The radioactivity concentration of 210Po, 226Ra, and U in Cauvery river basin was analyzed using radiochemical analysis, emanometry, and LED fluorimetry, respectively. Due to transfer with water in cracks and pores, leaching, and heavy usage of phosphate fertilizers, 210Po, 226Ra, and U radionuclides get into the environmental samples studied. The 210Po concentration ranges from 0.7 ± 0.11 to 5.0 ± 0.7 and from 0.83 ± 0.12 to 5.2 ± 0.8 mBq L–1; the 226Ra concentration, from 11.7 ± 1.8 to 62 ± 9 and from 10.5 ± 1.6 to 68 ± 10 mBq L–1; and the U concentration, from 0.08 ± 0.01 to 4.4 ± 0.7 and from 2.0 ± 0.3 to 7.4 ± 1.1 ppb in river and borewell water samples, respectively.