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Choice...depends...upon broad considerations of public purpose; in the last analysis upon how much the people of the United States care about preserving the natural conditions and scenery in the portion of the Grand Canyon selected for such preservation in 1908, and whether they are able and willing to pay the economic price of such preservation. 2. Values to be gained No additional values would be gained by inundating the 13 miles of canyon within the Park except that some 13 more miles of reservoir boating in the depths of the Grand Canyon would be made possible. This Service has recommended that the height of the proposed Bridge Canyon Dam be limited to 1783 feet (the normal river elevation at the west boundary of the Park) thus preventing encroachment on the Park. III. MARBLE CANYON-KAHAB CREEK TUNNEL It is recognized that plans for a possible Marble Canyon-Kanab Creek Tunnel are extremely tentative. Our analysis of its potential effects on Grand Canyon National Park are based on such limited project data as are available at this time. The proposed Marble Canyon Dam to be located some 12.5 miles upstream from Kankowoap Canyon at the northeast corner of Grand Canyon National Park would divert water into a tunnel some 44 miles long from a point east of the Park to Kanab Creek. According to preliminary plans it is probable that such a project, if authorized and constructed, would utilize for power most of the water available from the Colorado River in excess of 1,000 cubic feet per second, which might be released to flow through Grand Canyon National Park, for scenic purposes. It is recognized that the decision to reduce the normal, uncontrolled flow of the Colorado River through the Park was made when the Colorado River Storage Project was authorized by the Congress. The analysis with which we are here concerned is the difference in impact on the Park and its millions of visitors of a river flow of perhaps 20,000 cubic feet per second-the full amount of water released from Glen Canyon Dam and probably a dam in Marble Canyon, for power generation and other purposes-and a flow of perhaps only 1,000 cubic feet per second. If the tunnel is authorized and built, the Colorado River through Grand Canyon National Park would be dewatered-reduced to a trickle-for all the foreseeable future. 5Epson Perfection 4870 Photo, 400 dpi, 8 bit, 16,023,552 byte