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Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.


1120 SW Fifth Ave, Suite 600, Portland, OR 97204

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Seasonal supply planning

The Bull Run watershed, northwest of Mt. Hood in the Mt. Hood National Forest, is the primary source of drinking water for the City of Portland and much of the metro area. It is the largest drinking water supply in Oregon. The watershed receives on average 135” of rain per year – typically up to three times as much as Portland. The Bull Run water system is designed to capture and store rainfall from the rainy season to provide an adequate water supply during the dry summer months. The city also has the Columbia South Shore Well Field (CSSWF), the second largest source in the state. This additional high quality water source can be used in addition to the Bull Run supply during dry periods.

Each year, the Portland Water Bureau develops a Seasonal Water Supply and Contingency Plan. This plan evaluates the availability of water from the Bull Run and groundwater sources, projected weather forecasts, and water demands to ensure all supply and demand conditions can be addressed. Once the rainy season ends, the plan is regularly updated to account for changes in seasonal conditions. These updates assist the Water Bureau in determining if the supply needs to be augmented with groundwater through the summer and fall demand seasons.

Between careful management of the water supply and the region’s strong conservation efforts, PWB is prepared to meet the range of potential supply and demand conditions that could occur in the Portland water system.