Chamkhar Chu is the main river flowing through Bumthang that starts near Monla Karchung. As it flow down through the main Bumthang valley, it is joined by other tributaries. After it passes the Chokhor valley, it is joined by the major rivers of other valleys of Bumthang before it meets Mangdue Chu and then joins Manas and Brahmaputra to reach the ocean in Bay of Bengal.