The basin of the Arctic Ocean occupies 20.4 percent of Mongolia's territory. The river, Selenge and Khuremtei with its tributary rivers Ider, Delgermurun, Eg and Shishkhed are included in the basin.
Selenge River
The River Selenge begins from the confluence of the rivers Delger murun and Ider and this is the main tributary of Lake Baykal in Russia. The Selenge has a drainage area of 425,245 square kilometres of which 282,050 square kilometres or 66 percent flows in Mongolia's territory. The Selenge's length is 1024 kilometres.
Orkhon River
This is the biggest right hand tributary of the Selenge.The river has a drainage area of 132,855 square kilometres and it occupies 47 per cent of the basin of River Selenge. The Orkhon is 1124 kilometres long and is the longest river in Mongolia. The source of the river's basin is the north-western side of the Khangai Mountain. Mongolia's biggest waterfall Ulaan Tsutgalan is situated there. The rivers Tuul and Kharaa drain into the Orkhon.
The Pacific Ocean basin's major rivers are the Onon, Ulz, Khalkh and Kherlen, which are tributaries of the Ytil< hull tit pasture River Amar. The total length of the rivers with permanent flow is about 2000 kilometres and if rivers with seasonal flow were included, the total length would be about 8,000 kilometres.
