Irrigation Reference Charts
The data behind good irrigation decisions, in one place: crop coefficients, sprinkler and soil rates, pipe friction loss and lawn water needs. Every value is taken from a named, authoritative source.
How fast spray heads, rotors and rotary nozzles apply water, and the rate you get from any nozzle flow and head spacing.
- Typical rates by sprinkler type
- In/hr and mm/hr charts by flow and spacing
- Run times to apply ¼, ½ and 1 inch
- Formulas and matched precipitation
Sources: Colorado State University Extension; Hunter, Rain Bird and Toro published data
Related tool: Sprinkler precipitation rate calculator
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FAO-56 crop coefficients for 125 crops and crop conditions, from vegetables and cereals to orchards, vines and turf.
- Kc ini, Kc mid and Kc end with crop heights
- Growth stage lengths for US regions
- Climate adjustment formula with worked example
- Building a season-long Kc curve
Sources: FAO Irrigation and Drainage Paper 56, Tables 11 and 12
Related tool: Crop coefficient calculator
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How fast water soaks into sand, loam and clay, and the maximum rate sprinklers should apply on each soil and slope.
- Steady infiltration rates by soil texture
- USDA maximum sprinkler rates by soil and slope
- Comparing your soil with your sprinklers
- How to measure your own soil
Sources: USDA NRCS; University of Maryland Extension; FAO
Related tool: Soil infiltration rate calculator
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Pressure lost to friction in Schedule 40 and Class 200 (SDR 21) PVC pipe from 1 to 150 GPM, with velocities.
- psi per 100 ft for 1/2" to 4" pipe
- Maximum flow for each size at 5 ft/s
- Fitting losses as equivalent feet of pipe
- Hazen-Williams formula and worked example
Sources: Spears Manufacturing engineering data; USDA NRCS Practice Standard 430
Related tool: Irrigation pipe size calculator
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Water use, drought resistance, root depth and weekly watering for 13 warm- and cool-season lawn grasses.
- Water use and drought resistance by species
- Weekly water by grass type at three levels
- How often to water by soil and root depth
- Effects of mowing, shade and fertilizer
Sources: University of California Cooperative Extension, Publication 8395; FAO-56
Related tool: Lawn water requirement calculator
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How we build our reference charts
Each chart is transcribed from its original source, not from memory or other websites, and checked value by value. Where sources disagree, we show them separately rather than blending them, and where a source contains an evident error, we point it out on the page instead of silently correcting it. Calculated values, such as unit conversions and chart cells derived from a formula, are recalculated and spot-checked by hand.
Every chart names its sources, shows when it was last reviewed, and is checked by Daniel Reeves, PE, CID. Our methodology explains the formulas and constants we use. To turn chart values into answers for your own site, browse all calculators. Spotted an error? Let us know.