Kazakh Ertis
River rising in the Altai Mountains in Xinjiang autonomous region, China.
It flows west across the Chinese border and then northwest through Kazakhstan into Russian Siberia , where it becomes the largest tributary of the Ob River . It is 2,640 mi (4,248 km) long and is navigable for most of its course. Its main ports include Tobolsk, Tara, Omsk, Pavlodar, Semey, and Öskemen.