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and Tucson urban complex that would bear on the major reservoirs in this area. The primary benefits which will result from the provision of recreation facilities at reservoirs included in the plan are primarily intangible and, therefore, not subject to usual methods of measurement. Nevertheless, by using "A Method of Evaluating Recreation Benefits of Water Control Projects" adopted by the National Park Service in August 1957, and updated in February 1963, the measure of the benefits is related to a monetary evaluation of the benefits enjoyed by the individuals visiting the area. The monetary evaluation used in this report is 52 cents per visitor day as estimated by the National Park Service. The Colorado River mainstream reservoirs proposed in this report, however, do not represent average conditions. They would be located in one of the worlds most spectacularly scenic canyons and would become unique recreational attractions of worldwide renown. The monetary recreational values accruing to these reservoirs could well be many times the amount estimated. Although significant outdoor recreation opportunities will be created, a number of important intangible conservation and recreation values also will be adversely affected. Bridge Canyon Reservoir, as presently planned, would encroach on Grand Canyon National Park. A particular kind of "white water" boating experience that is becoming increasingly popular on the Colorado River would no longer be possible. However, only about 1000 persons have participated in this sport since John Wesly Powell first came down the Colorado in 1869. The estimated value of benefits accruing to recreation is presented in table 22. Greater detail on the derivation of these values and other aspects of recreation needs and costs are contained in the appended report by the Bureau of Outdoor Recreation. Area Redevelopment Benefits--Area redevelopment benefits would accrue to temporarily unemployed people in the Southwest, through the opportunity for employment during the construction of the facilities and the continuing use of some of this labor for operation and maintenance of the project facilities. A benefit value for this type of employment has been developed from utilizing data available from the construction of Glen Canyon Dam and other related activities in the Southwestern depressed areas. These values have been applied only to the proposed construction of Bridge Canyon, Marble Canyon, and the Central Arizona Project Aqueduct Complex. The resultant benefit values are shown in table 22. Economic Costs The estimated construction costs and periods of construction have been presented under the section dealing with plan of development. These costs, as well as interest during construction and the annual costs of VII-5Epson Perfection 4870 Photo, 400 dpi, 8 bit