8211

• UCREFRP Catalog Number: 8211
• Author: U.S. Bureau of Reclamation and Fish and Wildlife Service.
• Title: Final Environmental Assessment
• USFW Year: 1997.
• USFW - Doc Type: Providing Fish Passage at the Grand Valley Irrigation Company diversion Dam on the Colorado River.
• Copyright Material: NO

In periods when additional water is needed to operate the fish passage, water available to the
Recovery Program from Reclamation's Ruedi Reservoir could be used to augment streamflows if
the Service chose to use the available water for that purpose. Water in Ruedi committed to the
Recovery Program would be available to the Service to use as they see fit within certain
parameters that include flow limitations in the Fryingpan River, and only during certain times of
the year consistent with the Ruedi final environmental impact statement.
Appendix B contains a detailed evaluation of the water supply, historic flow data, opportunities to
enhance flows, and possible supplemental water supplies for this and other potential upstream fish
passageways. The Colorado Division of Water Resources (Division V) would be consulted to
coordinate operations of the fish passage and releases from Ruedi or other upstream reservoirs to
enhance flows.
The Service would monitor fish populations upstream and downstream of the passage to
determine if fish are using the structure. In addition, larval fish (recently hatched fish) would be
monitored to determine if upstream spawning is occurring.
Fish Screens
The Recovery Program recognizes that a fish screen may be needed at the entrance to the GVIC
Canal to prevent losses of endangered fishes as they return downstream. This possibility was also
addressed in the biological opinion on the project as discussed above. Historic records indicate
that losses of endangered fish to unscreened canals have occurred in the past (Quartarone 1993;
Pfeifer, 1994, personal communication). Various types of screens are available to exclude fish
from canals (Miller and Laiho 1997); all have advantages and disadvantages. A primary concern
is that screens with small openings, unless frequently cleaned, can collect trash and debris from
the river and actually reduce diversion capabilities. It is considered very important that, if needed,
the screens would have small enough openings to prevent sub-adult and adult squawfish and
razorbacks from entering the GVIC Canal. If needed, the screen would be designed, constructed,
operated, and maintained with costs borne by the Recovery Program and/or the Service.
Recently hatched larval fish are more difficult to screen than the larger fish. From the present
knowledge of endangered fish, it appears the distribution of the larvae is uniform across a reach
of river. Therefore, some percentage of the larvae would be lost in the canal. However, it must
be recognized that there is a large mortality rate for larval fishes under natural conditions. It is
believed that even though some would be lost to the canal, there would be a net benefit in efforts
to recover the fish because others would pass over the diversion to downstream reaches of the
river. Some larvae would survive to the adult stage and naturally reproduce to help develop self-
sustaining populations. Therefore, there will be no plan to attempt to design or build screens to
exclude the larval fish rom the canal. Consideration would mainly be given to screening larger
fish.
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