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BENEFITS TO ENVIRONMENT GLEN CANYON TO HOOVER DAMS by Cecil Baltzar Jacobson, 1 F. ASCE ., "'I ., :1 [Prepared for American Society of Civil Engineers Annual and National Environmental Engineering Meeting held on October 16-22, 1972 at Houston, Texas] INTRODUCTION As a subject of popular concern, ENVIRONMENT has risen to unprece- dented heights. Attention too often, however, is focused only on the so called negative effects. Particularly have the builders and operators of large dams been the target of unjust criticism with little credit given to positive effects. Outlined herein are. positive benefits, incident to the fundamental purpose and operation of Glen Canyon Dam, which effect the environment of a downstream reach of river and canyonland, including the Grand Canyon of the Colorado River, unparalled for its scenic beauty and recreational value. '" 'I r"1 t,~ . ;-., '~I , Almost equal in height to Hoover Dam of world fame, Glen Canyon Dam creates Lake Powell to a capacity of 27 million acre feet, approximately that of her sister downstream reservoir - Lake Mead. Between these reser- voirs, the two largest in the United States, extends Grand Canyon, one of nature's great wonders, through which the Colorado River plunges downward 1,900 feet in a distance of 255 miles. ~ : , ]" One mile deep at places, the Grand Canyon of the Colorado River constitutes a formidable barrier with bridge crossings separated over 300 highway miles from Hoover Dam to Marble Canyon near Lees Feny. Glen Canyon Dam is situated IS miles above Lees Ferry, the site of the historic river crossing established by the pioneer John D. Lee. :~ ..'. ~ ", , .A ~ ." .' The depths of Grand Canyon were first explored by John Wesley Powell in 1869, and, until the completion of Glen Canyon Dam, relatively few people risked negotiating the many wild river rapids throughout Grand Canyon, the trip being considered an expensive and dangerous adventure. In 1963 Glen Canyon Dam began regulating the river. Treacherous peak flows are now stored in Lake Powell, and storage releases are made to supplement the discharge of the low flow season. The resulting new river regimen is now particularly inviting to river travelers. In 1971 nearly 11,000 of these river runners sanely viewed the bottom sights of this great natural wonder, enjoying exhilarating "white water" boating with reason- able cost and safety. 1 Professor of Civil Engineering, Brigham Young University, Provo, Utah, and President, Utah Section ASCE.