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2) The second type is the effect on the interrelated biological, physical, and temporal <br />properties of the river system. Since 1992, the Service and ecologists have emphasized <br />the importance of maintaining the structure and functions of the Platte River processes. <br />To reduce the decline of Platte River endangered species habitat, measures must be taken <br />to improve: a) hydrologic processes that reincorporate sediment transport and vegetation <br />removal; b) open channel and sandbar creation and maintenance for roosting, nesting, and <br />wading birds, as well as instream aquatic habitat diversity; c) aquifer recharge for wetland <br />maintenance; d) backwater flooding for nutrient cycling; fish spawning, refugia, and <br />distribution; and e) water temperature and other water quality factors. <br />Cumulative depletions of normal high flows in the spring, which are elemental to the structure <br />and function of the Platte River ecosystem, include: <br />Reduction in frequency and duration of normal high flows in February /March and <br />May /June. These reductions adversely affect the formation and maintenance of wide, <br />alluvial channels; promote seedling establishment and expansion of riparian woodlands <br />along the river. Vegetation of sandbars and attachment of sandbars to river banks reduces <br />the amount of roosting habitat available for whooping cranes during migration, and <br />nesting and feeding habitats for terns and plovers. <br />Depletions to high flows adversely affect wet meadows adjacent to the river. In February <br />and March, rising groundwater levels thaw the soil and initiate biological responses of <br />soil organisms. Flow depletions during April, and in particular, May and June <br />incrementally reduce groundwater levels and decrease the frequency and duration of soil <br />column saturation. Groundwater levels during the growing season are important for <br />maintaining the long -term biological functions of wet meadows for federally listed <br />species and other fish and wildlife species. Incremental and cumulative changes of wet <br />meadows toward more xeric conditions adversely affects the productivity of aquatic and <br />semi - aquatic wet meadow communities, and contributes to fragmentation of the habitat <br />via conversion of wet meadows to other uses. <br />Decline of sediment load from reductions in magnitude, frequency, and duration of <br />normal high flows adversely affect sediment transport from the watershed and through the <br />river system. The transport of sediment is a principle benefit of spring pulse flows in <br />alluvial rivers such as the Platte. Reservoirs, diversion dams, and irrigation canals trap <br />sediment, reducing sediment load in the river. The supply and transport of sediment <br />through the riverine system are essential to sustain the alluvial channel habitats used by <br />federally listed species, and necessary for maintenance of a diverse channel morphology. <br />Assessment of Program Impacts <br />The above sections describe the influences of water development on the habitat of the target <br />4 <br />