhi River watershed in north-central Idaho to screen their diversions.
That effort has spread throughout the Salmon River drainage but has not been repeated across the state, for a variety of reasons.
Research released this year shows spectacular results. More than 70 percent of juvenile salmon migrating to the Pacific from the Lemhi drainage were trapped in times of median river flows before diversions were screened, research by Fish and Game and the National Oceanic and Atmospheric Administration showed. With screens, just 1.9 percent of the salmon get caught.
In lower flows, it was even worse, said Chuck Warren, a Fish and Game biologist who was one of the authors of the study.The same happens to resident fish in irrigation systems across the West, Warren said.
LAW AS LEVERAGE
But not every fish trapped in an irrigation ditch is critical to the fishery or to the fish population, said Idaho Department of Fish and Game Director Virgil Moore.
As a young fisheries biologist in the 1970s, Moore bristled at the lack of enforcement of the state law. But today, he says, blanket enforcement and spending millions of dollars to install and maintain screens wouldnt be wise.
Some places including stretches of the Henrys Fork of the Snake River meet fisheries objectives without screens, Moore said.And screens are expensive. Buying and installing them costs about $5,000 a cubic-feet-per-second of water diverted, and that doesnt include maintenance expenses.
The application of that directive (mandating screens) simply isnt needed, Moore said.
But the law does provide leverage to get screens installed when a new hydroelectric plant is built or someone is making a major change to a stream, Moore said.
BOISES WILDTROUT REBOUND
For decades, anglers and Fish and Game biologists had bigger worries about the Boise River than fish trapped in canals. The river nearly dried up in the winter as managers sought to fill reservoirs and ensure a water supply through the summer.
In the past 20 years, agreements have guaranteed minimum flows that ensure trout survive, triggering a revival in populations. Between 1994 and 2010, rainbow trout have increased 16-fold, said Joe Kozfkay, Fish and Game regional fisheries manager in Nampa.
In the stretch around Heron Creek in Southeast Boise, biologists estimate that the population of trout is more than 5,000 per mile.
Anything over 1,000 to 1,500 trout per mile is pretty good, Kozfkay said. Four thousand per mile is really good.
Richard Prange, a member of the Ted Trueblood Chapter of Trout Unlimited in Boise, was president of the Henrys Lake Foundation when it worked with ranchers to install screens on diversions of tributaries to the Henrys Fork, eastern Idahos blue-ribbon cutthroat stream. He knows irrigation districts and canal companies arent going to pay for Treasure Valley screens.
But he wants to begin a conversation in the Valley about whether there are better ways to protect stranded trout than simply sending volunteers into canals with buckets. The first thing needed is a study to determine where screens would be cost-effective, he said.Lets visit the possibility, he said.
FEDERAL AGENCY OWNS BIGGEST DIVERSIONThe U.S. Bureau of Reclamation owns the New York Canal, the largest diversion and canal in the Valley, carrying 2,800 cfs of water in irrigation season. The bureau has funded many of the screens installed in the Salmon River drainage and on the South Fork of the Snake in eastern Idaho, where Yellowstone cutthroat trout are on the edge of being listed as a threatened species.
Bureau engineers and hydrologists have helped increase the efficiency of the Lemhi River screens, Fish and Games Warren said.The New York Canal, which begins along Idaho 21 east of Boise, empties into Lake Lowell, which gives fish caught in its miles of diversion a place to go, said Jerry Gregg, the bureaus Snake River regional manager. If Fish and Game wants to study the issue on the Boise River, Gregg said, We would certainly do our share.
The Nampa-Meridian Irrigation District operates the 500-cfs Ridenbaugh Canal, which runs west through Boise and beyond beginning near Barber Park. Superintendent Greg Curtis said the district has worked with groups that have salvaged trout in the past, and he knows that other states are pushing screening. But he worries about the high costs of maintaining screens. And he said it would take much planning to ensure that screening does not wind up adding to the cost of delivering water to his customers farm fields and backyard sprinklers.
The districts position reflects the reality about the unenforced law that requires all diversions to be screened: We really havent looked at it because its not mandated, Curtis said.
Screening is not the only way to protect trout, Moore said. Fish and Game has considered asking irrigation districts to leave some water in some canals year-round, to support fish, provide wildlife habitat and serve as water features for nearby residents.
Moore supports the kind of broad talks that Trout Unlimiteds Prange suggests.Whatever we would configure has to be beneficial to irrigators, Prange said.