The first lake tap at Koyna was done under the supervision of Norwegian experts on March 13, 1999. It was a first-of-its-kind project in Asia and added nearly 1,000 MW of power generation then The second lake tapping will enable the phase IV of the Koyna hydro-electric project to generate power during summer. “The existing system prohibits power generation in the event of the Koyna water level going below 630-metre mark,” Deepak Modak, chief engineer of Koyna irrigation project, told reporters “With the new tunnel, power can be generated till water level touches 618 metre,” he added.
Chief minister Prithviraj Chavan, deputy chief minister and power minister Ajit Pawar and water resources minister (Krishna Valley Development Corporation Ltd) Ramraje Naik-Nimbalkar will attend the second lake tapping exercise at Koyna. The Koyna dam is located 193 km southwest of Pune. Primarily built for power generation, the dam water is also used for irrigation. After the water distribution tribunal set up in late 1990s, some 25 TMC water from the dam is to be given to Tembhu, Takari and Mhaisal lift irrigation projects, which are expected to benefit the drought-prone areas of Satara and Sangli districts.
Modak said, “The minimum water level of the dam was 630 m for phase IV. After the decision of the tribunal to supply water for Tembhu, Takari and Mhaisal lift irrigation, we decided to excavate another tunnel under the reservoir, which would be deeper than the existing one. The new tunnel is called 4-B. It is to be excavated at a deeper level and can carry water with sufficient pressure in summer also. The reversible turbines are used for power generation, which are also known for their higher efficiency.”
The total storage capacity of the dam is 105.25 TMC and since 1962, the dam water level had not gone down below 618 metre.
The cumulative power generation from the first three phases of Koyna project is 960 MW. The fourth phase would generate 1,000 MW power. Construction of the dam started in 1956, with the first two phases costing Rs 65.29 crore, followed by Rs 61.70 crore for the third phase. The fourth phase, the existing tunnel and its power plant cost Rs 1,526 crore, whereas the 4-B phase is expected to have a total investment of Rs 600 crore. So far, Rs 582 crore has been spent.