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Water Year 2003 Environmental Account Release Priorities Numerous hydrologic and biologic conditions must be considered throughout the year in determining EA releases. The duration and quantity of water to be released will depend on historic and existing conditions, Service target flow recommendations, EA volume, release priorities identified in this AOP, and experience. Based on predicted "very dry" conditions for the 2003 water year, the District's projected drought-conditions operation plans, and flow conditions experienced during the 2002 water year, the Service has identified priorities for each seasonal period as described in Table 3(pages 10-12). Winter/Early Spring (December-March): Nebraska experienced above average temperatures and below average snowpack, plains snow cover, and precipitation during the winter of 2002. As a result, the Platte River experienced lower flows and insignificant river ice cover during the winter, and no spring rise (i.e., pulse flows) occurred. In the absence of these important hydrologic processes (i.e., longer duration/higher magnitude pulse flows, ice formation, etc.), soil moisture in riverine habitats was not replenished and in-channel vegetation was able to mature and become more established. With no significant pulse flow events occurring in the past three water years, the Service and its partners are increasingly interested in exploring ways to use the EA to augment and/or create pulse flows to facilitate beneficial river processes. The Service recognizes, however, that using the EA to establish a regular regime of pulse flows in the central Platte River reach is limited at this time due to not yet completed Program water, land, and sediment components and system and institutional constraints. Regardless, pulse flows remain the Service's highest priority and opportunities to use the EA to facilitate a pulse will be explored in water year 2003, if an opportunity arises. Because of the many uncertainties associated with using the EA to augment or create pulse flows, the EA Manager will not undertake such an activity until adequate planning and coordination has been done. Whooping Crane Migration Season (Marcln 23-May 10): If projected flows of 600 cfs occur at Overton during this period, and gains similar to those experienced during water year 2002 reach Grand Island, shortages to the Service's dry year flow target of 1,700 cfs will occur during this important whooping crane migration period. Hydrologic conditions and the status of the whooping crane migration will be closely monitored during this time. If low flow conditions are not maintaining adequate base flows to provide stop-over opportunities for migrating whooping cranes in the central Platte River, EA releases may be made to augment flows during this period. Late Spring (May/June): Improvement of late spring pulse events is the Service's highest flow priority (Bowman 1994; Bowman and Carlson 1994). Existing long-term averages for pulse flows are well below Service targets, cunent projections suggest that below average flow conditions will again occur throughout most of the water year, and no spills are predicted. If conditions during winter/early spring (with or without EA releases) have not resulted in beneficial pulse flow(s) which promote natural river processes (e.g., in-channel vegetation removal, sandbaz formation), the Service will continue to look for opportunities to use the EA for pulse flow augmentation during this priority period. If conditions are favorable, EA releases may be made to improve the magnitude andior 30-day duration of natural peak events that result from mountain snow melt and/or uncontrolled runoff events in May and June. Water Year 2003 EA AOP 7 January 30, 2003