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| Rattlesnake Creek |
Missoula County, Montana |
Primary Project Type: Fish Passage
Secondary Type: |
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Located four miles from the mouth of Rattlesnake Creek is a dam, owned and opera... |
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Primary Problem: Dams, Irrigation Canals/Diversions
Secondary Problem: |
| Main Restoration Action(s): Culvert replacement, Fish ladder, Fish screens |
| Native Fish Focus: Bull trout, Westslope cutthroat |
Is this project part of a watershed scale restoration? No
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| Project Dates: 2001 to ongoing |
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Initial Monitoring:
Restoration Implementation:
Follow-up Monitoring: |
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Lead Agency:
Montana Fish, Wildlife and Parks
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| Project Partners: |
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| Project Location:
Rattlesnake Creek is a third order tributary to the Clark Fork River that originates in the Rattlesnake Wilderness and Recreation Area and flows approximately 23 miles to its mouth in the city of Missoula, Montana. The Rattlesnake Creek drainage is approximately 81 square miles and is located primarily in United States Forest Service, Lolo National Forest. The lower five miles of the creek runs through private property in the outskirts of Missoula.
To view a map of the project area, click here.
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| Project Description:
The Rattlesnake Creek watershed supports a diversity of land use and fish habitat, making it a popular recreation and fishing area for people and a priority for fishery managers. The upper 20 miles of the creek has excellent fish habitat conditions primarily because it is within the Rattlesnake Wilderness and National Recreation Area. There it has nine tributary streams originating from 45 high elevation lakes. The lower five miles of Rattlesnake Creek flows through developed land then through the outskirts of Missoula, where bike paths and fishing access line the creek. This urban landscape has created a number of conditions that have negatively affected fish populations: instream habitat complexity has been severely compromised due to channel straightening, levee construction to control flooding, side channel removal and/or degradation, and removal of large woody debris. Located four miles from the mouth of the creek is a dam, owned and operated by Mountain Water Company, which was formerly the primary water supply source for the city of Missoula, Montana. It now serves as the back-up water supply source for the city. For over a century, the ten-foot high dam has been a complete barrier to fish passage, especially for native westslope cutthroat trout (Oncorhynchus clarki lewisi) and the bull trout (Salvenlinus confluentus). Each year, large numbers of these fluvial trout have been documented at the base of the dam during their spawning periods. Upstream of the dam were isolated resident populations of cutthroat trout and bull trout that once migrated back and forth from the Clark Fork River. Although some of those fish still moved downstream over the dam, they were not able to return to spawn. Other passage concerns were four road culverts with that are a vertical barrier at all flows due to severe downstream scour and a velocity barrier at high flows; and six irrigation diversions in the lower Rattlesnake which utilize approximately 25 to 32 cubic feet per second (2 to 7 cfs each) during April through September. However, the greatest impact of the diversions to the fishery was entrainment of age zero and juvenile fish. |
| Project Goals: The primary goals of the Rattlesnake Creek restoration project were to enhance native migratory westslope cutthroat trout and bull trout populations by providing access to historical spawning habitat in Rattlesnake Creek and inhibiting entrainment of juvenile fish in the six irrigation canals in the lower Rattlesnake watershed. |
| Project Methods:
Fish passage mitigation included construction of a fish ladder around the Mountain Water Company dam and replacement of four culverts with bridges. To eliminate entrainment of age zero and juvenile fish, fish screens were placed at the mouth of four of the six irrigation diversions.
Click here for more information on project methods.
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The final fish ladder design included greater flow volume for attraction of fish... |
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Six irrigation diversions in the lower Rattlesnake, which utilize approximately ... |
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| Monitoring Data and Collection
Methods: To evaluate the efficiency of the test fish ladder and the permanent fish ladder, Montana, Fish Wildlife and Parks personnel conducted weekly snorkel surveys in the dam afterbay or tailrace from April to August to visually estimate fish abundance by species. This period included the expected migration times for spawning westslope cutthroat trout, bull trout, and rainbow trout. To evaluate the movement and range of migrations, all bull trout were implanted with passive integrated transponder tags, six bull trout were surgically implanted with radio transmitters, and cutthroat trout were marked with numbered plastic Floy tags. Fish passage via the permanent ladder was monitored using a weir trap installed at the upstream end of the sedimentation reservoir where trout exit the fish ladder and return to the stream. To evaluate bull trout spawning activity, bull trout redd monitoring was conducted between 1999 and 2003 on two reaches (1.0 and 2.25 miles) of Rattlesnake Creek upstream of the Mountain Water Company dam. In 2001 to 2003, both screened and unscreened diversion canals were sampled to estimate trout losses and evaluate the effectiveness of screens.
Click here for more information on monitoring.
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Was this project effective
and how was this determined? There is no question that upstream fish passage at the Mountain Water Company (MWC) dam is a positive step towards enhancement of native cutthroat trout and bull trout populations in the Rattlesnake Creek drainage. Snorkel surveys have confirmed that fluvial rainbow trout and westslope cutthroat trout were able to detect and enter the test ladder at all flow conditions. During high flow conditions, the tailrace area was extremely turbulent, and fish naturally congregated in the protected eddy at the ladder entrance. There they could easily detect and ascend the ladder. Montana Fish, Wildlife and Parks personnel estimated that 80 to 90 percent of the westslope cutthroat trout that congregated at the dam were able to ascend the ladder. The spawning period for bull trout has been later in the summer during lower flow conditions; during which time, they have naturally congregated in the large pool below the dam spillway. Consequently, bull trout passage over the fish ladder was approximately 50 percent. Recent actions to open the MWC dam sluice gates during bull trout migration has increased cutthroat and bull trout passage to nearly 100 percent. The primary monitoring tool for the project is bull trout redd counts in the upper watershed, which suggest a significant positive response to upstream fish passage. Redd counts are considered stable to increasing as consistent counts have occurred in the index counting sections along with the emergence of a new spawning area.
The effectiveness of the fish screens in minimizing fish entrainment has been mixed; problems were encountered such as a detached bypass pipe on the Coban fish screen and design limitations at the Hamilton-Day fish screen. However, these deficiencies were corrected in 2004 and effectiveness was improved at both sites. In 2006, fish screens were still working as desired, and plans for a new project are under way to activate a stream side channel on a floodplain that was previously diked.
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| Confounding Effects/Additional
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| Project
Specs (all specs are estimates): |
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| For more information on this project
contact: |
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Ladd Knotek (fish ladder, irrigation diversions), Montana Fish, Wildlife and Parks, Email: lknotek@state.mt.us
Brian Riggers (culvert replacements), U.S. Forest Service, Email: briggers@fs.fed.us
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| This information
was collected by: Kristin Keith |
| Project last updated on: 7/5/2007 |
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