As a part of its overall study of the mineral quality problem, the Colorado River Basin Water Quality Control Project (Project) carried out a thorough review and analysis of past water quality data, and made detailed field investigations of present conditions. This Appendix includes a discussion of the factors which affect mineral quality in streams, a description of the statistical methods used in the analysis of existing water quality data and a summary of the findings, a description of the methods employed in the field studies, and a summary of the findings regarding sources of mineral salts within the Colorado River Basin.