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200717200 - UPA Project - MVID West Canal Diversion and Headworks

Sponsor: Methow Salmon Recovery Foundation

Budgets: FY07: $249,900 | FY08: $10,900 | FY09: $14,950

Short description: Move POD 175' upstream by installing new concrete diversion headworks, realign 150' of West Canal intake and build new access road to connect new headworks, construct permanent channel-spanning natural rock roughened channel permanent diversion.

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Final Council recommendation (Nov 2006)

Funding category: Expense

Recommended budgets: FY07: $0 | FY08: $0 | FY09: $0


ISRP final recommendation: Fundable (Qualified)


The ISRP is not requesting a response, but the proposal would be improved by addressing the following comments: This proposal is to re-engineer a large water diversion intake on the lower Twisp River. The new irrigation intake will make the irrigation system more efficient. However, benefits to ESA-listed salmonids are hard to determine without more information about the project than is provided in the proposal. Reducing the amount of water withdrawn from the Twisp River should have biological benefits. The biological effects of other elements of the project were less clear. Under what flow conditions does the existing structure pose a significant migration barrier? What are the contingency plans in the event the roughened channel is damaged during freshets? Will the new headworks be screened to prevent entrainment of juvenile salmonids? Answers to these questions would have made the proposal easier to evaluate. The availability of a significant amount of in-kind support is a positive element of this proposal. Technical and scientific background: The existing diversion required annual construction of a late summer push-up dam, which was believed to hinder upstream migration of Chinook, steelhead, and bull trout, or even to block migration completely during exceptionally dry years. The narrative does not quantify the extent to which spawning migration has been hindered or blocked, and in fact almost all spawning occurs above the existing intake anyway. Streamflows appear to be the real limiting factor to spawning migrations. This project will provide improvement in flow for this particular reach. The existing diversion could divert 30 cfs and the new structure will reduce irrigation withdrawals to 11 cfs plus a few additional cfs for Chain of Lakes wildlife mitigation. Rationale and significance to subbasin plans and regional programs: The proposal does a generally good job of describing its relationship with the Methow subbasin plans and regional restoration programs. Relationships to other projects: The relationship to other efforts is described. Especially relevant are the passage and habitat projects that have been implemented in the Twisp River upstream of the project area. The proposal asserts that these upstream projects depend on improved fish passage at the intake site. This may be true, although the evidence that the current diversion is a significant limiting factor was not completely clear. Objectives: The objectives of the project are clearly explained and timelines are adequately described. One of the objectives is to discourage Chinook spawning in the vicinity of the diversion intake (which is dewatered when irrigation season is over). The proposal suggests that this be done by using very coarse substrate -- too large for spawning gravel. It is possible that spring freshets may re-sort the substrate in the spring and recreate suitable spawning conditions at the new intake. The full-spanning roughened channel structure is designed to withstand relatively high flows, but it might be damaged by bedload transport or fluvial large woody debris (LWD) during exceptional runoff events. Continued maintenance may be necessary, and the ability of the new structure to pass fish cannot be adequately evaluated until it is installed and has survived several seasons. Tasks (work elements) and methods: Most of the work elements are well described. The treatment of the revegetation aspect of the project was somewhat abbreviated. There also was no indication that the new headworks would be screened to prevent entrainment of juvenile salmon and trout in the irrigation canal. Unless reviewers missed it, surely WDFW will require screening. The revegetation plans seem adequate. Monitoring and evaluation: The monitoring plan includes assessment of the physical attributes of the project (flow, substrate, water depth etc.) and plans to take advantage of ongoing redd monitoring efforts to assess whether or not fish passage improves after the project. The monitoring plan also should evaluate spawning at the new intake (or lack of spawning), and entrainment of fish in the diversion pipe. Facilities, equipment, and personnel seem reasonable. Information transfer: Project completion reports and Bureau of Reclamation progress reports are the only mechanisms of information transfer mentioned. Availability of information on this project may be useful for similar projects in the basin and a more complete information transfer process would be valuable. Benefits to focal and non-focal species: It was difficult to estimate the benefits of this project given the information in the proposal, but some benefits to Chinook, steelhead, and bull trout seem likely. Some impact to non-focal species will occur during the construction phase of the project. Dewatering the Twisp River for 40-60 days during intake relocation will surely impact the benthic community in the 225 ft length that will be dried out. Increased numbers of spawning salmon and steelhead in the Twisp may provide a food resource for some non-focal species that consume carcasses.

State/province recommendation:

Review group:

Recommended budgets: FY07: (n/a) | FY08: (n/a) | FY09: (n/a)