Are India's big dams safe?
A recent survey by the Indian government has found out that more than 600 large dams in the country are located in high-intensity seismic zones - areas which are considered to be most vulnerable and prone to earthquakes.
India has more than 30 river basins, each with a catchment area exceeding several thousand square miles. Some 5,000 large dams have been built in 22 of its 29 states. At least 3,000 of these dams have been built in the last 50 years.
In a country where more than half the population is engaged in agriculture, the majority of these dams provide irrigation to some 90 million hectares of farmland. A minuscule 3% of these dams are used as a source for generating hydro-electricity.
Questions, however, have been raised over the safety of these dams after Japan's Fukushima nuclear power plant was devastated by the March 2011 earthquake and tsunami. More than 1,000 people were killed in the region.
Successive Indian governments have maintained that almost all the dams in the seismic zones can withstand any high-intensity earthquake or tsunami and safety reviews have been done on a regular basis.
India's Earth Science Minister Jitendra Singh recently assured the parliament that "not only dams but all nuclear power plants were inspected following the Fukushima incident and they are absolutely safe".
But many experts believe that several Indian dams are too old and becoming increasingly unsafe. They say these dams should be pulled down and replaced by new ones.
They point out that the US, with more than 65,000 small and large dams - some built as early as the 19th Century - has led the world in pulling down old dams and building new ones.
"At least 100 large dams in India were built more than a century ago. Most of these are vulnerable," says Himanshu Thakkar, coordinator of the South Asia Network on Dams, Rivers and People.
Dam disasters are not uncommon in India:
- The Morbi dam in Gujarat state collapsed in 1979 after excessive rain and massive flooding led to the disintegration of the dam's earthen walls. At least 5,000 people died and thousands were displaced in Morbi and Rajkot towns.
- In 2008, a dam on the Saptakoshi river on the India-Nepal border burst, triggering massive flooding in Bihar.
- Indian geologists say reservoir-triggered seismic activity - tremors induced by dams - was one of the reasons behind the earthquake in Maharashtra's Koynanagar in 1969, which left hundreds dead and thousands injured.
- Many say there are "genuine safety concerns" over the disputed 118-year-old Mullaperiyar dam. Although the dam is located in Kerala, the neighbouring state of Tamil Nadu operates it under an agreement to irrigate its farmland. Kerala demanded the dam be demolished as it was "dilapidated". Tamil Nadu insisted that the dam was safe and demanded its water level should be raised. India's Supreme Court has ruled in Tamil Nadu's favour.
Water officials in India say decommissioning dams is a long process and involves building alternative dams in advance - an expensive exercise.
Ashwin Pandya, head of India's Central Water Commission, feels India is a developing economy with increasing population pressure and demands for irrigation and electricity.
"Millions in India depend on agriculture only because the dams are in place. Indeed, their safety needs to be reviewed periodically, but if you bring down the old structures what will happen to people dependent on them for survival?" he says.
A proposed law to provide for surveillance, inspection, operation and maintenance of all dams is yet to be passed by the parliament.
Experts like Ramaswamy Aiyyar say there is not enough research in India before building dams.
"Several dams are in flood prone, landslide prone and geologically weak areas, especially the Himalayan and western Indian region. Since most are man-made and not natural they become hotbeds of dam induced seismicity which means large accumulation of water affecting the movement of earth beneath the surface.
"This leads to frequent high or low tremors in the affected regions," he explains.