Ogii Lake is located in the valley of the Orkhon River, 350 km west of Ulaanbaatar. The site is a mesotrophic, freshwater lake with an extensive alluvial plain. The Khogshin Orkhon River enters the lake from the west. A small river, Khooloin Gol, drains the lake. There are extensive wet grasslands along the valleys of these rivers, and small pools and marshy areas along the western side of the lake. The remainder of the site comprises grassland and mountain steppe. Intensive livestock grazing takes place throughout the year. A small-scale commercial fishery operates in winter, and recreation and tourism activities are on the increase. Overgrazing, grassland degradation in dry summers, poorly managed tourism activities and steppe fires pose serious threats to the site. The IBA contains Ogii Lake Ramsar Site.
The site regularly supports significant populations of the following Globally Threatened species: Dalmatian Pelican Pelecanus crispus (VU); Swan Goose Anser cygnoides (EN); Baikal Teal Anas formosa (VU); Pallas’s Fisheagle Haliaeetus leucoryphus (VU); Lesser Kestrel Falco naumanni (VU); Siberian Crane Grus leucogeranus (CR); White-naped Crane G. vipio (VU); Hooded Crane G. monacha (VU); Great Bustard Otis tarda (VU); and Relict Gull Larus relictus (VU). The site also supports at least 1% of the flyway populations of the following congregatory waterbird species: Great Crested Grebe Podiceps cristatus; Whooper Swan Cygnus cygnus; Swan Goose Anser cygnoides; Bar-headed Goose Anser indicus; Ruddy Shelduck Tadorna ferruginea; Common Goldeneye Bucephala clangula; Common Crane Grus grus; and Northern Lapwing Vanellus vanellus.
Non-bird biodiversity: Siberian Marmot Marmota sibirica (EN), Grey Wolf Canis lupus, Corsac Fox Vulpes corsac, Red Fox V. vulpes and Pallas's Cat Felis manul (NT) occur around the lake. Fish are abundant at the site, and include the nationally threatened Taimen Hucho taimen and Mongolian Grayling Thymallus revirostris.