FAQ: Water Source

What source options did TVWD and Hillsboro study?

All viable sources were evaluated: upper and lower Tualatin Basin, Columbia River groundwater wells, local groundwater, the mid-Willamette River, and water purchased through an agreement with Portland (Bull Run / Columbia South Shore Well Field). Water conservation was also considered to determine if more conservation could delay the need for a new supply.

What criteria were used to evaluate source options?

Potential sources were rated using these categories:

  • Source water quality
  • Treated water quality
  • Cost
  • Local ownership
  • Do-able (implementation risks)
  • Environmental impacts
  • Reliability
  • Redundancy
  • Responsiveness to demand growth
  • Operational complexity

Opinion research conducted through surveys, focus groups and public meetings determined that “water quality,” “cost” and “local ownership,” were customers’ highest priorities.

Why was the mid-Willamette chosen as the most viable option? 

The mid-Willamette River at Wilsonville offers significant benefits: excellent finished water quality, redundancy, ownership and control of the supply, year-round reliability, and better value.

Is the Willamette really a reliable water supply source? What about the effects of global warming?

The Willamette River is a reliable water supply for Washington County. The Willamette River upper tributaries originate in the mountains south of Eugene. The river flows northward through the Willamette Valley to its confluence with the Columbia River in Portland. The flow from the Willamette River accounts for 15% of water in the mighty Columbia River. Thirteen dams in the upper Willamette basin deliver reliable summer flows for the main stem Willamette River.

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Our Reliable Water

Program Timeline

Developing the new Willamette water source will take over a decade.

Willamette Water Supply Program

Willamette Water Supply Program