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thought to play the dominant role in the patterns and processes, structure and function, <br />and habitat of the Platte River valley ecosystem." (p. 3) <br />"Pulse flows which mimic the natural hydrograph are needed to restore, on a reduced <br />scale, certain annual effects characteristic of the historic natural hydrograph." (p.4) <br />"Pulse flows are necessary for sediment transport, for redistribution and deposition of <br />sediment in the central Platte River, and for shaping channel morphology into wide, <br />shallow channels. Pulse flows generate a diversity of habitats across the floodplain; drive <br />ecosystem processes in backwaters and wet meadows such as thawing and stimulation of <br />biological activity that ultimately produces food for animals and favorable habitat for <br />both animals and plants, including threatened and endangered species. Timing of pulse <br />flows coincide with or influence fish reproductive behavior and the availability and <br />quality of spawning, nursery, and rearing habitat, including backwater habitat of fishes <br />and mollusks. Flows pulses, especially those which move ice and sediment, scour <br />vegetation of different size and age classes and prevent reestablishment of vegetation." <br />(p• 4) <br />Mav 11 - September 15 Flows: <br />(Normal-1,200 cfs; Wet- 1,200 cfs; Dry- 800 cfs) <br />"Maintaining the components of biological diversity, e.g., plants, invertebrates, fishes, <br />and birds, during this period depends on the aquatic component of the ecosystem. Flows <br />are needed to provide essential habitat components for threatened and endangered <br />species, as well as other important native wildlife populations. ... Target flows for this <br />period, particularly May 11 to June 15, help prevent shore birds from nesting at such low <br />elevations in the river channel that their nests would be subject to flooding during <br />subsequent intervals of higher flows caused by local rainfall and/or flow regulation <br />practices. Instream flows provide a degree of barrier to terrestrial predators which would <br />otherwise more easily prey on shore bird nests. During summer, instream flow targets <br />prevent losses from the native fish community by curtailing rises in water temperatures to <br />levels that otherwise would be detrimental or lethal to a variety of life history stages of <br />aquatic organisms, including fishes. ... The flow target for this period will prevent or <br />reduce future harmful episodes to the aquatic community." (p. 5) <br />March 23 - May 10 Flows: <br />(Normal-2, 400 cfs; Wet-2, 400 cfs; Dry-1, 700 cfs) <br />"Flows contribute important nutritional and physiological conditions for birds preparing <br />to breed. For example, wet meadows are undergoing primary production of invertebrates <br />which are needed by cranes for protein. Whooping cranes migration habitat has been <br />severely degraded as a result of decreased flows and loss of night roosting habitat critical <br />at this time. Flows during this period also provide sandhill crane habitat. This is the time <br />of the year when Eskimo curlews are most likely to use the Platte River. Flows during <br />this period provide channel habitat for water-dependent organisms, including spawning <br />fish, mussels, and migratory waterfowl, wading birds, and shore birds. Environmental <br />education and ecotourism, e.g., crane watching, are very important public and economic <br />values during this time." (p. 5) <br />2