Radon/helium survey of thermal springs of Parbati, Beas and Sutlej valleys in Himachal Himalaya

India has more than 300 thermal springs spread over the entire geographical area of the subcontinent. Some of these springs have linkage with Indian mythology and are famous pilgrimage centres since historical times. The temperature of water recorded in these springs varies from 40 degC to that of steam. Some of them are being exploited as a source for geothermal energy. The purpose of this study is to measure radon and helium activity in the thermal springs of Himachal Himalaya. Radon is estimated in the soil and thermal waters using alpha spectrometry and scintillometry, respectively. The radon activity is maximum ( 716.3 Bq/l ) in thermal spring at Kasol and minimum ( 15.9 Bq/l ) in a natural spring ( bauli ) at Takrer. Radon concentration is highly variable in the Parbati valley with minimum value of 2230±430 Bq/m3 recorded at Chhinjra on the banks of river Parbati and a maximum value of 57700±2050 Bq/m3 at Dharmaur, the site of uranium ore exploitation by the AMD (DAE). Helium is estimated in the thermal springs by using a Helium Leak Detector (sniffing technique). The radon and helium contents of Kasol thermal springs are correlatable with high radioactivity in the soil of the area as revealed by Alpha Guard survey in the environs of Parbati valley. The helium content recorded in thermal springs is found to vary between 15-90 ppm. Radon and helium are well established as geochemical precursors for earthquake prediction studies. Helium/radon ratio seems to be a better predictive tool for earthquakes in comparison to individual radon and helium precursors. (author)