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The Difference Between Weather-Based and Soil Moisture Sensor Controllers

Article contributed by Chris Spain. Chris is president and CEO of HydroPoint, the makers of WeatherTRAK and Baseline smart irrigation systems. In addition to irrigation solutions, HydroPoint is a proven leader in smart water management solutions, making water – both indoors and out – simpler to manage through visibility and automation.

The two types of smart irrigation controllers – weather-based (ET) and on-site soil moisture sensors – will improve irrigation efficiency and save money by reducing water bills and manpower hours. However, the right solution depends on geographic location and landscape environment.

Weather-based controllers

Weather-based controllers, also referred to as evapotranspiration (ET) controllers, use local weather data to adjust irrigation schedules. Evapotranspiration is the combination of evaporation from the soil surface and transpiration by plant materials.

The best ET weather data uses four weather parameters: temperature, wind, solar radiation and humidity. It’s the most accurate way to calculate landscape water needs.

There are three basic forms of these weather-based ET controllers:

  • Signal-based controllers use meteorological data from a weather data provider and the ET value is calculated for landscape at the site. Take note, some weather data sources only use one weather parameter to calculate ET and therefore some providers are more accurate than others.
  • Historic ET controllers use a pre-programmed water use curve, based on historic water use in different regions. The curve can be adjusted for temperature and solar radiation.
  • On-site weather measurement controllers use weather data collected on site to calculate continuous ET measurements and water accordingly. Some of these on-site weather stations only use one weather parameter to calculate ET. Unless the weather stations measure all four weather parameters, the ET values they provide could be extremely inaccurate.

Soil moisture sensor-based controllers

Soil moisture sensor-based controllers use one of several well-established technologies to measure soil moisture content. When buried in the root zone, the sensors accurately determine the moisture level in the soil, which is a direct result of evapotranspiration, and transmit this reading to the controller.

There are two different soil moisture sensor-based systems available:

  • Suspended cycle irrigation systems, which are set like traditional timer controllers, but will stop scheduled irrigation when there is enough moisture in the soil.
  • Water on-demand irrigation requires no programming of irrigation duration, only start times and days of the week to water. It initiates irrigation when the soil moisture level fails to meet those levels.

Smart irrigation controllers save water and money

WT Central copyIf you’re looking for a smart water management solution, cloud-based HydroPoint WeatherTRAK or Baseline are good solutions to consider, depending on your site needs and location.

Weather-based WeatherTRAK provides centralized management with complete visibility and on-site or remote control of your irrigation site from any internet browser.

Baseline 3200Baseline offers solutions that cover both soil moisture sensor-based watering and weather-based watering. On the BaseStation 3200, for instance, you can combine Baseline’s soil moisture sensor-based intelligent watering technology with the industry’s best practices for weather-based irrigation.


Talk to your local Ewing store to find out which solution would best match your unique needs.

TAGS: HydroPoint, WeatherTRAK, Irrigation Controllers, Baseline, Irrigation