Irrigation Zone Runtime Calculator
ANA›Life Services Authority›National Calculator Authority›Irrigation Zone Runtime Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Irrigation Zone Runtime Calculator
Calculate the required runtime for an irrigation zone based on your plant water needs, system precipitation rate, and distribution uniformity.
Reference Evapotranspiration (ET₀) (inches/week)
Typical range: 0.5–3.0 in/week depending on climate and season
Crop / Plant Coefficient (Kc)
Lawn grass ≈ 0.8, shrubs ≈ 0.5, trees ≈ 0.9, vegetables ≈ 1.0
Precipitation Rate (inches/hour)
Rotary heads ≈ 0.5–1.0 in/hr; spray heads ≈ 1.5–2.5 in/hr; drip ≈ 0.1–0.5 in/hr
Distribution Uniformity (DU) (%)
Well-designed systems: 75–85%; older/poor systems: 50–65%
Irrigation Days per Week
Number of days per week the zone will be irrigated
Effective Rainfall This Week (inches)
Subtract any effective rainfall received; enter 0 if none
Calculate Runtime
function irrCalc() { const resultDiv = document.getElementById("irr-result");
const et0 = parseFloat(document.getElementById("irr-et").value); const kc = parseFloat(document.getElementById("irr-kc").value); const pr = parseFloat(document.getElementById("irr-pr").value); const du = parseFloat(document.getElementById("irr-du").value); const days = parseFloat(document.getElementById("irr-days").value); const rain = parseFloat(document.getElementById("irr-rain").value);
// --- Validation --- const errors = []; if (isNaN(et0) || et0 10) errors.push("ET₀ must be between 0.1 and 10 inches/week."); if (isNaN(kc) || kc 1.5) errors.push("Kc must be between 0.1 and 1.5."); if (isNaN(pr) || pr 10) errors.push("Precipitation rate must be between 0.1 and 10 in/hr."); if (isNaN(du) || du 100) errors.push("Distribution uniformity must be between 10% and 100%."); if (isNaN(days) || days 7 || !Number.isInteger(days)) errors.push("Irrigation days must be a whole number between 1 and 7."); if (isNaN(rain) || rain 10) errors.push("Effective rainfall must be between 0 and 10 inches.");
if (errors.length > 0) { resultDiv.style.display = "block"; resultDiv.innerHTML = "Please fix the following:" + errors.map(e => "").join("") + ""; return; }
// --- Core Formulas --- // Step 1: Crop water need (ETc) for the week const etc = et0 * kc; // inches/week
// Step 2: Net irrigation requirement (subtract effective rainfall) const netIrr = Math.max(0, etc - rain); // inches/week
// Step 3: Gross irrigation requirement (account for DU losses) const duDecimal = du / 100; const grossIrr = netIrr / duDecimal; // inches/week needed from system
// Step 4: Total runtime per week const totalRuntimeHrs = grossIrr / pr; // hours/week const totalRuntimeMins = totalRuntimeHrs * 60; // minutes/week
// Step 5: Runtime per irrigation session const runtimePerSessionMins = totalRuntimeMins / days; // minutes/session const runtimePerSessionHrs = runtimePerSessionMins / 60;
// Step 6: Cycle-and-soak recommendation (max 15 min per cycle to reduce runoff) const maxCycleMin = 15; const cycles = Math.ceil(runtimePerSessionMins / maxCycleMin); const cycleMin = (runtimePerSessionMins / cycles).toFixed(1);
// --- Format helpers --- function fmtTime(mins) { if (mins 0 ? m + " min" : ""); }
const noIrrigation = netIrr " + "Crop Water Need (ETc)" + etc.toFixed(2) + " in/week" + "Net Irrigation Needed" + netIrr.toFixed(2) + " in/week" + "Gross Irrigation (after DU)" + grossIrr.toFixed(2) + " in/week" + "Total Weekly Runtime" + fmtTime(totalRuntimeMins) + " (" + totalRuntimeMins.toFixed(1) + " min)" + "Runtime per Session (" + days + " days/week)" + "" + fmtTime(runtimePerSessionMins) + " (" + runtimePerSessionMins.toFixed(1) + " min)" + "";
if (runtimePerSessionMins > maxCycleMin) { html += "" + "💧 Cycle-and-Soak Recommendation:" + "Run " + cycles + " cycle" + (cycles > 1 ? "s" : "") + " of " + cycleMin + " min per session " + "with a 30–60 min soak period between cycles to reduce runoff and improve infiltration."; } }
html += "" + "Inputs Used: ET₀ = " + et0 + " in/wk | Kc = " + kc + " | PR = " + pr + " in/hr | DU = " + du + "% | Days = " + days + "/wk | Rainfall = " + rain + " in";
resultDiv.style.display = "block"; resultDiv.innerHTML = html; }
#### Formulas Used
1. Crop Evapotranspiration (ETc): ETc = ET₀ × Kc
2. Net Irrigation Requirement: Net Irrigation = max(0, ETc − Effective Rainfall)
3. Gross Irrigation Requirement: Gross Irrigation = Net Irrigation ÷ DU
4. Total Weekly Runtime: Total Runtime (hr) = Gross Irrigation ÷ Precipitation Rate
5. Runtime per Session: Session Runtime = Total Runtime ÷ Irrigation Days per Week
#### Assumptions & References
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