November 1, 2022

It’s probably the last mild day before winter hits. Among the golden cottonwoods, Rattlesnake Creek is the very image of an idyllic Montana trout stream. The water flows past us in a gentle roar, boiling over massive, pink and gray, stream-rounded boulders. But the story of a stream is anything but a still life. Spring torrents can rush through like freight trains, plucking boulders and debris, destroying the illusion of stability and giving birth to new habitat. And on this gentle fall day, I’m here with the Watershed Education Network (WEN) to see into the past and learn about the dynamic story of this stream. 

Brook Bauer, WEN’s citizen science coordinator, is wading carefully with Mackenzie Tenan and me along a transect line we’ve set up across the stream. We slip over treacherous boulders that carry threads of green algae, streaming out into the current. So far today, none of us have taken an inadvertent swim – and we’re trying not to. This water is cold. Kat Leister, WEN’s communications coordinator, stands at the end of the transect, holding a PVC tube upright. She’s waiting patiently, keeping our measuring tape and our carefully-leveled guide line taut.

Josh Murdock and Ben Smith, of The Missoulian, are also along with us today, covering the story of this field day. We’re approaching a deep pool now, bordered by a logjam on the far bank. This pool provides great habitat for coldwater fish.

Rattlesnake Creek: place of the small bull trout

“We’ve already seen so many little bull trout here,” Brook tells us.

Before settlers colonized this valley, Rattlesnake Creek was an important place for spawning bull trout (Salvelinus confluentus), which would swim upstream in the early fall from the Clark Fork River. The Salish place name for the Missoula area, Nɫʔay, or place of the small bull trout, continues to reflect this importance. 

But over the last century, the place where we’re standing today has gone through some drastic changes. In 1901, this section of the stream went underwater, submerged by the construction of the Rattlesnake Creek Dam. Originally built to store drinking water for the city of Missoula, the dam’s importance declined after 1983, when the city switched to the aquifer for its drinking water needs. Still, the dam remained, blocking the movement of bull trout and other fish that had traditionally swam up Rattlesnake Creek to spawn.

The native fish of Rattlesnake Creek – including bull trout, westslope cutthroat trout (Oncorhynchus clarkii lewisi), and mountain whitefish (Prosopium williamsoni) – were facing other challenges in addition to the dam. Fish stocking programs that began in the 1930s had successfully established non-native competitors – rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis) – in Rattlesnake Creek and the Clark Fork River. Besides competing with the native fish, these introductions also posed risks from hybridization. Brook trout mixed with bull trout, while rainbow trout mixed with westslope cutthroat. Biologists worried that these hybrid fish would change the genetics of the native trout populations, blotting out their distinctive, locally-adapted characteristics.

Removing the Rattlesnake Creek Dam

One thing was clear, though: for the spawning fish of Rattlesnake Creek, native or introduced, the dam was an impossible barrier to movement. In 2001, Montana Fish, Wildlife and Parks began catching spawning fish – particularly bull trout and westslope cutthroat trout – that were stuck below the dam and releasing them above it. Two years later, the installation of a fish ladder gave these spawning fish their first chance to move upstream under their own power in over a hundred years. 

The fish ladder helped, but it didn’t work for all fish all of the time. Meanwhile, the dam was costing money and continuing to age. In terms of function, it had become largely obsolete. 

In 2017, the City of Missoula took control of Mountain Water Company, the previous owner of the dam. Working with Trout Unlimited and a variety of other partners, the City started working on plans to remove the no-longer-useful dam.

Finally, in 2020 – 119 years after the dam first began to block spawning fish – Trout Unlimited and the City of Missoula removed the Rattlesnake Creek Dam. 

Bringing a stream back to life

“All of these riffles and pools… they designed these really specifically” says Stephie Novak, WEN’s Stream Team coordinator. It’s been a major project: building pools and meanders, constructing carefully-designed logjams on the stream bends, planting willows and other native species, and putting up fencing to minimize deer browsing. 

For the bull trout that give the Missoula area, Nɫʔay, its name, the dam removal wasn’t a full guarantee that they would be able to thrive in the future. But it was one less obstacle to their survival.

And so here we are today, at this pool where Brook has seen little bull trout, where three years ago the stream was blocked by an obsolete dam. The dam removal and stream restoration has been a huge project. This field day is one small part of the follow-up. We’re here to check on some cross-sections of this area that were first surveyed in 2017, when the restored stream channel was only an idea and a defunct reservoir still covered the floodplain. How does a stream change when we remove a dam and let it come back to life? These cross-section surveys will help us find out.

Mapping the streambed

We’ve been taking measurements every two feet along our transect. The transect includes not just the width of the stream itself, but also a section of the restored floodplain – up to and above the expected “bank full” depth of the stream. Using a stadial rod – a piece of PVC pipe with increments marked in tenths of feet – we read the vertical distance from the ground to our leveled guide line. Once we enter the stream, we also measure the water depth. In effect, the cross-section we’re measuring is a snapshot of the stream and its bed. And because these transects are permanent, and we’ll be surveying them every year, we can compare these snapshots over time.

“We can see this year’s shape of the channel, last year’s, the year before’s,” says Stephie Novak. And that’s especially interesting here, because this channel is only two years old. What we’re wading through today is a stream shape that has been engineered by restoration professionals. And the channel design, with these deep pools and their adjacent logjams, already seems to be paying off in terms of fish habitat. But how will the stream move and respond over time? With the data from these transects, we’ll be able to tell.

Deeper waters

Mackenzie and I have been switching off between reading the stadial rod and recording the measurements on a data sheet, with Brook coaching us. But as we get into the deep water of the pool, Brook takes over. It’s risky taking measurements in deep, flowing water. And if anyone takes an inadvertent, icy swim, then Brook, as a WEN staff member, wants that to be her rather than one of her volunteers.

Here we have to stack one stadial rod on top of another to reach up to our guide line. Brook takes a few more measurements, then opts to estimate the deepest part of the pool. Ideally we would measure it more precisely, but it isn’t worth the risk of overtopping our waders. After we estimate the deepest part, we cross the stream, wading the riffle above the pool, and continue with the transect, craning out over the water as we stand on the engineered logjam. 

All of this time, Kat has been good-naturedly standing at the end of the transect, keeping the lines tight for us.

“Cross-sections take many people to make it work,” Brook says.

Upstream of us, above the riffle, Stephie Novak is leading another group of WEN volunteers – Yvonne Sorovacu, Grace Spella, and WEN intern Abe Westereng – as they measure the next transect. After this, both of our teams will shift upstream for the final two cross-sections of the day. We expect the whole process to take around five hours.

The waters of Rattlesnake Creek

Water is central to every aspect of this place. I notice a late-season dragonfly zooming past, its nimble flight a metamorphosis from its watery larval origins. The cottonwoods (Populus balsamifera) and sandbar willows (Salix exigua), both water-loving trees, are still glowing orange and gold. Alongside them, in the cobbles of the restored floodplain, are more plants that are characteristic of the water’s edge. The leaves of the red-osier dogwood seedlings (Cornus sericea) are a rich burgundy. It hasn’t gotten cold enough yet to frost the wild mint (Mentha arvensis). Its leaves are still vibrant green.

Water has brought all of us together here today, in the easy camaraderie of folks who have a shared passion for streams. And among the teamwork of setting up transect lines, reading off measurements, and recording these snapshots of the stream, there’s plenty of time to ponder. There’s time to imagine Rattlesnake Creek a century and a half ago, before this dam first stopped the fish, when multitudes of small bull trout grew up in this stream near the meeting of waters known as Nɫʔay. 

There’s time to imagine the bull trout that now once again find shelter in the pool we measured today. They continue to face the challenges of non-native fish and habitat loss – but at least their life cycle in this stream will no longer be impeded by dams. There’s time to imagine the changes spring floods will bring, as the stream wakes up from over a century of impounded dormancy. And thanks to WEN and their volunteers, we’ll be able to see these changes as they happen, year to year.

Further Reading

Séliš-Ql̓ispé Culture Committee. (2015). The Salish people and the Lewis and Clark expedition. Retrieved from http://www.salishaudio.org/audio/salishpeoplebook/

Trout Unlimited, Watershed Education Network, & Montana Fish, Wildlife and Parks. (2021). Rattlesnake Creek Dam removal monitoring: 2021 report. Retrieved from https://www.montanawatershed.org/_files/ugd/ec4eb2_c3085e6ea6694aefac9ada65c10c2037.pdf

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