IDAHO FALLS, Idaho—Irrigators supplied by the Upper Snake River reservoir system will enter this winter with far greater storage carryover than they’ve had to start the past two winters, thanks largely to an abnormally wet August.
The rosier storage outlook represents a silver lining to a soggy weather pattern that has riddled Eastern Idaho wheat, barley and alfalfa with mold and sprout damage.
Lyle Swank, watermaster for the district that encompasses the Upper Snake, said the reservoir system now has 1.9 million acre feet of remaining storage, compared with a 30-average of just over 2 million acre feet.
With the irrigation season coming to a close after completion of sugarbeet harvest in mid-October, the system should finish at 30-40 percent full. Last season, the Upper Snake system had below 20 percent carryover, and carryover was less than 15 percent during the prior year.
Swank said the current irrigation season started with a 690,000-acre-foot deficit. The Bureau of Reclamation released 500,000 acre feet from Palisades Reservoir during early spring for flood control, though cool weather prevented the rapid runoff they feared. Eastern Idaho temperatures spiked in mid-summer, increasing the irrigation demand. Then, Eastern Idaho experienced one of the wettest Augusts on record. Swank estimates reduced irrigation demand and additional moisture flowing into reservoirs throughout the month saved the system roughly 500,000 acre feet.
Thanks to the heavy rains, Swank said, nearly 90 percent of water rights in the system operated on natural flows from the Snake River throughout August rather than from storage.
Due to the strong carryover, Idaho Groundwater Appropriators Executive Director Lynn Tominaga said his organization will owe no obligation this season to satisfy the Surface Water Coalition’s delivery call. Last season, IGWA owed about 12,000 acre feet to American Falls Reservoir District No. 2 and Twin Falls Canal Co.
Kail Sheppard, manager of New Sweden Irrigation District, which serves 31,000 irrigated acres west of the Snake River near Idaho Falls, said even if the winter is dry, his members will have ample storage water.
“We haven’t used very much storage at all this year,” Sheppard said. “We’ve got almost all of what we started out with yet.”
Steve Howser, general manager of Aberdeen-Springfield Canal Co., said his users switched back to natural river flows from Aug. 11 through Sept. 9, which saved his system roughly 60,000 acre feet of storage water. Prior to August, he’d expected to finish the year with less than 40,000 acre feet of storage.
“I could potentially see 90,000 to 100,000 acre feet, which would give me two-thirds of my average expected storage use next year,” Howser said.
Idaho’s state climatologist, Russell Qualls, said storage carryover could be especially important this winter as weather conditions appear to be in line with an El Nino pattern, which tends to bring below-average moisture to the Pacific Northwest. During a previous “analogue” year with similar weather conditions, Qualls said the Midwest and Eastern U.S. experienced a cold winter, while the PNW was warmer and drier than normal.
Source: www.capitalpress.com