Irrigation Efficiency
Enter water stored in the root zone and water actually applied to compute irrigation efficiency = (stored ÷ applied) × 100%, assessing system water loss and improvement room.
Input Data
Results
At a glance:Irrigation efficiency measures what fraction of water applied in one irrigation is actually used effectively — the share stored in the crop root zone and available for uptake, as a percentage of water applied. This indicator exists because irrigation water can be lost at every step from source to root: in conveyance, channel seepage, pipe leakage and surface evaporation lose some first; when applied to the field, if the rate exceeds soil infiltration or distribution is uneven, excess ponds and runs off downhill; once in soil, water beyond the root zone's holding capacity percolates below the roots and is too late for the crop (deep percolation); sprinkler also loses to airborne and canopy evaporation and wind drift. Subtracting all these losses, stored-and-used water divided by initially applied water is the irrigation efficiency: efficiency(%) = (water stored in root zone ÷ water applied) × 100. Closer to 100% means less loss and more efficient use. Methods differ greatly: drip/micro-irrigation delivers low-flow water right near the root zone, with little runoff, evaporation or deep percolation, so it is highest, often ~85–95%; sprinkler has good uniformity but airborne evaporation and wind drift, and may run off at high intensity, ~70–85%; surface irrigation (border, furrow, flood) flows by gravity across the field, with early deep percolation and later deficit, lowest uniformity and efficiency, possibly only 40–60%. Low-efficiency diagnosis usually includes: sustained application rate above the soil's instantaneous infiltration (runoff), uneven distribution (low uniformity forces over-application in wet zones to satisfy dry ones, raising deep percolation), conveyance leakage, single irrigation exceeding root-zone storage (inevitable deep percolation), and sprinkling in hot/windy conditions (more evaporation/drift). Improvements target these losses: switch to drip/micro, lower application intensity below infiltration or use intermittent irrigation, raise distribution uniformity (fix clogged/worn emitters, adjust pressure and spacing), control single-application volume and timing to root-zone available water, repair conveyance leaks, and avoid high-evaporation periods. Note that irrigation efficiency, distribution uniformity and leaching requirement are related but distinct: uniformity describes spatial consistency, efficiency the overall effective fraction, and with saline water the deliberately extra leaching water, though counted as deep percolation, is necessary — so separate necessary leaching from pure loss when judging efficiency. Irrigation efficiency is key to planning intake: once the net crop water need is known, gross intake = net need ÷ irrigation efficiency; lower efficiency means more water drawn, directly affecting water cost, energy and resource use.
Formula
Irrigation efficiency(%) = (water stored in root zone ÷ water applied) × 100.
Gross intake from net need: gross intake = net need ÷ irrigation efficiency.
Losses include runoff, deep percolation, conveyance leakage and evaporation/drift.
$$E_{irr} = \dfrac{W_{stored}}{W_{applied}} \times 100\%$$$$W_{gross} = \dfrac{W_{net}}{E_{irr}}$$How to Use
- Measure or estimate the water actually stored in the root zone after one irrigation (applied water minus runoff, deep percolation, evaporation).
- Enter the total water actually applied that time (same unit as stored water).
- The tool returns irrigation efficiency(%) for reading system loss, comparing methods and planning intake.
Typical efficiency and intake multiplier by method
| Method | Typical efficiency (%) | Applied for 40 mm net need (mm) |
|---|---|---|
| Drip / micro | 90 | 44.4 |
| Sprinkler | 78 | 51.3 |
| Furrow | 65 | 61.5 |
| Flood | 50 | 80.0 |
| Example (45/60) | 75 | 53.3 |
Lower efficiency needs more intake for the same net need; intake = net need ÷ efficiency.
Case Studies
Efficiency from applied and stored water
An irrigation applied 60 mm; root-zone storage gain measured ~45 mm, the other 15 mm lost to runoff and deep percolation.
Irrigation efficiency = 45 ÷ 60 × 100% = 75%.
Mid-to-high (near sprinkler level); improving uniformity and application intensity still has room.
Back-calculate intake from efficiency
Crop net need that time is 40 mm; system efficiency 75%.
Gross intake = 40 ÷ 0.75 ≈ 53.3 mm — about 53 mm must be applied to refill 40 mm in the root zone.
Switching to 90%-efficient drip needs only 40 ÷ 0.90 ≈ 44.4 mm, saving about 9 mm of intake.
FAQ
Is irrigation efficiency the same as distribution uniformity?
Related but not the same. Distribution uniformity (DU) describes how consistently water is applied across the field; irrigation efficiency describes what fraction of applied water is effectively used (stored in the root zone). Poor uniformity forces over-application in wet zones to satisfy dry ones, raising deep percolation and lowering efficiency, so improving uniformity usually also raises efficiency — but they are different metrics.
Why is drip so much more efficient than flood irrigation?
Drip delivers low-flow water right at the root zone, producing almost no surface runoff, little evaporation or drift, and less deep percolation, so the effective fraction is high (~85–95%). Flood irrigation lets water flow across the field by gravity — early zones percolate too deep, later zones often lack water; poor uniformity and much deep percolation/runoff give only 40–60%. The different loss mechanisms cause the efficiency gap.
How do I improve low efficiency?
Treat the cause: lower application intensity below the soil's instantaneous infiltration or use intermittent irrigation (less runoff); repair clogged/worn emitters and adjust pressure/spacing (raise uniformity); control single-application volume to root-zone available water (less deep percolation); fix channel and pipe leaks; avoid sprinkling in hot/windy periods (less evaporation/drift). Upgrade to drip or micro if necessary.
Does leaching water count as loss when computing efficiency?
Leaching water is counted as deep percolation and looks like loss, but with saline water or saline soils this part is deliberately used to flush root-zone salts away — 'necessary water', not waste. When judging efficiency, separate necessary leaching requirement from purely ineffective loss, otherwise you underrate the system's reasonable performance.
How do I measure water stored in the root zone?
Commonly measure the change in root-zone soil water content before and after irrigation (tensiometers, TDR/FDR sensors, or oven-dry samples), converted to water depth — that is the actual storage gain; or infer it as applied water minus observed runoff and deep percolation. Field measurement has error, so average multiple points and place sensors at representative spots.
Related Tools
References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.