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<br />Table S.l.
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<br />Flow requirements needed to produce important biological responses and .
<br />habitats in the San Juan River. 'iY
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<br />BIOLOGICAL RESPONSE! FLOW CHARACTERI~mc .-1"<
<br />HABITAT REQUIREMENT ".r;;
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<br />Reproductive success of Colorado pikeminnow lower in Mimicry of a natural hydrograph, especially during
<br />years with low spring runoff peaks, and higher in years relatively high runoff years,
<br />with high and broad runoff peaks.
<br />Decline in f1annelmouth sucker abundance, increase in Mimicry of natural hydrograph with higher spring flows
<br />bluehead sucker abundance, and increased condition and lower base flows.
<br />factor in both species,
<br />Bluehead sucker reproductive success. Ibp'[!{!!'S.-e:pon~rr'l:>er o! <!ays of sRrin~ runoff >5,000 and
<br /> 8,000 cfst~Q.&~!~.a':'!Yi~inJ5r["~e~ su~~ss.
<br />Speckled dace reproductive success, i~a!l!!a number of days of sprin~ runoff >5,000 and
<br />8,000 cfs~~ffdlafed;~t'fl;inci8ised'success.
<br /> -- . ,,___. - ..... .-,'- ..--'-,-... ..' .".., .-'
<br />Success of stocking yay Colorado pikeminnow and Mimicry of natural hydrograph has provided suitable
<br />subadu~ razorback sucker, habitat for these size-classes,
<br />Eddies, pools, edge pools, other low-velocity habitats Mimicry of natural hydrograph has lowered base flows
<br />year round for adult Colorado pikeminnow and to provide more low-velocity habitats, Rows> 10,000
<br />razorback sucker. ds provide more channel complexity which provides for
<br /> more habitat complexity.
<br />Flows to cue razorback sucker and Colorado Mimicry of natural hydrograph with higher spring flows.
<br />pikeminnow for migration and/or spawning.
<br />Adult Colorado pikeminnow and razorback sucker ~ Flows> 10,000 ds provide more channel complexity
<br />complex river areas. which provides for more habitat complexity, lower base
<br /> flows add to amount of low,velocity habitats.
<br />Clean cobble bars for spawning of all native species, Flows >8,000 cfs for 8 days to construct cobble bars,
<br />especially Colorado pike minnow. and >2,500 cts for 10 days to clean cobble bars, during
<br /> spring runoff.
<br />Backwaters and other low-velocity habitats are High spring flows create conditions for backwater
<br />important nursery habitats for Colorado pike minnow formation, low base flows allow them to appear in late
<br />and other native fishes. summer and fall, flows >5,000 cfs for 3 weeks create
<br /> and clean backwaters.
<br />Flooded bottomlands appear to be important nursery Overbank flows (> 8,000 ds) increase flooded
<br />areas for razorback sucker, but other habitats may be vegetation, and backwaters formed in association with
<br />used in the San Juan River. edge features maximize on receding flows of 8,000 to
<br /> 4,000 cfs,
<br />Temperatures of 10 to 14 .C at peak runoff for Proposed releases from Navajo Dam are too cool to
<br />razorback sucker spawning and near 18 to 20 .C at replicate pre-dam temperature timing, but
<br />bottom of descending limb for Colorado pike minnow temperatures are above spawning threshold for
<br />spawning. Colorado pikeminnow during the correct period.
<br />Reduction of nonnative fish abundance. Most nonnative fishes did not decrease during
<br /> research period, summer flow spikes reduce numbers
<br /> of red shiner in secondary channels in the short term.
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<br />Note: cfs = cubic feet per second. yay = young-of.the-year.
<br />
<br />SJRIP Biology Comminee
<br />February 1999
<br />
<br />Executive Summary
<br />Flow Report
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