Oregon hydrologist says early fall rains are 'a good start'
After an unprecedented and unexpectedly bad fire season this year, USDA hydrologist Scott Oviatt says a wet winter is definitely needed to prevent similar events in the future.
"We've had extreme periods of very warm and dry weather," Oviatt said in early September. "And we had that in winter, too. We had a very dry December and remained fairly dry and warm until March. This trend has been happening multiple years in the last decade (and led to) rapid melt out. Where we are today is pretty much a result."
"What occurred was unprecedented (and involved) low humidity and dry conditions we typically don't see in summer or early fall," Oviatt explained further.
In early September, the previous water year was ending with less than desirable numbers. Precipitation for the region sat at 87% of normal right before fires ignited all around the state.
So far this fall, precipitation has picked up, but the intermittent dry spells occurring between showers are a concern.
"We've had substantial precipitation about Clackamas and Multnomah Counties," Oviatt said. "We've established some early precipitation, which is good. Precipitation has been at 130% to 170% of normal since the fires, which is equivalent to about nine to 18 inches of rainfall. Since the water year began on Oct. 1, we've received about 120% to 160% of normal precipitation amounts, so about seven to 12 inches of rainfall."
While this early fall rain has been appreciated and needed, Oviatt says the jury is still out on what the water outlook will be for next spring, which will be determined by the next few months.
This time last year looked very similar to recent conditions. In October 2019, the precipitation in the Hood, Sandy and Lower Deschutes region was around 120% to 140% of normal, starting the water year off well, but that was followed by a dry spell in November through December.
"This has definitely been a good start," Oviatt explained. "Now we're in a holding pattern here. We hope we get these series of systems where we get consistent, sustained storm impacts."
"Our weak point over the last 10 to 15 years has been extended dry periods in winter," he added. "When that occurs, it prevents long-term precipitation build up in the mountains, which leads to some concern of potential water shortages in the spring. (Hopefully), we begin to get some fall rains and colder temperatures into winter."
Since the new water year has just begun, Oviatt says he is "neither pessimistic nor optimistic" about the season moving forward.
"The main take-home point is we're early in the water year and a lot could change before Jan. 1," he added. "We're in a wait-and-see mode and we're hoping for cooler temperatures."
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