Tritium concentration in hot spring water, (2)

It is important to know where water is supplied to ground hot spring water system for the conservation of hot springs. In this connection, tritium, a radioactive hydrogen with half-life of 12.3 years, originated from rain water, contains the information of time for the passage through strata. Thus, it provides with an indication of the water supply to hot springs. In the southern portion of Beppu hot springs, there is the regular distribution of waters with high and low tritium concentrations, implying the mix of recent rain water. The findings in the Uchikamado area, an extreme northern portion of Beppu hot springs, are described. While several hot springs have existed along seashore, in the hills behind, the development of hot springs was made relatively recently, thereby the state of tritium is still intact. In the Uchikamado area, the hot spring water presently acquired has stayed long in strata, and the water supply has been at low rate in the behind hilly zone. (J.P.N.)