Black Water Lake or Lake Khar Us is an one of the largest freshwater lakes in Mongolia located in the Khar Us Lake Basin (Khovd aimag), surrounded by Altai Mountains. Lake length - 72km, width - 26km; total area - 3350 square km; maximum depth - 4.4m (14.4ft). Lake area is home to 9 out of 23 endangered species of mammals that are included in the Mongolian Red Book such as saiga anteloppe, black tailed gazelle, bulrush pig and others. Ornithologists have determined that there are about 200 species of birds of 35 genus, 17 families in Khar Us Lake Basin. Out of that, 134 species migrate from tropical countries, 123 lay eggs, 49 stays in winter and 20 pass through. The 14 of all 19 kinds of birds, that are listed in the Mongolian Red Book such as Dalmatian pelican, spoonbill, whooper swan, swan goose, wild goose, white tailed sea eagle inhabit the area. There are approximately 330 species of vertebrates and 90 of them are mammals, 220 are birds, 11 are reptiles, 8 are fish and 1 is amphibian.