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Weather-Based Landscape Irrigation Control Systems  Public Access

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

ASAE  ANSI/ASABE S627.1   October  2022

Keywords: irrigation, landscape, turf, controllers, sensors, SWAT, Smart Water Application Technologies

1. Purpose and Scope

1.1 This standard describes a test method to determine an irrigation controller‘s ability to respond to weather and conditions found within the typical landscape. Sometimes called “smart control systems” or “smart controllers,” these are controllers or devices that respond to environmental conditions by estimating or measuring depletion of available plant soil moisture in order to operate an irrigation system, replenishing water as needed while minimizing excess water use. A properly programmed smart controller requires initial site-specific set-up and will make irrigation schedule adjustments, including runtimes and/or required cycles throughout the irrigation season without human intervention. The standard will measure the ability of the controllers to provide adequate and efficient irrigation while minimizing potential losses.

It is recognized that controlling the irrigation of turf and landscape is a combination of scientific theory and subjective judgments. The attempt in developing this standard is to use only generally recognized theory and to avoid judgments involving the art of irrigation. The standard then recognizes that only the theory of irrigation is controllable by the skill of the controller manufacturer.

1.2 The objective of this standard is to provide a test method that evaluates how well technology has integrated scientific data into a practical system that meets the agronomic needs of the turfgrass and landscape plants. This evaluation concept requires the use of accepted formulas for calculating crop evapotranspiration (ETc) or landscape evapotranspiration (ETL). Versions of this type of controller could include one or more of the following:

- On-site weather sensors to determine irrigation needs;

- Weather data received from an off-site source;

- Technology that is added to existing time-based controllers that interfaces with either the controller program or electrical output to zone valves; and

- Historical reference evapotranspiration (ETo) data characteristic of the site, in conjunction with other inputs.

1.2.1 This evaluation shall be accomplished by defining a virtual landscape and connecting an irrigation controller to a datalogger that records signals sent to irrigation control valves. Any weather sensors will be subjected to actual, real-time climate conditions. The output of the irrigation controller will be evaluated to determine the ability of the landscape irrigation control system to adequately and efficiently manage water applied to the landscape. The individual irrigation zones within the virtual landscape represent a range of landscape conditions. As a standard from which to judge the control system‘s performance, a detailed moisture balance calculation shall be made for each zone. Irrigation adequacy is determined by the total accumulated deficit of irrigation over the test period. The accumulated surplus and runoff of irrigation over the test period is a measure of irrigation excess.

1.3 A control system meeting this standard may include additional features not covered in this document.

1.4 This standard is not intended for testing control systems used in agricultural settings.

1.5 This standard is a testing document; therefore, inputs and values provided in Tables 1, 2, 3 and Figure 1 are used for illustrative purposes only, and may not reflect the conditions at any specific location.

1.6 Test Method #1 evaluates a controller for irrigation adequacy and irrigation excess over a minimum 30-day period using daily soil moisture balance calculations. It does not constrain the frequency of irrigation events; however, it does have a minimum runtime requirement.

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