The Kherlen River originates in the Khentii Mountains and flows 1,382 km through the eastern part of Mongolia, flowing into Lake Hulun in China, and then becomes one of the sources of the Amur River, passing through Russia and China before flowing into the Pacific Ocean north of the Japanese islands through the Agnuur Sea. The Great Khentii Mountains branch is named "Kherlen River" after the confluence of the Kherei Tolgoi, the Bogd River, which originates from the Budan Tsagaan, and the Tsagaan River, which originates from the Kherei Tolgoi at the foot of the Khentii Khan Mountain. The main feeders of the Kherlen River are the Bogd River, Khoriud, Iluur, Khongon, Terelj, Tenun, Gurvan Saikhan, Zorgol, western and eastern Burkh, Bayangol, Gutai, western, eastern and middle Baidlag, and 37 large and small rivers flowing in the areas of Umnudelger sum of Khentii aimag and Mungunmort sum of Tuv aimag. Below Baganuur, 4 rivers flow into it: Galuut River, Tsenkher River, Avarga River, and Murun River. It flows from the forest-steppe zone of the Khentii Range to the dry steppe zone, and the river is 2020 meters above sea level at its source and 625 meters at its end. Water and meteorological watchmen have been stationed along the Kherlen River and have been conducting regular observations and measurements. Based on the data of the guards, the average flow over many years was determined to be the highest in the Baganuur district, 23.5 m3/second, in the Chinggis city area 21.4 m3/second, in the Choibalsan city area 19.4 m3/second, and in the Altan Emeel city area of China 14.2 m3/second. The water level of the river in the warm season decreases to an average of 200-220 cm in the upper reaches of the river, around Baganuur district, 150-170 in the middle reaches, and 130-160 cm in the lower reaches, around Choibalsan city.