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C.::'l .l>- , ~, PARI' IV. FU'IURE DEV.El.OfMENr o A. Irrigation About 358,000 acres 01" nc..... land to be irrigated within the Upper Colo- rado River Basin under the recently authorized and proposed projects con- sidered in this report represent an increase of about 25 percent over the previously irrigated area. ApproxUnately 47 percent of this increase is included in two projects--the Seedskudee Project in Wyoming and the Navajo Indian Irrigation Project in New Mexico. The remainder consists prLmarily of lands on new project.:; in Colorado and Utah. Passage of the Colorado River Basin Project Act authorizes a number of projects in the Upper Colorado River Basin und the Central Arizona Proj- ect and reauthorizes the Dixie Project in the Lower Colorado River Basin. Water from the Colorado River for the Central Arizona Project ....ould be de- livered through the Grunite Reef Aqueduct and Pumping Plants. The Dixie Project, Utah, in the Virgin River Basin would provide u full water sup- ply to 6,900 acre~ of new land and a supplemental water supply to about 10,000 acres of existillg irrigatcd lands. The Bureau of Indian Affairs reports that 107,599 acres of land on the Colorado River Indian Reservation are planned for irrigation. ~lis includes the present (1966) devclopment of about 36}~1O acrcs. A major portion of the 18,97). acres of land on t.he fo't. Mohave Indian Reservation is under developmcnt cont.ract. Ninet.een hundred acres of land on the Cbernehuevi Indian ReGervution are planned to be fully developed by 1990. B. Depletions on New Projects The antici.put.c'd new deplt~tion:., of water from Federal projects re- cent.ly authori zed and other miscellaneous projC(~tf are indicated in Table No. 20. The 632,OOO-acre-foot depletion re~~ltinG from reservoir losses will occur gradually as the reservoir$ fill, with the full depletion de- pendent primarily upon the time required for filling Lake Powell. As of 1966 the annual evaporat.i.orl 103~~es are ,,-'st.i.mat.ed to be 314,000 ac!.e- feet. The remaining 1,930,000 acre-feet of depletions tabulated for the Upper .&lsin will be due to u:~es other than re:;ervoir evaporat.ion. The new de- pletions include about 700,000 acre-f~et of transmountain divercions. The Dixie Project will deplete the Virgin River Basin by 48,000 acre-feet. This depletion includ,"s the future annual stream depletions of 5,8.:>0 acre-feet. resultinG from trd.nsba"in exports to Cedar City, evap- oration from Kolob Resel~oir, and depletions to the Santa Clara River due t.o ....cll development on the Santa Clara River. Diversions frQ!!l Lake Mead for the recently authorized Southern Ne- vada Water Project ;.;il1 deplete the Colorado River Basin by an estimted additional 253,000 acre-feet annually. 18