9380

• UCREFRP Catalog Number: 9380
• Author: U.S. Bureau of Reclamation.
• Title: Grand Valley Irrigation Company Fish Screens ‎(Predesign)‎.
• USFW Year: 2000.
• USFW - Doc Type: Boise.
• Copyright Material: NO

The monthly flow data shown on Sheet 1 was then used to construct the Exceedance Curve

shown on Sheet 2 of Appendix C. The Exceedance Curve shows the percent of time various

flows in the river are exceeded. The fishscreen design approach used by Reclamation's Pacific

Northwest Region (PN Region) is to design the screens to meet all criteria between the 10

percent exceedance flow and the 90 percent exceedance flow. This approach recognizes the

difficulty in designing a screen to meet all criteria at extreme flow events in the river. The

Exceedance Curve shows the 10 percent exceedance flow to be 11,000 cfs, and the 90 percent

exceedance flow to be 600 cfs.

TvVica1 Screen Hvdraulics

The following general description of the typical screen hydraulics applies to all screen and louver

options. Data for the establishment of water surface elevations used in the design of the screen

structure was obtained from the Concept Development Report and from surveyed elevations by

WCAO-ND. The Concept Development Report states that based on conversations with the

GVIC superintendent, the typical range at which the water level is kept at the upstream side of

the headgates is between El. 4681.0 and El. 4682.5. The lower limit ofEl. 4681.0 can be

controlled by GVIC by closing the floodgates and adjusting the canal headgates. El. 4681.0 will

be assumed to be the lowest water elevation on the upstream side of the headgates for the design

of the screens.

The flow in the canal is measured at a weir section and staff gage approximately 500 feet

downstream from the headgates (see Photo 3 in Appendix A). When the canal flow is at the
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