State and federal climate officials offered some good news for this year's Columbia Basin water supply, and released a report documenting last year's climate statistics in Washington, Oregon and Idaho, and the impacts of droughts and floods that occurred.
The first Pacific Northwest Water Year Impacts Assessment was released Feb. 22, and is anticipated to become an annual report, Assistant Washington State Climatologist Karin Bumbaco said at a drought and climate outlook webinar.
"Systematic collection of water year impacts to multiple sectors is desired and would provide key information for responding to climate-related events in the future, using past impacts of climate events to show clarity around specific trigger points for action," the report states.
The report for the 2020 water year—from Oct. 1, 2019 through Sept. 30, 2020—includes impacts on different sectors, including drinking water, agriculture, forestry, fisheries, hydropower, recreation and stormwater.
Fisheries managers reported issues with reduced streamflow, warmer stream temperatures, poor water quality, blocked fish passage, reduced fish production and fish mortality due to dry conditions, and problems with fish spawning, water quality and landslides due to flooding, according to the report.
As for hydropower, the "dry start to the water year caused concern among hydropower utilities in the PNW and increased fall energy market purchases, as well as market uncertainty, but a wet winter subsequently increased power generation and eased concerns," the report says. "Later in the summer, low streamflows on the Deschutes and Clackamas rivers in Oregon reduced hydropower generation."
The report notes that the survey on the impacts from last year's drought or flood conditions was developed in the fall of 2020, and "wider distribution of the survey is needed to capture more regional impacts." The assessment is a collaboration between Washington, Oregon, Idaho and the NOAA National Integrated Drought Information System.
The drought webinar featured news about the 2021 water year so far, and the climate and drought outlook through May.
Bumbaco said mountain snowpack greatly improved in recent weeks. As of Feb. 17, snow water equivalent was above normal compared to the 30-year average from 1981 to 2010 throughout Washington state, she said. It was 115 percent above normal in the upper Columbia, and 114 percent above normal in the lower Columbia. Other parts of the region are doing better than they were one month ago, but some locations are still below average for precipitation for the water year so far, which began Oct. 1.
The Willamette River basin is at 94 percent; the middle Snake River basin is at 96 percent; the Salmon River basin is at 97 percent; and the upper Snake River basin is at 88 percent of average, according to her presentation.
For the first 15 days of February, Bumbaco said, most of the region was wetter and colder than normal, especially areas that missed out on precipitation earlier in the water year. "We're talking about accumulations of over a foot [of snow] in some areas," she said, mentioning southern Puget Sound and the Columbia Gorge, and significant ice storms in Portland.
With a cold spring in the forecast, that snow should stick around longer than usual.
Although areas with drought have receded, most of Oregon and much smaller parts of Washington and Idaho continue to experience moderate, severe or extreme drought. And while portions of seven counties in central Oregon and one county in central Idaho remain in extreme drought, most of the Northwest has improved with respect to drought level compared to Dec. 22. The persisting drought is largely due to conditions left from the 2020 water year, Bumbaco said.
So far, the 2021 water year has been warmer than average throughout the Northwest, despite recent colder weather, Bumbaco said. For the first four months of the water year, Montana tied for its fifth warmest on record since 1895, at 3.1 degrees Fahrenheit above average. Washington and Oregon tied for their ninth warmest and Idaho tied for its 17th warmest, with all three states about 2 F above average.
Andy Bryant, senior service hydrologist for the NOAA's National Weather Service said the Climate Prediction Center is calling for below-average temperatures throughout the Northwest over the next two weeks, and through March.
For the three-month outlook including March, April and May, below average temperatures are expected to continue in Washington, northern Idaho and northwestern Montana, while Oregon and southern Idaho have equal chances for above- or below-average temperatures. Bryant said near- to above-average precipitation is also predicted through spring, although the certainty of that forecast is not as strong as it is for temperature.
"We are sort of likely to see continued building of snowpack through the spring, which will be especially beneficial where we have ongoing drought conditions," he said.
Current forecasts for May, June and July, however, are for warmer and drier than average throughout the entire region.
Bryant said most models predict La Niña will transition to neutral conditions—neither La Niña nor El Niño—by summer. He said the April-to-September water supply forecast is expected to be near to above average in the northern regions, including Washington and northern Idaho, and below average in the southern region all the way from southwest Oregon through southern Idaho.