KIMBERLY, Idaho—University of Idaho Extension irrigation specialist Howard Neibling expects most Eastern Snake Plain well users will find relatively painless ways to meet a mandate to cut water consumption by 13 percent.
Irrigators with Idaho Ground Water Appropriators, Inc., recently agreed to curb their water usage to help stabilize a declining aquifer. Many specific details of the agreement, reached to avert the Surface Water Coalition’s call based on declining spring flows into the Snake River due to groundwater pumping, are still being negotiated.
Neibling has been working to help irrigators in Nevada, Northern California and Montana facing more acute shortages reduce water use by more than a quarter.
“Relative to (cuts) I see some other groups are having to make, it looks like in most cases people will still be able to do it and still maintain the same acreage, and hopefully grow the cropping mix they want to grow,” Neibling said.
He believes growers will implement new irrigation technology and pay greater attention to maintenance.
He said fixing leaky irrigation systems is a good place to start. In a commercial study he conducted a few years ago, Neibling evaluated 30 wheel lines, finding losses due to leaks averaged 16 percent. Growers lost another 13 percent due to worn or incorrectly sized nozzles.
The 30 pivots he tested had few leaks, but about 60 percent of them didn’t meet industry standards for uniformity of water distribution. Neibling said pivot pressure regulators and nozzles should be replaced every five to seven years to avoid uneven distribution.
Growers with hand and wheel lines who irrigate on 12-hour sets should test soil moisture to determine if it’s penetrating below crop root zones, Neibling said.
“The normal set in Kimberly, we were applying two hours too much and had to cut back a coupe of hours,” Neibling said.
In fields heavy in rock outcroppings, Neibling said, growers can avoid unnecessary watering by using variable-rate pivot irrigation.
On flat, sandy soils, Neibling’s research of pivots in Arco, Idaho, shows growers can improve soil moisture penetration by 20 to 30 percent by using hoses that lower nozzles from 6 feet off the ground to closer to the crop canopy. The method avoids evaporation and wind-blown water droplets, he said.
American Falls grower Jim Tiede has chosen to remove the end guns from pivots on 720 acres of sugar beet fields to comply with the agreement.
“It’s not a real efficient way to water,” Tiede said.
Neibling estimates growers can save 13 percent of their water by turning off end guns and leaving the corners of fields fallow. Yields on corners tend to be 17 percent lower, anyway, due to inefficient watering, he said.
IGWA Executive Director Lynn Tominaga anticipates growers will also conserve water by cutting out late-season irrigation of grains, when crops are still green but kernels have mostly filled in.
“It’ll mean we have to manage the water better but yet make sure our crops get finished and we have good quality,” Tominaga said.
Tominaga said agreement negotiations must prioritize protecting growers who have already implemented conservation measures and have less room for improvement.
Source: www.capitalpress.com