Lake Powell is a reservoir on the Colorado River in Utah and Arizona, United States. It is a major vacation destination visited by approximately two million people every year. It holds 24,322,000 acre-feet (3.0001×1010 m3) of water when full, second in the United States to only the downstream reservoir of Lake Mead – though Lake Mead has fallen below Lake Powell in size several times during the 21st century in terms of volume of water, depth and surface area.