What is a weather-based ET controller and how does it operate?

• A. A device that records rainfall amounts for landscaping purposes.
• B. A controller that uses ET data and weather inputs to adjust irrigation scheduling automatically.
• C. A sensor that measures soil moisture to replace ET data.
• D. A manual timer that runs irrigation at fixed times only.

Answer: (B)

A weather-based ET controller automatically matches watering to what plants actually need by using evapotranspiration data and current weather conditions. It gathers data from a weather station or online source—temperature, humidity, solar radiation, wind, and any rainfall—and converts that evapotranspiration (the amount of water plants use and lose to the atmosphere) into an irrigation need for each zone. The controller then sets appropriate run times or water volumes, adjusting for factors like soil type, plant type or root depth, and irrigation efficiency. It also reduces or skips irrigation after rainfall and increases watering on hot, dry days. In short, it uses real weather-driven plant water demand to schedule irrigation automatically, instead of relying on fixed times or only soil moisture readings.