MISSOULA — As drought and the summer heat cause streams to dwindle, water will once again be released from Silver Lake to bolster Warm Springs Creek and the upper Clark Fork River.
On Wednesday, the state of Montana announced that it had finalized an agreement with the City and County of Butte Silver Bow to provide daily water releases from Silver Lake into Warm Springs Creek to keep the creek and the upper Clark Fork River from dropping to levels dangerous for fish.
According to the state announcement, the releases will start on Friday and continue until Aug. 27.
About a mile east of Georgetown Lake, Silver Lake is a reservoir fed by high mountain lakes where Butte Silver Bow owns the water rights. Some of the water is promised to various businesses, but in 2006, the Montana Department of Natural Resources and Conservation allowed some of the water rights in Warm Springs and Silver Bow creeks to go to instream flows for fisheries.
The instream water right authorizes the release of up to 40 cubic feet per second, but the release amount in the agreement is limited to 32 cubic feet per second each day because that’s what one pump can produce. In 2021, releases using that amount of water dropped Silver Lake by almost 12 feet.
Similar agreements were reached to conduct pilot programs in 2017, 2019 and 2021. After the 2021 releases, Trout Unlimited wrote an evaluation of the results, which were shown to be helpful for fish.
In 2021, the releases occurred much later in the summer, between Aug. 2 and Sept. 20, because the drought that year wasn’t as bad. Stream gage data showed that Warm Springs Creek was able to retain the full 32 cfs as far as Anaconda and then it slowly decreased to 24 cfs as the stream reached Warm Springs before it flows into the Clark Fork River. Another 4 cfs was lost by the time the Clark Fork flows past Deer Lodge, but that’s still 20 cfs more than the river would have had.
As of July 9, Warm Springs Creek near Anaconda is flowing at 96 cfs, well below the median value of 138 cfs. Adding 32 cfs would bring the creek up closer to the median. Further downstream near Deer Lodge, the Clark Fork River is almost lower than Warm Springs Creek, flowing at 99 cfs, which is half of the median value measured since 1991.
The U.S. Fish and Wildlife Service identified 90 cfs as the minimum flow measured at the Deer Lodge flow gage to support a fishery in the Clark Fork River. However, the flow has regularly dropped below 90 cfs in the summer over the past four decades, and it’s close to dropping below that now. Another 20 cfs would be helpful, so the state decided to start the program now before river flows become critical.
The other benefit of the releases is that they provide cold water to streams that have begun to warm. In 2021, that helped keep Warm Springs Creek cooler than 59 degrees Fahrenheit, which bull trout need to stay healthy. The Clark Fork River didn’t show any sign of a temperature benefit, but it has a lot more river water to cool.
On Tuesday, the water temperature in the Clark Fork near Deer Lodge peaked at 74º, which is starting to get dangerous for trout. If it continues for three days, Montana Fish, Wildlife & Parks will have to impose hoot-owl restrictions.
Under the agreement, Butte Silver Bow will be paid for the releases from the Upper Clark Fork River Basin Restoration Fund - Aquatic Flow Allocation, which is managed by the Natural Resources Damage Program. The program will pay $8,000 for the first day of water release and $5,850 for all the other days a release occurs. If water is released all 47 days, the total would be almost $280,000.
The additional water may help the Clark Fork River above Deer Lodge. But below Deer Lodge, the West Side Ditch diverts about half the river’s flow in mid- to late-summer during a normal year. In drought years, it can take as much as 90% of the flow out of the river. A few times, the river flow readings below the West Side Ditch diversion have dropped to single digits.
A recent lawsuit against the Grant Kohrs Ranch National Historic Site alleges that bull trout are harmed when the river gets so low, and the plaintiffs have asked the judge to prohibit use of the West Side Ditch when the Clark Fork River drops below 110 cfs.
The Natural Resources Damage Program is partnering with the Watershed Restoration Coalition, Montana Trout Unlimited and the Clark Fork Coalition to monitor the Silver Lake flows and coordinate irrigation withdrawals with Butte Silver Bow’s instream flow right to try to keep sufficient water in the streams.
In its 2021 report, Trout Unlimited recommended developing a long-term agreement to annually set aside water in Silver Lake to provide drought relief in Warm Springs Creek and the Clark Fork River. But that has yet to happen. The 2025 agreement only says that parties will negotiate to reach an agreement by May for the 2026 releases and/or try to develop a longer term contract.
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.
