9512

• UCREFRP Catalog Number: 9512
• Author: Anderson, R. and G. Stewart.
• Title: Riverine Fish Flow Investigations Federal Aid Project f-289-R6.
• USFW Year: 2003.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

Table 1. Recommended mean monthly flows [Osmundson et al (1995)] for the 15-Mile
Reach in cubic ft/sec. The exceedence percent indicates frequency that the given flow
should be met. For example, during aten-year period, half the years should exceed a
mean flow of 1630 cfs in August, September and October; three of the years should
exceed 1240 cfs; and two years should exceed 810 cfs for a mean monthly flow.
Exceedence July
Mean Monthly
(cfs) August
Mean Monthly
(cfs September
Mean Monthly
(cfs) October
Mean Monthly
(cfs)
50% (Wet) 5,370 1,630 1,630 1,630
80% (Normal) 3,150 1,240 1,240 1,240
100% (Dry) 1,480 810 810 810
Since the recommendations from Osmundson et al. (1995) are presented as
averages, minimum flows are not the primary consideration. For example, the minimum
flow for 2000 was 542 cfs and it was 477 cfs in 2001. The median minimum sunulier
flow for the period of record (11 years) was 588 cfs. Even though flows were less than
810 cfs for 32 days in both 2000 and 2001, these years do not violate Osmundson et al
(1995) recommendations. Summer flows in 1999 exceeded the 50% exceedence (wet
year) recommendations for all months except July (Table 2) indicating Osmundson
considered flows in 1999 optimal. Summer flows in both 2000 and 2001 exceeded the
100% (dry year criteria) in all months except July (Table 2). The federal
recommendations, however,, will not be "met" if another "dry year" occurs before 2009.
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