Reports from India say that new cracks in the Koyna dam may have affected the integrity of the structure in the Indian state of Maharashtra. The dam is located on the Koyna river upstream from the state of Karnataka. The government of Karnataka has urged the federal government of India to intervene to ensure the safety of the dam and lower states. Downstream of the Koyna dam are major dams such as the Alamatti, Narayanpur and Nagarjuna Sagar dams, and the Srisailam project.
The new cracking is attributed to two earth tremors which struck the Koyna-Warna region some 200km south of Bombay, in early September. The two quakes which measured at 5.0 and 3.5 on the Richter scale, were located within a 12km radius of the Tandoli and Koyna dams.
The 103m high Koyna concrete dam was completed in 1964. The dam site in western India has been seismically active since impounding of the reservoir.
Seismicity peaked in 1967 when an earthquake of magnitude 6.3 killed 200 people and damaged much of the Koyna Nagar town. Subsequently, bursts of seismicity have occurred during 1973, 1980 and 1993 to 1995.
Data obtained from monitoring the area suggests that the epicentres of recent quakes are concentrated around the newly impounded Warna reservoir with a head of over 60m.
The Koyna multi-purpose project (stages I to IV), with a total installed capacity of 1920MW, is expected to serve as a peaking station. The 1000MW stage IV of the project is nearing completion while stage V, which envisages the generation of 400MW, is still in the planning stage.