What secret is kept by the Irtysh River

The water system of River Irtysh is the 6th longest in the world. Only the Amazon, Nile, Yellow River and Mississippi are longer. The river is born on the eastern slopes of the Mongolian Altai mountains. On the way, it takes in a thousand small rivers, forming a powerful stream, carrying almost 400 km3 of water from the center of the Asian continent to the Arctic Ocean per year.