Radiochemical measurements of the concentrations of thorium and uranium isotopes were carried out for a total of 10 samples of hot springs, mineral springs and lakes collected in the vicinity of the Nevada Test Site. The uranium to thorium ratios in these water samples were found to be generally much greater than those in soils and in rainwater. The apparent
230Th ages calculated from the
230Th/
232Th and
234U/
238 ratios for most of these water samples were less than 100 years.