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Topic "Did you know? Mini knowledge about hot springs"

What is a hot spring?

What is referred to as a hot spring?
I've heard that even cold water can be called a "hot spring".
Is that true?

Simple illustration of a hot spring (summer)

Hot springs are defined by a law called the "Hot Springs Law",
as hot water, mineral water, and steam or other gases that emerge from the ground,
● with a temperature of 25°C or higher when collected from the source or,
● containing one or more of 19 specified substances in a certain amount

and are all referred to as "hot springs".

Therefore, even if the temperature is below 25°C, groundwater containing, for example, a certain amount of carbon dioxide is called a "hot spring". Of course, if the temperature is 25°C or higher when it emerges, it is undoubtedly called a hot spring. In addition to this definition, there is a regulation called the "Guideline for Mineral Spring Analysis" set by the Ministry of the Environment, which provides for "therapeutic springs" (hot springs expected to have effects for the purpose of treating diseases), and hot springs that meet the criteria for therapeutic springs are given a spring quality name.

Definition of "Hot Spring" under the Hot Springs Law

  1. Temperature: 25°C or higher (temperature when collected from the hot spring source).
  2. Substances: (Must contain at least one of the following substances.)
Total dissolved substances
(excluding gaseous substances)
1,000mg or more
Fluoride ion 2mg or more
Free carbon dioxide 250mg or more Hydroarsenate ion 1.3mg or more
Lithium ion 1mg or more Metaarsenite 1mg or more
Strontium ion 10mg or more Total sulfur 1mg or more
Barium ion 5mg or more Metaboric acid 5mg or more
Ferro or ferric ion 10mg or more Metasilicic acid 50mg or more
Manganese ion 10mg or more Sodium bicarbonate 340mg or more
Hydrogen ion 1mg or more Radon 20×10-10Ci or more
Bromide ion 5mg or more Radium salt 1/100,000,000mg or more
Iodide ion 1mg or more    

(Content per kilogram)