Rara Lake also known as Mahendra Lake is the largest fresh water lake in the Nepalese Himalayas. It is the main feature of Rara National Park, located in Jumla and Mugu Districts of Karnali Province.[1] Rara National Park stretches over 106 km2 (41 sq mi).

History
Rara Lake was included as part of Rara National Park in 1976. In 1976, citizens of the two villages Chapra and Rara were resettled to Nepalgunj. In September 2007, it was declared as a Ramsar site, covering 1,583 ha (6.11 sq mi) including the surrounding wetland. Currently, this area along with the national park is being protected by the Nepali Army.

Features
Rara Lake lies at an elevation of 2,990 m (9,810 ft), has a water surface of 10.8 km2 (4.2 sq mi), a maximum depth of 167 m (548 ft), is 5.1 km (3.2 mi) long and 2.7 km (1.7 mi) wide. It drains into the Mugu Karnali River via the Nijar River. Its water quality is characterized by high pH, conductivity and total hardness. It has been classified as oligotrophic as it is slightly polluted. The lake changes its colour up to 5 times a day depending on the climate. Rara Lake is surrounded by thickly forested hills named Chuchemara Danda at 4,087 meters and Murma at 3630m. Behind the hills, the beautiful view of Saipal Mountain of Himalayan Range can be seen from the lake. One revolution of the lake by foot takes almost five hours. During, summer season, birds as far as Siberia can be found migrating to this area.

Flora and fauna
Rara Lake, being surrounded by Rara National Park, has unique floral and faunal importance with rare and vulnerable species. The park was established in 1976 to preserve the beauty of the lake and protect it from sedimentation and adverse human activities. The Park flora consists of 1074 species, of which 16 are endemic to Nepal; the fauna includes 51 species of mammals and 214 species of birds. The hills surrounding the lake is covered with coniferous forest like Himalayan cypress, West Himalayan Spruce, Black Juniper and Oak . The national flower of the country Rhododendron can also be found here.

The lake holds three endemic fish species Nepalese snowtrout (Schizothorax macrophthalmus), (S. nepalensis) and the Rara snowtrout (S. raraensis) and one endemic frog, Rara Lake frog (Nanorana rarica). Rara snowtrout (S. raraensis), is the fish recorded only in this lake. 236 different species of birds can be found in the lake. Winter visitor water birds such as gadwall (Anas strepera), mallard (Anas platyrhynchos), northern shoveler (Anas clypeata), common teal (Anas crecca), tufted duck (Aythya fuligula), common golden eye (Bucephala clangula), common merganser (Mergus merganser), common coot (Fulica atra), and solitary snipe (Gallinago solitaria) reside and rest at this lake.

Source:https://en.wikipedia.org/wiki/Rara_Lake