{
  "slug": "irrigation-water-need",
  "title": "Irrigation Water Requirement Calculator",
  "heading": "Irrigation Requirement Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/irrigation-water-need",
  "summary": "Inches of water, gallons, and run time for a field or garden.",
  "description": "Work out the irrigation deficit from evapotranspiration and rainfall, convert it into gallons for your area, and translate that into system run time at your flow rate.",
  "formula": "Deficit = (ET × Kc − rainfall) ÷ efficiency. 1 acre-inch = 27,154 gallons.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=irrigation-water-need",
  "inputs": [
    {
      "id": "area",
      "label": "Area",
      "kind": "number",
      "hint": null,
      "default": 1,
      "unit": "acres",
      "min": 0.001,
      "max": null
    },
    {
      "id": "et",
      "label": "Reference ET this period",
      "kind": "number",
      "hint": null,
      "default": 1.4,
      "unit": "in",
      "min": 0,
      "max": null
    },
    {
      "id": "kc",
      "label": "Crop coefficient (Kc)",
      "kind": "number",
      "hint": null,
      "default": 1.05,
      "unit": null,
      "min": 0.1,
      "max": 1.5
    },
    {
      "id": "rain",
      "label": "Effective rainfall",
      "kind": "number",
      "hint": null,
      "default": 0.3,
      "unit": "in",
      "min": 0,
      "max": null
    },
    {
      "id": "eff",
      "label": "System efficiency",
      "kind": "number",
      "hint": null,
      "default": 80,
      "unit": "%",
      "min": 20,
      "max": 100
    },
    {
      "id": "gpm",
      "label": "System flow rate",
      "kind": "number",
      "hint": null,
      "default": 25,
      "unit": "gpm",
      "min": 0.1,
      "max": null
    }
  ],
  "outputs": [
    {
      "id": "applied",
      "label": "Water to apply (inches)",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "gallons",
      "label": "Total gallons",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "hours",
      "label": "System run time (hours)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "need",
      "label": "Net crop need (inches)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "acreInches",
      "label": "Acre-inches applied",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Area: 1 acres",
      "Reference ET this period: 1.4 in",
      "Crop coefficient (Kc): 1.05",
      "Effective rainfall: 0.3 in",
      "System efficiency: 80 %",
      "System flow rate: 25 gpm"
    ],
    "outputs": [
      "Water to apply (inches): 1.46",
      "Total gallons: 39,713",
      "System run time (hours): 26.48",
      "Net crop need (inches): 1.17",
      "Acre-inches applied: 1.46"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter area (acres).",
      "Enter reference et this period (in).",
      "Enter crop coefficient (kc).",
      "Enter effective rainfall (in).",
      "Enter system efficiency (%).",
      "Enter system flow rate (gpm).",
      "Read your water to apply (inches) on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "area": 0.6,
        "et": 0.84,
        "kc": 0.63,
        "rain": 0.18,
        "eff": 50,
        "gpm": 15
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "area": 1,
        "et": 1.4,
        "kc": 1.05,
        "rain": 0.3,
        "eff": 80,
        "gpm": 25
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "area": 1.6,
        "et": 2.2399999999999998,
        "kc": 1.5,
        "rain": 0.48,
        "eff": 100,
        "gpm": 40
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "Where do I get reference ET?",
      "a": "State extension networks and most weather services publish daily ET₀ by region. Sum it across the days since your last irrigation."
    },
    {
      "q": "What's a crop coefficient?",
      "a": "A multiplier for crop stage. Seedlings sit near 0.3, full canopy near 1.1–1.2, and senescence drops back down."
    }
  ],
  "related": [],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Irrigation Water Requirement Calculator (https://www.revenuelab.fyi/toolbox/irrigation-water-need)"
}