High Dams in Central Himalaya in Context of Active Faults Seismicity and Societal Problems

India's two highest dams would be located close to the active faults that have been repeatedly reactivated in the Quaternary. These heavy structures are being built in the region of high seismicity where the probability of occurrence of major earthquakes appears to be very high. The probable high-magnitude earthquake will release quite a few hundred times more energy than the earthquakes for which the Tehri Dam is designed. The 50 percent failure probability accepted by the dam builders is at alarming variance with the globally accepted minimum standard of 16 percent (safety level of at least 84%). Impoundment of water in reservoirs upstream of the darns is likely to intensify and trigger landslides in the large reservoir areas particularly in the zones of active faults. Submergence of upstream lands in the most productive and populated valleys in Uttarakhand and western Nepal would cause great loss of forest and agricultural resources. In view of the horrifying implications of high dams it would be prudent to go in for a large number of smaller dams at much lower costs and risks, and which would confer greater benefits to all.