The site comprises the valley of the Onon and Balj Rivers in Dadal soum, Kentii aimag. It includes the confluence of the Balj and Galttai Rivers, Ikh Tsagaan and Baga Tsagaan Lake, and the area around Khurkheree Lake, The Onon and Agats Rivers and their confluence. The site supports diverse vegetation types, including steppe, willow groves and numberous small-sized rivers, streams, lakes and ponds. There is no agriculture and the area is used only for livestock pasture and hay making. At present, livestock grazing takes place at a comparatively low level. Tourism is starting to develop rapidly, however, the most serious problem at the site is forest and steppe fires, which often occur is spring when birds are nesting.
The following Globally Threatened species regularly occur at the site: Swan Goose Anser cygnoides (EN, breeding); Baikal Teal Anas formosa (VU, passage); Pallas's Fish-eagle Haliaeetus leucoryphus (VU); Greater Spotted Eagle Aquila clanga (VU); Eastern Imperial Eagle A. heliaca (VU, breeding); Saker Falcon Falco cherrug (EN); Lesser Kestrel F. nuamanni (VU, breeding); Siberian Crane Grus leucogeranus (CR, passage); White-naped Crane G. vipio (VU, breeding); Hooded Crane G. monacha (VU, passage); and Great Bustard Otis tarda (VU, breeding). The site supports an assemblage of species restricted to the Eurasian steppe and desert biome. The site also supports at least 1% of the flyway populations of the following congregatory waterbird species: Swan Goose Anser cygnoides; Ruddy Shelduck Tadorna ferruginea; Common Pochard Aythya ferina; Common Goldeneye Bucephala clangula; White-naped Crane Grus vipio; Demoiselle Crane Anthropoides virgo; and Common Crane Grus grus.
Non-bird biodiversity: Mammals occurring at the site include Daurian Ground Squirrel Spermophilus dauricus, Grey Wolf Canis lupus and Racoon Dog Nyctereutes procyonoides. Rare fish species found in the Onon and Balj Rivers indlude Eastern Brook Lamprey Lampetra reissneri, Amur Sturgeon Acipenser schrenckii, Chadary Coregonus chadary, Haitej Sculpin Mesocottus haitej and Alpine Bullhead Cottus poecilopus.
BirdLife International (2020) Important Bird Areas factsheet: Onon-Balj. Downloaded from http://www.birdlife.org on 28/01/2020.