Wet December, dry January leave water managers guessing
By JOHN O'CONNELL
Just a month ago, snowpack was abundant and irrigators had every reason to expect a banner water year, but after a dry January, they're crossing their fingers for a wet spring to deliver close to an adequate supply.
After a hot and dry 2012 growing season, relief came to growers in October, November and December, with storms drenching lower elevations and dumping snow on high ground.
"Unfortunately, temperatures weren't cold enough. Mid to low elevations just got rain," said Jeff Anderson, a Natural Resources Conservation Service hydrologist in Idaho.
The snowpack above 6,500 feet was nonetheless ample to support a rosy storage water outlook.
But January, typically the wettest month, started with a high-pressure system setting up over the Pacific Northwest, forcing the biggest storms north. Major storms also missed California.
Water is the lifeblood of western agriculture, allowing farmers to grow more and higher value crops. Forecasters say the next few months will be critical in shaping the coming water year, but the indicators, which have been less reliable than normal thus far, seem to point to more dryness.
Throughout Idaho, January precipitation ranged from 40 to 70 percent of average. In Washington's Yakima River Basin, where snowpack is critical for filling the system's five reservoirs, January snowfall was just 38 percent of average. Oregon received between a one-third and half of its usual January snowfall.
"We had a really wet start to the winter and we're just about hitting average now," added Jeanine Jones, interstate resources manager with the California Department of Water Resources. "We had one big storm at the end of December that dumped a whole lot of water. After that, we had a fairly dry period."
Despite the dry spell, water managers are far from panicking. Though the numbers fell from their lofty December peaks, February started with Washington's overall snowpack at 120 percent of normal, Oregon at 103 percent of normal, Idaho at 90 percent of normal and California at 93 percent of normal, according to the NRCS.
"By the end of January we're normally looking at having 60-70 percent of our snow on the ground," said Scott Pattee, a water supply specialist with the NRCS in Mount Vernon, Wash. "Honestly, we have that now for the most part, but that's only because we had a huge month of December."
If February and March bring average precipitation, Steve Howser, general manager of southeast Idaho's Aberdeen-Springfield Canal Co., expects to have an adequate water supply for his members.
"Less than that, I'll have to look real hard at maximizing our conservation when we get to April 1," Howser said.
Through January, snowpack in the Snake River Basin above Palisades Reservoir, which provides Howser's water supply, was at 91 percent of normal.
Clair Bosen, president of Twin Lakes Canal Co., depends on the Bear River Basin, which ended the month with 80 percent of normal snowpack, to fill his company's three reservoirs.
"We always get really nervous when it comes to the first of February if we are below normal. It seems like we can never catch up then," Bosen said.
If his area doesn't receive above average snowfall during the next month, Bosen predicts several growers will shift from thirsty crops to grains for their water efficiency.
Idaho reservoirs that were full to start 2012 are now reduced to near average capacity. The eight reservoirs in the Upper Snake system are more than half full, still well above average for this time of year. The Boise system is normal, and the Payette system is 110 percent of normal.
In-stream flows, predicted to be strong for the 2013 season in late December, are now expected to be 90 percent of normal.
"We'll know more in late March or early April, but right now there's the possibility that water supply could be a pretty important factor irrigators and people planting crops need to take into consideration," said Lyle Swank, watermaster over the Upper Snake River system. "Natural-flow water rights might see cutoff quicker than they would otherwise."
Mike Schwisow, with the Washington State Water Resources Association, expects a normal year in the Columbia River Basin. Reservoir storage and snowpack within the Yakima River Basin, a system he described as fully appropriated, is also better than average.
Pattee said the Blue Mountains near Walla Walla have the state's lightest snowpack, at 80 percent of normal.
"My prediction going out into spring is even if we don't get a lot more snow, most areas will be OK as long as they have reservoir storage," said Pattee, who also believes an average snowpack should be sufficient for growers who rely on natural flows.
Oregon reservoirs, averaging 86 percent of normal fill through Jan. 1, have been lower than last year. But Melissa Webb, an NRCS hydrologist based in Portland, Ore., believes the wet December should protect her state's growers from water shortages.
She said southeast Oregon, where the snowpack ranges from 55 to 60 percent of normal, could use more moisture to bolster in-stream flows, projected to be well below average in that corner of the state.
"We had a wet fall across most of Oregon. ... In some areas it was the wettest as far as precipitation we've seen," Webb said. "We've come down a little since Jan. 1. Normally we're accumulating this time of year."
Due to a wet start to winter, reservoirs in California's expansive Central Valley are as full to date as permitted for flood control purposes.
However, February began with below-average snowpack in the Sierra Nevada Mountains, ranging from 91 percent of normal in the southern mountains to 97 percent of normal in the north.
Jones said the Golden State will need a wet February and March to avoid a "dry year."
The National Oceanic and Atmospheric Administration recently released a three-month forecast predicting continued dryness throughout most of California, southwest Oregon and Idaho's southwest and eastern regions. Elsewhere in Oregon, Washington and Idaho and in Northern California, equal chances of wet or dry weather are predicted.
"Right now (the water outlook) is good, but December, January and February typically supply about half of the state's annual precipitation," Jones said. "What happens now is really important."
A unpredictable year
Pattee has seen one long-term prediction of another late spring for his region, which would release snowpack evenly and prolong the start of the irrigation season.
He's also seen indicators that little moisture may be in store for the Pacific Northwest, though NOAA lists most of the region as being in a neutral pattern.
"The theme of the long-range forecast right now is we're really not going to get that much more (snow)," Pattee said.
He advised irrigators to take the information with a grain of salt. Uncertainty has been the broader and more definitive theme of the winter, he said.
"The problem with this year is it's been such an odd year. We haven't really seen a year like this ever," Pattee said. "Really the advice given to us has been don't believe anything more than five days out."
Pattee explained long-range forecasts utilize comparisons with similar past years. This winter's weather patterns have been unprecedented, he said.
"What we're seeing this winter is weather coming in waves. December was wet and dumped tons of snow in the Cascades, and then boom, shut off. It's like somebody turned a faucet off," Pattee said.
Idaho NRCS water supply specialist Ron Abramovich said weather models that typically align to tell a story can't find agreement.
"The seven-day forecasts are changing every day," Abramovich said. "Hopefully, we'll rebound in February."