The purpose of the USDA Natural Resources Conservation Service Water Resources Handbook for Economics is to provide guidance for the economic analysis of water resource projects. Established economic theory and principles, and the economic concepts stated in the Economic and Environmental Principles and Guidelines for Water and Related Land Resource Implementation Studies (P&G) serve as the primary foundation for this document. P&G was issued March 10, 1983, by the Water Resources Council. The economist must blend the economic principles with a good sense of practicality. To encourage the economist to be creative and to allow for differences between projects, the handbook is not intended to be a "cook book." The first Economics Handbook for Water Resources was published in 1958 and then revised in 1964. Draft revisions occurred in 1974, 1987, and 1992.