CHAPTER 1 - INTRODUCTION
The order of chapters, or even sections within chapters, will not match all reader preferences or needs. Readers are not expected to read this manual from beginning to end. Individual readers have their own needs and can find required subjects and sections in the index and table of contents. Also, this manual does not attempt to fully cover advanced water measurement technology or theory. Nor is the manual meant to be a substitute for codes or standards such as International Organization for Standards (ISO) (1975) (1983) (1991) or American Society of Mechanical Engineers (ASME) (1992). These or other standards may be deemed necessary by regulation or management decision. When advance application approaches are needed, the reader should go to references at the end of each chapter. Good office references to have on hand are Bos (1989), which thoroughly covers water measurement devices; Bos et al. (1991) on flumes; and Clemmens et al. (1993), which provides software and excellent discussions of long-throated flumes and broad-crested weir computer design and calibration. The U.S. Government (1980) compiled a handbook containing information and references concerning most kinds of devices and techniques for open and closed channel flow. This publication also contains information concerning developing gaging stations with both permanent and shifting controls, both manmade and natural. The American Society of Mechanical Engineers (1971) and International Organization for Standards (ISO) (1991) provide considerable information on venturi meters and orifices in pipelines and give approach length requirements for various valve and bend combinations upstream from these meters. The Agricultural Research Service (ARS) Field Manual (Brakensiek et al., 1979) has information on H-flumes, triangular short-crested weirs, current metering, and other devices and methods used in agricultural hydrology.