About Willamette Water 2100

Oregon’s fertile Willamette River Basin is the state’s most populous as well as one of its most important forest and agricultural regions. Anticipating how water supply, land use, and water scarcity in the basin are expected to change in the 21st century under the drivers of climate change, population, and economic growth is the subject of the Willamette Water 2100 (WW2100) project. Like many places in the West, the Willamette River Basin faces water scarcity resultingfrom declining snowpack. Among the project’s key findings, researchers learned that under climate change, rising temperatures are expected to reduce snowpack, creating less than favorable conditions for existing forests while increasing the frequency of wildfires. Urban water demand could double as the basin’s urban populations rise throughout the 21st century. However, water demand for agriculture could stay about the same or even slightly decline as farmlands near high-growth urban areas are converted for urban use. Primarily funded by the National Science Foundation, WW2100 employed the Envision modeling platform used by CIRC researchers in the Big Wood Basin and Tillamook County.



  • Jaeger, William K., Andrew J. Plantinga, Heejun Chang, Kathie Dello, Gordon Grant, David Hulse, J. J.McDonnell et al. “Toward a formal definition of waterscarcity in natural-human systems.”
    Water Resources Research 49, no. 7 (2013): 4506- 4517.

  • Turner, David P., David R. Conklin, Kellie B. Vache, Cynthia Schwartz, Anne W. Nolin, Heejun Chang, Eric Watson, and John P. Bolte. “Assessing Mechanisms of Climate Change Impact on the Upland Forest Water Balance of the Willamette River Basin, Oregon.”Ecohydrology 10, no. 1 (2017). https://doi.org/10.1002/eco.1776.

  • Turner, David P., William D. Ritts, Robert E. Kennedy,Andrew N. Gray, and Zhiqiang Yang. “Effects ofHarvest, Fire, and Pest/Pathogen Disturbances on the West Cascades Ecoregion Carbon Balance.”Carbon Balance and Management 10, no. 1 (2015): 12. https://doi.org/10.1186/s13021-015-0022-9.

  • Turner, David P., David R. Conklin, and John P. Bolte. “Projected climate change impacts on forest land cover and land use over the Willamette River Basin, Oregon, USA.”

    Climatic Change 133, no. 2 (2015): 335-348.


  • Vano, Julie A., Tapash Das, and Dennis P. Lettenmaier.

    “Hydrologic Sensitivities of Colorado River Runoff toChanges in Precipitation and Temperature.”
    Journal of Hydrometeorology 13, no. 3 (2012): 932- 949.


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    Lettenmaier. “Seasonal Hydrologic Responses toClimate Change in the Pacific Northwest.”
    Water Resources Research 51, no. 4 (2015): 1959- 1976. https://doi.org/10.1002/2014WR015909.

  • Vano, Julie A., John B. Kim, David E. Rupp, and Philip W. Mote. “Selecting Climate Change Scenarios Using Impact-Relevant Sensitivities.”
    Geophysical Research Letters 42, no. 13 (2015): 5516- 5525.


  • Vano, Julie A., John B. Kim, David E. Rupp, and Philip

    W. Mote. “Selecting Climate Change Scenarios Using Impact-Relevant Sensitivities.” Geophysical Research Letters 42, no. 13 (2015): 5516-5525. https://doi.org/10.1002/2015GL063208.


  • Partners included numerous state and federal agencies, extension services, local governments, non-governmental organizations, educators, and others.

  • Effectively modeled Willamette River Basin under multiple climate change, land use, and demographic scenarios to theyear 2100.

  • Project has resulted in roughly twenty-eight publications.  


  • By the year 2100, the Willamette River Basin is projected to be between 1 to 7 degrees Celsius (2 to 13 degrees Fahrenheit) warmer than the historical baseline (Project Website: http://inr.oregonstate.edu/ww2100/).
  • Human-caused climate change (anthropogenic forcing) shows up as a clear signal in the temperature data. Anthropogenic forcing, the result of increasing human-caused greenhouse gas concentrations, dominates the long-term variability in temperature throughout the 21st century (Project Website).
  • Due to rising temperatures, precipitation in the Willamette River Basin is increasingly likely to fall as rain instead of as snow, resulting in a decreased snowpack for the basin.
  • For every 1 degree Celsius (2 degrees Fahrenheit) increase in annual mean temperature, there is a roughly 15 %decrease in summer flow in the lower Willamette River Basin. However, as temperatures get significantly higher thanthe historical average, the spring snowpack is essentially absent. Thus, additional temperature increases have only amarginal effect on streamflow.
  • Among the key changes for water availability is the transformation of upland forests (Project Website).
  • The snowpack—measured as snow water equivalent as a proportion of cumulative water-year precipitation—is expected to decline markedly across the Willamette River Basin as the climate warms. Declines are expected to vary greatly across the Basin (Project Website).
  • By the middle of the 21st century, Willamette River sub-basins with little snow historically, such as the middle Willamette, are projected to receive virtually no snow in the future (Project Website).
  • By the middle of the 21st century, Willamette River sub-basins that historically have receive the most snow, such as North Santiam, are projected to experience winter snowpack declines of one-quarter to two-thirds (Project Website).
  • The majority of climate scenarios employed showed a general trend of wetter winters and drier summers in the Willamette River Basin. However, there was not a unanimous agreement between models and scenarios simulating either a drier or wetter future (Project Website).
  • The small projected increases in total winter precipitation did not significantly offset snowpack losses resulting fromincreased warming (Project Website).