Turnout Flow Calculator | Duck Valley Irrigation

1. Gate size

2. Flow condition

Which one do I pick?

Free flow: water on the downstream side is below the top of the gate opening — water pours out freely.
Submerged: the outlet is drowned — downstream water is above the top of the gate opening. You need the water level on both sides for this one.
Pipe not full: if the water is below the top of the pipe and the opening isn't fully covered, use Pipe Not Full.

3. Gate opening

inches

How far the gate is open, from your calibrated stem (zero the stem with the gate fully closed).

4. Staff gauge reading (upstream)

feet

My gauge is zeroed at:

4. Change in head (ΔH)

feet

Upstream water surface minus downstream water surface, in feet.

Calculate ΔH from two gauge readings

Upstream reading (ft)

Downstream reading (ft) — same datum

Both gauges must be set to the same level (datum). ΔH fills in automatically.

3. Water depth in the pipe

feet

My staff gauge is zeroed at:

Reading is the water depth above the bottom (invert) of the pipe.

Calibration coefficient C

Leave at 1.00 unless this turnout has been field-calibrated. Tune per turnout with a current meter.

Field-calibrate C from current-meter measurements

Enter measured depth and metered flow pairs for this turnout. The best-fit C makes the formula match your meter.

Depth h (ft)	Measured Q (CFS)