Early-winter runoff
Wednesday, December 28, 2005 12:22 PM PST
Larry Meyer Argus Observer
NYSSA
Runoff in streams and rivers is something normally associated with spring.
This year, though, runoff is occurring across the region just as winter starts. The early-winter runoff has pushed storage in at least one local reservoir far above normal for this time of year.
The reasons for the early-winter runoff can be traced to the fact warm weather - in the wake of several snow squalls and cold temperatures - evaporated as warm fronts rolled off the Pacific and into southeastern Oregon.
According to data posted on the United States Bureau of Reclamation's (BOR) Web site, both the major river drainages, the Owyhee and the Malheur, have seen large spikes in water flows over the past few days.
On the Owyhee River, above the reservoir, the runoff spike began slowly on Thursday with water going by the BOR's automatic measuring station at Rome at about 700 cubic feet per second, and by midnight BOR measured a jump to 900 acre feet. Twenty-four hours later, on Christmas Eve morning, flows were measured at more than 8,000 cfs, peaking at 8,749 at 1 a.m., according data from the BOR gauge.
Flows stayed above 2,200 cfs through Christmas day and was still above 1,000 cfs as of Tuesday afternoon. However, overall velocity showed a decline.
The outcome of those flows was that usable water storage in Owyhee Reservoir was at 400,288 acre feet, at the start of the holiday weekend, and by Tuesday afternoon, was more than 434,000 acre feet.
Average storage for this time of year is just under 390,000 acre feet.
Flows on the Malheur River have also increased and according to the BOR's measuring station near Drewsey, there was a spike in the flow to 1,400 cfs early Tuesday morning.
BOR's data also showed significant increases in storage, with Warm Springs Reservoir containing less than 26,000 acre feet of water through Saturday and having more than 29,000 acre feet by Tuesday afternoon. Beulah Reservoir was at 17,416 acre feet and Bully Creek at 13,228 acre feet.
The snow pack in the Owyhee watershed has dropped, Jay Chamberlin, manager of the Owyhee Irrigation District said.
“We went from 81 percent of normal down to 66 percent,” he said.
He noted the reservoir had gained 25,000 to 35,000 acre feet in four or five days. The conditions which were conducive to the runoff began last fall, Chamberlin said.
“We got good soil moisture because of the rains last fall,” he said.
Then cold temperatures arrived, he noted.
Because the snow sat on frozen soil, when the temperatures warmed up the water had nowhere else to go and was flushed into the streams.
“We went from one extreme to the other,” he said. “It hasn't been getting cold in the upper country.”
Chamberlin said he was unsure about the longterm impact of the early-winter runoff.
“It's early yet,” Chamberlin said. “We're not even through half of the season yet.”
With the amount of water going into the reservoir, Chamberlin said the warming trend was not bad.
However, he said if the snow pack did not rebuild, that could impact stream flows into the summer.
Chamberlin said, though, as the water in the reservoir keeps getting closer to the top, officials will be keeping an eye out for the big storms, which could dump a lot of water and create flood conditions.
