lake in Armenia, with an area of 525 sq mi (1,360 sq km). Lying at 6,250 ft (1,905 m) above sea level in a mountain-enclosed basin, it drains by the Hrazdan River into the Aras River and to the Caspian Sea, but most of its water is lost by evaporation rather than by runoff. The lake is in two connected parts, the smaller but deeper Maly Sevan (northwest), with a maximum depth of 282 ft, and the Bolshoy Sevan (southeast), reaching 131 ft in depth. The construction of six hydroelectric plants on the Hrazdan led to a fall of the lake level. To stabilize its level, a 30 mi (49 km) tunnel to divert water from the Arpa River was constructed in the late 1970s. Lake Sevan is rich in fish, especially trout, and fishing is important. Several ancient Armenian churches lie along the shores.