9641

• UCREFRP Catalog Number: 9641
• Author: Hedrick, T. N., K. R. Bestgen and K. D. Christopherson.
• Title: Entrainment of Semi-Buoyant Beads and Razorback Sucker, Xyrauchen texanus, Larvae into Flood Plain Wetlands of the Middle Green River, Utah.
• USFW Year: 2009.
• USFW - Doc Type: C-6/RZ-ENTR,
• Copyright Material: NO

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STUDY AREA

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The Green River study area is near the town of Vernal in northeastern Utah (Figure 1).

Flow of the Green River is partially controlled by Flaming Gorge Dam, located near the Utah-

Wyoming border. Green River flow is supplemented by tributary flow, particularly that from the

Yampa River, which is confluent with the Green River in Dinosaur National Monument. The

Green River downstream of the Yampa River is designated critical habitat for recovery of the

razorback sucker (U. S. Fish and Wildlife Service 1991; U. S. Fish and Wildlife Service 2002).

The flow pattern of the Green River near Jensen, Utah, is dominated by a large spring peak

generated from snowmelt runoff in the headwaters of the Green and Yampa rivers, and has a

relatively low base flow during the rest of the year (Figure 2). Post-dam Green River flows have

lower and shorter duration flow peaks than during the pre-dam period. Reach 2 of the middle

Green River (Muth et al. 2000) is mostly an alluvial reach downstream with two known

spawning areas and many well-developed flood plain areas thought important for survival of

razorback sucker larvae and recruitment. The two known spawning bars in this reach are at

Razorback Bar and Escalante Spawning Bar, both of which are just upstream ofthe Thunder

Ranch (RKM 492.1) flood plain wetland (Figure 3). Over the course of the study, five flood

plain sites were sampled: Thunder Ranch, Stewart Lake (RKM 482.8), Bonanza Bridge (466.2),

the Stirrup (443.4), and Leota-7 (414.9) (L-7).

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