Qinghai Lake is the largest lake in China. Located in an endorheic basin in Qinghai Province, to which it gave its name, Qinghai Lake is classified as an alkaline salt lake. The lake has fluctuated in size, shrinking over much of the 20th century but increasing since 2004. It had a surface area of 4,317 km2 (1,667 sq mi), an average depth of 21 m (69 ft), and a maximum depth of 25.5 m (84 ft) in 2008.