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<br />Table 5.1.
<br />
<br />Flo,,:", req.uirements neede~ to produce important biological responses and~~,:
<br />habitats In the San Juan River. .' 0)
<br />
<br /> "-'1
<br />BIOLOGICAL RESPONSE! FLOW CHARACTERISTIC , . ..~"
<br />HABITAT REQUIREMENT
<br /> ';':~
<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 flannelmouth 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. ....,...:.' 'Y!" "
<br />~('_c.t~~~ f}_~~~er 91 d,~V~,?.f.sPJin!=l runoff >5,000 and
<br /> 8 000 cfs?e:orrelaledWlthii1creased ~u~2e~,
<br /> . .,--._. ~.".,,-.." .--' ". "' ,. ...... ,
<br />Speckled dace reproductive success. Increaslld number of days of sprinQ runoff >5,000 and
<br />.-.' '-'-"^ '~~"''''''l'l'''''''~' -'p"" - .. ,- .4"~" ~ .'__E<" '7'~
<br /> 8,000 cfs~l'.ciffelated ~t~incie!.sed suqcie~~,
<br />Success of stocking YOY Colorado pikeminnow and Mimicry of natural hydrograph has provided su~able
<br />subadull 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, cfs 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 andlor spawning,
<br />Adult Colorado pikeminnow and razorback sucker ITs.; Rows> 10,000 cfs 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 pikeminnow, and >2,500 cfs 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 pikeminnow 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 cfs) 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 01 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 pikeminnow 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,
<br />
<br />..
<br />
<br />Note: cfs = cubic feet per second, YQY = young-of-the-year.
<br />
<br />..
<br />
<br />SJRIP Biology Committee
<br />February 1999
<br />
<br />5-4
<br />
<br />Executive Summary
<br />Flow Report
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