Author
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Howell, Terry |
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Submitted to: Meeting Abstract
Publication Type: Proceedings Publication Acceptance Date: 1/20/2003 Publication Date: 2/1/2003 Citation: Howell, T.A. 2003. Water loss comparison of sprinkler packages. Proceedings of the Central Plains Irrigation Short Course and Exposition. p. 54-69. Interpretive Summary: Center pivot sprinklers have a large range of options for applying water. Sprinkler packages are based on the sprinkler system application design comprising the sprinkler device selection (impact sprinkler, spray head, etc.), the sprinkler spacing choices, and the choice of application mode [overhead, low elevation spray application (LESA), low pressure in-canopy (LPIC), and low pressure precision application (LEPA)]. Each of the packages can have water losses in differing components from droplet evaporation in the air, evaporation from water, crop, or soil surfaces, from differing runoff potential (or just water movements on the soil without runoff from the field), and from percolation below the crop root zone. The soil intake rate and its slope affect the runoff potential for a particular sprinkler package. Water losses can be up to 10% from direct droplet evaporation and up to 10% evaporation from the wetted canopy. Runoff can be minimized through good design, selections, and agronomic management; however, in a bad case it can be as high as 50%. Usually for center pivots, runoff is not a great concern. It is important to use good designs, select appropriate application devices and application modes to achieve both high uniformity and efficiency to use water resources effectively. Technical Abstract: Design and selection of sprinkler packages affect the irrigation uniformity and efficiency of center pivot systems. Several factors determine the description of a sprinkler package. Three spacing patterns - uniform, variable discharge; uniform discharge, variable spacing; and semiuniform spacing, variable discharge were discussed. The types of commonly used sprinkler devices were described along with the varying modes of application. The spacing, sprinkler device, and application mode combine to form the "sprinkler package". Differing sprinkler packages have differing water loss components, e.g., droplet evaporation, canopy evaporation, water and soil evaporation, runoff or water redistribution, and percolation beneath the root zone. Evaporative losses are usually 3-5% but can be as high as 10%. Canopy evaporation can be another 5-10%, but few studies have documented this water loss. Redistribution and runoff should be negligible under ideal cases, but they can be as large as 50% on low intake soils, higher slopes, and when surface tillage is not used to provide surface storage. Percolation can result from irrigation scheduling or management methods or when runoff occurs from uplands to lower areas in the field. With good designs, proper equipment and application mode selections, several sprinkler packages should be available for almost any soil or slope condition to achieve good uniformity and efficiency. |
