Sean C. Morgan
Rain’s been falling in buckets the past few days, and it should continue at least through the end of the week, but most of the Willamette Valley is lagging behind normal precipitation thus far this year.
“We have been drier than normal to start this year – significantly in some areas,” said Jeremiah Pyle, a meteorologist with the National Weather Service in Portland.
Right now, the official Salem site is 3½ inches low for the water beginning in October, Pyle said. Oregon had a fairly wet fall.
But from the beginning of the year, numbers have been lagging, he said. In Salem, McMinnville, Corvallis and stations across the valley, rainfall is running up to 10 inches below normal.
Based on U.S. Army Corps of Engineers measurements at Foster Dam, Sweet Home is lagging around 17 inches behind last year, which was wetter than normal. As of April 8, Sweet Home has had 13.42 inches of rain compared to 30.24 on April 9, 2012 and 20.94 on April 11, 2011.
In the short term, the Weather Service was predicting storms over the weekend, with a couple more systems rolling through during the week.
It’s difficult to forecast further out, Pyle said, but the National Oceanic and Atmospheric Administration’s Climate Prediction Center is projecting rain through June to be a little below normal and cooler temperatures.
The cause is difficult to pin down, Pyle said. “We don’t have a real well-defined climate pattern,” Pyle said, but the area has had a high-pressure area most of the year, and that means warmer, drier conditions.
River basins that rely on snowfall should be in decent shape this year.
“We’ve had a fairly normal year in terms of snowfall,” Pyle said. “The snowpack is a little low, but not by much. We’ve built up a pretty good base.”
The snowpack isn’t particularly important to the Willamette Basin, which includes Foster and Green Peter reservoirs.
“We are primarily a rain-driven system,” said Corps Spokesman Scott Clemans. “Both February and March have only been about 60 percent of average in terms of total precipitation.
“However in all but the worst-case scenario, our regulators are predicting we should be able to fill almost all of our reservoirs in the Willamette Basin.
“I haven’t really seen anything with regard to what the summer will look like.”
Right now the Corps is focusing on getting its reservoirs as full as possible this spring, Clemans said. The Corps has had to release a little bit more water this year than it has in the past couple of years. With less rain, the Corps must augment the naturally occuring flows to reach minimum target flows in Salem.
“We’re only about 9 percent below where we would want to be for this time of year,” Clemans said. “We’re really not in bad shape at all. Green Peter is about 12 percent over the rule curve, so we’re doing really well there.”
The past couple of years have been tremendously wet, Clemans said, and the Corps has not had to make a lot of choices.
“We’ve been spoiled,” he said, and there’s been plenty of water to go around for everything. Good summer snow runoff helped out the past couple of years.
The snowpack doesn’t account for much of the system, but it does count for about 10 percent of total storage in the system.
The snowpack doesn’t fill the reservoirs. The reservoirs are usually full by the time snowpack is melting, and it allows the Corps to keep the reservoirs full later into the summer.