Irrigation Audit Calculator

How the result changes with Mean catch volume (mL)

What each input means

Number of catch cans

Total catch cans placed in the test grid.

Mean catch volume (mL)

Average volume collected across all catch cans.

Low-quarter average (mL)

Average volume of the lowest 25% of catch can readings.

Minimum reading (mL)

Lowest single catch can volume.

Maximum reading (mL)

Highest single catch can volume.

Can diameter (in)

Inside diameter of the catch cans used.

Test duration (min)

How long the system ran during the test.

System flow rate (GPM)

Total system flow rate for waste calculations.

Field size (acres)

Field area being evaluated.

What each result means

Distribution Uniformity (%)

DU low quarter — industry standard uniformity measure. >85% is good.

Christiansen CU (%)

Christiansen's Uniformity Coefficient. >80% is acceptable.

Coefficient of Variation (%)

Statistical variability in application. <15% is good.

Application rate (in/hr)

Average application depth per hour.

Scheduling coefficient

Multiply target depth by this to ensure low areas receive enough water.

Rating (1=Excellent, 4=Poor)

1=Excellent (>90%), 2=Good (80-90%), 3=Fair (70-80%), 4=Poor (<70%).

Over-irrigation factor (%)

Extra water applied to compensate for non-uniformity.

Savings if improved to 90% DU (%)

Water savings potential from improving uniformity to 90%.

Water wasted (gal/hr)

Gallons wasted per hour due to over-application for uniformity.

Mean catch depth (in)

Average catch depth converted to inches.

Max/Min ratio

Ratio of highest to lowest catch — ideally close to 1.0.

How this is calculated

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