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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Soil and Water Management Research » Research » Publications at this Location » Publication #233084
Title: Compensating inherent linear move water application errors using a variable rate irrigation system

Author
item Chavez Eguez, Jose
item PIERCE, FRANCIS - WASHINGTON STATE UNIV.
item Evans, Robert

Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2009
Publication Date: 3/1/2010
Citation: Chavez Eguez, J.L., Pierce, F.J., Evans, R.G. 2010. Compensating inherent linear move water application errors using a variable rate irrigation system. Irrigation Science. 28(3)203-210.

Interpretive Summary: Linear move and center pivot irrigation systems apply water unevenly due to their towers stop and advance pattern. In general, water application errors tend to occur more or less in the same location of the irrigated field; with under irrigation in some locations and over irrigation on other locations, in relation to target amounts. Thus, to correct for these errors, the irrigation system stop advance pattern was studied and water application errors were modeled considering the average nozzle travel speed, location in the field, as well as field elevation by location. As a result, water application errors were reduced from over 20% to values around 5%, when the error model was used with an irrigation system retrofitted with solenoids on each nozzle; which made the system capable of applying variable water depth amounts by location in the field.

Technical Abstract: Continuous move irrigation systems such as linear move and center pivot irrigate unevenly when applying conventional uniform water rates due to the towers/motors stop/advance pattern. The effect of the cart movement pattern on linear move water application is larger on the first two spans which introduces errors on site-specific irrigation. Therefore, the objectives of this study were to model the linear move irrigation system tower movement and to develop an algorithm to compensate or adjust variable irrigation in order to minimize the distributed irrigation application errors. The tower movement modeling mainly considers terrain attributes, average nozzle travel speed, and high frequency DGPS (differential global positioning system) tower positioning readings. The paper describes the use of a new irrigation monitoring and control system, DGPS, GIS techniques, and statistical analysis utilized in the modeling process. The irrigation monitoring and control system is composed of a single board computer, a relay board controller, DGPS units, electric solenoid valves, two wireless ethernet bridge units, high frequency spread spectrum radios, as well as in line and in the field sensor networks. This technology allows for continuous, real-time data acquisition and irrigation system management through the internet. This study has shown that irrigation application errors have been reduced from over 20% to values around 5%, on the subsequent irrigation correction event.