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Last modified
7/14/2009 5:02:33 PM
Creation date
5/22/2009 4:57:14 PM
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UCREFRP
UCREFRP Catalog Number
8188
Author
Muth, R. T., et al.
Title
Flow and Temperature Recommendations for Endangered Fishes in the Green River Downstream of Flaming Forge Dam.
USFW Year
2000.
USFW - Doc Type
\
Copyright Material
NO
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<br />Final Report <br /> <br />1-6 <br /> <br />September 2000 <br /> <br />flows in an unregulated river. Seasonal variation decreases as a result of water storage and <br />intentional limitation of releases to accommodate power-generation capacities. Daily variation <br />increases as hydroelectric generation fluctuates in response to daily demands for electricity. Changes <br />in natural seasonal and daily flow patterns affect riverine ecology in a number of ways. Lower spring <br />flows are less effective than higher flows in transporting sediment, forming and rehabilitating <br />important in-channel habitats, scouring encroaching riparian vegetation, and maintaining habitat <br />complexity. In unregulated rivers, overbank flooding in spring during wetter years inundates <br />floodplain wetlands that supply nutrients and organic material to the main channel and serve as <br />important growth and conditioning habitats for some native fishes. Connections between these warm, <br />productive habitats and the river are eliminated or reduced at lower spring discharges resulting from <br />typical dam operations. Higher summer flows limit the formation of backwaters, used as primary <br />nursery areas by many nati ve fishes, and they reduce water temperatures. Higher winter flows flood <br />low-velocity habitats and can potentially displace and stress fish. Daily fluctuations in flow may <br />affect the stability and productivity of nearshore quiet-water habitats (e.g., backwaters). <br /> <br />Effects of regulation on river flow, sediment load, and temperature diminish at increasing <br />distances downstream of dams. Daily flow fluctuations are naturally attenuated by longitudinal <br />changes in channel morphology, and river water warms naturally as it is exposed to sunlight and <br />heated land surfaces along the channel margin. Tributary inputs also ameliorate effects of dams on <br />flow, sediment, and temperature. Tributaries can contribute significant quantities of sediment to the <br />main channel and replenish sediment deposits, particularly during peak-flow events. Tributaries also <br />can restore a more natural seasonal pattern of flow, reduce daily fluctuations produced by <br />hydropower operations, and increase water temperatures. The relative influence of tributaries <br />depends on the size of their drainages, their sediment-load characteristics, and the degree of river <br />regulation. <br /> <br />The natural ecology of rivers also has been affected by widespread increases in nonnative <br />fishes that were intentionally (to create or support sport fisheries) or accidentally introduced into the <br />basin. Reductions in the distribution and abundance of native fishes in the Colorado River basin have <br />been attributed partially to the establishment of more than 60 nonnative fishes (Carlson and Muth <br />1989). Introduced species vary in body size, environmental tolerances, and habitat preferences and <br />are widely distributed and abundant. For example, more than 95% of small-bodied fishes found in <br />Green River backwaters occupied by native fishes in early life stages are nonnative cyprinids (Haines <br />and Tyus 1990; McAda et a1. 1994a; Bestgen and Crist 1999; Day et a1. 1999a, 1999b; Trammell and <br />Chart 1999). Because of their wide distribution, high abundance, and diets ranging from herbivory <br />to piscivory (Tyus and Karp 1989; Tyus and Karp 1991; Muth and Snyder 1995), introduced fishes <br />are potential competitors with or predators of native fishes in nearly all life stages. Although both <br />cold-water (e.g., rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta) and warm-water <br />species (e.g., red shiner Cyprinella lutrensis, common carp Cyprinus carpio, channel catfish <br />Ictalurus punctatus, green sunfish Lepomis cyanellus, and small mouth bass Micropterus dolomieui) <br />can adversely affect native fishes (Hawkins and Nesler 1991; Lentsch et a1. 1996b; Tyus and <br />Saunders 1996), warm-water species have the greatest potential impact because their habitat <br />preferences are similar to those of most native species. <br />
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