A lake tap involves excavating a tunnel almost to the water/rock contact and then blasting out the final protective rock to allow water to suddenly inflow into the tunnel from the lake. The first lake tapping was carried out at Koyna dam 13 years ago. For the second lake tapping, an additional tunnel, 4 km long, had been excavated, approximately 40 m below the surface of the lake.
This tunnel is expected to carry water with a tremendous force and run turbines to generate 1,000 MW power. The water from the dam is released in Kolkewadi dam.