Irrigation Water Calculator
Calculate water volume needed per acre based on crop water use, soil type, and irrigation method efficiency.
Results
Visualization
How It Works
One acre-inch of water equals 27,154 gallons. The gross application must exceed the net crop need because no irrigation system is 100% efficient — water is lost to evaporation, wind drift, runoff, and deep percolation.
The Formula
Gross Application = Net Deficit ÷ System Efficiency
Total Gallons = Gross Inches × 27,154 × Acres
Pump Time = Total Gallons ÷ (GPM × 60)
Total Gallons = Gross Inches × 27,154 × Acres
Pump Time = Total Gallons ÷ (GPM × 60)
Variables
- Deficit — Inches of water the crop needs (from ET data or soil moisture monitoring)
- Efficiency — Center pivot 85%, drip 95%, flood 65%, sprinkler 75%
- 27,154 — Gallons in one acre-inch of water
Example
130 acres needing 1 inch via center pivot: Gross = 1.18 in × 27,154 × 130 = 4.16M gallons. At 800 GPM = 87 hours pumping.
Tips
- Corn at peak water use (VT-R3) consumes 0.30-0.35 inches per day.
- Soil moisture sensors (watermark, capacitance) are more accurate than ET scheduling.
- Drip irrigation saves 30-40% water vs flood but has higher installation cost.
- Schedule irrigation to avoid runoff — sandy soils hold ~1 inch, clay holds ~2 inches.