7418

• UCREFRP Catalog Number: 7418
• Author: Tyus, H. M. and C. A. Karp.
• Title: Stream Flow Needs of Rare and Endangered Fishes, Yampa River, Colorado.
• USFW Year: 1988.
• USFW - Doc Type: Vernal, Utah.
• Copyright Material: NO

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downstream areas. Water development in the Yampa River could alter the
natural flow/sediment transport-deposition dynamics of the entire upper Green
River system.
Several workers have evaluated relationships between discharge, sediment
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load, and maintenance of spawning habitat for fishes in the Yampa Canyon
(reviewed by Butler 1988). The results of those studies suggested that
sediment transport equilibria in the spawning reach can be attained under
reduced Elow regimens. However, attainment of such equilibria would not
preclude downstream changes (Butler 1988) ,and the accompanying chan;a_s in
sediment load and channel morphometry would permanently modify existing fish
habitat. Reductions in sediment load resulting from water withdrawal may cause
downstream erosion of shoreline areas, and destabilization of riparian
communities. For example, sediment depletion due to closure of Flaming Gorge
Dam has reduced 'sank width of the Green River between Flaming Gorge and Ouray,
Utah, by 10%, and this stretch has not yet attained its new dynamic
equilibrium (Andrews 198b).
Butler (19$8) evaluated different scenarios Following completion of
water development projects in the Yampa River. pie Found that sediment load in
sipper Green River system would be robbed of about 626,800 tons of sediment on
an annual basis (a 24°o sediment reduction), following completion of Juniper
Project. Thus, the lower Yampa River (downstream from Little Snake River)
would become an aggrading system due to loss of scouring spring flows.
Hydrology of Little Snake River also warrants study because 77% of the
sediment delivered to the lower Yampa River is derived from the Little Snake
River (O'Brien 1984). Further losses are implicated as potential effects of
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