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Parshall Flume Flow Tables

Standard free-flow discharge tables for irrigation infrastructure.

Discharge Table (cfs)
Free-flow discharge (Q in cfs) for standard Parshall flumes. Values are based on standard equations. Verify flume dimensions and ensure free-flow conditions (modular limit typically 70-80%).

Source: Water Measurement Manual, U.S. Dept. of the Interior. Wright Water Engineers, Inc.

1 cfs = 448.8 gpm1 cfs/day = 1.98 AF/day
Accuracy Checklist
  • No water level drop through the flume throat?
  • Level end to end?
  • Level side to side?
  • Entrance conditions satisfactory?
  • Exit conditions satisfactory?
  • Staff gage properly set?
Formulas

3" throat

Q = 0.992hₐ^1.547

6" throat

Q = 2.06hₐ^1.58

9" throat

Q = 3.07hₐ^1.53

12" throat

Q = 3.95hₐ^1.55

18" - 72" throat

Q = 4.00Whₐ^1.522(W^0.026)