The sources of the Congo are in the highlands and mountains of the East African Rift , as well as Lake Tanganyika and Lake Mweru , which feed the Lualaba River . This then becomes the Congo below Boyoma Falls . The sources of the Congo are in the highlands and mountains of the East African Rift , as well as Lake Tanganyika and Lake Mweru , which feed the Lualaba River , which then becomes the Congo below Boyoma Falls .