Tamagawa Hot Spring

The Tamagawa Hot Spring in Senboku, Akita Prefecture, Japan is the highest flow rate hot spring in Japan. Tamagawa Hot Spring has a flow rate of 150 liters/second. The Tamagawa Hot Spring feeds a 3 meter wide stream with a temperature of 98°C. The water from Tamagawa Hot Spring is also very acidic, with a pH of about 1.1. There is also radioactive radium gas and other radioactive materials dissolved in the water from Tamagawa Hot Spring.

There are deposits of the radioactive mineral hokutolite near the spring. Hokutolite is composed of a type of barite (barium sulfate), including lead and traces of strontium and calcium. The hokutolite is about ten times as radioactive as the standard background. There is at least one more hot spring in Tamagawa. Nibukawa Hot Spring is also in Tamagawa.