| Issyk | |
| Mouth: | Ili |
| Mouth Location: | Kapchagay Reservoir |
| Mouth Coordinates: | 43.7602°N 77.3704°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Kazakhstan |
The Issyk (Kazakh: Есік|translit=Esik) is a river in Kazakhstan that crosses the Issyk Lake (not to be confused with the much greater Issyk Kul Lake in Kyrgyzstan) and the town of Esik. It is a tributary of the river Ili.[1]
One of the largest rivers on the northern slope of the Trans-Ili Alatau, its headwaters come from 32 active glaciers that cover an area of 43km2. The largest glaciers are the Zharsai with an exposed length of 3.8km (02.4miles) and an area of 6.37km2, the Grigoriev with a length of 3.6km (02.2miles) and an area of 5.86km2, and the Pal'gov at 3.8km (02.4miles) long with a surface of 6.95km2. They descend from the crest of the main divide, which has an average absolute height of more than 4000m (13,000feet). Within the mountains the river is 22km (14miles) long, the gradient of its longitudinal profile is 102m (335feet) per kilometer, and the basin area is 210km2.
In its upper reaches the river flows down a very steep slope (10-15°) over the deposits of a moraine overgrown with some vegetation and forms a deep (as much as 70 m) canyon; then, in front of the terminal vegetation-free moraine of the Pal'gov glacier, its longitudinal profile flattens out abruptly_ Here the river forms numerous branches over an outwash plain. Below Lake Akkul' (its absolute elevation is 3,140 m), the longitudinal profile undergoes another sharp drop because a large mountainous obstruction damming the lake and, perhaps, because of moraines buried under the obstruction.
In 1963, the overspill of Issyk Lake caused a large flood.