Environmental isotope studies in the Jalore and Barmer areas show that
deep groundwaters have depleted H-2 O-18 compared to the present day
precipitation and have negligible tritium. Radiocarbon levels indicate
groundwater ages ranging from 2400 to 7400 BP, Shallow groundwaters,
on the other hand, show bomb tritium indicating some component of mode
rn recharge. Studies on the effect of the Indira Gandhi canal on groun
dwater environment helped in differentiating the areas waterlogged by
canal seepage and those affected by return flow of irrigation. A study
on the buried channel of the legendary 'Saraswati' river in Jaisalmer
district indicates shallow waters are old with C-14 content of 54.9 p
MC to 58.8 pMC (uncorrected ages: 4950 to 4400 BP) with a velocity of
about 20 m/a.