Expert foresees threat to Koyna

Expert foresees threat to Koyna
UNITED NEWS OF INDIA

VISAKHAPATNAM, FEB 2: The killer quake in Gujarat should send a note of caution to the governments of Andhra Pradesh, Karnataka and Maharashtra about a possible breach of the Koyna dam which has been developing cracks due to a string of tremors since 1967, according to noted environmentalist T shivaji Rao.

Since Koyna, like Alamatti and Narayanpur dams, has been designed on the basis of very low seismic coefficients, a catastrophic quake could jolt them, more so considering that their location is on the vulnerable cymatogenic arch of Belgaum-Kakinada, he said in a statement here.

``The latest mapping of earthquake highways and high-risk seismiczones places Koyna and Alamatti in the centre of the high-seismic risk zones of Koyna-Kurudwadi-Bellary triangle,'' pointed out Prof Rao, who is advisor to both the centre and Andhra Pradesh Government on several irrigation and environmental projects.

Alamatti even faces a threat of collapse, along with Narayanpurdam, due to ``serious under-estimation'' of the seismic coefficient used for design of dams, he maintained.

Prof Rao said Koyna was subjected to reservoir-induced seismicity and the recent tremors caused serious cracks in excess of the limits. Due to lack of adequate knowlede on seismic potential of the pertinent locations, most of the dams in the country were under-designed, and ``even Sardar Sarovar project is no exception.''

``The Koyna region is full of shears and small dislocations with a gravity high corresponding perhaps to a mantle upward. It has several hot springs nearby indicating unusual thermal activity,'' he noted.