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r` <br />. .. ...~ <br />_.. __~ ____ _-. / { ~ ~~-, rte, <br />2qq SMALL CANAL STRUCTURES <br />~. <br />- <br />... _ - .i ..•1 r <br />. T-'~ ~ I 11 j <br />.. I r, s: I~ ~ ti 11~~~ <br />J ( ~.. ~ i <br />.. '~",~:I~ '~::5 ~'li~r. ill ,t' f'(f//.JJ <br />.'.r lia•,.r 1 i <br />FiSmr t._1, Concrete weir structure with standard i ~,>~ ;'` <br />cunrracteJ Cipolletti weir. PX-D-7261 I ' - ~ <br />~t ~ `f ,~~ r: t Y„s~ ~~ <br />I. :i ., <br />'f .~ r ,•. <br />`°~ ~ <br />tt r <br />Figure S-0. Open-flow meter atlachcd to a <br />concrete pipe. 222-D-JJSgfi <br />B. RARSHALL FLUMES <br />5-2. Drscrrprinn.-Parshall Ilumcs arc <br />speci;illy designed inline open ch;uurcl <br />measuring structures in which carat wafer <br />Ilows over a broad, flat-converging section <br />through ,i narrow downward sloping throat <br />section :uul Ihcn diverges on an upward sloping <br />floor(lig. ti-51. <br />l he Ilnnr of Ihc• converging srclion is Ihr <br />crest of Ihc flume. I[ is Icvrl both <br />Inngiludiicilly and laterally and is usD,dly set <br />ahoy Ihc upslrc:un canal invert. <br />The tlirme geometry lixccs the water at <br />Irco-flow conditions to pass through critical <br />drPth un thr crest, thereby Providing a means <br />of dcirnnining the r;rtc of Ilow Irom a single <br />water depth measurement. Prcc-Ilow <br />conditions occur when Ihc downstream c:mal <br />nailer surface (taihvater) is~low enough to h:rve <br />no alfecl nn Ihr drplh of water on tho crest. <br />Thctic renditions prevail over a wick range of <br />tailwatcr depths. The tailwatcr elevation may <br />be appreciably higher than the flume crest <br />without affecting the free-flow discharge <br />Through the flume. However, i( the <br />,. <br />.. ~ .,.. a• cR \, <br />ONM Gngt w~u."•. -'d=~~ -~•t ''s;t 'ti.'~ ,f, <br />NaaE _ <br />~, ~ . ri,v,,,l; `e <br />~, ~`~',- <br />,. r"~~,,, PARSHALL FLUME ~~ -'~~'• • <br />Figure S-S. Artist xkctch showing Parshatl ^umc <br />in a canal. (,TPX-D-31408. <br />