a city (until 1961, a settlement) under republic jurisdiction and administrative center of Sevan Raion, Armenian SSR. Located on the northwestern shore of Lake Sevan. Highway junction; railroad station 63 km from Yerevan. Sevan has plants manufacturing actuating mechanisms and electrical glass insulation, as well as a tobacco-curing plant. There is an industrial technology technicum in Sevan.

(also Gokcha), a mountain lake in the Armenian SSR and the largest lake in the Caucasus. The area of the lake in 1978 was 1,200 sq km. The average depth is 28.5 m, and the maximum depth, 83 m. The lake lies at an elevation of approximately 1,900 m in the Armenian Highland and is surrounded by mountain ranges—the Pambak in the northwest and the Shakhdag (Sevan) in the northeast; the Gegam and Vardenis ranges border the lake on the west and the south. Sevan occupies the central part of an intermontane tectonic depression. Two capes divide the lake into two sections: a smaller, northwestern, section, called Malyi Sevan, and a larger, widened, southeastern section, called Bol’shoi Sevan; the two sections are connected by a broad strait. Malyi Sevan has the greatest depth (86 m), and its shores are more rugged. The bottom of Bol’shoi Sevan is smooth, the shores are less rugged, and depths range to 35 m. The rocky bluffs of Sevan Island formerly rose above the surface of the northwestern part of the lake. After a portion of the lake water was released, the island became connected with the shore, forming a peninsula. The Sevan Monastery is located on the peninsula.

Twenty-eight small rivers drain into Lake Sevan, and the Razdan (Zanga) River flows out of the lake. The water surface has a deep azure color; the water transparency ranges to 11 m, and the average mineral content is 716 mg per liter. The annual range of fluctuations in level reaches 60 cm, with the highest levels in July and August and the lowest in February and March. In the lake’s water balance, surface runoff (72 million cu m per year) accounts for the largest share; precipitation provides 491 million cu m. Of the lake’s water loss, evaporation accounts for 1,083 million cu m and underground runoff is 85 million cu m; the Razdan River drains 50 million cu m (data on the components of the water balance are adjusted to fit conditions of the lake at its natural level). The average temperature of the surface layer in July and August is 17°-19°C, with a maximum of 24°C; in January and February the temperature is 1.5–1.8°C. For most of the year the water temperature is uniform throughout the lake. The entire lake freezes only in exceptionally cold winters.

Fish caught in Lake Sevan include the Sevan trout, Barbus, Varicorhinus, and the naturalized Onega whitefish. The waters of the lake and the Razdan River are used in the Sevan Hydroelectric System. In order to increase the water resources of the lake and the Sevan Hydroelectric System, a 48.6-km tunnel designed to carry water from the Arpa River to Lake Sevan is being constructed (1977). The city of Sevan is located on the lake. Lake Sevan is a favorite recreation place for the inhabitants of Armenia and a popular tourist area.