Donets River [Donec'], also known as Dinets and Donets Siverskyi (sometimes incorrectly called the Northern Donets owing to the confusion of the Russian severnyi with siverskyi). (Map: Donets River.) The largest tributary of the Don River, it flows into the Don from the right, 210 km above its mouth. The Donets is 1,050 km long and has a basin area of 98,900 sq km. Almost the entire stretch of the river lies within Ukrainian ethnic territory, and 950 km of it lie within Ukraine. The Donets rises in the Kursk region, south of the Central Upland, at an altitude of 215 m. Its upper stretch, above Belgorod, is narrow; farther down, the river attains a width of 100 m and an average depth of 1 m. Below Belgorod the river forms the Pechenihy Reservoir (86 sq km in area), which supplies Kharkiv with water. From there the right bank of the Donets is usually high and frequently dissected (especially the chalk hills called the Holy Hills [Sviati Hory] below Izium). The left bank is flat. About 220 km above its mouth the Donets cuts into the Donets Ridge near Hundorivka. The river basin is asymmetrical, the larger tributaries—Korocha River, Vovcha River, Oskil River, Aidar River, Derkul River, Kalytva River—being distributed on its left side. Of the shorter tributaries on the right side the most important are the Udy River, the Kazennyi Torets River, and the Luhanka River. The Donets derives its waters from rain and snow. The highest water level occurs from February to April. The average water discharge 119 km from the river mouth is 159 cu m/sec. The total annual discharge is 5 cu km. The river freezes at the beginning of December and thaws in mid-March.
The Donets is the main source of water for most of the inhabitants and industry in the Kharkiv oblast and the Donbas. The Donets-Donbas Canal was constructed in 1954–8 to improve the water-supply system. Excessive use of the river's waters has resulted in the lowering of the groundwater level, deforestation, and pollution. About 220 km of the Donets, up to the town of Donetske, is open to ships. Some of the towns that lie on the river are Belgorod, Chuhuiv, Zmiiv, Izium, Lysychansk, and Kamensk-Shakhtinskii.