Abstract
The isotopic and chemical studies were carried out in three regions of the Indus Basin to ascertain the source of groundwater salinity. Samples of rain water, river/canal water and groundwater were collected from the Faisalabad area in Rechna Doab, Chaj Doab and Mardan Valley. Electrolytic conductivity (EC) and pH measurements were made in situ while the stable isotopic (δD, δ18O and δ34S) and chemical (major cations/anions) analyses were made in the laboratory. The isotopic and chemical data suggest that salinity in Indus Basin is not of marine origin. Dissolution of salts from soil sediments appears to be the dominant mechanism of groundwater salinization. Evidence is also presented for part of salinity due to evaporation.