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Snow + Water Supply

Icon of a bear.

Nearly every location in Oregon has seen a

decline in spring snowpack, and it will continue

to significantly decline through mid-century,

especially at lower elevations.

Most of the Northwest will see decreases in April 1 snowpack in excess of 56%. 

Oregon’s mountain snowpack serves myriad economic, ecological, and social functions, and the snowcapped volcanic peaks are part of the state’s cultural identity.

Photo of snowy mountain

These changes in snowpack present a dual risk to the state.

In winter, increases in average streamflow will be the result of precipitation falling as rain instead of snow and rapid runoff, increasing flood risk in some basins.


Summer flows may be reduced by as much as 50% in some basins, presenting challenges to junior water rights holders, hydroelectric power generation, and those not served by reservoir or groundwater storage. Lower flows also impact important commercial and tribal fisheries.

Graph of stream flow in Willamette River for 2040-2069

This figure shows the monthly non-regulated streamflow in the Willamette River at Salem for 2040-2069 under high and low emission scenarios and over the 1971-2000 historical baseline.

cfs = cubic feet per second

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