Author
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Replogle, John |
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Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/26/2001 Publication Date: N/A Citation: N/A Interpretive Summary: This paper traces the developments in low-cost, effective flow metering, useable in irrigation and other water resource applications, that have come to fruition mostly in the last few decades. It describes these methods and points out the importance of collateral developments in electronics and computer sciences that have made many of these systems practical for irrigated agriculture. While their roots may trace back to the beginning o the century, and in a few cases to before the millennium, their wide application and use in water management have been relatively recent. Without irrigated agriculture, expansion of cropped land into humid areas would have been needed, and it is doubtful that the rain forests of the world would still exist. We face severe problems in making irrigation efficient enough to outpace the world's population bulge, which is 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. Beneficiaries of this work are agricultural producers and consultants, irrigation water projects, environmental interests, and the public. 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 principals recognized as useable for measuring flows have remained basically unchanged, the range and accuracy of monitoring these physical effects have ebeen vastly improved by collateral developments in electronics and compute 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 latter 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. This extension virtually eliminates concern for vertical elevation of the throat, which can be adjusted to accommodate ditch flow conditions after installation. Other recent developments include the vortex-shedding meters, ultrasonic flow meters of both the Doppler and transonic types, and simplifications of construction and application of Pitot tubes for measuring flow in irrigation wells. |
