The biggest river in Dornod area is Khalkh River. The west bank of the river is taller than the east bank. If you see from the east bank, it looks like wall that covers over, so that it is called as “Khalkh” river which means “shield” in Mongolian. The river that flows through Khalkhgolsoum of Dornodaimag is 233 km long and flows into Buir Lake determining the border line between Mongolia and China. The Khailaast River flows into the Khalkh River. In 1939 an undeclared war was held between Japan - Manchu and The Soviet Union – Mongolia near the Khalkh River.