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Show PART I PRODUCTION Studies concerning water utilization and irrigation practices were made "by the Soil Conservation Service in cooperation with appropriate State and Federal agencies. Data from all available sources were uti- lized and adjusted to regional, State, and subregional "boundaries for the 1965 level of development. Consumptive use rates were estimated on an annual basis by the Blaney-Criddle method and on the basis of the latest data on local seasonal crop coefficients.!/ The region was divided into 6l evaluation areas for determining local consumptive irrigation require- ments. The average water supply, irrigated acreages, and crop distribu- tions were evaluated for each area. The U.S. Census of Agriculture for 1959 has the most consistent data regarding the total amount of water diverted for irrigation. Actual return flow measurements are available only at scattered locations and were considered inadequate for study purposes. Definitions pertaining to water utilization for irrigation, as used in the appendix, are listed below. Full supply irrigated land is irrigated land with a full and ade- quate water supply. Short supply irrigated land is irrigated land with a short and inadequate water supply. Surface sources of water include streams, lakes, reservoirs, and drainage ditches. Ground water sources relate to wells (pumped or flowing) and water taken directly from springs. Other definitions, methodology, and assumptions concerning water utiliza- tion for irrigation are presented in Appendix V-Water Resources-and in the "Framework Study Glossary" of the Pacific Southwest. Water quality is a term used to describe the chemical and physical characteristics of water regarding its suitability for irrigation. Basic data for this section of the appendix were furnished by the Water Quality, Pollution Control, and Health Factors Work Group from current studies made of the Colorado River system. The effects of irrigation return flow on water quality are covered in Appendix XV-Water Quality, Pollution Control, and Health Factors. Water right is a legally protected right, granted by State law to divert water and put it to beneficial use. Water rights as they pertain to irrigation are summarized briefly in this appendix from data furnished by appropriate States and by the Legal and Institutional Environments Work Group. Drainage, as it pertains to irrigation, is the act, process, or mode of relieving lands of excess water and salt. Drainage water collected by a drainage system may derive from surface water or from water passing through soil and may be of a quality suitable for reuse, or it may be of T/Refer to Appendix V, Water Resources, for further detail concern- ing water utilization criteria. |