Lake Sevan is the largest body of water in both Armenia and the Caucasus region. It is one of the largest freshwater high-altitude (alpine) lakes in Eurasia. The lake is situated in Gegharkunik Province, at an altitude of 1,900 m (6,234 ft) above sea level. The total surface area of its basin is about 5,000 km2 (1,900 sq mi), which makes up 1⁄6 of Armenia’s territory. The lake itself is 1,242 km2 (480 sq mi), and the volume is 32.8 km3 (7.9 cu mi). It is fed by 28 rivers and streams. Only 10% of the incoming water is drained by the Hrazdan River, while the remaining 90% evaporates.
The lake provides some 90% of the fish and 80% of the crayfish catch of Armenia. Sevan has significant economic, cultural, and recreational value. Its sole major island (now a peninsula) is home to a medieval monastery.
Sevan was heavily exploited for irrigation of the Ararat plain and hydroelectric power generation during the Soviet period. Consequently, its water level decreased by around 20 m (66 ft) and its volume reduced by more than 40%. Later two tunnels were built to divert water from highland rivers, which halted its decline and its level began rising. Before human intervention dramatically changed the lake’s ecosystem, the lake was 95 m (312 ft) deep, covered an area of 1,416 km2 (547 sq mi) (5% of Armenia’s entire area), and had a volume of 58.5 km3 (14.0 cu mi). The lake’s surface was at an altitude of 1,916 m (6,286 ft) above sea level.