For identifying sources of groundwater salinization in Lenjanat Plain, samples were seasonally collected from groundwater, surface water and industrial wastewater. The results of field and laboratory measurements show a gradual increase in major (Na, Ca, Cl, SO4) and minor (Li,Br,Sr،I,Ba،F,Si) elements through groundwater flow direction. Electrical conductivity varies between 561 and 11390 μS/cm. The chloride ion, as an indicator of groundwater salinization, is highly correlated with EC and the elements Mg, Ca,Brand Sr. Certain ratios, the saturation index and geochemical graphs indicate that both the dissolution of evaporation deposits (halite and gypsum) and cation exchange are the most important processes affecting the chemical composition of groundwater. Mass ratios of conservative elements Cl/Br for groundwater samples in Lenjanat plain range from 329 (at the borders) to 4492 (center of the plain). These data confirm the reported Cl/Br ratios for groundwater affected by the dissolution of evaporation deposits but overlap with range of Cl/Br ratios for domestic sewage effluent groundwater.