One of the tributaries of the Krishna River in western part of Maharashtra is the Koyna River. It rises near Mahabaleshwar, a famous hill station in the Western Ghats. The river is just 100m wide and flows slowly. Unlike most of the other rivers in Maharashtra which flow East-West direction, the Koyna River flows in North-South direction. The river is famous mainly because of the Koyna Dam, which is built across the river. It is the largest hydroelectric project in the state. The dam is situated in Koyna Nagar, which is in the Western Ghats. Due to its electricity generating potential through Koyna Hydroelectric Project, Koyna River is known as the Life Line of Maharashtra. The 50km long Shiv Sagar Lake is also formed by the river. The river merges with the Krishna River at Karad in Satara district of Maharashtra.

Rich in algae and aquatic plant life, the water of the river has an olive green shade during the dry months and a bluish brown shade during the monsoon months. The impounded water of the Koyna Dam though has submerged a significant amount of Rain forest of the Western Ghats, it has helped a lot to the surrounding forest by supplying water all round the year. Hence a wide biodiversity of plants and animals is observed in the evergreen forest surrounding the river.

Geography and History of Koyna River
Mahabaleshwar is the source of five rivers namely Krishna River, Koyna, Venna, Savitri, and Gayatri. The source is at the Panchganga Temple in old Mahabaleshwar. The legendary source of the river is a spout from the mouth of a statue of a cow in the ancient temple of Mahadev in Old Mahabaleshwar. Legend has it that Krishna is Lord Vishnu himself as a result of a curse on the Trimurtis by Savitri. Also, its tributaries Venna and Koyna are said to be Lord Shiva and Lord Brahma themselves.

Dam on Koyna River
The Koyna Dam is one of the largest dams in Maharashtra. It is a rubble-concrete dam constructed on Koyna River which rises in Mahabaleshwar, Sahyadri Ranges. It is located in Koyna Nagar, Satara district, nestled in the Western Ghats on the state highway between Chiplun and Karad.

The main purpose of dam is hydroelectricity with some irrigation in neighboring areas. Today the Koyna Hydroelectric Project is the largest completed hydroelectric power plant in India having a total installed capacity of 1,920 MW. Due to its electricity generating potential Koyna River is considered as the “life line of Maharashtra”. It has 6 radial gates. The dam plays a vital role of flood controlling in monsoon season.

Koyna Wildlife Sanctuary
Koyna Wildlife Sanctuary is a wildlife sanctuary located near the Koyna River. The sanctuary is nested in the Western Ghats, covering an area of around 423.55 sqkm. It was notified in 1985 as a wildlife sanctuary situated in Maharashtra. It forms the northern portion of the Sahyadri Tiger Reserve, with Chandoli National Park forming the southern part of the reserve. The Sanctuary is well protected by the large extent of Shiv Sagar reservoir and steep slopes of the Western Ghats on both the sides.

The sanctuary has a diverse variety of mammals including the keystone species, Bengal tigers. Also, Indian leopards, Indian bison, sloth bears, sambar deer, barking deer and mouse deer, common Gray langurs, Smooth-coated otters and Indian Giant Squirrels are common. Many species of birds are found in the sanctuary including the distinctive Heart-spotted Woodpecker, Rufous Woodpecker, and Brown-capped Pygmy Woodpecker, Asian Fairy Bluebird, Long-tailed Nightjar and Crested Goshawk. The large reptiles, Indian pythons and King cobras are found here. A unique endemic frog "Bufo koyanansis" has its only habitat in this protected area.

Koyna Nagar - A Town near Koyna River
Koyna Nagar is a town situated on the Chiplun-Sangli state highway on the banks of Koyna River. The town is small but famous for Koyna Dam. Koyna Nagar is nestled in the Western Ghats and hence has a tolerable climate for most of the year. The Nehru Gardens, the Botanical Gardens and Kumbarli Ghat viewpoint are the most popular destinations in the vicinity.