Introduction: "The nation's growing determination to control or abate pollution, culminating in the Water Pollution Control Act of 1965 which provided for state water quality standards, has raised many questions about the nature and extent of water quality changes resulting from irrigation. This is a complex subject. It has economic, political, legal, and philosophical implications, as well as physical and technological ones. For more than a century irrigation has been utilized in developing the land and water resources of the West. Recently irrigation to supplement rain and alleviate drought has been initiated throughout the usually humid East. In irrigation, pure water is extracted by the plants from the water supply, resulting in an inevitable concentration of those dissolved solids which are characteristic of all natural water supplies. Other uses add something to the water, but irrigation basically takes some of the water away, concentrating the residual salts. Irrigation may also add substances by leaching natural salts or other materials from the soil or washing them from the surface. Irrigation return flow is a process by which the concentrated salts and other substances are conveyed from agricultural lands to the common stream or the underground water supply. This study is concerned primarily with the physical and chemical processes as they are now understood, with possible ways to alleviate detrimental effects, and with economic and legal aspects of the problem."--P. [1]. Includes bibliographical references (pages 203-237).

Summary generalizations -- Introduction. Development of irrigation in the United States ; Economic importance of irrigation ; Importance and mechanics of return flow ; Nature and extent of the pollution problem of irrigation return flows ; Relation of irrigation return flow problems to present legislative water quality standards and general pollution control problems ; Special problems due to consumptive use -- Irrigation practice. Mechanics of irrigation ; Salt balance concept ; Consequences to irrigation return flow ; Impact of poor water quality on the irrigation farmer ; Principal effect of salinity -- The quality problem. Scope and magnitude ; Water quality requirements for crops ; Nature of pollutants involved ; Sources of pollutants in irrigation water and return flow ; Testing and monitoring -- Effects of pollutants in irrigation return flows on other beneficial uses. Quality requirements for municipal water supplies ; Summary of effects of potential pollutants in irrigation return flows on municipal water supplies ; Quality requirements for industrial water supplies ; Effects of potential pollutants in irrigation return flows on industrial water quality requirements ; Effects of return flow on fish and wildlife ; Water quality requirements for aquatic life ; Water quality requirements for farmstead and lifestock ; Quality requirements for recreational and aesthetic uses of water -- Maximum use and quality management of irrigation water. Maximum use of water for irrigation ; Quality management ; Return flow control ; Desalinization and contaminant removal -- Economic aspects. Economic considerations ; Agricultural income impacts ; Other impacts ; Alternative courses of action ; Selected research and literature on the economics of irrigation return flow and water quality -- Legal aspects. Legal framework for irrigation water use ; Federal views on water rights ; General rules of law relating to waste, seepage and return waters ; Return water ; Legal recognition of water quality criteria ; Legal conflicts between irrigation water rights and water quality standards -- Research needs and recommendations. Quantity of return flow ; Quality of return flow ; Leaching and salt balance ; Precipitation and exchange reactions ; Translating to the field ; Organic wastes ; Thermal pollution ; Matching use to quality ; Treatment and management of return flow waters ; Groundwater ; Public health ; Legal and economic considerations.