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27 f\.'l> ~ CO Q 1966-90 Changes-These are depletions that have come into being since the Comprehensive Framework Study estimates were prepared. These include 5,000 acre-feet of private rights developed for municipal and industrial purposes. Values shown were provided by the New Mexico Interstate Stream Commission. Navajo Reservoir Evaporation-Reservoir evaporation is based upon a Colorado River Storage Project study made in 1973. Animas-La Plata Project (Colorado-New Mexico)-See the discussion of the Animas-La Plata Project in the "Colorado" section. San Juan-Chama Project-The San Juan-Chama Project was authorized by Public Law 87-483. Transbasin diversions began in 1971. The May 1957 Supplemental Project Report indicates that diversions are expected to average about 110,000 acre- feet a year, although more recent hydrologic studies performed by the Southwest Regional Office indicate that the long-term average annual yield may be closer to 104,000 acre-feet. For purposes of this report, 110,000 acre-feet have been selected as the level of existing and future average depletions. Navajo Indian Irrigation Project-Various estimates for projected agricultural use depletions have been prepared, including the studies for the all-sprinkler irrigation system for the Navajo Indian Irrigation Project (NIIP) prepared by the Southwest Region of the Bureau of Reclamation. This study estimated agricultural consumptive use of 226,000 acre-feet. Several other estimates have been made, and a 5-year field study was made to determine actual consumptive use on the project. Technical estimates reported by the Secretary of the Department of the Interior report, Economic Study, May 1980, are 254,000 acre-feet for agricultural depletions. 'The State of New Mexico has stated that the projected depletion estimates for the NIIP under full project development will not reach 267,000 acre-feet and that a more reasonable estimate of the maximum project consumptive use would be 254,000 acre-feet annually. The 267,000-acre-foot depletion value is based on the full 110,630 acres being irrigated each year. Based on historical data, at least 5 percent of the total irrigable acreage has been fallow in anyone year since 1981. In November 1981, it was concluded and agreed by the Assistant Secretary, Department of the Interior, Land and Water Resources and Assistant Secretary, Department of the Interior, Bureau of Indian Affairs that the productive acreage of the project should be 110,630 acres, rather than the 105,000 acres which had been assumed in the past, Correspondingly, the annual depletion estimate has been revised from 254,000 acre-feet to 267,000 acre-feet. The first block of land (about 9,300 acres) was irrigated in 1976. In 1985, blocks 1 through 5 were in production. and some water had been delivered to block 6. Although some return flow from the project has been observed, the depletion of river flow is nearly equal to the water diverted from Navajo Reservoir, Return flow to the river will increase as deep percolation from irrigation charges the aquifer.