Lake Mead is the reservoir created by the construction of The Hoover Dam (between 1931 and 1936) on the Colorado River.

In theory it is the largest reservoir in the USA. However, as you can see in this photo (taken in 2012), it is not at full capacity, and in fact was last at full capacity in 1983. A combination of persistent drought and increased demand has caused the reservoir to gradually shrink, reaching a low-point in May 2022, when it sat at just under 27% of theoretical capacity. Since then the introduction of water conservation measures has led to an increase in water volume in the reservoir.