7145

• UCREFRP Catalog Number: 7145
• Author: Inslee, T. D.
• Title: Spawning of Razorback Suckers
• USFW Year: 1981.
• Copyright Material: NO

Thus we view high spring flows as important in shaping and maintaining the
river bed, resulting in a complex of braided channels important to adult
squawfish; with descending flow, some of these side channels are cut off
at their upstream end and backwaters are formed at the mouth, resulting in
important potential nursery habitat for young squawfish. In addition,
backwaters may provide refugia for young squawfish so they are not en-
trained in main channel currents and transported long distances down-
stream.
When storage projects are located in the headwaters above major sources of
sediment, such as in the upper Colorado River, they have little effect on
reducing sediment recruitment to downstream segments. Coupled with a
reduced flow regime, sediment input rates are likely to exceed transport
rates and sediment depositional problems (aggradation) are likely to occur
with time (Reiser et al. 1989). Vegetation encroaches on stream channels
during periods of low flow, thereby stabilizing areas of deposition
(Maddock 1978). When such situations persist over a period of years,
riparian encroachment into the active channel can occur, resulting in a
change in channel size and shape. Flushing flows for channel maintenance
are needed when vegetation encroachment begins to affect flow transport
capacity and channel shape thus predisposing the reach to further en-
croachment and sedimentation (Reiser et al. 1989).
Peak flows in the 15-mile reach in 1988 and 1989 were only 10,796 and
6,641 cfs, respectively. During these years, many pools and mouths of
backwaters in the Grand Valley silted in and tamarisk and willow seedlings
became established on new sand/silt bars. During 1990, maximum daily peak
flow was estimated at 9,469 cfs in the 15-mile reach and was insufficient
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