The Chu (Shu or Chüy) (, شۋ; , چۉي; (from , Chǔ); ) is a river in Northern Kyrgyzstan and Southern Kazakhstan. Of its total length of , the first 115 kilometres are in Kyrgyzstan, then for 221 kilometres the river is the border between Kyrgyzstan and Kazakhstan and the last 731 kilometres are in Kazakhstan. It is one of the longest rivers in Kyrgyzstan and in Kazakhstan. It has a drainage basin of . The Chüy Region, the northernmost and most populous administrative region of Kyrgyzstan, is named after the river; so are Chüy Avenue, the main street of Bishkek and the city of Shu in Kazakhstan's Jambyl Region. Course The Chu is formed by the confluence of the rivers Joon Aryk and Kochkor, in the Kochkor District of the Naryn Region. After approaching within a few kilometres of Lake Issyk-Kul (near Balykchy), without either flowing into the lake or draining it, it turns towards the northwest. In the 1950s an old riverbed called Ketmaldy (also Buugan) linked the Chu River and Issyk Kul. During floods part of Chu water would reach the lake, but such outflow has not been seen since the construction of the Orto-Tokoy Reservoir. After passing through the narrow Boom Gorge (, Boomskoye ushchelye), the river enters the comparatively flat Chüy Valley, within which lie the Kyrgyz capital of Bishkek and the Kazakh city of Shu. Much of the Chu's water is diverted into a network of canals, such as the Great Chüy Canal, to irrigate the fertile black soils of the Chüy Valley for farming, on both the Kyrgyz and Kazakh sides of the river. As the Chu flows through the Chüy Valley, it forms the border between Kyrgyzstan and Kazakhstan for more than a hundred kilometres, but then it leaves Kyrgyzstan and flows into Kazakhstan, where it flows at the northern edge of the Moiynkum Desert, with lake Kokuydynkol close to its channel . In wet years it may reach the drainless salt lake Akzhaykyn, located among the vast solonchaks of the Ashchykol Depression. History The area of this river was originally home to the Iranian Sughds who spoke Soghdian, an East Iranian language. During the Middle Ages, the area was strategically important. It was the setting of Suyab, the capital of the Western Turkic Khaganate and Balasagun, the capital of the Qara Khitai (Western Liao dynasty). The Chu River posed a risk