Irrigation efficiencies should be raised to the highest practical level in any river basin to assure that the maximum volume of high quality water is available for all conjunctive users. Changes in irrigation efficiency must be considered as a part of basin-wide water management plans and not simply as a solution to a local problem. Application of the leaching fraction concept, to the natural system as well as to the irrigation system hydrology, will put irrigation system improvements in the proper perspective as salinity control measures.