Japan’s nuclear accident exposes the dilemma of whether to build power plants on tsunami-prone coasts or inland sites where water supplies are unreliable, a problem likely to be aggravated by climate change, experts say.

Many of the world’s 442 nuclear power reactors are by the sea, rather than by lakes or rivers, to ensure vast water supplies for cooling fuel rods in emergencies like that at the Fukushima plant on Japan’s east coast.

“It’s quite a conundrum,” said Ian Jackson, a nuclear energy fellow at Chatham House in Britain. “If you are in a geologically stable area, a coastal location is still the best option.”