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Common Features and Objectives for All Action Alternatives <br />- - ---- ----- - - - - -- ------ <br />? Keep water levels higher during tern and plover nest initiation and construction to reduce nest <br />loss that may result from later uncontrolled high summer flows <br />Short-Duration Near-Bankfull Flows <br />For purposes of the recovery and maintenance of desirable channel habitat conditions for the target avian <br />species, various pulse flow recommendations based on different concepts have been proposed (Johnson, <br />1994; Bowman and Carlson, 1994; Murphy et al., 2004). Flows of approximately 3- to 5-days' duration, <br />with magnitudes approaching but not exceeding bankfull channel capacity through the Central Platte <br />Habitat Area, are currently proposed on an annual or near-annual basis along with other measures (e.g., <br />clearing and leveling adjacent vegetated areas) to test the ability of the Program to scour vegetation <br />encroaching on Program channel areas and to mobilize sand and build ephemeral sandbars to benefit the <br />nesting target species. <br />Current bankfull capacity in the Central Platte Habitat Area is greater than or equal to 10,000 cfs. Desired <br />short-duration near-bankfull flows would be in the range of 6,000 to 9,000 cfs. For Program accounting <br />purposes, when Program waters are released to achieve these flows, those releases also would be counted <br />toward the Program objective of 130,000 - 150,000 acre-feet of improvement in attaining flow targets. <br />Based on information currently available, various opinions exist among scientists on channel forming <br />processes, and on the physical and biological effects of high flows of various magnitudes and frequencies <br />(e.g., see NRC, 2005, p.142). Investigations by the Reclamation and the Service (Murphy et al., 2004) <br />have highlighted the importance of testing near-bankfull flows in the Central Platte Habitat Area as a <br />long-term management strategy for maintaining and/or restoring channel conditions essential to the <br />recovery of the three bird species, within the Program-designed framework of adaptive resource <br />management. As such, the effectiveness of "near-bankfull" flows in achieving Program channel- <br />restoration objectives remains to be determined through the Program's adaptive-management process. <br />River Habitat for the Pallid Sturgeon <br />One goal (or purpose) all action alternatives is to provide offsetting measures for impacts from the <br />program to the pallid sturgeon in the Lower Platte River and provide benefits if possible. The "Program <br />Benefits for the Pallid Sturgeon" section, later in this chapter, describes the process that the Program will <br />follow to provide offsetting measures and benefits if necessary for the pallid sturgeon during the First <br />Increment. <br />Program Management of Flows <br />The action alternatives improve achievement of flow targets at Grand Island through a combination of <br />three general approaches: <br />? Reducing consumption of riverflows: Consumptive use5 of water in the Basin is reduced <br />typically by reducing the irrigation of crops. This allows far reduced diversion of river water, <br />thereby increasing riverflows and the achievement of flow targets. Reducing consumptive use of <br />5 Consumptive use is the amount of water taken from a stream system that is lost to the system, usually through conversion <br />to crops or other unrecoverable losses.