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L <br />CHAPTER III <br />AFFECTED ENVIRONMENT <br />The Upper Colorado River Basin is on the west side of the Continental Divide <br />and includes parts of Arizona, Colorado, New Mexico, Utah, and Wyoming. It <br />encompasses an area of 109,580 square miles in the Upper Colorado River <br />drainage. The Proposed Action will affect the Upper Basin above Glen Canyon <br />Dam, but excludes the San Juan River and its tributaries (see Figure III-1). <br />1 Following is a detailed discussion of resources within the Upper Basin that <br />potentially could be affected by the Recovery Implementation Program and the <br />"No Action" alternative. <br />A. Water Resources <br />The Upper Basin is naturally divided into three major drainage systems: the <br />upper mainstem of the Colorado, the Green, and the San Juan Rivers. Average <br />annual precipitation ranges from over 50 inches in the high elevation <br />headwaters to less than 6 inches in desert areas. Large variations in annual <br />discharge occur due to variations in precipitation and long-term climatic <br />trends. The average natural flow (undepleted) of the Colorado River at Lee's <br />Ferry was 15,328,000 acre-feet for the period 1906 to 1986, with extremes of <br />24,511,000 acre-feet in 1984 and 5,014,000 acre-feet in 1977. Water storage <br />facilities conserve limited precipitation and release it when needed for <br />agricultural, municipal, and industrial uses. In addition, water storage <br />facilities are managed to provide flood control, hydropower, recreation, and <br />fish and wildlife benefits. <br />I 1. Water Management <br />Water management efforts contemplated in the Proposed Action and "No <br />Action" alternative will affect the hydrologic regime of the Upper Basin. <br />a. Federal Water Management <br />Three major Federal water projects represent most of the Federal water <br />management activity in the basin: the Colorado-Big Thompson Project, <br />the Fryingpan-Arkansas project, and the Colorado River Storage <br />Project. These Federal projects have changed riverine conditions, <br />affecting endangered fish. Reclamation has agreed to consult on all <br />existing Reclamation projects in the Upper Basin. Consultation was <br />recently completed for Ruedi Round II/Green Mountain water sales and <br />will be completed in the future for Flaming Gorge Reservoir and the <br />Aspinall Unit. <br />III-1