Spring precipitation is always a wild card, experts say
By DAVE WILKINS
Storms dumped record snow in the Sierra Nevada early this winter, and more is expected across the West, increasing the chances that farmers will have adequate irrigation supplies for the new crop year.
In Northern California, snowpack levels were at record levels in early January. The Lake Tahoe, Carson River and Walker River basins reported snowpack levels more than twice the long-term average.
Snowpack levels in the southern half of the Pacific Northwest were also well above average, while the north lagged somewhat.
Snowpack levels in Idaho on Jan. 5 were the 10th highest in 50 years, said Ron Abramovich, a water supply specialist with USDA's Natural Resources Conservation Service.
This year's strong La Niña weather pattern is a good omen for Pacific Northwest snowpack, Abramovich told irrigators attending a North Side Canal Co. meeting in Jerome, Idaho.
"If the past is any indication of the future, expect more cold, wet weather," he told water users Jan. 6.
A strong La Niña weather pattern is in play this winter over the Northern Pacific Ocean, experts said. That typically means above-average precipitation and colder-than-normal temperatures in the Northwest and drier and warmer conditions for the Southwest.
Snowpack levels in the Upper Snake River region were about 21 percent above the long-term average in early January, Abramovich said. In the Bear River basin in southeastern Idaho, snowpack was about 54 percent above normal.
In Oregon, snowpack levels were 31 percent above average in the Upper Deschutes basin, 44 percent above average in the Klamath basin and 61 percent above average in the Lake County and Goose Lake basins.
Washington and Northern Idaho lagged behind the rest of the region, with snowpack levels about 10 to 20 percent below average.
Reservoir levels were in good shape across much of the Northwest in early January. In some locations, water managers were starting to plan for possible flood control releases.
"We're going to stop operating conservatively for (reservoir) refill and start operating conservatively for flood control," Michael Beus, lead hydraulic engineer with the U.S. Bureau of Reclamation's Snake River office, told irrigators attending the North Side Canal Co. meeting.
Beus said American Falls reservoir was within about 10 feet of being full. Erosion becomes a concern when the water level gets higher than that, he said.
In the Yakima basin, the Kachess reservoir was 64 percent full on Jan. 9, and the Cle Elum reservoir was 51 percent full, Reclamation data showed.
In the Deschutes River basin, Wickiup Reservoir was 72 percent full on Jan. 9, and Prineville Reservoir was 59 percent full.
The big wild card is always spring precipitation, water experts said.
Heavy spring rains increase soil moisture, reduce early season irrigation demand and boost reservoir levels.
The unpredictable nature of spring precipitation adds to the challenge of managing reservoirs, Beus said. It can quickly shift the focus from refill to flood control.
"It can flip-flop our water operations," he said.
In Idaho, heavy spring precipitation the past two years has helped to make up for snowpack levels that have been below average to average.