LOLO — What used to be a death trap will soon become a sort-of joy ride for wild fish in Lolo Creek.
Weather permitting, a fix on the Lolo-Maclay Diversion Ditch should solve a century-old problem that’s kept thousands of trout from reaching the Bitterroot River, one of Montana’s most-popular fishing destinations. By Thanksgiving, a new no-maintenance, no water-loss fish screen should not only restore a crucial link in the piscatorial environment, it might revolutionize the relationship between anglers and agriculture.
"Over 10,000 fish a year die in this ditch — it’s staggering,” said Jed Whiteley, a project manager for the Clark Fork Coalition which helped pull the project together. “This is the third-biggest tributary on the whole Bitterroot River, after the East Fork and West Fork headwaters. It’s been the highest priority for Montana Fish, Wildlife & Parks in this whole area for years.”
The Lolo Creek drainage covers about 245 square miles west of the town of Lolo to the Montana-Idaho border. The watershed supports huge populations of native bull and westslope cutthroat trout, as well as mountain whitefish and introduced species like rainbow and brown trout.
But a remarkably efficient irrigation ditch just a few minutes’ drive west of the Travelers’ Rest gas station on Highway 12 has the capability, and the water rights, to divert three-quarters of Lolo Creek’s fall flow down its four miles of manmade canal to hayfields in the Bitterroot Valley. By early September in some dry years, no water at all makes it to the Bitterroot River. Neither do any fish.
That means the blue ribbon gets pulled off the Bitterroot’s “blue ribbon” fishing status after the river reaches Lolo. From there down to the confluence with the Clark Fork River west of Missoula, the floating is lovely but the fishing is lousy.
Montana Fish, Wildlife & Parks biologist Ladd Knotek has been working on the Lolo Ditch problem for 17 years. He said the Bitterroot River below Lolo was so recruitment-limited that it resembles Flint Creek (a relatively tiny tributary of the Clark Fork River near Drummond). But it has the potential to be much more.
“That’s why Montana fisheries are world-famous,” Knotek said. “They’re all wild trout. A lot of people who move to western Montana don’t realize our trout fisheries set by natural reproduction, spawning and rearing. In Idaho, they stock their streams.”
Although rainbow, cutthroat and brown trout grow big in the Bitterroot River, they spawn in the tributary streams. When Lolo Creek’s fall flow falls to 45 cubic feet per second and the ditch takes 35 cfs, fish swimming downstream turn right at the headgate and follow the water to their deaths in hayfields between Lolo and Florence, instead of staying left and reaching the Bitterroot.
For the past several falls, FWP biologists and volunteers rushed to rescue the stragglers after the headgate closed and the ditch dewatered. They regularly found 20-inch trout floundering in shrinking pools along with scads of smaller fish. Those still alive would get a truck ride back to the river to swim another day.
Next year, those fish will run into a $280,000 contraption that looks like a concrete water slide with a corrugated tin roof. The wavy surface has sieve-like holes in the dips of the waves. Just enough water stays on top of the screen to slide a fish along, like the spray of water on a pool slide that keeps your swimsuit from sticking. The rest of the water — the 35 cfs demanded by the irrigators who own the ditch rights — still goes into the ditch and out to the fields. But the fish slide off the surface and into a chute that leads back to Lolo Creek.
Fish screens on active creeks and rivers must be custom-designed for each location. In the past, older designs have required regular cleaning and maintenance as everything from floating leaves to falling trees plug up the works. The new Lolo design eliminates all the moving parts and essentially cleans itself.
The Lolo Creek fish screen design was confidence-inspiring enough, all 40 members of the Lolo Ditch irrigation system agreed to support it. The Clark Fork Coalition was also able to rally financial support from dozens of groups willing to give it a chance. Whiteley added its functional simplicity made it possible for CFC to commit to 20 years of maintenance service on the fish screen, confident it would have very little debris to worry about.
As construction projects go, this one couldn’t have faced many more environmental obstacles if it was built on a volcano. The southside road to the work site passes under a dangerously steep slope that had been burned off during the 2017 Lolo Peak wildfire, leaving a huge erosion and rock-slide risk. Then the spur road to the ditch itself was so steep a cement truck would probably never make it down upright. Fortunately, landowners Gayland and Patti Enockson gave permission for a pumper truck to drive across their field on the north side of the creek and extend an extra-long boom hose across the water to the ditch channel.
“We came out to look at the work, and they (the construction engineers) saw us and waved to us,” Gayland Enockson said. “Ten minutes later they’re in our front yard working out access.”
Then came that end-of-October record snowstorm. First the arctic cold disabled one of the main dewatering pumps, allowing the ditch to fill and freeze at the work site. The subsequent record-high temperatures sent extra-high fall flows down Lolo Creek and right into the spot prepared for the concrete pour, ruining a week’s work.
Montana firm Jackson Contracting Group has approved overtime to squeeze in its final ground prep in what little weather window is left, Whiteley said. Once the concrete is poured and the screen is in place, the project’s lack of moving parts should keep it almost maintenance-free. That was a major breakthrough in fish screen design. Maintenance worries have discouraged many landowners from upgrading their canals.
Success of the Lolo project could convince other irrigators along the Bitterroot to add similar screens. Most of the valley’s diversion dams lack any fish control. The new screen’s ability to reroute fish without losing water or adding maintenance should go a long way to proving angling and agriculture can co-exist.
“With a lot of projects, you know you’re helping but it’s hard to quantify,” Whiteley said. “Next year, I know that 10,000 fish will not go down that ditch and die. This is the highest-impact project I’ve ever been a part of.”