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"However, the Service realizes, and experts at the May workshop pointed out, that the <br />capacity of some channel sections of the North Platte and the Platte Rivers have become <br />reduced, yet high flows are still necessary to maintain channel capacity." (p. 2) <br />"Recruitment of cottonwoods should be managed by the magnitude of pulse flows rather <br />than by continuous inundation of the active channel during the period of seed deposition <br />and viability. ...For purposes of seedling removal, the optimal time at which the late <br />winter pulse flows in table 3 should occur is during ice break-up" (p. 2) <br />"River stage is most frequently the dominant influence on groundwater levels in wet <br />meadows, and composition and structure of biological communities in grassland is most <br />closely associated with the environmental variable of soil moisture. ... Some wet <br />meadows have elevated groundwater, and added pulse flows would rehabilitate a number <br />of these potentially "active" wet meadows in the ecosystem." (p. 3) <br />Necessary Effects of May/June Pulse Flows: <br />[Very Wet (May 1- June 30)- > 16, 000 cfs; Wet (May 1- June 30)- > 12, 000 cfs; Normal <br />(May 20 - June 20)- > 3, DDD cfs; Dry (May 11 - June 30) - noneJ <br />"1. Maintain and enhance the physical structure of wide, open, unvegetated and braided <br />river channel characteristics for resting, feeding, and roosting by migratory birds. <br />2. Maintain and enhance the occurrence of soil moisture and pooled water for the lower <br />trophic levels of the food chain in low grasslands, and biologically diverse communities <br />in the ecosystem over the long term. <br />3. Help maintain and rehabilitate aquatic characteristics of large river habitats in the <br />lower Platte River for animals such as the endangered pallid sturgeon. <br />4. Maintain and rehabilitate backwaters and side channels as spawning and nursery <br />habitats; to promote critical stages in the life cycles of fishes, mollusks, and other aquatic <br />organisms; to promote movement and (re)distribution of fishes, mollusks, and other <br />aquatic organisms; and to facilitate nutrient cycling in the floodplain." (p. 3) <br />Necessary Effects of February/March Pulse Flows: <br />[Very Wet (Feb 1- March 31)- >16, 000 cfs; Wet (Feb 15 - March 15) - > 12, 000 cfs; <br />Normal (Feb 15 - March I S)- 3,100-3, 600 cfs; Dry (Feb 15 - March 1 S)- 2, 000-2, S00 <br />cfsJ <br />"1. Bring the groundwater levels in grasslands up near to soil surface in areas of <br />grassland and above soil surface in some lowest areas of grasslands. One effect of this is <br />to bring up soil organisms to near or above the soil surface for predation by migratory <br />birds and other animals, and to provide pooled water for other aquatic organisms preyed <br />upon. <br />2. Cause and/or contribute to break up of ice and move ice for the effect of scouring <br />vegetation off sandbars in the active channel; this effect is especially important in years <br />of low flow. <br />3. Redistribute sediment in the active channel and maintain the geomorphology of the <br />channel. <br />4. In years with little or no ice formation, pulse flows are necessary for soil saturation in <br />meadows." (p. 4) <br />4