Chagan River (tributary of Irtysh River)

The Chagan (sometimes also spelled as Shagan) is a river in the east of Kazakhstan and a left-bank tributary of the Irtysh River. It is not to be confused with the Chagan River in the west of Kazakhstan, which is a tributary of the Ural River. The length of the riverbed is 275 km.

It is the only surface waterway on the Semipalatinsk Test Site, which was used as the primary testing venue for the Soviet Union's nuclear weapons. The river flows along the eastern boundary of the test site and fills the "Atomic Lake" Lake Chagan (or Lake Balapan), a lake created by the Chagan nuclear test.