Onon River
takes its source from the hot mineral water of the Khentii Mountains. Its drainage area is a about 94,010 square kilometres, its total length is 808 kilometres, of which 298 kilometres flow through the territory of Mongolia. The river Shilca originates from this 298-kilometer flow which is a tributary of the rivers Onon and Amar. The river Onon flows through mountainous areas with forests.
Kherlen River
takes its source from the southern side of a mountain, which is one of the major ranges of the Khentii Mountains and situated 1750 meters high above sea level. It gradually flows to the east, then it flows to the south and joins the Lake Dalai in China. The Kherlen is 1264 kilometres long and 1090 kilometres flow through Mongolian territory. This river flows between mountains with dense forests, turns to the east and flows on to the wooded steppe.
Ulz River
It takes its source from mountains, situated in the eastern side of the Khentii Mountain range, and flows between rivers Onon and Kherlen. The Ulz drains into the Lake Tooroi in Russia.
Khalkh River.
This river flows from the Ikh Khyangan Mountains and branches into two parts near the Lake Buir. Its left branch drains into Lake Buir and its right branch into the river Orshuun. The length of the river is 233 kilometres and its drainage area is 30,465 square kilometres, of which 12,775 square kilometresare on Mongolia's territory.
