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~ ,.o) .:) (Q (,..~ ~ SUMMARY This appendix evaluates the need for land and water for irrigation in the Great Basin Region to the year 2020. The projected food and fiber requirements allocated to irrigated agriculture are based on the OBE-ERS (Office of Business Economics and Economic Research Service) projections of March 1968. I. I" I i. I, I The practice of modern irrigation in the Region began in the mid- 1800's along the base of the mountain ranges on the extreme eastern and western. rims of the Region where streamflow was most plentiful. Most of the subsequent development has also been in these same general locattons. Land area developed for irrigation by 1965 totaled 2,1l4,ooo acres. Of this amount 1,998,000 was irrigated and the remainder idle. Irrtgation water diversions amounted to about 7 millton acre-feet, of which 3 million was consumed. Land requirements for irrigation wtll tncrease by 65,000 acres by 2020. Rehabilitation of idle land to production will sattsfy 59,000 acres of this need. However, 21+5,000 acres of additional land wtll need to be developed to meet the remaining 6,000 acres required for produc- tion and to replace 239,000 acres of irrigated land converted to other uses, principally urbanization. The Region contains about 12 million acres of suitable land that could be developed for irrigation. Water consumed for irrigation will tncrease by about 0.5 million acre-feet annually by 2020. Thts includes providing supplemental wa- ter for presently deficient trrigated lands as well as an adequate supply for new lands. Diversion efficiencies (ratio of water consumed to that diverted) are expected to increase an average of 5 percent re- gtonwide, This increase in efficiency provides a substantial amount of the water for consumption without a correspond.ing increase in di- versions. Facilities to regulate and deliver additional water supply will be required. Regulation fac.J.lities consist principally of multipurpose storage reservoirs on the major stream systems. Existing conveyance and distribution systems would be extended and enlarged to serve new develop- ments adjacent.to existing irrigated land; however, much of the new land would require delivery facilities as the new lands are more remote from the water supply sources. In the desert valley areas where ground water is available, limited development of water could be made from this source-- eliminating the need for storage regulation and long conveyance facil- ities. Additional drains will be required to control the water table on 226.,000 acres of irrigated land. On-farm improvements such as land level- ing, sprinkler or irrigation systems, improved management practices, and crop varieties will be needed to meet production requirements.