Water is essential for all life. Good water quality protects the health of Portlanders. It’s also critical for the fish and wildlife that live in or migrate through Portland. Many species, including salmon, are sensitive to even small amounts of pollution or changes in water temperature. Understanding the condition of Portland’s rivers and streams helps us target resources to improve water quality throughout the city.

The Water Quality indicator is an index score that is composed of measurable attributes of the environment that represents some aspect of ecological function, like the ability to support habitat, in our rivers and streams. The Water Quality indicator is presented as an index score, from 0 to 10, with a score of 0 representing no ecological function and score of 10 representing excellent ecological function. The score changes slowly, as individual components of the score are updated annual to create a rolling average. 

The Water Quality indicator is based on eight water quality parameters:

1. ammonia-nitrogen;
2. dissolved copper;
3. dissolved oxygen;
4. E. coli;
5. temperature;
6. total mercury;
7. total phosphorus, and
8. total suspended solids.

These water quality parameters were selected as they allow us to assess possible threats to both human health and aquatic life.

The City collects water quality samples as part of the Portland Area Watershed Monitoring and Assessment Program (PAWMAP). The data and samples from PAWMAP are used to calculate the Water Quality indicator. PAWMAP is a long-term monitoring effort designed to meet the City’s permit-required monitoring and measure the condition of Portland’s current and changing ecological resources. You can learn more about this program at the PAWMAP webpage.

You can find more information about Portland’s Water Quality Health Index at the Watershed Report Cards webpage. Watershed Report Cards provide an at-a-glance view of conditions in Portland’s rivers, streams, and watersheds.