3 Brilliant Studies Support Smart Irrigation Controllers

Posted on 10/14/14

These three studies supporting evapotranspiration (ET) based smart irrigation controllers were from over 100 education sessions at the most recent WaterSmart Innovations Conference. The first two studies focused on what happens in regards to the way water and smart irrigation controllers are used in the field by real people. The third was a controlled study proving significant water savings from ET based smart irrigation controller.


Morgan Shimabuku from the Center for ReSource Conservation in Boulder, CO presented Where’s the Water Going? Factors Related to Outdoor Water Use.  While not directly related to smart irrigation controllers the study included results from over 2000 water audits conducted over four years and water use data from seven years. In the Boulder area over 50% of water is used outdoors of which up to 40% of the water is wasted due to overwatering. Their study determined the only statistically valid root cause for overwatering was bad irrigation controller scheduling. Smart Irrigation Controllers using daily ET data automatically adjusts the schedule so every schedule is a good schedule.


Dennis Gegen and Sean Ainsworth from the, Southern Nevada Water Authority (SNWA) presented After the Initial Romance is Over, Do People Still Love Their Smart Controller? Living in the Mojave Desert means average annual rainfall less than 4 inches, temperatures ranging from 15 – 115 F, humidity less than 20%, bright sunshine, few clouds and a very high ET rate. In Southern Nevada over 70% of the water is used outdoors with about 33% of the outdoor water being wasted.

Since  SNWA offers a rebate for smart irrigation controllers they surveyed the people who had taken advantage of the rebate. While over 60% of the controllers were in automatic ET mode almost 40% were in standard or dumb water wasting mode. The primary reasons for switching away from automatic ET mode include the following.

Majority of respondents using clock in standard mode didn’t “trust” controller [It didn’t run every day…go figure]

*Clock was not initially installed or programmed properly
*Controller or weather station had malfunctioned or lost signal
*Some respondents didn’t realize the controller was not in Auto (Smart) mode

They also found customers who were comfortable with the Internet of Things (i.e. multiple technologies in the house, smart phones, tablets, etc.) were most likely to have the smart irrigation controller in automatic mode. In other words if you have any devices flashing 12:00 you may want to seek professional help to set up the ET smart irrigation controller.


Brian Vinchesi, President of Irrigation Consulting presented Water Savings of ET vs. Timed Water Applications. This study was conducted over 27 months in central Florida to compare and measure the water conservation capabilities of a conventional timer based control system operating on a set duration and frequency versus a weather driven ET derived control system. Twelve identical plots of grass were installed. Four plots were used for control, four plots were on a standard irrigation controller and four plots were on an ET based smart irrigation controller.

The time based plots were watered 0.75 – 1 inch of reclaimed water per week on Tuesdays and Thursdays as mandated by South Florida Water Management District statute. The ET based plots were watered based on information from the weather station located 30 feet away as needed without restriction on how many days per week.

Study Results – Irrigation Run Time

*In all but one month the average monthly run time showed the time based scheduled irrigation operated longer than the ET based schedule.
*In May, June and July the two schedules were closer together time wise compared to rest of the year.
*In some months, the timed plots were operating over a 100 minutes more.
*Except for one month in the spring of 2011, the ET based schedule used less water than the time based schedule

Study Results – Irrigation Water Use

*ET based plots used ~64 inches of water and approximately ~9,500 gallons
*Time based plots applied ~100 inches of water and used over 15,000 gallons
*Net results were 36% water savings from the ET based smart irrigation controller
*Some months resulted in water savings over 50%

While each of these studies were from different parts of the country and different climates, the results were the same: ET based smart irrigation controllers significantly reduce outdoor water use and saves money.


by Alan Harris, ValleyCrest Landscape Companies