Irrigation

Sprigg's irrigation engine is the heart of the platform. Every day, it analyzes weather data, disease risk, soil conditions, and your water budget to generate per-zone watering recommendations. This page explains how it all works.

The Zones Page

The Zonespage in the main navigation shows one card per zone: its current state (watering now, watering today, resting, or skipped), weekly water progress split into rain and irrigation, the most recent run, and the latest zone photo. Today's full plan and Sprigg's reasoning stay on the Home page; the full run and decision history lives on the Irrigation History page, linked from the Zones page. See the Zones docs for the overview page, zone detail, and the Science panel.

How the AI Advisor Works

Each day, Sprigg runs an analysis cycle for your property. The AI advisor (powered by Claude) receives a comprehensive data package and produces zone-by-zone watering recommendations.

Input Data

The advisor considers:

• Current weather — Temperature, humidity, wind speed, dew point, cloud cover
• 5-day forecast — 3-hour interval forecasts including precipitation probability
• Disease risk scores — Per-disease risk levels based on temperature and humidity patterns
• Root-zone soil moisture — A per-zone estimate of how much water is actually available to the roots (the advisor's preferred hydration signal)
• Weekly water budget — Target vs. applied vs. rainfall for each zone
• Run history — Last 7 days of irrigation events from your controller
• Calendar events — Recent and upcoming lawn care activities (e.g., fungicide applied, aeration scheduled)
• Property context — Grass type, USDA zone, region, soil type, expertise level

Output

For each zone, the advisor produces:

• Whether to water or skip
• Runtime in minutes
• Number of cycles and soak time (for sloped zones)
• Estimated water amount in inches
• Suggested start time
• Detailed reasoning (multiple bullet points explaining the decision)

Active vs. Audit Mode

Sprigg supports two irrigation modes that control how recommendations are acted upon:

Start in Audit modeto review Sprigg's recommendations for a few days before switching to Active mode for fully automated irrigation.

Daily Recommendation Flow

Here's what happens behind the scenes each day:

1. Cron trigger — An hourly cron job checks which properties are due for analysis, sharded by timezone to avoid thundering herd issues.
2. Data collection — Weather, forecast, disease risk, water budget, and run history are gathered for the property.
3. AI analysis — The data package is sent to Claude Sonnet, which generates per-zone recommendations with detailed reasoning.
4. Safety validation — Recommendations are validated against safety constraints (max 0.75" per event, min 0.05" per event).
5. Storage & notification — Results are stored in the analysis history and the user is notified.
6. Execution (Active mode only) — Watering commands are queued and sent to your controller, with retry logic for failures.

Manual Watering

You can manually water zones at any time, regardless of mode. Go to the Irrigation History page and use the manual watering controls to:

• Start a specific zone for a set duration
• Log manual watering you've already done (enter inches or duration)
• Stop all running zones

Manual watering is tracked in your water budget, so Sprigg accounts for it in future recommendations. You can also use the Ask Sprigg chat to start and stop zones with natural language.

Soil Moisture Tracking

Sprigg models the moisture in each zone's root zone like a bucket: rainfall and irrigation fill it, and daily evapotranspiration drains it. The bucket's size comes from your soil type's water-holding capacity and the zone's root depth, reconstructed from the last 21 days of weather and watering history.

When the modeled moisture drops below the allowable depletion threshold, the zone genuinely needs water; when it's still comfortably full, watering can safely wait — even if the weekly budget says the zone is "behind". The advisor treats soil moisture as its preferred hydration signal, with the weekly water budget as a supporting guardrail.

If you have Ecowitt soil-moisture sensors mapped to your zones, their live readings override the modeled estimate — a real probe in the ground always beats a model. See the Integrations page for setup.

Water Budget

Sprigg tracks a weekly water budget for each zone to ensure your lawn gets the right amount of water — not too much, not too little.

How the Target is Calculated

The weekly water target starts from your configured base (default 1.0"/week) and is adjusted by:

• Evapotranspiration (ET) — Actual ET from weather stations or estimated via the Hargreaves method, scaled by a 0.8 crop coefficient
• Shade factor — Shaded zones need less water (0.5x to 1.0x adjustment)
• Seasonal patterns — Based on latitude and day of year

Budget Tracking

For each zone, the budget tracks:

• Target inches — Adjusted weekly target
• Applied inches — Water delivered by irrigation
• Rainfall inches — Effective rainfall captured (adjusted by soil type efficiency)
• Remaining inches — What's still needed this week
• Pace status — Compares actual progress to expected progress for the day of the week

Pace Status Levels

Cycle-Soak

For zones on slopes or with compacted soil, applying water too fast causes runoff. Sprigg automatically splits long watering sessions into shorter cycles with soak periods between them.

The cycle-soak calculation considers:

• Soil infiltration rate — How fast water absorbs into the ground
• Precipitation rate — How fast your sprinklers deliver water
• Slope factor — Steeper slopes reduce effective infiltration
• Zone efficiency — Runtimes are corrected for how efficiently each zone's sprinklers actually deliver water, so the prescribed inches really land on the lawn

If the precipitation rate exceeds the infiltration rate, Sprigg splits the watering into cycles where each cycle delivers only as much water as the soil can absorb, then pauses for a soak period to let it soak in before the next cycle.

Wind-Adjusted Runtimes

On breezy mornings, spray heads lose part of their water to drift and evaporation before it ever reaches the lawn. Sprigg extends runtimes slightly to make up for that loss, so the inches prescribed are the inches that actually land.

How it works:wind degrades each zone's effective application efficiency, and the adjustment is capped at about a 25% runtime increase. Beyond roughly 15 mph, running longer mostly throws more water into the drift stream — at that point the right fix is rescheduling to a calmer window, not a longer runtime.

Frost & Freeze Alerts

When frost or a hard freeze shows up in your 5-day forecast, Sprigg warns you ahead of time and adjusts its advice: skip evening irrigation before a frost night (water on foliage freezes and worsens leaf damage), and hold off on nitrogen until the risk passes (late nitrogen pushes tender growth that frost damages most). You can toggle frost warnings in notification settings.

How it works: Sprigg follows National Weather Service agricultural conventions — forecast lows at or below 36°F allow radiative frost to form on turf (leaf surfaces run a few degrees colder than the air on clear, calm nights), and 32°F or below is treated as a hard freeze, where ice forms in leaf tissue.

Winter Dormancy

Dormant grass doesn't need a weekly water target, and Sprigg knows it. When your lawn goes dormant, watering advice changes by grass type: dormant cool-season turf (fescue, bluegrass, ryegrass) gets no irrigation at all, while dormant warm-season turf (bermuda, zoysia) gets only occasional light water during cold, dry, windy spells to prevent desiccation.

How it works:Sprigg tracks the trailing week of soil temperatures (with an air-temperature fallback) and flags dormancy when readings hold below the threshold for your grass category — about 45°F soil for cool-season turf and 55°F for warm-season. A single cold snap doesn't flip the state; the majority of the week has to agree. Sprigg also detects the "entering" and spring "greening" transitions.

Forecast Accuracy Learning

Weather forecasts miss differently at every address — some microclimates get consistently more rain than predicted, some less. If you have a Tempest weather station, Sprigg learns your location's forecast bias and corrects for it, so a forecast that habitually overpromises rain stops causing skipped waterings your lawn pays for.

How it works:each day Sprigg snapshots what the forecast predicted (rain amount, rain probability, highs and lows), then compares it against what your gauge actually measured. Once enough days accumulate, it derives correction factors — for example, "forecasts here overpredict rain by ~20%" — weighted toward recent weeks so the correction tracks seasonal shifts in forecast skill.

Sprinkler Calibration (Catch-Cup Test)

Most watering math starts from an assumed precipitation rate, and assumed rates are often wrong by a wide margin. A 20-minute catch-cup test replaces the assumption with a measurement, and calibrated zones show a Calibrated badge in Settings → Zones.

To run a test:

1. Set out catch cups (or straight-sided containers) spread evenly across the zone — 8 or more gives a reliable result
2. Run the zone for a fixed time, e.g. 15-20 minutes
3. Measure the water caught in each cup (milliliters)
4. In Settings → Zones, click Calibrate on the zone and enter the cup volumes, cup opening area (cm², printed on standard catch cups), and runtime

How it works:Sprigg computes the zone's measured precipitation rate and its distribution uniformity (how evenly the driest quarter of the lawn is watered) using standard Irrigation Association audit math. Both replace the assumed values in runtime calculations, so runtimes are sized for what your sprinklers really deliver. You can remove a calibration at any time to return to the assumed rate.

Decision History

Every irrigation decision is logged with full context — the reasoning, weather conditions at the time, disease risk level, and outcome. You can review the decision history in the Irrigation History page to understand why Sprigg watered or skipped on any given day.

Up to 500 decision log entries are retained per property, with the oldest entries automatically trimmed.