Irrigation Estimator

Note This is not updated.

Irrigation Estimator custom component for Home Assistant. Based on https://github.com/jeroenterheerdt/HAsmartirrigation. Compared to HAsmartirrigation there are several changes:

• This component does not use reference evapotranspiration values
• It does not interact with OpenWeatherMap API. Simply select proper sensors from a separate OpenWeatherMap integration.
• It does not provide events for starting irrigation.

Bear in mind this is just an evapotranspiration model. It does not take into account:

• Water loss due to other factors, as an example water sinking deeper into the ground.
• Future weather conditions, e.g. if the forecast is it will be raining - it's on you to not schedule watering.

What this component does, is it provides three sensors that are updated at midnight each day:

• Evapotranspiration
• Bucket delta - difference between precipitation and evapotranspiration over the previous day, i.e. moisture lost yesterday
• Bucket - accumulated bucket deltas.
• Run time - the time needed to run your irrigation system to compensate for the moisture loss accumulated in the bucket.

This uses the fao56 model from [lib]. Note this is for the reference crop as specified in [].

https://www.rainbird.com/professionals/irrigation-scheduling-use-et-save-water. The component uses the PyETo module to calculate the evapotranspiration value (fao56). Also, please see the How this works Wiki page.

Visual representation of what this component does

1. Snow and rain fall on the ground add moisture. This is tracked /predicted hourly depending on the operation mode by the rain and snow attributes Together, this makes up the precipitation.
2. Sunshine, temperature, wind speed, place on earth and other factors influence the amount of moisture lost from the ground(evapotranspiration). This is tracked / predicted hourly depending on the operation mode.
3. The difference between precipitation and evapotranspiration is the netto precipitation: negative values mean more moisture is lost than gets added by rain/snow, while positive values mean more moisture is added by rain/snow than what evaporates.
4. Once a day (time is configurable) the netto precipitation is added/substracted from the bucket, which starts as empty. If the bucket is below zero, irrigation is required.
5. Irrigation should be run for daily_adjusted_run_time amount of time (which is 0 is bucket>=0). Afterwards, the bucket needs to be reset (using reset_bucket). It's up to the user of the component to build the automation for this final step.

There are many more options available, see below. To understand how precipitation, netto precipitation, the bucket and irrigation interact, see example behavior on the Wiki.

Getting the best results

In order to get the most accurate results using sensors is preferable. You can substitute missing data using a weather component, e.g. OpenWeatherMap.

TODO list sensors needed and options

Configuration

In this section:

• One-time set up
• List of events, services entities and attributes created
• Example automation

Step 1: configuration of component

Install the custom component (preferably using HACS) and then use the Configuration --> Integrations pane to search for 'Smart Irrigation'. You will need to specify the following:

• Names of sensors that supply required measurements (optional). Only required in mode 2) and 3). See Measurements and Units for more information on the measurements and units expected by this component.
• Number of sprinklers in your irrigation system
• Flow per spinkler in gallons per minute or liters per minute. Refer to your sprinkler's manual for this information.
• Area that the sprinklers cover in square feet or m² After setting up the component, you can use the options flow to configure the following:

  Option	Description	Default
  Maximum duration	Maximum duration in seconds for any irrigation, including any lead_time. -1 means no maximum.	-1
  Solar Radiation calculation	From v0.0.50 onwards, the component estimates solar radiation using temperature, which seems to be more accurate. If for whatever reason you wanted to revert back to the pre v0.0.50 behavior (which used a estimation of sun hours) disable this.	True

Step 2: checking services, events and entities

After successful configuration, you should end up with three entities and their attributes, listed below as well as three services.

Services

For each instance of the component the following services will be available:

Service	Description
smart_irrigation.]instance]_reset_bucket	Resets the bucket to 0. Needs to be called after done irrigating (see below).

Entities

sensor.smart_irrigation_base_schedule_index

The number of seconds the irrigation system needs to run assuming maximum evapotranspiration and no rain / snow. This value and the attributes are static for your configuration. Attributes:

Attribute	Description
number of sprinklers	number of sprinklers in the system
flow	amount of water that flows through a single sprinkler in liters or gallon per minute
throughput	total amount of water that flows through the irrigation system in liters or gallon per minute.
area	the total area the irrigation system reaches in m2 or sq ft.
precipitation rate	the output of the irrigation system across the whole area in mm or inch per hour

sensor.smart_irrigation_hourly_adjusted_run_time

The adjusted run time in seconds to compensate for any net moisture lost. Updated approx. every 60 minutes. Attributes:

Attribute	Description
precipitation	the total precipitation (which is the sum of rain and snow in mm or inch)
evapotranspiration	the expected evapotranspiration
netto precipitation	the net evapotranspiration in mm or inch, negative values mean more moisture is lost than gets added by rain/snow, while positive values mean more moisture is added by rain/snow than what evaporates, equal to precipitation - evapotranspiration
adjusted run time minutes	adjusted run time in minutes instead of seconds.

sensor.smart_irrigation_daily_adjusted_run_time

The adjusted run time in seconds to compensate for any net moisture lost. Updated every day at 11:00 PM / 23:00 hours local time. Use this value for your automation (see step 3, below). Attributes:

Attribute	Description
bucket	running total of net precipitation. Negative values mean that irrigation is required. Positive values mean that more moisture was added than has evaporated yet, so irrigation is not required. Should be reset to 0 after each irrigation, using the smart_irrigation.reset_bucket service
maximum_duration	maximum duration in seconds for any irrigation, including any lead_time.
adjusted run time minutes	adjusted run time in minutes instead of seconds.

You will use sensor.smart_irrigation_daily_adjusted_run_time to create an automation (see step 3, below).

Step 3: creating automation

Since this component does not interface with your irrigation system directly, you will need to use the data it outputs to create an automation that will start and stop your irrigation system for you. This way you can use this custom component with any irrigation system you might have, regardless of how that interfaces with Home Assistant. In order for this to work correctly, you should base your automation on the value of sensor.smart_irrigation_daily_adjusted_run_time as long as you run your automation after it was updated (11:00 PM / 23:00 hours local time). If that value is above 0 it is time to irrigate. Note that the value is the run time in seconds. Also, after irrigation, you need to call the smart_irrigation.reset_bucket service to reset the net irrigation tracking to 0.

The last step in any automation is very important, since you will need to let the component know you have finished irrigating and the evaporation counter can be reset by calling the smart_irrigation.reset_bucket service

Example automation 1: one valve, potentially daily irrigation

Here is an example automation that runs when the smart_irrigation_start event is fired. It checks if sensor.smart_irrigation_daily_adjusted_run_time is above 0 and if it is it turns on switch.irrigation_tap1, waits the number of seconds as indicated by sensor.smart_irrigation_daily_adjusted_run_time and then turns off switch.irrigation_tap1. Finally, it resets the bucket by calling the smart_irrigation.reset_bucket service. If you have multiple instances you will need to adjust the event, entities and service names accordingly.

- alias: Smart Irrigation
  description: 'Start Smart Irrigation at 06:00 and run it only if the adjusted_run_time is >0 and run it for precisely that many seconds'
  trigger:
   - event_data: {}
     event_type: smart_irrigation_start
     platform: event
  condition:
  - above: '0'
    condition: numeric_state
    entity_id: sensor.smart_irrigation_daily_adjusted_run_time
  action:
  - data: {}
    entity_id: switch.irrigation_tap1
    service: switch.turn_on
  - delay:
      seconds: '{{states("sensor.smart_irrigation_daily_adjusted_run_time")}}'
  - data: {}
    entity_id: switch.irrigation_tap1
    service: switch.turn_off
  - data: {}
    service: smart_irrigation.reset_bucket