9508

• UCREFRP Catalog Number: 9508
• Author: Valdez, R. A. and P. Nelson.
• Title: Green River Subbasin Floodplain Management Plan.
• USFW Year: 2004.
• USFW - Doc Type: Lakewood, Colorado.
• Copyright Material: NO

4.0 Prioritization Of Reaches And Sites

4-1

April 2004

4.0 PRIORITIZATION OF REACHES AND SITES

4.1 Priority River Reaches

Priority river reaches and floodplain sites were identified for this Plan to focus
management actions on those areas most likely to benefit razorback sucker and to assist species
recovery. Prioritization of river reaches by life stages of razorback sucker was determined for the
Green River Subbasin for geomorphology research (LaGory et al. 2003) and was used as the
basis for prioritization in this Plan. Of 10 reaches identified for research, three were designated
as important to razorback sucker. Reach-habitat scores for all life stages of razorback sucker
were highest for Split Mountain to Desolation Canyon (RM 319-216), and high scores were
assigned to larvae and juveniles for Labyrinth and Stillwater Canyons (RM 76-0) and Gray
Canyon to Labyrinth Canyon (RM 132-76) (Figure 4-1). Of eight habitat types identified for
actual and potential use by larval razorback sucker, flooded bottomlands (i.e., floodplains) in
restricted meander reaches received the highest scores.

Members of the Green River Team also identified Split Mountain to Desolation Canyon
as the most important reach for razorback sucker in the Green River Subbasin, and confirmed the
relative importance of Labyrinth and Stillwater Canyons and Gray Canyon to Labyrinth Canyon,
based on recent captures of larval and juvenile razorback sucker (Gutermuth et al. 1994; Muth
and Wick 1997). Subsequent inventory of the last two reaches revealed few floodplain
depressions and primarily tributary and canyon inflows that function as main channel backwaters
or terrace floodplains (Nelson and Soker 2002). The only other reach ofthe Green River
Subbasin identified with large numbers of floodplains was Browns Park (RM 396-362), but
razorback sucker are not currently in this reach, and are not likely to inhabit the reach because of
cool water releases from Flaming Gorge Reservoir (Bestgen 1990). Prioritization of reaches for
the Green River was determined for razorback sucker as:

1. Split Mountain to Desolation Canyon (RM 319-216);
2. Labyrinth and Stillwater Canyons (RM 76-0); and
3. Gray Canyon to Labyrinth Canyon (RM 132-76).

Other reaches of the Green River identified by LaGory et al. (2003), including Flaming
Gorge Dam to Browns Park, Browns Park, Lodore Canyon, Yampa River to Island Park, Island
and Rainbow Parks, Split Mountain Canyon, Desolation and Gray Canyons, are not included in
this Plan either because razorback sucker are not in the reach, or because there is little or no
floodplain habitat available. Green River tributaries, including the Yampa River, Little Snake
River, Duchesne River, White River, Price River, and San Rafael River, are also not included in
this Plan for the same reasons. These or other tributaries may become important as self-
sustaining populations of razorback sucker become established and the fish disperse. Razorback
sucker captured at tributary confluences, such as the San Rafael River (Chart et al. 1999), are
considered to have originated in the mainstem Green River and use these inflows transiently.