A triangular concavity enclosed between mountains stretching from the north-west to the south-east form the Lake Sevan basin. The Lake itself is surrounded by the Vardenis ridge from the south, the Geghama ridge from the west, the Areguni ridge from the north-west and the Sevan ridge from the north, ranging from 2,200-3,800 m above the sea level and with average heights from 300-1,800 m above the Lake level. Only in the north-western part of the basin, near the town of Sevan, the watershed line height tends down to the Lake level where the only outflowing river of the Lake, the Hrazdan, begins.

Before the decline of the Lake water level, there was an island in the north-western part of it with 63 m height and 0.3 km2 area. Due to the water level lowering it turned into a peninsula (in 1955), with a rocky hill at the altitude of 1,982.3–meters. in its eastern part.

Continental alpine–steppe climate dominates at the Lake Sevan basin with cold and snowy winters, warm and sunny summers; spring and fall seasons are short. The Lake basin is exposed to intensive UV and solar radiation , accompanied with significant fluctuations of temperature during the day, and strong winds. These factors have their own share in the process of climate formation of the Lake’s catchment basin. Solar hours range from 2,600–2,800 annually.

Different parts of the Lake Sevan basin are distinguished by diverse climatic conditions. The average surface water temperature in summer (July –August) is about +19°+20°C. From time to time the hot sunny weather can affect the water temperature to reach +23°+24°C. In winter, the Lake’s surface can be partly frozen. Occasionally, an extremely cold winter can generate the entire Lake freezing.

The total atmospheric precipitation in the Lake catchment basin averages from 500 mm to 600 mm.

The total catchment area of the lake basin is approximately 4,891 km2, with the surface area of about 1,270 km2 and the shoreline length of about 400 km.

In total 28 rivers and streams, 2 large springs (Lchavan and Lichk) inflow into the Lake. Four tributaries inflow into Minor Sevan, others into Major Sevan.

The 48-km-long Arpa–Sevan and the 21.6-km-long Vorotan-Arpa underground tunnels (exploited since 1981 and 2004, respectively) play an important role in the Lake water balance, transferring the waters of the Arpa and Vorotan riversinto the Lake.

The only outflowing Hrazdan River is turned into a system of canals and streams used for irrigation purposes.

The Lake basin is located in Gegharkunik province. The province is bordering with Tavush (in the north), Kotayk and Ararat (in the west) and Vayots Dzor (in the south) provinces, as well as Azerbaijan (in the east). In total Gegharkunik province includes 5 towns – Gavar, Chambarak (former Krasnoselsk), Martuni, Sevan, Vardenis and 87 rural settlements. The administrative center is the town of Gavar. By its area, Gegharkunik is the largest province of Armenia occupying 18% of its territory. There are 238,000 people living in the province.

Sevan National Park (established in 1978) is located in Gegharkunik province . Its area is included into the central zone of the Lake ecosystem based on the “Law on Lake Sevan” (dated 15 May 2001). The National Park area is divided into 4 territorial-functional zones: national reserves, sanctuaries, recreational zones, economic use zones.

There are 4 national reserves on the Park territory: “Norashen”, “Lichk–Argich”, “Gilli” and “Artanish”, as well as 2 sanctuaries: “Gavaraget” and “Juniper-Oak Relict”. Resorts, hotels, recreational facilities in the recreational area are targeted for individual leisure. The economic zone includes fish farms and forests.