Watershed / Cuenca Hidrológica
A watershed refers to the flow of water over land. It encompasses the land from which surface water, sediment, and dissolved substances travel from small streams and tributaries into the same place, a lake, river, wetland, or other body of water1,2.

The Willamette Valley watershed includes the area surrounding the Willamette River and its tributaries. The boundaries of the Willamette Valley watershed are:

  • North - Portland and the Scappoose Bay on the Columbia River, and extending north of St. Helens
  • South - Eugene, more specifically south of Cottage Grove
  • East - the Cascade Mountains
  • West - the Coast Range

Large tributaries to the Willamette include the Coast Fork and Middle Fork of the Willamette River, the McKenzie, the Long Tom, Mary's, Calapoola, North and South Santiam, North and South Yamhill, Mollala, Tualatin, and Clackamas rivers3. The Pudding River may also be considered a tributary for the Willamette based on maps.

Watershed / Cuenca Hidrológica Translation Needed

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1. United States Geological Survey (2009) Water Science for Schools: What is a watershed? Available at ga.water.usgs.gov/edu/watershed.html (accessed July 2009).
2. Strahler, A. & Strahler A. (2005) Physical Geography: Science and Systems of the Human Environment, Third Edition (USA: John Wiley & Sons, Inc).
3. Willamette River Keepers (no date) Tributaries. Available at willamette-riverkeeper.org/WRK/tributaries.html (accessed June 2009).

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