Lake Powell is an artificial 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 is the second largest artificial reservoir by maximum water capacity in the United States behind Lake Mead, storing 24,322,000 acre-feet (3.0001×10¹⁰ m³) of water when full. However, 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.