Navajo Reservoir Operations Vol. II

• File Number: 8220.105.I
• Description: Colorado River-Water Projects-Navajo-Environmental Studies
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/1/2002
• Author: BOR
• Title: Navajo Dam EIS-Draft EIS-Navajo Reservoir Operations-Volume II
• Water Supply Pro - Doc Type: EIS

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Table 5.1.

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Flow requirements needed to produce important biological responses and
habitats in the San Juan River.

BIOLOGICAl RESPONSE! FLOW CHARACTERISTIC
HABITAT REQUIREMENT
Reproductive success of Colorado pike minnow lower in Mimicry of a natural hydrograph, especially during
years wijh low spring runoff peaks. and higher in years relatively high runoff years.
with high and broad runoff peaks.
Decline in flannelmouth sucker abundance, increase in Mimicry of natural hydrograph with higher spring flows
bluehead sucker abundance, and increased condition and lower base flows.
factor in both species.
Bluehead sucker reproductive success. Increased number of days of spring runoff >5,000 and
8,000 cis correlated wijh increased success.
Speckled dace reproductive success. Increased number of days of spring runoff >5,000 and
8,000 cfs correlated with increased success.
Success of stocking YOY Colorado pikeminnow and Mimicry of natural hydrograph has provided suitable
subadult razorback sucker. haMat for these size-classes.
Eddies, pools. edge pools, other low-velocity habitats Mimicry of natural hydrograph has lowered base flows
year round for adult qolorado pikeminnow and to provide more low-velocity habijats. Flows> 1 0,000
razorback sucker. cfs provide more channel complexity which provides for
- more habitat complexity.
Flows to cue razorback sucker and Colorado Mimicry of natural hydrograph with higher spring flows.
pikeminnow for migration and/or spawning.
Adult Colorado pike minnow and razorback sucker use Flows> 10,000 cis provide more channel complexity
complex river areas. which provides for more habitat complexity, lower base
flows add to amount of low-velocity habitats.
Clean cobble bars for spawning of all native species, Flows >8,000 cis for 8 days to construct cobble bars,
especially Colorado pikeminnow. and >2,500 cfs for 10 days to clean cobble bars, during
spring runoff.
Backwaters and other low-velocity habitats are High spring flows create condijions for backwater
important nursery habitats for Colerado pikeminnow lonnation, low base flows allow them to appear in late
and other native fishes. summer and fall, flows >5,000 cfs for 3 weeks create
and clean backwaters.
Flooded bonomlands appear to be important nursery Overbank flows (> 8,000 cis) increase flooded
areas for razorback sucker, but other habijats may be vegetation, and backwaters fonned in association with
used in the San Juan River. edge features maximize on receding flows of 8,000 to
4,000 cIs.
Temperatures of 1 0 to 14 0 C at peak runoff lor Proposed releases from Navajo Dam are too cool to
razorback sucker spawning and near 18 to 20 oC at replicate pre-dam temperature timing, but
bonom 01 descending limb for Colorado pikeminnow temperatures are above spawning threshold for
spawning. Colorado pikeminnow during the correct period.
Reduction 01 nonnative fish abundance. Most nonnative fishes did not decrease during
research period, summer flow spikes reduce numbers
of red shiner in secondary channels in the short tenn.

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Note: cis = cubic feet per second, yay=- young-of-the--year.

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SJRIP Biology Committee
May 1999

8-4

Executive Summary
Flow Report.

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