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Flow measurement with long-throated flumes under uncertain submergence




Gill, Tom, author
Niblack, Mark, author
U.S. Committee on Irrigation and Drainage, publisher

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The evolving circumstances under which irrigation districts operate include growing demands for more accurate knowledge and accountability of flow throughout the conveyance network, along with increased needs for timely awareness when unexpected flow conditions are present. For open channel conveyance systems, critical-flow structures (flumes or weirs) offer the simplicity of a direct correlation between upstream water level and a corresponding discharge. Unfortunately at many locations where flow measurement is desired there may be insufficient head available for operation of a critical-flow measurement structure under all flow conditions that may occur. In recent years following development of computer-based design and calibration software, long-throated flumes have gained increasing popularity as the class of critical-flow structures which offer the greatest submergence tolerance. Numerous long-throated flumes have been installed at sites where head availability is marginal. In some cases after a flume has been installed it becomes apparent that the head is not sufficient under all operating conditions for critical-flow measurement. Reclamation's Hydraulic Investigations and Laboratory Services Group and Yuma Area Office Water Conservation Field Services Program are field testing a system for measuring flow with long-throated flumes under submerged or unsubmerged conditions. The initial scope this field study targeted specifically selected for continuously submerged conditions. The project scope has been expanded to include occasionally submerged sites in recognition that numerous long throated flumes have been installed at sites where submergence conditions that exceed the flume's modular limit exist under some operating conditions.


Presented at Irrigation district sustainability - strategies to meet the challenges: USCID irrigation district specialty conference held on June 3-6, 2009 in Reno, Nevada.

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