With a capacity of , Lake Powell is the second largest man-made lake in the United States by total water capacity (after only Lake Mead), extending upstream through the canyons of Arizona and Utah. The lake covers at its full pool elevation of . The active, or useful capacity is . The minimum water level required for power generation is , corresponding to storage of , and the "dead pool", the lowest point at which water can be released through the dam, is with storage of . When Glen Canyon Dam was first built, the reservoir capacity was estimated at , but some of this has since been lost to siltation. Because of the hundreds of bays and sinuous side canyons, including those formed by the San Juan, Escalante and Dirty Devil Rivers, Lake Powell has an exceptionally long shoreline for a lake of its size – about at full pool, longer than the entire west coast of the continental United States.