Drought confuses smart-irrigation controllers

Confounded by Texas weather? So are most “smart” electronic irrigation controllers, according to a Texas AgriLIfe Extension Service expert.

“Over the last two years, in a testing program, we found that Texas’ variable and erratic weather confuses many of the controllers being sold in the state,” said Dr. Guy Fipps,  AgriLife Extension irrigation engineer, College Station.

Smart controllers refer to irrigation units that use weather data to calculate and apply the correct amount of water needed by lawns and landscape plants. Ordinary “dumb” controllers rely on timers and require human intervention, which, due to human error or lack of management, often apply two to three times more water than necessary, Fipps explained.

Among the weather factors smart controllers use is evapotranspiration, commonly abbreviated as ET, which is an estimate of the total amount of water needed by plants. Smart controllers either use historical ET data or calculate it from weather sensors measuring rainfall, heat, amount of sunlight and other factors.

For more than three years at a College Station site, Fipps and Charles Swanson, AgriLife Extension landscape irrigation specialist, have been testing various brands of smart controllers sold in Texas. They have found that although the controllers are smart in theory, in actual use, some over-irrigate as often as their human counterparts who use guesstimates rather than calculations, according to Fipps.

However, the smart controllers have become smarter as manufacturers continue to tweak designs in response to such tests, he said. Still, during the third year of tests — which spanned 238 days from March 29 through Nov. 22, 2010 — many controllers still did not perform as consistently as expected.

“The 2010 results showed an increase in controller performance compared to the year-one and year-two results,” he said. “However, we continued to see controllers irrigating excessively; some irrigated in excess of ET, even though 17 inches of rainfall fell during the 2010 study.”

And that was before the drought worsened. During the drought of 2011, most of the controllers’ performance was erratic, Fipps said.

“Three of the eight smart controllers over-compensated and applied excessive amounts of water, and the remaining five did not apply enough irrigation water for all the irrigation zones and plant materials, although two of the controllers provided adequate amounts of water for five out of the six zones,” he said. “The problem is likely due to which weather factors the controller uses.”