Lake Zaysan is a freshwater lake in eastern Kazakhstan. It is located in a hollow between the Altai Mountains to the northeast and the Tarbagatay Mountains to the southwest.
With a surface area of 1,810 km² (700 mi²), it is the biggest lake in the East Kazakhstan Province. In Mongolian it’s called "Zaisan nuur", which means "noble lake". The Chinese border is only 60 kilometers to the east of the lake.
The Oldest Lake in the World?
Lake Baikal, formed about 25-30 million years ago, is generally credited as being the oldest lake in the world. However, Lake Zaysan is thought to exist since the late Cretaceous Period, which would make it at least 65 million years old and the oldest lake on the planet by a long margin. The Cretaceous Period lasted from 136 million years ago to 65 million years ago.
A direct indication of Lake Zaysan’s age is very difficult to find, but modern paleontological and geological studies may suggest that its basin has never dried, which would mean that Lake Zaysan is exceptionally old, formed about 70 million years ago.
The lake is situated at an altitude of 386 meters, it has a length of 105 kilometers and a width between 22 and 48 kilometers. Its maximum depth is 15 meters, and its most important inflows are the Black Irtysh (Kara Irtysh) and Kendyrlyk. The lake’s only outlet (albeit a very important one) is the Irtysh River (the White Irtysh).
The lake is abundant in fish, even though it is frozen from the beginning of November until the end of April. The construction of the Bukhtarma dam on the Irtysh downstream in 1966 has caused the level of the lake to rise with 6 meters (20 ft) above its natural level. Consequently, the lake’s surface area nearly doubled to 3,500 km². The Buqtyrma (Bukhtarma) Reservoir of which it is part of, has a total surface area of 5,500 km².
Ivan Bukholts was the first Russian to reach the area, in his search for gold. However, in 1715 he was driven back by the Oirats, who established the Zunghar Khanate. The Zunghar state was conquered by the Chinese Qing Empire in the 1750s. This created concern in Russia because it was theoretically possible for a Chinese fleet to sail from Lake Zaysan down the Irtysh into Western Siberia. However, the theory was dismissed in 1764 by a Russian expedition at Lake Zaysan.
During the 19th century, the lake was used for fishing expeditions by the Siberian Cossack Host, even though the region was part of the Qing Empire. The Protocol of Chuguchak left Lake Baysan on the Russian side. The Qing Empire’s presence in the Irtysh basin came to an end during the Dungan revolt, which took place between 1862 and 1877.
Fishing is very important in the region. Most important fish species include sturgeon, carp, sterlet, taimen and pike.