Studies the effect of irrigation return flow on downstream irrigation water quality in the Sevier, Colorado, and Rio Grande river systems, and in the Imperial Valley of Southern California. The report begins by reviewing significant literature on irrigation return flow. Next, water quality criteria are listed, specifically total salt content or conductance, sodium (percentage of total citations), and boron content (parts per million). The impact of various return flow salt, sodium, and boron concentrations on the soil structure in downstream irrigation projects is reviewed. The report next outlines quality measurement procedures and guidelines such as Richard's salinity laboratory classification, Doneen's effective salinity, and Chistiansen and Olsen's suggested ratings. A discussion of salt balance follows, accompanied by an explanation of the leaching requirement. The leaching requirement refers to the amount of irrigation water needed to maintain a salt balance within the root zone of the crops grown. Discussions also include soil weathering, gypsiferous soils, and high sodium content soils. Finally, the report considers irrigation-related water quality changes in the farm regions specified above. A list of conclusions, references, and a brief further commentary on salinity laboratory C-S classification concludes the report.