| OCR Text |
Show PART I INTRODUCTION "OBERS" is used in connection with water and land needs or demands for irrigation, it will be on the basis of this "Regional Interpretation," except as stated otherwise in Part V. The Water Resource Planning Act was passed on July 22, 1965, by Pub- lic Law 89-80, 89th Congress, 1st Session. The Water Resource Council was established on April 10, 1966, as a result of this act. By letter of October 10, 1966, the Water Resource Council requested the Pacific South- west Interagency Committee (PSIAC) to coordinate comprehensive studies in the Pacific Southwest, including the Upper Colorado Region. Authorization for preparation of this appendix followed. Methodology, Definitions, and Assumptions One of the basic factors considered in Appendix X was the inventory of land resources of the region to determine the total irrigated and po- tentially irrigable acreage. This was accomplished as a joint effort of several Federal agencies and appropriate States. Criteria for irrigation land classification were established by the Irrigation and Land Classifi- cation Seminar held in Salt Lake City, Utah, on July 18-19, 1967, and subsequent studies by an ad hoc Task Force of the Coordinated Planning Subcommittee, (l) Presently irrigated land was inventoried as of the base year, 1965- By definition, irrigated land is land receiving water by artificial means for agricultural purposes by gravity, sprinkler, or sub irrigation. It ex- cludes lands watered by water spreading, such as range improvement. Re- sponsibility for inventorying irrigated acreage in the region was assigned to the Land Use and Management Work Group. Methodology and assumptions used in the study are described in Appendix VI-Land Resources and Use. The Irrigation and Drainage Work Group was responsible for inventory- ing potentially irrigable land in the region. The Bureau of Reclamation furnished basic data for the study from its land classification surveys. Additional information was solicited from other Federal and State agencies involved in surveys of agricultural lands, including the New Mexico Soils Task Force Group, Bureau of Indian Affairs, Committee on Arable Land Re- sources of Utah, and the Soil Conservation Service. These data were used directly or were interpreted and adjusted to show their suitability for irrigation development. The lands were identified on Geological Survey topographic work maps, scale 1:250,000, transferred to a regional map, scale 1:1,000,000 and subsequently printed on three subregional maps for the appendix. By definition, potentially irrigable land is land having soil, topography, drainage, and climatic conditions suitable for irriga- tion development. It may or may not be located where water supply is or can be made available at costs presently conducive to development. It comprises land in classes 1 to h which, if occurring in adequately sized units and properly provided with essential improvements in leveling, ir- rigation structures, and drainage, have sufficient productive capacity to support sustained irrigation. |
