Submitted to: US Committee on Irrigation and Drainage/Environmental and Water Resources Institute Conference
Publication Type: Proceedings
Publication Acceptance Date: March 1, 2002
Publication Date: July 13, 2002
Citation: Replogle, J.A. 2002. Correcting unreliable velocity distributions in short culverts and canal reaches. US Committee on Irrigation and Drainage/Environmental and Water Resources Institute Conference. p. 129-141. Interpretive Summary: Good water measurement is an important part of water conservation activities. Field conditions often force installation of pipe flow meters and canal flow measuring flumes closer to upstream disturbing devices, such as elbows, valves, and canal curves, than specified by standard installation recommendations. Because of the increasing emphasis on quantifying flow rates and volumes in existing water resource projects, retrofit applications are more common than new designs, are usually difficult, and require innovation to achieve suitable results within the space and sizing limitations imposed. This discussion summarizes several options currently available to irrigation districts and municipal well operators who are faced with the need to retrofit existing pumping systems with flow meters when standard installation requirements cannot be met, and describes efforts to improve on these options in terms of effectiveness and economics. This in turn will allow economical upgrading of water management facilities to conserve water and energy.
Technical Abstract: Irrigation water management increasingly depends on good water flow measurement. Too frequently, flow disturbances from upstream elbows, the well pump, or other pipe fittings, produce distorted flow profiles that are detrimental to the proper installation and operation of common flow meters used in pipes, and the flumes and weirs used in canals associated with irrigated agriculture. Field conditions often force installation of pipe flow meters and flumes closer to these upstream disturbances than specified by standard installation recommendations. Special methods to condition flows to generate usable flow profiles over short distances are commercially offered for pipes meters. Less expensive methods have been used in irrigation applications, but have been only partially studied to define their application limits. The historical installation recommendations for pipe meters and flumes are summarized and still recommended for inclusion in future constructions. For retrofit situations the field experiences and limited laboratory information on alternate approaches are presented. Suitable flow profiles for acceptable metering results in pipes can be obtained at distances about one-half to one-third the usual, historical, pipe-length requirements. These profiles, while nearly symmetrical, may be more uniform, or piston-like, than the fully-developed shape.