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The Columbia River Basin

Study Area Background

The Columbia River, originating from the Rocky Mountains in British Columbia, is the largest river in the Pacific Northwest of the U.S. The river is 2,000 km long and flows initially northwest, then turns south and heads towards the border between Oregon and Washington before heading west to the Pacific Ocean. It is the fourth-largest river in the US by volume, and it produces hydroelectricity from 14 hydroelectric dams on its main stem and many more in its tributaries, such as the Willamette, Snake, and Spokane Rivers. The basin’s hydrology is complex, reflecting varying topography, elevation gradient, and proximity to the ocean. The basin drains portions of five U.S. states and two Canadian provinces and has been an important resource for urban settlement and development, agriculture, transportation, recreation, fisheries, and hydropower generation. Due to the decline of most salmonid species in the basin since the last century, the concept of environmental flow was introduced to adaptive river management (Arthington et al. 2010 and references within). Environmental flows are a minimum flow required for fish migration and suitable habitat. Potential climate change, projected population migration, production, and trade will likely decrease future water supply and increase summer water demand in the CRB. The upcoming renegotiation about the Columbia River compact between US and Canada will further complicate the basin-wide water issues. 

No studies have yet examined regional water resource vulnerability in the CRB that simultaneously considers water supply, quality, and demand. Here we examine all three dimensions of water resource vulnerability in the US portion of the Columbia River basin (CRB), the largest river basin in the Pacific Northwest, at the scale of the county. We were limited to the US portion of the basin because insufficient biophysical and social data were available at a consistent scale in the Canadian portion of the basin (i.e. no comparable county-level data were available).

We used U.S. counties as a unit of our analysis for the following three reasons. First, the county is the smallest spatial scale for many socioeconomic and water consumption data; hence, biophysical and socioeconomic data can be analyzed together without the problem of ecological fallacy, a problem in statistics when small scale characteristics are inferred from large scale summary characteristics. Second, the county contains the most consistent and readily available datasets, allowing for systematic analysis across a large river basin. Third, the county scale is one of the smallest land and water resources planning and management units, therefore the results of this study can be used for future planning and management purposes at this scale. As a result, counties allow for relatively swift and tailored actions for addressing specific stressors. 

Our study area, comrised of the U.S. counties that are within or partially within the Columbia River Basin are outlined in red in the map below. The Columbia River Basin is outlined in gray.