Property constants
Hard-coded inputs to the ET₀ calculation — physical facts about the property, not tunable settings
| Constant | Value | Used for |
|---|
| Latitude | 35.72983843° N | Solar declination / extraterrestrial radiation |
| Elevation | 1,095 ft (333.756 m) | Atmospheric pressure, clear-sky radiation |
| Anemometer height | 1.97 m | Wind speed adjustment to the FAO-56 standard 2m height |
| Reference surface | Clipped, well-watered grass | What ET₀ itself represents |
What is ET₀?
ET₀ is the depth of water, in inches per day, that would evaporate and transpire from a
standardized reference surface — a short, uniform, well-watered grass — under the day's actual
weather. Multiply ET₀ by a crop coefficient (Kc) specific to the grass type and the calendar
month, and you get ETc: the actual water need for that grass, that day. The formula here is
FAO-56 Penman-Monteith, the internationally standard method for computing ET₀.
Source
Allen, R.G., Pereira, L.S., Raes, D., Smith, M. (1998).
Crop Evapotranspiration — Guidelines for Computing Crop Water Requirements,
FAO Irrigation and Drainage Paper 56. —
fao.org/4/x0490e/x0490e00.htm
Crop coefficients (Kc)
Monthly multipliers applied to ET₀ to get each grass type's actual water need (ETc = ET₀ × Kc)
Source
Meyer, J.L. et al. (1985), widely cited turfgrass crop-coefficient reference (UC ANR / extension programs).
Other tunable constants
| Constant | Value | Where it lives | Meaning |
|---|
| Bermuda deficit threshold | 0.65 in (80% watch: 0.52 in) | Dashboard script (DEFICIT_THRESHOLD_IN) | Shortfall level treated as needing irrigation for Bermuda |
| Fescue deficit threshold | 0.45 in (80% watch: 0.36 in) | Dashboard script (DEFICIT_THRESHOLD_IN) | Same, for Fescue — cool-season turf shows stress sooner |
| Bermuda guide stations | 1, 2, 6, 7 | Dashboard script | Representative zones for the water-balance chart |
| Fescue guide stations | 3, 4 | Dashboard script | Representative zones for the water-balance chart |
| Default precip rate | 0.3 in/hr | irrigation_zones.precip_rate_in_per_hr | From catch-cup testing; converts sprinkler runtime to inches applied |
| Mister / flower bed precip rate | 0.75 in/hr | irrigation_zones.precip_rate_in_per_hr | Higher-output zones |
| Target watering | 1.5 in/week | irrigation_zones.target_in_per_week | Reference target, not currently enforced automatically |
Defined terms
| Term | Meaning |
|---|
| ET₀ | Reference evapotranspiration — water loss from a standardized grass surface, in/day |
| ETc (shown as "water needed") | Crop evapotranspiration — ET₀ × Kc, the actual water need for a specific grass type |
| Kc | Crop coefficient — monthly multiplier converting ET₀ into ETc for a given grass type |
| Shortfall / deficit | Running total of (ETc − rain − irrigation), floored at 0 each day |
| Feels-like (high/low) | Heat index (high) and wind chill (low) |
| Precip rate | How fast a zone's sprinklers apply water, in inches per hour |
| Station number | B-hyve's numeric zone identifier, mapped 1:1 to this property's zone_number |
Data sources
| Source | Feeds | Docs |
|---|
| Ambient Weather station | weather_daily | ambientweather.docs.apiary.io |
| Orbit B-hyve | irrigation_runs | Unofficial API — no public docs |
| Kress fleet.kress.com | mower_activity | Unofficial, reverse-engineered — no public docs |