7245

• UCREFRP Catalog Number: 7245
• Author: Rose, K. L. and D. R. Hann.
• Title: Consolidated Instream Flow Report, Habitat Modeling on the Green River Using the Physical Habitat Simulation System.
• USFW Year: 1989.
• USFW - Doc Type: Grand Junction, Colorado.
• Copyright Material: NO

Table 17. A periodic chart of the optimal flow and approximate flow ranges
which will maintain 90 percent of the weighted-useable-area for
adult and depositional life stages of Colorado squawfish and adult
razorback suckers.

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JanFebMarADrMaYJunJulAuQSeoOctNovDec

Jan

Dec

1500 ( 500-2700) Colorado squawfish: Adult

Mid-Jun SeD
4200 (2200-5600)'
Colorado squawfish: Deposition

May Jun
5600 (1600-7700)
Razorback sucker: Adult

Jul Nov
1900 (1400-2700)
Razorback sucker: Adult

RECOMMENDED FLOW

Jan

May Mid-Jun Jul

SeD Oct

Dec

1700------------------ 2700 2200-------------------- 1700---------

Mean monthly flows from 1930 to 1982
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
2546 3000 2415 5519 9653 8776 3777 1934 1495 2360 2566 2607

predict that habitat is maximized at flows that are quite low relative to the
range of historic flows. From November to April a flow of 1700 cfs is only 55
percent of the average historical flow during this time period (3109 cfs).
The flow for May (2700 cfs) is only 30 percent of the mean historical flow
(9653 cfs). Similarly in June and July, a 2200 cfs flow is only 35 percent of
the historical monthly mean (6276.5). According to Tyus, Jones and Trinca
(1987) optimum Colorado squawfish spawning and initiation of migration
occurred between 2820 and 13100 cfs, with mean values ranging from 4400 to
8797 cfs. They also estimated that elevated flows during the primary nursery
period (August to September) were detrimental to larval survival and that a
flow between 1931 and 2338 cfs would optimize young-of-year habitat.

Further studies must be made to help verify these results. They are
surprisingly low flow recommendations and don't agree with previous research
results such that one tends to question their validity. Future experiments to
include the modeling of a greater variety of life stages which tend to
dominate in eddy and backwater areas may provide a more complete picture.

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