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Trapezoidal Flumes for Measuring Flow in Irrigation Channels

Robinson, A.R. (1968) Trapezoidal Flumes for Measuring Flow in Irrigation Channels. USDA-ARS No. 41-140. 15 pp.

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Experience and research have shown that,
in many respects, trapezoidal flumes are
superior to the rectangular or Parshall-type
flumes, particularly for measuring_ smaller
flows. The shape conforms to the normal
shape of ditches, particularly those that are
lined. This minimizes the amount of transition
section needed as compared to that required
when changing from a trapezoidal shape to a
rectangular one and back to the trapezoidal.
The trapezoidal shape is also desirable since
the sidewalls expand as the depth increases.
This means that one structure can convey a
larger range of flow. Also, the entire range
of depth for a given range of discharge is

Operational characteristics of trapezoidal
flumes are also superior. Generally, less
backwater will result and a shallower section
Will be required than for a rectangular shape.
Another desirable feature of the trapezoidal
flume is the flat bottom throughout rather
than a dropped section such as with the
Parshall flume. No particular advantage of a
crest section with a drop in the floor such
as that in the Parshall flume has been found.
The trapezoidal flume will operate under a
higher degree of submergence than the Parshall
flume without corrections being necessary.
The loss in head, i.e., total head loss, through
the trapezoidal structure, may be less for
comparable discharges.

Item Type: Technical Bulletin
NWISRL Publication Number: 0097
Subjects: Research methodology
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:57
Last Modified: 15 Mar 2017 21:47
Item ID: 1107