Koyena dam is built on the river Krishna. Let's understand this in detail:

Introduction:
Koyena dam is a hydroelectric dam built on the river Krishna. It is located in Satara district of Maharashtra state, India. The dam is named after the river Koyena, a tributary of river Krishna.

Features of Koyena Dam:
- Koyena dam is a concrete gravity dam with a height of 103 meters and length of 807 meters.
- It has a storage capacity of 2,910 million cubic meters of water.
- The dam is used for hydroelectric power generation and irrigation purposes.
- It has four hydroelectric generators with a total installed capacity of 1,960 MW.

Importance of River Krishna:
- River Krishna is one of the major rivers in India, flowing through the states of Maharashtra, Karnataka, Telangana, and Andhra Pradesh.
- It originates from the Western Ghats and flows into the Bay of Bengal.
- The river is an important source of water for irrigation and hydroelectric power generation.
- It is also a major source of drinking water for many cities and towns along its course.

Conclusion:
Koyena dam is an important hydroelectric power project built on the river Krishna. The dam not only generates electricity but also provides water for irrigation and drinking purposes. The river Krishna is a vital source of water for many regions in India and its importance cannot be overstated.

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