Climate change threatens this natural storage by changing the timing of snowmelt and the amount of water available in streams and rivers (streamflow) throughout the year. The snowpack melts and replenishes streams and rivers in the late spring and summer, when there is very little rainfall. Much of the Northwest's water is stored naturally in winter snowpack in the mountains. Oregon State University's Oregon Climate Change Research Institute (OCCRI) ExitĪ reliable supply of water is crucial for energy production, agriculture, and ecosystems.Forest Service: Pacific Northwest Global Change Research Exit Fish and Wildlife Service: Climate Change in the Pacific Northwest USGCRP, Global Climate Change Impacts in the United States: Northwest.Climate Change 2014: Impacts, Adaptation, and Vulnerability Exit
Summer precipitation is projected to decline by as much as 30%, with less frequent but heavier downpours. Changes in average annual precipitation in the Northwest are likely to vary over the century. In Washington state, record low snowpack values were measured in April 2015 and in seventy-four percent of long-term monitoring stations. Declines in snowpack and streamflows have been observed in the Cascades in recent decades. Precipitation in the region has seen a decline in both the amount of total snowfall and the proportion of precipitation falling as snow. Temperatures are projected to increase by approximately 3☏ to 10☏ by the end of the century, with the largest increases expected in the summer. Over the last century, the average annual temperature in the Northwest has risen by about 1.3☏. East of the mountains, it is typically sunnier and drier throughout the year, winters are colder, and summers can be significantly hotter. West of the mountains, year-round temperatures are mild, winters are wet, and summers are dry. The region is home to the Cascade Mountain Range that runs north-south through Washington and Oregon, resulting in large climatic differences on the western and eastern sides of the range. The Northwest is best known for its vast Pacific coastline and rainy weather. Sea level rise is projected to increase erosion of coastlines, escalating infrastructure and ecosystem risks.Higher temperatures, changing streamflows, and an increase in pests, disease, and wildfire will threaten forests, agriculture, and salmon populations.Climate change will likely result in continued reductions in snowpack and lower summer streamflows, worsening the existing competition for water.Warming temperatures and declines in snowpack and streamflow have been observed in the Northwest in recent decades.The Pacific Northwest DEWS is a collaborative federal, tribal, state, and local interagency effort to improve early warning capacity and resilience to drought in the region. While the coastal regions experienced an unprecedented single-year drought, the eastern portions of Oregon and Idaho had been suffering under prolonged drought for multiple years. In 2015, virtually the entire region reached historic drought conditions. The region experienced multiple droughts in the early 21st century. Despite its soggy reputation, even the coastal regions of the Pacific Northwest are no strangers to drought.
It is an ecologically diverse region heavily reliant on snowpack, precipitation, groundwater, and highly managed rivers like the internationally regulated flow of the Columbia River for its water supply. The Pacific Northwest is often associated with rainy forecasts, foggy days on the coast, and large-scale irrigated agricultural projects in the arid interior.
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