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Irrigation Calculator

Calculate water requirements, design irrigation systems, and create efficient watering schedules. Save water and maintain healthy plants with science-based irrigation planning.

Irrigation Planning Calculator

Measurement System:

Weather & ET Data

Local weather station data

Last 7 days

Distribution uniformity

Irrigation Zones

Zone 1

Cost Analysis (Optional)

Understanding ET & Crop Coefficients

What is ET?

Evapotranspiration (ET) is water lost through plant transpiration and soil evaporation. Reference ET (ETo) is measured from a grass reference surface.

  • Low ET (0.1-0.2"): Cool, humid, cloudy days
  • Medium ET (0.2-0.3"): Typical spring/fall days
  • High ET (0.3-0.4"): Hot, dry, windy summer days
  • Very High ET (>0.4"): Extreme heat conditions

Crop Coefficients (Kc)

Kc values adjust ET for specific plants. Plant ET = ETo × Kc

  • Low Kc (0.3-0.5): Native plants, drought-tolerant
  • Medium Kc (0.6-0.8): Established trees, shrubs
  • High Kc (0.8-1.0): Lawns, groundcovers
  • Very High Kc (>1.0): Vegetables, annual flowers

Irrigation Calculator Guide

Efficient irrigation saves water, reduces costs, and promotes healthier plants. This calculator uses scientific principles including evapotranspiration (ET) and soil water balance to create optimal watering schedules.

Key Irrigation Principles

1. Water Deep but Infrequently

  • Encourages deep root growth
  • Improves drought tolerance
  • Reduces disease problems
  • Saves water compared to daily light watering

2. Consider Soil Type

  • Sandy soil: Low water holding, frequent irrigation needed
  • Loam soil: Ideal balance, moderate frequency
  • Clay soil: High water holding, less frequent but longer runtime

3. Adjust for Conditions

  • Sun exposure: Full sun areas need more water
  • Slope: Steep slopes need shorter, more frequent cycles
  • Wind: Increases ET and reduces sprinkler efficiency
  • Season: Adjust schedules monthly as ET changes

Irrigation System Efficiency

  • Drip irrigation: 85-95% efficiency
  • Rotary nozzles: 80-85% efficiency
  • Rotor heads: 75-80% efficiency
  • Spray heads: 70-75% efficiency
  • Hand watering: 50-70% efficiency

Best Practices

  • Water early morning (4-8 AM) to minimize evaporation
  • Avoid watering during windy conditions
  • Check and maintain system regularly
  • Use rain sensors to prevent overwatering
  • Group plants with similar water needs
  • Mulch to reduce evaporation

Cycle and Soak Method

For clay soils or slopes, use multiple short cycles instead of one long runtime. This allows water to infiltrate without runoff. For example, instead of 30 minutes once, run 3 cycles of 10 minutes with 30-60 minute breaks between.

Seasonal Adjustments

  • Spring: Gradually increase watering as temperatures rise
  • Summer: Peak water needs, may need daily watering
  • Fall: Reduce frequency as temperatures drop
  • Winter: Minimal or no irrigation in many climates

Want Smart Irrigation Recommendations?

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