Pump Discharge For Field Calculator

Work out pump discharge for field instantly with clear inputs, formula shown and shareable results.

About Pump Discharge For Field Calculator

One millimetre of water over one hectare is 10 cubic metres. Multiply the area by the depth to get the net volume, divide by application efficiency for the gross volume the pump must lift, then divide by the hours available to get the discharge rate the pump and delivery pipe have to sustain.

Formulas

Volume

Net volume (m3) = area (ha) x 10,000 x depth (mm) / 1000

Discharge

Discharge (m3/h) = net volume / efficiency / hours; L/s = m3/h / 3.6

Worked example

With the default values below, Pump Discharge For Field Calculator returns Required Pump Discharge of 33.07. Change any input above and every figure here is recalculated in your browser.

Inputs used

Area To Irrigateminimum 0.01 ha: 1 ha
Water Depth To Applyminimum 1 mm: 50 mm
Available Irrigation Hoursminimum 0.1 h: 6 h
Application Efficiencyaccepts 10–100 %: 70 %

Results

Required Pump Discharge: 33.07
Discharge In m3/hour: 119.05
Gross Water Volume: 714.3
Net Water Delivered To Crop: 500.0

Step by step

1Values used
2Volume
3Discharge
4Required Pump Discharge= 33.07
5Discharge In m3/hour= 119.05
6Gross Water Volume= 714.3
7Net Water Delivered To Crop= 500.0

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How do I convert discharge to a pump rating?

Take the required L/s with your total head (suction lift + delivery height + friction losses) to a pump curve. Hydraulic power in kW is roughly 9.81 x L/s x head (m) / 1000, divided by pump and motor efficiency.

Why does efficiency raise the discharge?

Water lost to runoff, wind drift and deep percolation never reaches the root zone, so more must be pumped than the crop receives. Efficiency turns the crop requirement into a pumping requirement.