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<br />o <br />C'") <br />I'~ <br /> <br />i....... <br /> <br />~ <br />.;:.. <br /> <br />Table 5.1. <br /> <br />Flow requirements needed to produce important biological responses and <br />habitats in the San Juan River. <br /> <br />BIOLOGICAL RESPONSE! FLOW CHARACTERISTIC <br />HABITAT REQUIREMENT <br />Reproductive success of Colorado pikeminnow lower in Mimicry 01 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 />Decfine in flannel mouth sucker abundance, increase in Mimicry of natural t1ydrograph with higher spring flows <br />bluehead sucker abundance, and increased condilion and lower base flows. <br />factor in both species. <br />Bluehead sucker reproductive success. Increased number of days of sprinq runolf >5,000 and <br /> 8.000 cis correlated with increased success. <br />Speckled dace reproductive success. Increased number of days of sprinq runoff :>5,000 and <br /> 8,000 cfs correlated with increased success. <br />Success of stocking YOY Colorado prkemrnnow and MImicry of natural hydrograph has provided sLlItable <br />subadu\t razorback sucker. habitat lor 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. Flows> 1 0,000 <br />razorback sucker. cfs provIde more channel complexity which provides for <br /> more habrtat complexity. <br />Flows to cue razorback sucker and Colorado Mimicry 01 natural hydrograph with higher spring flows. <br />pikeminnow for migration and/or spawning. <br />Adult Colorado pikeminnow and razorback sucker use Flows> 1 0,000 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 01 all native species, Flows >8,000 cts for 8 days to conslruct 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 tor razorback SLIcker, but other habitats may be vegetation, and backwalers tormed 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 oC at peak runoff for Proposed releases from Navajo Darn are too cool 10 <br />razorback sucker spawning and near 18 to 20 oC at replicate pre-dam temperature timing, but <br />bottom of descending limb for Colorado pikeminnow temperatures are above spawning threshold for <br />spawning. Colorado pikemlllnow during the correct perrod. <br />Reduction of nonnative fish abundance Most nonnative fishes did not decrease durrng <br /> research period, summer flow spikes reduce number5 <br /> of red shiner In secondary channels In the short term. <br /> <br />Note: C15 = cubic teet per second, YOY = young-ol-the-year. <br /> <br />SJRIP Biology Committee <br />February 1999 <br /> <br />Executive Summary <br />Flow Report <br /> <br />5-4 <br />