US Northwest hydropower outlook remains weak after a dry, warm March

Dry, warm weather across the Pacific Northwest in March caused meltoffs in mid- to lower snow elevations, which led to declines in the water-supply forecast at several reservoir locations.

The Northwest River Forecast Center expects big deficits in May, June, and July until summer baseload conditions are reached, Henry Pai, senior hydrologist, said during the NWRFC's April 4 water supply briefing.

"We've been trailing for the water year," Pai said about water supply forecasts, with the exception of February, when warmer weather caused precipitation to fall as rain, which then flowed into rivers and filled up reservoirs. "As we transition to April, we have a lot of melt possibly going into our reservoirs."

Lack of precipitation

The lack of precipitation in March kept some snow pillows from accumulating, Pai said. The snow pillow measures how much water is in the snowpack by weighing the snow with a pressure transducer, according to the National Resources Conservation Service.

Year-to-date precipitation and current snowpack are stratified geographically, with well-below-normal conditions in the northern, mountainous areas and near- to well-above-normal conditions in the south, Pai said.

Accumulated precipitation above Grand Coulee is at 80% of normal, down three points from February, Pai said, adding it remains below the 30-year average. Accumulated precipitation for the Colorado River Basin at The Dalles is at 88% of normal, also below the 30-year average, but above the previous two water years.

Meanwhile, accumulated precipitation for the Snake basin above Lower Granite Dam is at 98% of normal, which is higher than the past two water years.

The southern portion of the NWRFC's territory has had more precipitation leading to "a little too much water for that point in time," Pai said about flooding concerns.

"Water-supply forecasts largely mimic precipitation and snow conditions, with extremely dry forecasts in the north [Canadian portion of the Columbia River basin] and very wet forecasts in the south," Pai said.

Conditions at The Dalles

Conditions at The Dalles Dam, located on the Columbia River on the Oregon-Washington state border, serve as the barometer for hydro conditions in the region. Less hydro generation in the Pacific Northwest translates to less generation available for exports to neighboring regions.

The water supply forecast at The Dalles Dam is currently at 81% of normal for the April-September forecast period, three percentage points lower than a month ago and four points lower than a year ago, according to NWRFC data.

"We do see declines due to that drier than normal month of March," Pai said about water supply forecasts.

Inflows into The Dalles Dam averaged about 127,060 cubic feet/second in March, up 1% from February and a 24% year-on-year increase, according to US Army Corps of Engineers data. Likewise, generation at The Dalles averaged about 700 MW for March 1-26, up 40% from February and a 12.2% year-on-year increase.

Hydro generation's market share has averaged 70.9% of the total fuel mix so far this year, up nearly a half percent from 2023, but below the annual averages for 2018 through 2022, according to Bonneville Power Administration data.

Power forwards

Despite a weaker hydro outlook, power forwards are trending lower than year-ago packages on weaker gas forwards and a mild weather outlook.

Mid-C on-peak June is in the mid-$40s/MWh, down nearly 28% from where its 2023 counterpart was a year ago, although prices climbed about $5 from February, according to data from Platts, part of S&P Global Commodity Insights. Likewise, the Sumas June contract is around $1.573/MMBtu, 22.7% below its 2023 counterpart.

The three-month outlook indicates a greater probability for above-normal temperatures across most of the West, with the exception of Southern California and parts of the Desert Southwest, which has equal chances for above- and below-normal temperatures, according to the US National Weather Service's Climate Prediction Center.