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Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings Publication Acceptance Date: 6/22/2012 Publication Date: 7/29/2012 Citation: King, B.A., Dungan, R.S., Bjorneberg, D.L. 2012. Evaluation of center pivot sprinkler wind drift and evaporation measurement technique. ASABE Annual International Meeting, July 29 - August 1, 2012, Dallas, TX. Paper No. 12-1336891. p.1-11. Interpretive Summary: Wind drift and evaporation losses (WDELs) are an often discussed topic in regards to center pivot sprinkler irrigation efficiency. Opinions on the magnitude of WDELs vary widely, in part due to the wide variation in WDEL values published in the literature. The objective of this project was to develop and evaluate a methodology for measurement of WDEL from center pivot sprinklers using a combination of applied water collectors, bromide tracer and air samplers. The evaluation criteria were the magnitude of water volume balance error. A methodology for measuring wind drift and evaporation loss from center pivot sprinklers was developed and field tested under limited wind speed conditions. Volume balance errors ranged from 0.1 to 7.1%. The cause for the large errors on two occasions has not yet been determined. The percent of applied water aerosolized and measured as drift was found to be linearly correlated with wind speed. Overall, the limited tests show the methodology to be feasible for measuring WDEL from center pivot sprinklers. Tests in higher wind speeds are needed to validate the methodology as is determination and elimination of the cause for the high volume balance errors. Technical Abstract: Wind drift and evaporation losses (WDELs) are an often discussed topic in regards to center pivot sprinkler irrigation efficiency. Opinions on the magnitude of WDELs vary widely, in part due to the wide variation in WDEL values published in the literature. The magnitude of WDELs reported in the literature range from 2 to 45%. The common technique employed to measure WDEL is to use catch cans and compare the measured volume of catch with the volume of water applied based on sprinkler nozzle size, operating pressure and spacing with the difference being WDEL. The inaccuracies of catch cans resulting from wind effects on catch efficiency and evaporation of water from the catch can prior to measurement have led to the wide range in WDEL reported in the literature. The objective of this project was to develop and evaluate a methodology for measurement of WDEL from center pivot sprinklers using a combination of applied water collectors, bromide tracer and air samplers. The evaluation criteria were the magnitude of water volume balance error. A methodology for measuring wind drift and evaporation loss from center pivot sprinklers was developed and field tested under limited wind speed conditions. Volume balance errors ranged from 0.1 to 7.1%. The cause for the large errors on two occasions has not yet been determined. The percent of applied water aerosolized and measured as drift was found to be linearly correlated with wind speed. Overall, the limited tests show the methodology to be feasible for measuring WDEL from center pivot sprinklers. Tests in higher wind speeds are needed to validate the methodology as is determination and elimination of the cause for the high volume balance errors. |
