Data from eight evaporation pans containing brines of different salinity and ionic composition were analyzed to quantify the effect of salinity on evaporation. The common procedure of correcting fresh water evaporation by an empirical ratio (α) of salt water to fresh water evaporation rates is shown to be only approximate. A more accurate approach based on the effect of salinity on saturation vapor pressure is described. The activity coefficient of water (β) was computed based on the pan evaporation data. Various analytical methods to compute the effect of salinity on saturation vapor pressure based on ionic composition of the solution are described and applied with Dead Sea data. These approaches can be applied in many engineering applications including water balance calculations for saline lakes, salt production ponds, and evaporation ponds used for disposal of saline effluents.