Sean C. Morgan
Sweet Home’s local reservoirs are handling a lot more rain in recent weeks after Green Peter, in October, reached its lowest level since its construction in 1967.
Green Peter reached a low of 899 feet at the end of October. That number is the level of the reservoir surface above sea level, and in Green Peter’s case, it’s 9 feet above minimum power pool, the level required for power generation. It’s about 116 feet below full pool, 111 feet below maximum conservation pool and 23 feet below the year-round Thistle Creek boat ramp.
The U.S. Army Corps of Engineers, in mid-September, warned that the pools at Detroit and Green Peter were receding below minimum conservation elevations, a level the Corps usually holds throughout the winter, putting the lowest-level boat ramps out of service.
Outflow was exceeding inflow.
As of Sunday, Green Peter was at 938.7 feet, slightly higher than last year. The pool peaked at the beginning of May at 984 feet. Since then, the level decreased until the end of October.
The Corps was releasing 3,280 cubic feet per second from Green Peter Sunday evening. The inflow was 3,353 cfs.
Foster Lake, which represents about 2 percent of the water in the 13-dam Willamette Project, filled and remained full through the summer. The reservoir was not substantially impacted by low precipitation this year.
Several reservoirs were at their lowest point since construction or within the second or third lowest level on record, said Corps Spokeswoman Amy Echols. Water levels never got low enough to cause any issues, but the Corps had contingency plans in place for several projects, and Corps officials were meeting with other agencies to plan for flows needed for the fish population, power generation and other issues, should levels have gone much lower.
“We’re getting some rain, so they are coming up again,” Echols said. “It went up dramatically. It went from 900 to 945 in about three weeks. We’re tracking very well right now on where we should be.”
Green Peter’s “water control diagram” calls for a minimum level of about 922 feet through the winter.
On Dec. 1, 2014, Green Peter was at 936 feet.
“We had a lot of rain in December (2014), actually,” Echols said. Green Peter reached 960 feet in the third week of December 2014.
“We haven’t had our meeting with the National Weather Service yet,” Echols said, but the Corps is getting weather briefings. “We’re not in drought-planning mode with the rain. It’s a nice wet start.”
But last year was a wet start too, leading to one of the driest years on record for the Willamette Valley.
“We’re hoping for rain,” Echols said.
Meterologist Laurel McCoy of the National Weather Service in Portland, called the current weather patterns “pretty typical.”
The rain was expected to continue through the middle of this week, a new system every 24 hours or so.
In a longer-term outlook, “it’s kind of hard to say in an El Niño year,” McCoy said. Oregon is on the edge of the wetter weather that hits California and the south during El Niño, which means the weather could go either way.
In any case, meteorologists anticipate more rain this year, she said. “We’ll likely see around normal or a little less than normal.”
Even if it’s lower than normal, it’ll seem like a lot of rain, McCoy said. Eugene and Portland both recorded one of their top three driest years in history last year.
Sweet Home didn’t break 20 inches of precipitation this year until after Nov. 8. This week precipitation is at 28.09 inches to date, more than 8 inches, nearly half of all the rain that fell in 10 months, in a single month.
Even if the rain ended now for the year, it would remain one of the four driest years on record, McCoy said. The past year did set the record for low snowpack.
In any case, meteorologists have a lot of uncertainty about what to expect, she said.
“It would be very, very abnormal to have two record low years, back-to-back,” McCoy said.