Testing of climatologically-based irrigation controllers in Florida

Abstract

Water resources are limited in Florida similar to other parts of the United States experiencing water shortages. It was found in recent research performed by the University of Florida that 64% of residential water use was used for irrigation in central Florida. Though automatic in-ground irrigation systems are the most commonly installed system, they have been shown to increase residential water use. The irrigation industry has developed so-called smart irrigation controllers that are designed to use water efficiently while maintaining landscape quality. Climatologically-based controllers are one type of smart irrigation controller that use an estimation of reference evapotranspiration (ETO) for automatic irrigation scheduling. The objectives of this study were to evaluate the ability of three brands of climatologically-based controllers to schedule irrigation for a virtual landscape compared to a simulated soil water balance and determine the variability in irrigation scheduling by ET controllers of the same brand. The ET controllers were as follows: Smart Line Series controller (Weathermatic, Inc., Dallas, TX), Intelli-sense (Toro Company, Inc., Riverside, CA) utilizing the WeatherTRAK ET Everywhere service (Hydropoint Data Systems, Inc., Petaluma, CA), and Smart Controller 100 (ETwater Systems LCC, Corte Madera, CA). Results showed that there were no differences in weekly water application between controllers of different brands ranging from 14.7 mm/week to 16.5 mm/week. There were also no differences in weekly irrigation application within each brand. However, irrigation scheduling techniques were different between controllers of different brands. There was an inverse relationship between irrigation amount per event and number of events per week with extreme averages ranging from 3.0 mm/event and 5.2 events/week for the Weathermatic to 25.7 mm/event and 0.57 events/week for the soil water balance model. Some irrigation scheduling techniques did not account for reasonable irrigation system hydraulics. The ET controller’s ability to handle rainfall is the key to the water conservation potential of the controller in Florida. Despite the possible drawbacks to the technology, the ET controllers were able to schedule irrigation so that weekly water application was similar to what was calculated as the water needs for the specified landscape.