Evaluation of Fish Passage at Roza Dam, Yakima River, Washington
Roza Dam is operated as the headworks to a large irrigation project on the Yakima River, Washington. Its standard operations are thought impede outward migration of juvenile salmon. At the suggestion of the Yakima Nation, National Oceanic and Atmospheric Administration (NOAA) Fisheries and other entities, Reclamation periodically tucks the roller gates on the dam to aid the downstream passage of fish. Opening the dam to allow fish passage results in loss of agricultural delivery water and power and can only be accomplished with coordination of all agencies involved in water deliveries. The question we seek to answer is:
* Can we develop reliable and easy to use technology to help us estimate the buildup of juvenile salmon behind Roza dam and use this to optimize operations to minimize impacts to water delivery?
Need and Benefit
Currently, Reclamation does not have any ability to determine the whether Roza Dam is actually impeding the outward migration of juvenile salmon, and the return to the sea of adult steelhead that have spawned upstream of the dam. Operators do not have an accurate way to determine whether juvenile salmon densities are building up behind Rosa Dam. Visual observations of fish dimpling the surface of the reservoir indicate substantial numbers are there during peak outmigration periods. At this time, it is simple guess work as to whether fish need to be passed over the dam, or if a sufficient number are getting through without any changes in operations.
Similarly, it is known that adult steelhead may also stack up behind the dam after spawning, though numbers are few. The mode of operation now is to de-water the irrigation turnout and tuck the roller gates on the dam, allowing water to go over the top and below the spill gates. Typically, selection of timing for this tuck is based on water flows and peak outmigration times. A time is usually selected when there is a high natural flow event during the migration period. However, it takes a considerable amount of coordination before a tuck can occur. Anything Reclamation can do to help optimize the way this operation is completed would be extremely beneficial to streamlining the operation.
Right now, there is no way to measure how effective this tuck is. Visual observations at the dam indicate some fish do go over the gates, but managers are not sure how long each period of operation should last. There needs to be some method to determine when enough fish have passed so that normal operations can resume. Reclamation has many facilities such as Roza Dam, that are essentially run-of-the-river diversions. Ensuring that these structures are operated in an optimal manner is increasingly important, as competing uses such as endangered species and other fisheries issues continue to be important. Our ultimate goal will be to have an automated system at Roza Dam that operators can call up via the internet on a daily basis to get an estimate of fish biomass building up behind the dam. Systems similar to this have been developed in other regions of the country to do this. We are hoping the same technology will be applicable to Reclamation facilities when fully developed.
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