Irrigation Efficiency Calculator

Compare two irrigation systems to see how much water you can save by upgrading. Enter your Net Crop Water Requirement (ET), field acreage, and the efficiency percentages for your current and target systems — including losses to deep percolation, wind drift & evaporation, and field runoff. You'll get the water savings in inches, total acre-feet saved per year, and a breakdown of where those savings come from.

inches/year

The amount of water the crop actually needs (Evapotranspiration). Typically 12–36 inches per year depending on crop and climate.

acres

Used to calculate total acre-feet of water saved per year. Leave blank to see savings in inches only.

%

Overall irrigation efficiency of your existing system (e.g. flood = ~55–65%).

%

Percentage of applied water lost to deep percolation in your current system.

%

Percentage of applied water lost to wind drift and evaporation in your current system.

%

Percentage of applied water lost to field runoff in your current system.

%

Overall efficiency of the irrigation system you plan to convert to (e.g. drip = ~85–95%).

%

Percentage of applied water lost to deep percolation in your target system.

%

Percentage of applied water lost to wind drift and evaporation in your target system.

%

Percentage of applied water lost to field runoff in your target system.

Results

Total Water Savings

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Total Water Saved (Acre-Feet/Year)

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Savings as % of Current Gross Water Use

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Current System Gross Water Requirement

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Target System Gross Water Requirement

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Savings from Reduced Deep Percolation

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Savings from Reduced Wind Drift & Evaporation

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Savings from Reduced Field Runoff

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Water Savings by Loss Category (inches/year)

Results Table

Frequently Asked Questions

What is irrigation efficiency and how is it calculated?

Irrigation efficiency is the percentage of applied water that is actually used by the crop (ET). It is calculated as: Efficiency (%) = (Net ET / Gross Water Applied) × 100. A system with 65% efficiency means 35% of water is lost to deep percolation, runoff, wind drift, or evaporation.

What is Evapotranspiration (ET) and where do I find my value?

ET is the combined water lost from soil evaporation and plant transpiration — essentially what the crop 'uses.' You can find local ET values from your state's agricultural extension office, weather station network (like CIMIS or AZMET), or USDA NRCS irrigation guides. Typical annual values range from 12 inches in cool climates to 48+ inches in hot, arid regions.

What are typical efficiency values for different irrigation systems?

Furrow/flood irrigation typically runs 50–65% efficient. Sprinkler systems range from 70–80%. Center pivots reach 80–90%. Drip and micro-irrigation systems are the most efficient at 85–95%. The difference between systems represents water that can be saved through conversion.

What is deep percolation loss in irrigation?

Deep percolation occurs when more water is applied than the crop root zone can hold, causing water to drain below the roots where it cannot be used by the plant. It is a major source of inefficiency in flood and furrow irrigation systems. While some of this water may recharge aquifers, it represents a direct loss from the irrigation perspective.

How are water savings converted to acre-feet?

Water savings in inches per year are converted to acre-feet using the formula: Acre-Feet = (Savings in Inches × Acres) / 12. For example, saving 10 inches/year on 100 acres equals 83.3 acre-feet of water saved annually. One acre-foot equals approximately 325,851 gallons.

Why might my actual water savings differ from this estimate?

This calculator provides rough estimates based on system-level averages. Actual savings depend on soil type, crop variety, local climate, irrigation scheduling practices, system maintenance, and field topography. For precise assessments, consult a certified irrigation specialist or your local cooperative extension office.

What percentage of savings should I expect from wind drift and evaporation versus runoff?

This varies significantly by system type and climate. Sprinkler systems in windy or hot conditions may lose 10–20% to wind drift and evaporation. Flood systems may lose 5–15% to field runoff. The savings breakdown in this calculator shows which loss category contributes most to your total savings when upgrading systems.

Can this calculator help me choose between multiple irrigation system upgrades?

Yes — run the calculator multiple times with different 'target system' efficiency values to compare scenarios side by side. For example, compare converting from flood irrigation to sprinklers versus drip irrigation. The total acre-feet saved and percentage savings metrics make it straightforward to rank your options by water conservation impact.

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