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o W N ,.l:;,. PART IV. AUTHORIZED DEVELOPMENT A. Irrigation About 353,000 acres of new land to be irrigated within the Upper Colorado River Basin under the recently authorized projects considered in this report represent an increase of about 25 percent over the pre- viously irrigated area. Approximately 50 percent of this increase is included in two projects--the Seedskadee project in Wyoming and the Nav- ajo Indian Irrigation project in New Mexico. The remainder consists . primarily of lands on new projects in Colorado and Utah. The .only new lands which have been authorized for development in the Lower Colorado River Basin above Imperial Dam are within the Colo- rado River Indian Reservation below Parker, Arizona. One hundred and eight thousand (108,000) acres of land on this reservation are reported to be planned for development. Present (1964) development is about 32,000 acres. Because the time schedule for development of these lands is uncertain, they have not been considered in estimates for this report. The recently authorized Dixie project in Utah would add 11,615 acres of new land to the area of 9,445 acres presently irrigated in the project area in the Virgin River Basin. . B. Depletions on New Projects The anticipated new depletions of water from Federal projects re- cently authorized and other miscellaneous projects are indicated in Table No. 19. The 632,000-acre-foot depletion resulting from reservoir losses (Increment No.1) will occur gradually as the reservoirs fill, with the full depletion dependent primarily upon the time required for filling Lake Powell. Of the remaining 1,936,000 acre-feet of deple- tions tabulated for the Upper Basin, it is estimated that about 743,000 acre-feet of depletion will occur by 1975 and the remainder thereafter. The new depletions include about 709,000 acre-feet of transmountain diversions. . . The Dixie project will deplete the Virgin River Basin by 62,000 acre-feet, including 8,300 acre-feet for a municipal supply for Cedar City, Utah. Diversions from Lake Mead for the recently authorized Southern Nevada Water Supply Project will deplete the Colorado River Basin by an estimated additional 253,000 acre-feet annually. Additional salvage of water by the authorized channelization of the Lower Colorado River upstream from Imperial Dam will increase the 15