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<br />Arkarsas River Water Needs Assessment - Section 1. Executive Summary <br /> <br />FIGURE 1-7 <br /> <br />Arkansas River Flow Preferences - Fish Population Habitat <br /> <br />-- Fry ~ <br />-Juvenile E <br />...Spawning ~ <br />-Adult 0 <br /> <br />-.,.,. <br />... .... <br />. <br />"-._- ,. <br />. <br />. <br /> <br />~ <br />y <br />~ <br />~ <br />~" <br />J! .~ <br />f ~ <br />"" '" <br />~:E <br /> <br />i:i: <br /> <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. . <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />.... ." <br />..."'..... <br /> <br /> <br />'" <br />". <br /> <br />............................ <br /> <br />~ <br />0 <br />ce <br /> 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 <br /> 1'l 0 0 0 0 R 0 0 0 ~ 1'l. 0 0 0 0 5 0 <br /> m .,. "' "" <X> '" q "" ;': ~ "". ~ <br /> ~ ~ ~ ~ <br /> Flow (cfs) <br /> <br />Note: Fish population habitat preferences are shown for the We!lsville Stockyard <br />location, which is considered representative of the reach from Turquoise <br />Lake to Pueblo Reservoir. Flows below 300 cfs were not modeled. <br /> <br />of 12.0 to 36.0 inches. Juvenile brown trout have <br />optimum habitat depths ranging from 0.9 to 1.7 <br />feet. Finally, because brown trout are bottom- <br />oriented, visual feeders, greater depth creates condi- <br />tions that reduce the capture of drifting insects. <br /> <br />In coldwater environments, ttout growth is a good <br />indicator of the health of an aquatic ecosystem <br />because it integrates all the biotic and abiotic <br />variables that impact organisms and growth also <br />reflects secondary effects of chronic stress. Pre- and <br />post-runoff periods (April-May and July-September) <br />are critical for brown trout growth and survival <br />because there is a strong correlation between brown <br />trout growth and discharge in the Arkansas Rivet. <br />Warmer water temperatures and poor ptey avail- <br />ability make August and September particularly <br />critical months for trout growth. The negative <br />impacts from higher flows are not offset by releases <br /> <br />of cooler water from Twin Lakes in August and <br />September because these releases will not decrease <br />water temperature for any appreciable distance <br />downstream. <br /> <br />To optimize the amount of available brown trout <br />and rainbow trout habitar, IFIM analysis showed <br />that a year-round flow of 300 to 500 cf.; should be <br />maintained, measured at the Wellsville gage. This <br />flow applies to all life stages on the Arkansas River <br />from near Leadville to Pueblo Reservoir. However, <br />agencies that manage fish populations and fish <br />habitat recognize that the spring runoff must be <br />passed through the system. The most beneficial <br />operation for the fish population would be to ramp <br />down runoff flows as soon as possible. This <br />approach creates a greater period of time when <br />maximum habitat area is available to the fish popu- <br />lation during warm temperature periods. <br /> <br />Water Needed to Protect or Promote Critical Resource Values -1-21 <br />