1991 North Platte Hydrology Study

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I. INTRODUCTION a. Purpose and Authority for Investigation The principal purpose of the study is to investigate, describe, and evaluate the operation of the Bureau of Reclamation (Reclamation) facilities in the Platte River Basin to ensure compliance with Sections 7(a)(1) and (2) of the Endangered Species Act. The initial phase of the, study will focus on the North Platte and Platte Rivers. Sectio J&)(- requires every Federal agency to utilize its authorities in consultation with the Fish and Wildlife Service to further the purposes of the ESA by carrying out conservation programs for listed species. SectiOQ*N 2).. requires every Federal agency to ensure through consultation with the Fish and Wildlife Service (Service) that any action it authorizes, funds, or carries out is aft likely to jeopard3je the continued existence of any listed species or result in the destruction or adverse modification of critical habitat. The authority for this investigation is based on responsibilities pursuant to the aforementioned sections of the ESA. Following completion of this study, if it is determined that Reclamation's operation of its facilities in the Platte River Basin may be adversely_ affecting listed species or their habitats, formal consultation will be conducted in accordance with regulations which implement Section 7(a)(2). In accordance with Section 7(a)(1) of the Act, opportunities will be identified that may exist through operational changes to conserve and recover threatened and entangered species and their habitat to the extent practicable. The study wili.also odentify. opportunities and 'actions that would promote conservation of ether sig- nifteant .biolog,3.a" seseacces, such as-riparian habitat, fisheries, and migratory birds. Compliance with the National Environmental Policy Act (NEPA) would be required if any implementation plari. resulting- from this study constitutes a significant rederal'-sction b. Description of the Study Area The study area includes the North and South Platte Rivers from the project facilities downstream to the confluence of the Platte River with the Missouri River. The Platte River Basin channel, as shown on the map, Figure 1, extends from the mouth of the Platte River near Louisville, Nebraska, to the headwaters of the South and North Platte Rivers. The drainage area includes about 71,000 square miles that contribute to surface runoff. The Platte River tributaries originate in the Rocky Mountains flowing in a north to northeasterly direction until they enter the plains and then continue in an easterly direction to the confluence with the Missouri River. The mainstem of the Platte River includes 310 river miles of main channel from the mouth to North Platte, Nebraska, and the river elevation rises from 940 MSL to 2750 MSL. The 1