Lake Powell exists as a reservoir.
Lake Powell is a reservoir on the Colorado River , straddling the border between Utah and Arizona ( most of it , along with Rainbow Bridge , is in Utah ) . It is the second largest man-made reservoir by maximum water capacity in the United States behind Lake Mead , storing 24,322,069 acre.ft of water when full . The reservoir is named for explorer John Wesley Powell , a one-armed American Civil War veteran who explored the river via three wooden boats in 1869 .