Irrigation Efficiency Calculator
Calculate application efficiency, distribution uniformity, scheduling coefficient, and water loss analysis.
About this calculator
Irrigation efficiency isn't one number — this calculator separates out several distinct efficiency metrics that each answer a different question. Application Efficiency (Ea) compares water beneficially used by the crop against water actually applied at the field, capturing losses to deep percolation and runoff during a single irrigation event. Distribution Uniformity (DU), typically measured with catch-can tests, describes how evenly that water lands across the field — a low DU means some areas get soaked while others stay dry even though the average depth looks fine. Because uneven distribution means the driest quarter of the field receives less than the average, the calculator derives a Scheduling Coefficient (100 ÷ DU) — a multiplier telling you how much extra gross water you need to apply so that even the driest spot gets an adequate amount, which is a more honest planning number than average depth alone.
Multiplying Ea by conveyance efficiency (water actually delivered to the field versus water diverted at the source, which accounts for canal or pipeline losses upstream) yields overall system efficiency, the true end-to-end picture. The calculator also splits total losses between deep percolation (water moving below the root zone, unrecoverable and a groundwater contamination risk if it carries fertilizer or salts with it) and surface runoff, based on your estimated split, and multiplies losses out over a full season to estimate total gallons wasted. The comparison against flood irrigation's typical 55% efficiency is a useful benchmark for justifying an upgrade to drip or well-managed sprinkler, but real flood-irrigation efficiency varies widely by field slope and soil type, so treat that 55% baseline as a reference point, not a universal constant.
Inputs
Results
Application efficiency (%)
73.3
Scheduling coefficient
1.33
How to Use This Calculator
- Enter water applied in inches and water beneficially used in inches for your system.
- Set distribution uniformity (DU%) from catch-can tests or manufacturer specs.
- Enter conveyance efficiency percentage for your delivery infrastructure.
- Set field area in acres and number of irrigations per season for seasonal loss estimates.
- Review Application efficiency (%), Scheduling coefficient, and Seasonal water loss (gallons) to identify improvement opportunities.
How the result changes with Water applied (in)
| Water applied (in) | Application efficiency (%) | Scheduling coefficient |
|---|---|---|
| 0.75 | 100 | 1.33 |
| 1.13 | 97.3 | 1.33 |
| 2.25 | 48.9 | 1.33 |
| 3.75 | 29.3 | 1.33 |
What each input means
- Water applied (in)
- Total water depth applied per irrigation event.
- Water beneficially used (in)
- Water stored in root zone and used by the crop (must be ≤ water applied).
- Distribution uniformity (%)
- DU = avg low quarter / overall avg × 100. Drip=85-95%, sprinkler=70-85%, flood=40-70%.
- Conveyance efficiency (%)
- Water delivered to field vs. water diverted. Pipe=95-100%, lined canal=85-95%, earthen=60-80%.
- Deep percolation fraction (%)
- Fraction of losses going to deep percolation vs. runoff.
- Field area (acres)
- Total irrigated area for seasonal loss calculations.
- Irrigations per season
- Number of irrigation events during the growing season.
What each result means
- Application efficiency (%)
- Percentage of applied water beneficially used by the crop.
- Distribution uniformity (%)
- How evenly water is distributed across the field.
- Scheduling coefficient
- Multiplier to ensure driest area receives adequate water (1/DU).
- Overall efficiency (%)
- Combined application and conveyance efficiency.
- Deep percolation loss (in)
- Water lost below root zone per irrigation.
- Runoff loss (in)
- Water lost to surface runoff per irrigation.
- Seasonal water loss (gal)
- Total water lost over the irrigation season.
- Savings vs. flood (%)
- Water saved compared to flood irrigation (55% efficiency).
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersWater applied (in) = 1.5, Water beneficially used (in) = 1.1, Distribution uniformity (%) = 75, Conveyance efficiency (%) = 90 = 7 input(s) provided
- Calculate Application efficiencyApplication efficiency = (waterBeneficiallyUsedIn / waterAppliedIn) * 10073.3 = 73.3
- Calculate Scheduling coefficientScheduling coefficient = 100 / duPct1.33 = 1.33
- Calculate Distribution uniformityDistribution uniformity75 = 75
- Calculate Overall efficiencyOverall efficiency = (applicationEffPct * conveyanceEffPct) / 10066 = 66
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
What's the difference between application efficiency and distribution uniformity?
Application Efficiency (Ea) is a single field-wide ratio: water beneficially used by the crop divided by water applied, capturing losses like deep percolation and runoff. Distribution Uniformity (DU) describes something Ea can't — how evenly that applied water lands across the field. A system can have a decent average Ea while still having poor DU, meaning some areas are overwatered and others underwatered even though the field-wide average looks fine.
Why does low distribution uniformity increase the scheduling coefficient?
The scheduling coefficient is calculated as 100 divided by DU, so a lower DU produces a larger coefficient. It represents how much extra gross water you must apply, above the average target, so that even the driest quarter of the field (which gets less than average under poor uniformity) still receives an adequate amount — the worse the uniformity, the more you have to overwater the whole field just to keep the driest spot from being shorted.
How is overall efficiency different from application efficiency by itself?
Overall efficiency multiplies application efficiency by conveyance efficiency and divides by 100, combining two separate loss points into one end-to-end figure. Application efficiency only accounts for losses at the field (deep percolation, runoff), while conveyance efficiency accounts for losses further upstream in canals or pipelines before water even reaches the field — overall efficiency is the true full-system picture, and it's always lower than application efficiency alone whenever conveyance efficiency is below 100%.
How does the calculator decide how much loss is deep percolation versus runoff?
Total loss per irrigation event (water applied minus water beneficially used) is split using the deep percolation fraction you enter: that fraction of total loss is assigned to deep percolation, and the remainder to runoff. This split isn't derived from the physics of your field — it's a direct input, so its accuracy depends on how well you estimate that fraction from field observation, slope, and soil infiltration characteristics.
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