Water Supply Outlook Suggests Near Normal Snowpack, Late Runoff

White River glacier, Mt. Hood

It’s been a colder winter for us in the Pacific Northwest, which has meant a healthy snowpack and a later runoff for now.

Dr. Henry Pai, senior hydrologist, Northwest River Forecast Center, NOAA, provided a briefing to the Council in April about current water supply conditions and expectations for the upcoming water management season. This information is critical for informing decisions about dam management, hydropower production, and fisheries operations across the basin.

Pai noted that cooler temperatures since November have kept snowpack conditions elevated relative to seasonal precipitation values. Decreased melt and rain have meant that observed runoff to date remains well below normal. The April through September water supply forecasts remain mostly normal to below normal, with the exception of southern Idaho, where forecasts are much higher than normal.

“We’re looking at a healthy snowpack, but it’s melting more slowly,” said Pai. “When it melts more slowly the water tends to seep down into the water table.”

The Council’s fish and wildlife program calls for federal agencies to implement measures to understand and track climate and river conditions to manage the hydrosystem in ways that will protect and improve conditions for fish.

Water Supply Forecasts as of April 10, 2023 (Percentage of Normal at the Dams for April to September)

Upper Columbia Basin Mica 79%
Duncan 90%
Queens Bay 84%
Libby 82%
Hungry Horse 85%
Grand Coulee 85%
Snake River Basin American Falls 114%
Lucky Peak 106%
Dworshak 93%
Lower Granite 88%
Lower Columbia Basin The Dalles 84%

NOAA holds monthly water supply briefings through late spring on the first Thursday of each month.