Data collected for Irrigation Efficiency Rewards program
By JOHN O'CONNELL
Standard wheel lines wasted 30 percent of their water on average through leaks and worn nozzles in testing of irrigation equipment used on several Southern Idaho farms.
Furthermore, 60 percent of center pivots tested needed new sprinkler packages due to uneven moisture distribution, caused by clogged nozzles, broken sprinklers or bad regulators.
Throughout last summer and fall, University of Idaho Extension irrigation specialist Howard Neibling tested 30 center pivots and more than 1,000 hand and wheel line sprinkler heads from Bliss to Burley, running each system over a row of cups to take water measurements.
He also analyzed leaks caused by bad bearings, drain valves and other hardware problems.
Idaho Power funded the research to provide better pricing data for its Irrigation Efficiency Rewards program, which shares costs toward about 700 irrigation projects per year. The utility's agricultural engineer, Quentin Nesbitt, explained the program pays a portion of specified irrigation improvements, ranging up to 75 percent depending on potential power savings.
Uses of the systems in Neibling's study ranged from pasture to potatoes. Neibling said his results suggest many Idaho farmers are using irrigation packages too long and aren't inspecting them enough.
"I was surprised the uniformity was as low as it was under the pivots, and I was definitely surprised that I saw water losses as high as they were under set systems," Neibling said.
Standard wheel lines in his study pumped 16 percent more water than necessary due to leaks and lost 14 percent through worn or incorrectly sized nozzles. More modern wheel lines lost 12 percent of water to leaks and 11 percent to bad nozzles. Hand lines, used mostly on pastures in his study, lost 30 percent of water to leaks and another 16 percent to worn nozzles.
Pivots wasted less than 5 percent of water, likely because their leaks are easily spotted.
Neibling advises updating pivot packages every five to seven years, depending on crop rotation and said wheel lines tested well with up to four to six years of use. He saw no evidence that a system's age affected performance, provided that growers kept up with maintenance and replacing sprinkler packages.
Proper maintenance of irrigation systems offers a quick return on investment, he said. Excessive and insufficient water application both hurt yields in most crops and chemical application through poorly functioning irrigation systems is ineffective, Neibling said.
"We had a few leaks that were as large as 6-7 gallons per minute," Neibling said.
Rupert grower Duane Grant typically updates irrigation packages on his wheel lines whenever a field rotates to potatoes.
"We start to see real distinct deviations in water pattern after about five years," Grant said.
Chuck Buchta, manager with Knudsen Irrigation in Aberdeen, Idaho, said most growers in his area replace nozzles in hand and wheel lines every four years as they rotate into potatoes. He suggests annual testing of pivots with rain gauges.
"People put a lot of emphasis on chemicals and a lot of other things, and they really discount irrigation," Buchta said. "Timely and even irrigation will make your crop."