Zone configuration

Main page: Configuration
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Specify one or more irrigation zones here. The integration calculates irrigation duration per zone, depending on size, throughput, state, module and sensor group. A zone can be:

• disabled: The zone is then not calculated and duration will be set to 0.
• automatic: The zones duration is automatically calculated.
• manual: You can specify the zones duration yourself.

When entering any values in the configuration of this integration, take notice of the labels provided so you enter values in the correct units.

Multi-zone support

For irrigation systems that have multiple zones which you want to run in series or independent you need to create multiple zones. The configuration should be done for each zone, including the area the zone covers and the corresponding settings.

Adding a zone

You need to specify the following to add a zone:

• Name: The name of your zone, e.g. 'garden'
• Size: The size of this zone (m² or sq ft)
• Throughput: The flow of this zone (liter/minute or gallon/minute)

After entering the information, click Add zone to add the zone. Each zone is shown as an entity in Home Assistant. After adding a zone, make sure to further configure your new zone.

Actions on all automatic Zones

You can perform the following actions on all automatic zones:

• Update all zones: Retrieve the weather data for all sensor groups for all automatic zones.
• Calculate all zones: Calculate irrigation duration for all automatic zones. This will also delete weather data after calculation.
• Reset all buckets: Set the buckets for all automatic zones to 0.
• Clear all weatherdata: Remove all collected weather data for the sensor groups used by any automatic zone.

Configuring a zone

To configure a zone, the amount of water that flows through the irrigation system (throughput) and the area the irrigation system reaches (size) must be known. If you do not know these values for your system, you can also directly enter the precipitation rate (in mm/h or in/h) for the zone. To determine the precipitation rate, place a straight-sided container in the zone, run the irrigation for exactly one hour, and measure the depth of water collected: that depth, in mm (or inches), is your precipitation rate per hour.

You can change the following settings on a zone:

• Name: change the name of a zone

• Input method: choose how the zone's precipitation rate is determined:

  • Throughput & area (default): the rate is calculated from Size and Throughput.
  • Precipitation rate: enter the rate directly.

• Size: change the size of a zone (only used with the Throughput & area input method)

• Throughput: change the throughput of a zone (only used with the Throughput & area input method)

• Precipitation rate: change the directly entered rate (only used with the Precipitation rate input method)

• Drainage rate: how fast a saturated root zone drains, in mm/h, which is the soil's saturated hydraulic conductivity. It only applies when bucket > 0, meaning the soil is above field capacity. It is the full rate at saturation, when the bucket reaches the maximum bucket; below that it falls steeply with how much surplus is left, following Brooks and Corey, Eq. 4-6. The drainage over a calculation is worked out from that rate law exactly, so a surplus drains quickly at first and more and more slowly as it empties. Indicative values, from the texture-class averages in Rawls, Brakensiek and Saxton (1982): about 210 mm/h for sand, 60 for loamy sand, 26 for sandy loam, 13 for loam, 7 for silt loam, 2 for clay loam and under 1 mm/h for clay. The default, 50.8 mm/h, is fast for most garden soils. A drainage rate of 0 means a surplus never drains: rain above field capacity then stays in the bucket until evaporation removes it, and the next irrigation is delayed by however many days that takes.

• State:

  • Automatic: the zone is updated and calculated on its own. It needs a sensor group.
  • Manual: only updated and calculated when you ask. No sensor group required.
  • Disabled: nothing is updated or calculated for this zone.

• Evapotranspiration: how this zone's water need is worked out, in three answers. Calculated by Smart Irrigation, from your measurements (temperature, humidity, wind, sun), which is FAO-56 Penman-Monteith. Provided by a sensor or a service, when you already have an evapotranspiration in millimetres and it is taken as it is. A fixed amount, so many mm a day whatever the weather. The calculation engine behind your answer is created and reused for you, one per zone; there is nothing to create by hand and no engine to choose.

  On the advanced panel, the engine's own setting appears with it: Look ahead, the number of days to come that are averaged into today's need (0 by default), for a zone calculated by Smart Irrigation, and the fixed amount for a zone that uses one. Each zone has its own, so changing it here changes nothing anywhere else.

• Sensor group: Choose the sensor group that provides the weather data for this zone.

• Bucket: Either calculated or manually set. If bucket >= 0 then no irrigation is necesarry, if bucket < 0 irrigation is necessary. See automations for examples on how to use this value to decide to irrigate.

• Maximum bucket: how much water the root zone can hold above field capacity before it is saturated, so it only applies when bucket > 0. Anything beyond it runs off, and it is the saturation reference the drainage curve is scaled by. It is not the total water your soil holds for the plant, and it never changes when a zone starts watering.

  Physically it is (saturation - field capacity) x root depth: the soil's drainable porosity over the depth the roots use. The same averages give about 0.35 for sand, 0.19 for loam and 0.08 for clay, so for a 20 cm root zone roughly 70 mm for sand, 40 mm for loam and 15 mm for clay. Take them as a starting point: they move with how field capacity is defined, and a real soil is not a class average.

  Sand gets the larger value, not the smaller. Its big pores hold a lot of water for the short while it takes to drain and little once it has; clay is the reverse. Earlier versions of this page gave 30 mm for clay and 12 mm for sand. Those are closer to the available water capacity, which belongs to the other way of counting soil water, and they are inverted for this one. See discussion #783 for how this was worked out.

• Lead time: Time needed to warm up your irrigation system (in seconds), e.g. time to establish a connection, start a pump, build pressure, etc. After the duration is calculated, the lead time is added but only if the duration is > 0.

• Maximum duration: The maximum duration of the irrigation, to avoid flooding, wasting water, etc.

• Multiplier: The crop factor Kc. It scales the evapotranspiration to the water your crop actually uses, ETc = ET0 * Kc, so the bucket is depleted at the crop's rate rather than the reference one. It is applied to the evapotranspiration and not to the rain that fell on it, nor to the resulting duration. For lawns, it is recommended to set the multiplier depending on your grass type (See this discussion for more details):

  • Cool-reason grasses (such as fescue, bluegrass) should be set to 0.8
  • Warm-season grasses (such as bermuda, zoysia) should be set to 0.7.

  It carries plant density too, not just species. The reference the calculation starts from is a continuous grass surface, so the figure quoted for a species assumes it covers the ground. A zone that does not is using less water per square metre than that figure says, because there is less leaf there to lose it. A hedge on a drip line, measured over the strip its emitters wet, is close to full cover once it has grown together and the species figure is about right. A young or widely spaced planting is not, and its factor should come down roughly in proportion to how much of the zone the canopy actually shades. The landscape literature writes this as the species factor multiplied by a density factor, which is the same idea.

  This is why the area you enter and the crop factor have to describe the same patch of ground. If you take the whole bed as the area for a drip line, you are claiming a canopy over all of it; if you take the wetted strip, you are claiming one over the strip, which for an established hedge is true. Either can be made correct, but not by mixing one area with the other's factor.

  A dry spell waters the same as it always did: the crop factor ends up multiplying the same total either way. What changes is a period with rain, where a factor below 1 used to credit only that fraction of the millimetres that fell and therefore over-watered, and the moment irrigation becomes necessary, which now arrives at the crop's rate of depletion rather than about 1/Kc times too early.

• Irrigation threshold: how much of a soil moisture deficit to let build up before watering at all, in mm or inch. 0, the default, waters as soon as anything is missing, which is what every installation did before this setting existed; it is not what agronomy recommends for anything, a lawn included. Set a threshold and the zone stays dry until that much water is owed, then delivers all of it in one deep run: a lawn wants a small one because its roots are shallow, a tree or a hedge a large one. It changes when a zone waters, not how much: once the threshold is reached the run still covers the whole deficit. It follows that a zone never waters less than its threshold, so it also rules out very short runs. In soil terms this is the management allowed depletion (MAD).

To pick a value, work from the water your soil actually holds for the plant, the total available water: TAW = available water capacity of the soil x root depth. As a rough guide the available water capacity runs about 60 to 90 mm per metre in sand, 130 to 170 in loam and 150 to 200 in clay, and the root depth is what matters for that planting, perhaps 0.15 to 0.3 m for turf and a metre or more for an established tree. The threshold is then a fraction of that, p x TAW, with p around 0.5 as a starting point (FAO-56 gives per-crop values, mostly between 0.4 and 0.6). A lawn on loam at 0.2 m therefore lands somewhere near 15 mm.

Do not derive it from the Maximum bucket: that setting caps the surplus above field capacity, which is the other side of zero and a different quantity entirely.

The default of 0 is there to keep existing installs behaving exactly as before, not because watering the instant anything is missing is good practice. Deep and infrequent watering suits a lawn too, it simply wants a smaller threshold than a tree because its roots are shallower.

• view weather data. View the last 10 records of the associated sensor group.
• view watering calendar. View a yearly watering calendar based on the location and normal weather patterns.
• delete the zone.

Main page: Configuration
Previous: General configuration
Next: Module configuration