Based on the need for indexing documents and interest profiles within a selective dissemination of information (SDI) system, the Bureau of Reclamation, Department of the Interior, has compiled this thesaurus of terms related to water resources. Development terms describing design and construction activities, as well as biological and physical science terms related to water resources, are emphasized. The 6,585 terms are arranged according to lead terms, together with both broader and narrower hierarchical relationship terms and related terms. USE references are noted to satisfy desirable standardization requirements. Additional sections in the thesaurus include: (1) an explanation of and examples for using the terms, (2) a subject category index of 22 major subject fields, each of which is subdivided into groups, and in some cases, subgroups, and (3) a hierarchical index displaying those descriptors having no broader terms and having one or more subordinate levels. (BL)