In 1983 a diagnostic analysis workshop was held in Sri Lanka to present the results of research on existing irrigation systems conducted by 5 interdisciplinary teams chosen from specific Mahaweli project areas. This report contains general descriptions of the study area with regard to location, climate, soils, topography, cropping patterns, socioeconomic conditions, and an operational plan of the irrigation system; describes the disciplinary methodologies used in collecting and analyzing the data; and summarizes the teams' reports, which treated irrigation from viewpoints of agronomy, engineering, economics, sociology, and the role played by women. The findings of each discipline are detailed in the appendices, which also contain a glossary (including abbreviations, definitions of terms, and units of measure) and a list of references used in preparing the report. A total of 49 figures and 58 tables are included.