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Draft FInal Completion Report to UDWR for Contract #93-1070. Amendment 3 Vll which secondary channel habitat is maximized also decreases in years following a large flood. Generally, these changes occur as in-channel relief decreases. This conceptual model shows that the role of large flOOl.ls is to occasionally rebuild bank-attached compound bars. Although habitat availability is low in the low flow season immediately following flood recession, habitat availability may be greatly increased for a few years thereafter. Table ES 1 summarizes the measured and modeled response of habitat availability within the lO-km reach to flood passage and antecedent conditions. The geomorphic setting and total area of available nursery habitat change significantly during overwinter flows. Winter base flows are presently much higher than they were prior to completion of Flaming Gorge Dam. The role of winter base flows in changing habitat distribution should be investigated. To promote habitat formation and maintenance for juvenile Colorado squawfish, releases from Flaming Gorge Dam should (I) occasionally increase the magnitude of the annual peak flow, especially in those years when the Yampa River's flood peak is already high. an~ (2) provide annually varying base flows which differ depending on the antecedent conditions and flood magnitude of each particular year. Generally, base flows should be higher when bars are of high elevation and lower in years when bars are of low elevation. The present mandated summer and fall base flow at Jensen probably does not achieve its intended objective in many years. Table ES I. The effects of floods on Colorado squawfish nursery habitat availability on the 10-km reach. Flood magnitude, increasing from left to right Antecedent conditions Less than bar top flood Less than bankfull Greater than bankfull Low-elevation bar tops Increase availability of deep habitats. J' "- '? " , Decrease availability of shallow habitats. 1"\ , '? .'\ High-elevation bar tops Increase shallow habitat availability. Rearrangement of habitats. Maintain the increased availability of deep habitats. Decrease deep habitat availability. Net change in habitat availability unknown Maintain or decrease availability of shallow habitats.