The oldest hydel project in Himachal Pradesh is Shanan. It was commissioned in 1963. The other options are not correct.
Shanan Hydroelectric Project is a run-of-the-river hydroelectric power station located in the Shanan valley in the Kinnaur district of Himachal Pradesh, India. The project is owned and operated by the Himachal Pradesh State Electricity Board (HPSEB).
The project has an installed capacity of 250 MW and an annual generation of 860 million units. The project uses the water of the Shanan River, which is a tributary of the Sutlej River. The water is diverted from the river through a 10.5 km long headrace tunnel and then through a 120 m high surge tank. The water then flows through a 1,000 m long penstock and then through four Francis turbines to generate electricity.
The project was commissioned in 1963 and was the first major hydroelectric project in Himachal Pradesh. The project has played a significant role in the development of the state’s economy.