Chapter 3: Description of Alternatives

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Chapter 3- Description of the Alternatives Taken together, these peak and annual pulse flows are expected to serve multiple functions, listed below, at different times of the year: In February and March % Bring the groundwater levels in grasslands and wet meadows adjacent to the river up near to the surface in some areas and above soil surface in some lowest areas of grasslands. This causes soil invertebrates (worms, insects, and others) to move up to the soil surface where they are more available for consumption by migratory birds and other animals.4 ? Cause and/ar contribute to the breakup and movement of ice to scour vegetation off sandbars in the active channel; this effect is especially important in years of low flow. ? Redistribute sediment in the active channel to reduce ongoing erosion and downcutting of the river channel. ? Help provide spawning cues for pallid sturgeon in the Lower Platte River. ? Help maintain and rehabilitate pallid sturgeon habitat in the Lower Platte River. In May and June ? Maintain and enhance the physical structure of wide, open, unvegetated, and braided river channel characteristics for resting, feeding, and roosting by migratory birds ? Maintain and enhance the occurrence of soil moisture and pooled water for the lower trophic levels of the food chain in low grasslands and promote biologically diverse communities in the ecosystem over the long term ? Facilitate upstream migration far spawning pallid sturgeon and downstream transport of eggs and larvae ? Help maintain and rehabilitate pallid sturgeon habitat in the Lower Platte River ? Maintain and rehabilitate backwaters and side channels as spawning and nursery habitat to: o Promote critical stages in the life cycles of fishes, mollusks, and other aquatic organisms o Promote movement and (re)distribution of fishes, mollusks, and other aquatic organisms o Facilitate nutrient recycling in the flood plain (Bowman and Carlson, 1994) 4 The Service's discussion of pulse flows recognizes the value to the river and adjacent wet meadows of springtime flood events which may exceed bankfull capacity of the river. These events help keep the river connected to the floodplain and maintain the hydrology of wet meadows. The Service recognizes the value of ensuring that these natural events continue. However, if a Recovery Implementation Program is implemented, the Program would not create or contribute to out-of-bank flooding by releasing Program water. All Program water releases would be made within existing safe channel capacity.