FLOW MEASUREMENT WITH LONG-THROATED FLUMES UNDERUNCERTAIN SUBMERGENCE

摘要

The evolving circumstances under which irrigation districts operate include growingdemands for more accurate knowledge and accountability of flow throughout theconveyance network, along with increased needs for timely awareness when unexpectedflow conditions are present. For open channel conveyance systems, critical-flowstructures (flumes or weirs) offer the simplicity of a direct correlation between upstreamwater level and a corresponding discharge. Unfortunately at many locations where flowmeasurement is desired there may be insufficient head available for operation of acritical-flow measurement structure under all flow conditions that may occur.In recent years following development of computer-based design and calibrationsoftware, long-throated flumes have gained increasing popularity as the class of criticalflowstructures which offer the greatest submergence tolerance. Numerous long-throatedflumes have been installed at sites where head availability is marginal. In some casesafter a flume has been installed it becomes apparent that the head is not sufficient underall operating conditions for critical-flow measurement. Reclamation’s HydraulicInvestigations and Laboratory Services Group and Yuma Area Office WaterConservation Field Services Program are field testing a system for measuring flow withlong-throated flumes under submerged or unsubmerged conditions.The initial scope this field study targeted specifically selected for continuouslysubmerged conditions. The project scope has been expanded to include occasionallysubmerged sites in recognition that numerous long throated flumes have been installed atsites where submergence conditions that exceed the flume’s modular limit exist undersome operating conditions.