Comparative Loss Study of Four Different Sprinkler Packages on Center Pivot Systems under South Georgia Conditions

The efficiency of water use from irrigation systems is influenced by temperature, wind, humidity, and solar radiation. Accepted values for water loss efficiency are the results of years of tests; however, most of these values do not take areas of high relative humidity into account. The actual losses of water under different conditions are a critical component of proposed cost share programs for water conservation with agricultural irrigation. The potential benefits of these different sprinkler packages require real world results under actual field conditions. This information can be passed on to farmers so they can obtain better use of the water they are pumping. Since center pivot irrigation represents a large percentage of the irrigation systems in the state of Georgia [over 344 000 ha (850,000 ac)], the potential water conservation benefits from changing to more efficient sprinkler packages is one aspect of the conservation initiative. The main objective of this research was to determine and compare water losses in center pivot systems due to the evaporation and wind interference. In order to determine an appropriate location along the center pivot boom where the tests should be run, uniformity tests were developed and conducted for two months. After this process, the loss tests were conducted during different times of the day in varying weather conditions. This paper includes the procedures used and the initial results from the first season of the loss evaluations. Results show the variability on the average water catch among sprinkler packages as well as the difference of average collections for atmospheric conditions. Initial results indicate a 10% increase in losses when the relative humidity is low (40 to 70%) as compared to a relative humidity between 71 and 99%. Using spray nozzles on top of the pivot boom resulted in the lowest losses within the relative humidity tests, followed by spray nozzles on drops (an additional 6% loss), high angle impact sprinklers (additional 16% loss) and low angle impact sprinklers (additional 22% loss). Additional data is required to determine if the added cost for drops with spray nozzles on center pivot irrigation systems are justified for water conservation in humid areas.