The lake currently covers an area of about 16,400 km2 (6,300 sq mi). However, like the Aral Sea, it is shrinking as a result of the diversion of water from rivers that feed it. The lake is divided by a strait into two distinct parts. The western part is fresh water, while the eastern half is saline. The eastern part is on average 1.7 times deeper than the western section. The largest city near the lake is also named Balkhash and has about 66,000 inhabitants. Major industrial activities in the area include mining, ore processing and fishing.
While the size of the lake is temporarily growing, there is concern about the lake's shallowing due to desertification and industrial activity.
From as early as 103 BC up until the 8th century, the Balkhash polity was known to the Chinese as 布谷/布库/布苏 "Pu-Ku/Bu-Ku". From the 8th century on, the land to the south of the lake, between it and the Tian Shan mountains, was known in Turkic as Jetisu "Seven Rivers" (Semirechye in Russian). It was a land where the nomadic Turks and Mongols of the steppe mingled cultures with the settled peoples of Central Asia.
During China's Qing dynasty (1644–1911), the lake formed the northwestern-most boundary of the Empire. In 1864, the lake and its neighboring area were ceded to Imperial Russia under the Protocol of Chuguchak. With the dissolution of the Soviet Union in 1991, the lake became part of Kazakhstan.