MISSOULA — After the U.S. Department of the Interior failed to uphold its part of a legal settlement, two organizations have renewed their lawsuit to try to save bull trout in the upper Clark Fork River.
On Tuesday, Save the Bull Trout and the Alliance for the Wild Rockies filed a complaint against the Department of the Interior and the West Side Ditch Company in Butte federal district court, alleging that the irrigation withdrawals from the upper Clark Fork River have reduced bull trout habitat in the river near the Grant-Kohrs Ranch National Historic Site.
This isn’t a new claim. The two plaintiffs filed a similar lawsuit in 2022. Eventually, the Interior Department agreed to a settlement where it would pay to upgrade the West Side Ditch so bull trout wouldn’t swim into the irrigation ditch and return flows wouldn’t degrade the river. But the Trump administration had stopped funding the projects so the plaintiffs have returned to court.
Designated in 1972, the Grant-Kohrs Ranch west of Deer Lodge was preserved to commemorate the frontier era of U.S. history. It allows the public to see a working cattle ranch that employs historic ranching tools such as beaver slides for haying. But that hay is the product of about 400 acres of flood irrigation with water provided by the West Side Ditch Company.
The West Side Ditch diverts water from the Clark Fork River near Deer Lodge and conveys it to multiple users along its 13.6-mile channel. The Grant-Kohrs Ranch owns 16% of the ditch company.
The problem is the West Side Ditch ends up diverting a lot of water, about half the river’s flow in mid- to late-summer during a normal year. But in drought years, it can take as much as 90% of the flow out of the river, according to court records. Over the past 16 years, 10 have been characterized by extremely low flows in the upper Clark Fork. Based upon this year’s conditions, this summer will produce even lower flows in the Clark Fork River.
Such low flows are harmful to fish, especially bull trout, which need more cold, clear water than some species. The bull trout was listed as threatened in 1999 due to the increasing loss of habitat, and in 2010, the U.S. Fish and Wildlife Service designated almost 63 miles of the upper Clark Fork, including the stretch along the Grant-Kohrs Ranch, as critical habitat that bull trout depend on for migration, spawning and survival.
The U.S. Fish and Wildlife Service identified 90 cubic feet per second as the minimum flow measured at the Deer Lodge flow gage to support a fishery in the Clark Fork. However, the flow has regularly dropped below 90 cfs in the summer over the past four decades. Last year was a severe drought year and the Clark Fork was below 90 cfs almost constantly from mid-July through early October. A few times, the river flow readings below the West Side Ditch diversion have dropped to single digits. With water barely trickling through the cobble, there's no way a fish can survive, let alone seek deeper, safer waters.
In one of their requests to the court, the plaintiffs have asked that no water be diverted to the West Side Ditch when flows drop below 110 cfs.
According to the complaint, “the DOI’s ‘cultural’ agricultural watering at the (Grant-Kohrs Ranch) and the West Side Ditch diversion practices have effectively dewatered the UCF at crucial time periods, resulting in not enough instream flow for the bull trout to survive.”
The plaintiffs argue that the Fish and Wildlife Service 2023 biological opinion was flawed because it didn’t consider the effect of any irrigation withdrawals other than the water that went to Grant-Kohrs, even though the West Side Ditch serves several users and more water is taken out of the river along the 20 miles that the agency analyzed.
The biological opinion found that 8 of 19 habitat indicators, including water quality and quantity, along the 20 miles were at risk of reduced functioning while 11 were at unacceptable risk. Still, the Fish and Wildlife Service concluded that the existing conditions wouldn’t destroy or modify critical habitat in the river. This conclusion apparently led to the Interior Department withdrawing its funding.
The plaintiffs allege the biological opinion is inadequate, and therefore, the Grant-Kohrs Ranch and the ditch company are contributing to the unpermitted taking of bull trout. In addition, the groups say bull trout can get trapped in the irrigation canals because the century-old diversion structure has no fish screen. However, at low flows, the structure probably acts as a barrier to any fish passage.
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.
