Snowpack is a vital part of Oregon’s water supply, especially in mountain watersheds like those in the Cascades and the mountains of Eastern Oregon. When snow melts in spring, it feeds streams, replenishes groundwater and sustains rivers through dry summer months. However, as the climate changes, Oregon’s snowpack is shrinking, threatening this critical meltwater supply.

Snow hydrologists use a term called “Snow Water Equivalent” to describe how much water can melt from the snowpack. Think of it this way: fluffy, dry snow has less water than dense, wet snow. Snow Water Equivalent measures the water content in snow and helps predict how much meltwater will flow into rivers and aquifers. In Oregon, most snow melts between March and May, but the timing can shift depending on elevation, weather and year-to-year conditions.

Climate projections show that warming temperatures will have significant impacts on Oregon’s snowpack in the following ways:

• Less snow, more rain: By 2050, snow accumulation could drop by 25% or more in many areas, with fewer snowy winters and more “snow droughts.”
• Earlier melt: Peak snowmelt is already happening one to three weeks earlier than it did in the early 1980s. This trend will likely continue, shortening the snow season.
• Longer dry spells: While Oregon’s total annual precipitation is expected to remain stable or increase, more of it will fall in intense winter storms, with drier summers in between.

These changes pose challenges for forests, farms and communities. The snowpack acts as a short-term reservoir for slow meltwater release. Shorter snowmelt seasons result in reduced streamflow, lower water tables and longer dry seasons. Forests may face more drought stress, increasing wildfire risk. Farmers and stream habitats may see less reliable water during critical late summer months.

Adapting to these challenges will require creative solutions. Examples include:

• Forest management: Research shows that thinning overly dense forests not only reduces wildfire risk but also helps conserve water. This is because thinning reduces water loss from trees, leaving more water in the soil and streams.
• Water efficiency: Improving irrigation systems and cutting overall water use will be essential for drought resilience.
• Planning for change: Communities can prepare for shorter snow seasons by developing long-term strategies to adapt to changing water availability. This might include preserving or restoring natural features like wetlands, which store water and support ecosystems during droughts, or implementing policies that support sustainable land and water management.

References

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• Almazroui, M., et al. (2021). Projected changes in temperature and precipitation over the United States, Central America, and the Caribbean in CMIP6 GCMs. Earth Systems and Environment, 5, 1–24.
• Bales, R. (2024). Making up for Lost Snow in Forested Mountain Headwaters. Presented at the Annual American Geophysical Union Meeting, Washington, D.C., December 9–13. Abstract H53U-05.
• Bulman, T. (2015). Atlas of Oregon Climate and Climate Change: A Classroom Atlas. Center for Spatial Analysis and Research at Portland State University.
• Fleishman, E. (Ed.). (2023). Sixth Oregon Climate Assessment. Oregon Climate Change Research Institute, Oregon State University, Corvallis, OR. Retrieved from Oregon Climate Assessments.
• Rupp, D. E., L. R. Hawkins, S. Li, M. Koszuta, and N. Siler. (2022). Spatial patterns of extreme precipitation and their changes under ~2°C global warming: a large-ensemble study of the western USA. Climate Dynamics, 59, 2363–2379.
• Siirila-Woodburn, E. R., et al. (2021). A low-to-no snow future and its impacts on water resources in the western United States. Nature Reviews Earth & Environment, 2, 800–819.
• Sproles, E. A. (2012). Climate change impacts on mountain snowpack presented in a knowledge-to-action framework. (Doctoral dissertation). Oregon State University, Corvallis, OR.
• USDA Climate Hub. (n.d.). Snow Water Equivalent (SWE) – Its Importance in the Northwest. Retrieved December 15, 2024, from USDA Northwest Climate Hub.
• Vano, J. A., J. B. Kim, D. E. Rupp, and P. W. Mote. (2015). Selecting climate change scenarios using impact-relevant sensitivities. Geophysical Research Letters, 42, 5516–5525.