CALDWELL, Idaho — The large amounts of snowfall that fell in basins across Idaho and Eastern Oregon last winter will benefit irrigators into the 2018 water year.
“Last year was so exciting and set the stage for the coming year,” Ron Abramovich, a Natural Resources Conservation Service water supply specialist, said during University of Idaho’s Ag Outlook Seminar in Caldwell Dec. 7.
Some reservoirs in Idaho are at or near record high storage levels for this time of year, he said.
“There is a tremendous amount of water in the reservoirs now and flows are above normal, too,” Abramovich said. “We are going to put less emphasis on snow this year because there is so much water in the reservoirs.”
Snowpack levels are below normal so far this season in many basins of the region but the amount of water in reservoirs that was carried over from the 2017 water season has provided a significant buffer that could insulate irrigators from even a below-average snow year this winter.
For example, the overall snowpack level in the Owyhee River basin was only 26 percent of normal as of Dec. 11 but the Owyhee Reservoir has 449,000 acre-feet of water, which means that reservoir is already 63 percent full with the rest of the winter still to come.
The Owyhee basin feeds the Owyhee Reservoir, which provides water to 118,000 acres of irrigated land in Eastern Oregon and part of Idaho.
“An average year for us is 300,000 acre-feet of carryover. We’ve done much better than that this year,” said Owyhee Irrigation District Manager Jay Chamberlin. “We’re sitting in real good shape.”
Even if snowpack in the Owyhee basin is slightly below normal this winter, growers who depend on the reservoir for their irrigation water would have a full season of water next year, he said.
Many basins in the state produced near-record natural stream flow levels this year and many had near-record amounts of carryover water, said Terrell Sorensen, a University of Idaho Extension educator in Power County.
Idaho’s overall 2017 water season “ranks right up there in the top (ever),” he said. “It was a really good water year.”
Natural river flow in the Upper Snake River basin this year was the second highest in the last 106 years.
At the end of the 2017 water season, the Upper Snake reservoir system had the highest amount of carryover water in its history, said Lyle Swank, watermaster for Water District 1, which is Idaho’s largest and provides water for more than 1 million acres of irrigated farmland.
On Nov. 7, the system was 78 percent full, which is twice the normal average for that date, Swank said.
“The benefits of 2017’s high snowpack are still helping us out heading into the 2018 water season,” he said. “We’re in excellent position as far as reservoir storage carryover.”