The Tokyo Metropolitan Government will regulate drilling for new hot springs in the capital, alarmed that a recent rush by developers to build spas might cause the water supply to dry up and the land to sink.
A panel of experts studying the ramifications of “onsen” (hot spring) facilities released a report last month, recommending that developers drilling 500 meters or deeper in the ground for new onsen to get consent from operators within a 1-km radius to ensure that the water paths do not dry up.
It also recommends the metro government limit the amount of underground water pumped into homes.
While little is known about the groundwater mechanism, it can take a long time to replace the groundwater once it’s drained, as it originates in rainwater and seawater from long ago. If the water under Tokyo is drained, the ground could sink, metro official Hirohisa Kato said.
In a decade through March, the number of onsen drilled or waiting for government approval has doubled to 82. Of those, 27 took water from 500 meters or deeper in the ground, Kato said, adding that even some condominiums are being equipped with hot-spring baths.
Last year, three major theme parks opened in Tokyo with onsen as their main attractions.
The therapeutic value of the water in the new spas is unknown, Kato said, pointing out that the Hot Spring Law qualifies any natural water source with temperatures of 25 or more as an onsen.
“In Tokyo, if you dig deep enough, you can easily get water warmer than 25 degrees,” Kato said. “Whether that water has an effect is another issue.”
Based on the report, the metro government will soon release an outline of regulation details, he said. (T.O.)
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