Reports

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TR-364

Initial Evaluation of Smart Irrigation Controllers: Year Two (2009) Results

C. Swanson, G. Fipps

A smart controller testing facility was established by the Irrigation Technology Center at Texas A&M University in College Station in 2008. A two-year testing program was initiated in order to evaluate smart controller testing methodology needed to determine their performance and reliability under Texas conditions from an "end-user" point of view. The "end-user" is considered to be the landscape or irrigation professional (such as a Licensed Irrigator in Texas) installing the controller. During the first year (2008), six (6) controllers were evaluated over a 60- day period. Details were provided by Swanson and Fipps (2008). This report details the results of the second year (2009) evaluations.

Four additional controllers were provided by manufacturers for the 2009 evaluations, bringing the total number of controllers evaluated to 10, and the evaluation period was extended to 13 weeks. As in the first year, the 10 controllers were programed for College Station, Texas using a modified version of the virtual landscape as defined in the IA (Irrigation Association) SWAT (Smart Water Applicator Technologies) 7th draft testing protocol.

Programing the controllers according to these virtual landscapes proved to be problematical, as most of the controllers did not allow the direct programing of all of the parameters needed to define the virtual landscape and irrigation system. In addition, it was impossible to see the actual values that some controllers used for each parameter or to determine how closely these followed the values of the virtual landscape.

The 2009 results showed some improvement in controller performance over Year One results. There were no software or hardware problems observed. Only one controller had communication problems which were reported to the manufacturer's representative but not corrected during the study.

Seasonal Irrigation Amounts

  • When looking at total seasonal irrigation amounts for the entire landscape, two (2) controllers were within the recommendations of the TexasET Network, six (6) were within 50% of ETo, and five (5) were with 80% of a simple ETc model (ETo x Kc, neglecting rainfall).

Individual Station (zone) Irrigation Amounts

  • The results showed considerable inconsistency by the 10 controllers, with total irrigation volumes within the same station (or zone) ranging from 3 to 5 times as much water from controller to controller.
  • When compared to a simple ETc model (ETo x Kc; neglecting rainfall), irrigation amounts exceeded ETc 37% of the time even though over 14 inches of rain occurred during the study.
  • Controllers produced irrigation amounts exceeding ETo 20% of the time. About 14% of the irrigation amounts were within the recommendations of the TexasET Network and Website.
  • Based on the 2009 performance, controllers with onsite sensors for determining water requirements irrigated much closer or within the recommendations of TexasET. As in the First Year results, controllers that received ET/ETo and rain information remotely irrigated much higher than the recommendations.

Such high irrigation amounts are hypothesized to be related to the source and values for the ETo used by the controllers, default values used to define landscape parameters, and/or the methodologies used to account for rainfall. We have used the results of the past two years of evaluations to establish updated protocols for future studies.

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