Exploring Techniques to Reduce Lamprey and Salmonid Entrainment into Canals
This proposal uses a set of sub-questions and sub-hypotheses to answer the overarching question: 'Can alternative
techniques be used to reduce juvenile lamprey and salmonid entrainment by reducing the proportion of migrating fish
that enter the canal or interact with current fish screens?' We developed three sub-questions and their correlated
hypotheses based upon observations and through discussions with interested parties. Additional idea development
could result in additional test treatments with research questions and hypotheses in out-years.
Q1. Does the angle of the headworks and fish screens at an irrigation diversion intake (in relationship to channel
thalweg) significantly affect entrainment rates of larval/juvenile lamprey, juvenile salmon, and fine sediment within the
H1. A more acute headwork and fish screen angle (in relationship to channel thalweg) will result in less entrainment of
larval/juvenile lamprey, juvenile salmon, and fine sediment within the diversion compared to those with a more
Q2. Could entrainment of larval/juvenile lamprey be reduced significantly by dredging or blowing out the fine sediment
upstream of the headworks and/or within the diversion prior to or at the end of irrigation season?
H2. Removing fine sediment upstream of the headworks and/or within the diversion by either dredging or blowing out
will reduce larval/juvenile lamprey entrainment and subsequent dewatering mortality significantly.
Q3. Could entrainment of larval/juvenile lamprey be reduced significantly by installing flow barrier structures (such as
ecology blocks, concrete, metal, etc.) in a manner that reduces entrainment of fine sediment into the diversion and its
deposition in front of fish screens?
H3. Installing flow barrier structures in a manner that reduces entrainment of fine sediment into the diversion and its
deposition in front of fish screens will reduce larval/juvenile lamprey entrainment significantly.
Need and Benefit
Many Reclamation projects have fish screens in place designed to protect salmonids, but recent interest in
understanding and reducing Reclamation project effects on lamprey have developed information regarding lamprey
entrainment. Lamprey juveniles, called ammoecoetes (pre-outmigration stage) or macropthalmia (out-migration
stage)are physically and behaviorally very difficult to protect with conventional screening. Research to date shows that
larval and juvenile lampreys are vulnerable to entrainment in irrigation diversions. According to Rose and Mesa
(2012), entrainment and impingement rates were very high for many of the commonly used screen types (62-65%
entrainment for 12- and 14-gauge wire cloth screens and 36-62% impingement for interlock screens). Not only young
of the year fish, but many age classes of lamprey (even 3-5 year-old lamprey) are vulnerable to entrainment and
impingement. Surveys conducted after dewatering in diversions within the Yakima Basin showed that thousands of
lamprey are found entrained downstream of the fish screens each year (Lampman et al. 2015). Of these, most are the
more common Western brook lamprey, but about 7% were Pacific lamprey. Sunnyside and Wapato diversions have
consistently carried the largest number of entrained lamprey by far within the Yakima Basin and the estimated number
was 11,664 and 7,423, respectively, based on a mark-recapture study in 2014. Sutphin et al (2013) investigated
lamprey entrainnment in Reclamation projects on the Umatilla River in Oregon and found very few lamprey entrained,
whereas juvenile lamprey have been observed in relatively large numbers in other canals in the same area. Interagency
discussions have led us to hypothesize that the angle of canal and hydraulic properties of the intake may be
contributing to the variation in lamprey entrainment rates. Replacing screens with different mesh that may provide
better protection for lamprey would be very expensive, may not even be feasible, and would be very difficult to
maintain. The tight knit relationship between lamprey entrainment and fine sediment accumulation was documented
by the partners working on this project (Lampman et al. 2014). The distribution of fine sediment within the diversion
was effective in predicting where larval lamprey were found, potentially indicating that fine sediment and lamprey are
traveling together in the rivers and streams. As a result, even if the movement of lamprey cannot be controlled directly
and effectively, by focusing and controlling the fine sediment movement and transfer, entrainment of lamprey can
likely be diminished or reduced. Solutions that targeted and controlled the movement of fine sediment was
consequently pursued as a promising venue to reduce lamprey entrainment.
Additionally, accumulation of fine sediment in reservoirs as well as entrainment of fine sediment into associated
diversions and canals cause operation and maintenance issues for the facilities managed by Reclamation. At many of
the facilities that are part of this study, fine sediment is annually dredged, removed, and transported out of site, all of
which are recurring operation and management costs to the projects. In addition, lampreys are often found in this fine
dredged sediment, making the salvage efforts exceedingly difficult. As a result, pursuing effective ways to reduce fine
sediment collection and accumulation in and near diversions will be a promising alternative to effectively reduce
lamprey entrainment, serving two dual purposes.
Contact the Principal Investigator for information about partners.
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