Author
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Replogle, John |
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Submitted to: National Irrigation Symposium
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/16/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Developments in low-cost, effective flow metering, useable in irrigation and other water resource applications, have come to fruition mostly in the last few decades. While their roots may trace back to the beginning of the century, and in a few cases to before the millennium, their wide application and use in water management has been relatively recent. Without irrigated agriculture, expansion of cropped land into humid areas would have been needed, and it is doubtful that the rainforests of the world would still exist. We face severe problems to really make irrigation efficient enough to outpace the world's population bulge, expected to peak above 10-12 billion people, and still protect the environments of the world in a meaningful sense. The measurement of applied irrigation water has been and will be one of the major links in efforts to improve irrigation management to achieve this needed efficiency. Technical Abstract: A brief historical look at the origins of flow metering in the last millennium is offered that touches on some of the developments we use today in open-channel and pipeline flows. While the basic physical principles recognized as useable for measuring flows have remained basically unchanged, the range and accuracy of monitoring these physical effects have been vastly improved by collateral developments in electronics and computer technology. For example, the ultrasonic properties of a fluid medium have long been recognized, but only in the last decade have the practical and inexpensive means to exploit these properties become available. Some of the newer developments in the later quarter of the past century include the long-throated flume that is computer calibrated. A recent extension to the computer-calibrated flume's repertoire includes the adjustable-throat flumes that aid in placement in earthen channels because they virtually eliminate concern for vertical elevation of the throat, which can be adjusted to accommodate ditch flow conditions after installation. Other recent developments discussed include the vortex-shedding meters; ultrasonic flow meters, both the Doppler type and the transonic types; and a special gated-response Doppler meter that can produce a limited number of point measurements throughout a flow cross-section. |
