About Portland's Watershed Report Cards

Graphic reads: Explore Portland's Watershed Report Cards. Wheel to the right is divided into 4 even sections: Water quality, habitat, fish and wildlife, and hydrology.
Portland’s watershed report cards provide an overview of watershed health in the city. These science-based report cards summarize complex scientific information from the city’s environmental monitoring program and other data.

What Are Watershed Report Cards?

The report cards provide an at-a-glance view of conditions in Portland’s rivers, streams, and watersheds. They help us:

  • Understand the current health of Portland’s watersheds.
  • Assess the outcomes of our restoration projects.
  • Track changes in watershed health over time.
  • Identify where we need to do additional work.

Environmental Services produced the first watershed report cards in 2015. Report cards for each of Portland’s unique watersheds are updated every four years with the latest available data.
The report cards are a way for people to learn more about Portland’s environment and the actions we’re taking to promote healthy watersheds. Report card scores also illustrate how people’s individual actions, such as tree planting and reducing use of lawn chemicals, can add up to positive changes.

What We Measure

Graphic shows a wheel divided into 4 even sections: Water quality, habitat, fish and wildlife, and hydrology.
The watershed report cards assign grades for four major watershed indicator groups.

To evaluate watershed health, Environmental Services looks at 21 different environmental indicators or “vital signs.” These indicators tell us about the broader environmental conditions in each watershed. Environmental Services analyzes data and calculates scores for each indicator. These indicators serve as the foundation of our assessment of watershed health and fall into four indicator groups:

  • Hydrology
  • Water Quality
  • Habitat
  • Fish and Wildlife

The indicators are described in more detail below.


Aerial image of creek meandering through a green space full of trees and plants.
Hydrology is how water flows across land or in rivers and streams. Water flows through natural and built – things like pipes – drainage systems.

Hydrology affects fish, wildlife, infrastructure, and property. Trees and other green infrastructure slow and absorb the rain and reduce the amount of water flowing into pipes and streams. Without proper management, stormwater can cause erosion and damage to property, streams, and roads. The report cards include two indicators to measure hydrology inexpensively and consistently across our watersheds:

  • Effective impervious area is a hard land surface (such as a street or roof) that sheds rain into a river, stream, or storm drain without first collecting or filtering it. Impervious area creates higher runoff volume and speed which can cause erosion and flooding, destroy habitat, flush biological communities like fish out of the system, and wash pollutants into rivers and streams.
  • Stream connectivity measures how much of a stream flows freely, and how much flows through a pipe, culvert, or other structure. It is difficult, and often impossible, for fish and other aquatic organisms to move through pipes or culverts. These obstacles prevent them from accessing habitat. Pipes confine and concentrate stream flows, which causes flooding and sedimentation upstream. Downstream, increased flow velocities can cause erosion, destroy habitat, and flush aquatic insects out of the system. This indicator is not used along the mainstem Willamette River since there are no dams, culverts, or other physical structures that confine or concentrate flows in the City.

Water Quality

Photo shows Environmental Services field scientist taking river water samples from the Firehouse Dock with the Willamette River and downtown Portland in the background.
An Environmental Services' field scientist takes samples of Willamette River water for water quality testing.

Water is essential for all life. Good water quality protects the health of Portlanders, but 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. The report cards include eight indicators to measure water quality across our watersheds:

  • Ammonia-nitrogen is the amount of inorganic, dissolved ammonia in water measured in milligrams per liter (mg/L). Sources of ammonia-nitrogen include sewage, fertilizers, animal waste and some industrial use. In high concentrations, ammonia-nitrogen dissolved in water can harm aquatic species growth and damage gills. At higher concentrations it can also be toxic to aquatic life.
  • Dissolved copper is the fraction of copper remaining in a water sample after filtering the water. We measure it in micrograms per liter (µg/L). Sources of dissolved copper include household plumbing, pesticides, herbicides, and automotive brakes. Dissolved copper is toxic to aquatic species, particularly salmon. It can cause decreased growth, changes in olfactory response, and cell or organ damage.
  • Dissolved oxygen is the amount of oxygen dissolved in water measured in milligrams per liter (mg/L). Fish and other aquatic organisms need dissolved oxygen to survive. Nutrients and organic matter in water, especially when water temperatures are high, can reduce dissolved oxygen levels. Low levels of dissolved oxygen can harm fish and other aquatic organisms.
  • Escherichia coli or E. coli is a bacteria measured as the number of E. coli organisms in 100 milliliters of water. Excessive E. coli in the water indicates the presence of fecal matter from humans and animals. Some kinds of E. coli can cause serious illness in humans.
  • Temperature of the water is measured in degrees Celsius. Low summer stream flow and impoundments, such as ponds, can increase stream temperatures. Temperature influences dissolved oxygen and ammonia-nitrogen concentrations in streams. Warm temperatures impact the spawning, rearing, feeding, and migration behavior of salmon and other aquatic species that rely on cold water.
  • Total mercury is the amount of organic and inorganic mercury in water measured as micrograms per liter (µg/L). Most of the mercury in water comes from atmospheric pollutants that settle on the ground and then wash into rivers and streams by stormwater runoff or erosion. Mercury sources include incinerators, crematoriums, metal smelting and refining, cement kilns, coal-fired power plants, and forest fires. Mercury accumulates in fish tissues. Because mercury can impact human health, it is a higher concern in waterways where people fish for food. It can also impact wildlife.
  • Total phosphorus is the amount of phosphorus in the water measured in milligrams per liter (mg/L). Phosphorus occurs naturally in streams at low concentrations. Streams in urban or agricultural areas often have higher concentrations of phosphorus from fertilizers and other landscape chemicals. Phosphorus can cause excessive algal growth, which increases pH and decreases dissolved oxygen in streams, and adversely impacts the health of aquatic species.
  • Total suspended solids are particles suspended in water measured in milligrams per liter (mg/L). Materials like silt, decaying plants, industrial waste, and sewage contribute to suspended solids. High concentrations of suspended solids in the stream can cover stream bed gravels and smother fry in salmon spawning grounds, affect fish feeding behavior, and clog fish gills. Suspended solids also blocks sunlight and may decrease food sources for aquatic species. Sources include untreated runoff from impervious surfaces (primarily roadways) and erosion of stream bed and banks.


Photo shows still waters of the Columbia Slough with large trees with rootwads resting in the water.
To survive, all living things need access to food, water, air, and shelter. For fish like endangered salmon, the area in and around a water body provides habitat.

To survive and thrive, all creatures need food and shelter or places to rest and hide from predators. For fish and wildlife, places like parks, natural areas, buffers along streams, neighborhood rain gardens, trees, and native plants help provide habitat in the city. The watershed report cards use the following eight indicators to assess habitat in Portland’s watersheds.

  • Stream bank condition is a measure of the percentage of stream bank that has been artificially hardened by riprap, seawalls, or other structures. Rivers and streams are naturally dynamic and change form in response to changes in flow. Structures that confine a stream will:
    • Prevent it from adapting to variable flows.
    • Hinder interaction of a river with its floodplain.
    • Reduce in-stream habitat complexity.
    • Increase water velocity.
    • Degrade stream structure.
  • Floodplain condition is the percentage of a floodplain covered by human structures. Floodplains provide fish and wildlife refuge during high flows, store flood waters, and reduce downstream flooding. The floodplain measure applies primarily to the Willamette mainstem, Columbia Slough, and Johnson Creek because these watersheds have the topography and hydrology that support significant floodplain development.
  • Large wood is a measure of the volume of large wood pieces within a stream. In-stream large wood creates pools, stores sediment and organic matter, maintains stream complexity, and provides refuge and food for salmon.
  • Riparian integrity is a measure of vegetation cover, including trees, within 300 feet of a stream. Vegetation, especially trees, in the riparian area shades and cools streams, provides overhead cover, filters sediments and runoff, provides food for aquatic species. Riparian areas also are a source of large wood for stream channels, control stream bank erosion, and reduce sediment inputs.
  • Shallow water refugia is a measure of any length of the river that is less than 20 feet deep along the mainstem Willamette River. Shallow water in large rivers provides juvenile salmon with rearing habitat and refuge from predators. A lack of shallow water habitat in large rivers limits salmon productivity. River dredging and channelization have reduced the amount of shallow water habitat. This indicator applies only in the Willamette River mainstem.
  • Stream accessibility is a measure of stream miles that are currently accessible by juvenile and adult salmon and steelhead. Culverts, dams, weirs, and other in-stream structures create barriers for these migrating fish.
  • Substrate composition is a measure of the fine sediment and gravel in a stream. Salmon need gravels and small cobbles for spawning and incubation. The aquatic insects that form the base of stream food webs live in between the gravels in the stream bed. Fine sediment harms aquatic insects, incubating salmon eggs and fry, and juvenile salmon. This metric is not applied to the mainstem Willamette River or Columbia Slough since the substrates in these larger rivers are naturally fine grained. 
  • Tree canopy is a measure of tree foliage covering the watershed. Trees provide wildlife habitat, reduce stormwater runoff, cool air and water, and are a food source for fish and wildlife.

Fish and Wildlife

Photo shows a female coho salmon with male coho in the background during spawning season in Crystal Springs Creek. Photo taken underwater.
Fish, like this coho salmon, are key to knowing how healthy a watershed is. They are like the "canaries in the coal mine." We look to see if fish are present, how many, how many different kinds, and if they are thriving.

Fish and wildlife are some of the best indicators of watershed health, and are primary drivers for our work to improve watershed health. Fish, aquatic macroinvertebrates, and birds are sensitive “canaries in the coal mine.” Data about them can help the City identify trends in water quality, and issues that might become bigger problems if not addressed. Some species are also protected under the Endangered Species Act or are at risk of becoming threatened.

  • Birds are indicators of the health of biological communities and watershed conditions. The Bird Integrity Index (BII) measures avian community health to determine the health of larger riparian areas. The score for this indicator is still under development for the mainstem Willamette River because health indicators for a large river system are different from what we use for smaller streams. This index, designed specifically for use in Portland, takes into account the presence of native or non-native species, migratory patterns, foraging and nesting needs, and other factors.
  • Fish spend their entire lives in the water and many are highly sensitive to pollution or impacts to habitat. One indicator of the health of Portland’s streams is the population of fish, especially salmon. The Index of Biotic Integrity (IBI) measures fish population health, including:
    • Species richness and composition.
    • Number and abundance of indicator species.
    • Reproductive behavior.
    • Condition of individual fish.
  • Photo shows underside of the rock with small insect larvae with shells and tails.
    Macroinvertebrates, like these insect larvae on the underside of this rock, are food for fish. These water insects are another key indicator that we measure.
    Aquatic macroinvertebrates live in water for all or part of their lives, have no backbone, and are visible to the naked eye. Examples include freshwater mussels, mayflies, stone-flies, and other bottom-dwelling critters. These organisms process organic matter and are an important food source for fish, birds, and other wildlife. Macroinvertebrates are good indicators of watershed health because they are sensitive to the biological conditions of a stream. The PREDictive Assessment Tool for ORegon (PREDATOR) developed by the Oregon Department of Environmental Quality assesses aquatic macroinvertebrate communities. The scores for this indicator are not applicable for the mainstem Willamette River and Columbia Slough because healthy reference communities for macroinvertebrates are not known for larger, slower-moving, water bodies.

How Scoring Works

After collecting and analyzing data for each indicator, we translate the data into an index score on a scale of 0 to 10.

  • Scores 0 to 3: An index score of 3 or lower means the watershed health indicator is not properly functioning or providing little to no function to support a healthy watershed.
  • Scores 4 and 7: Scores in the middle mean the indicator is providing some function to support healthy watershed conditions. But, it may take continued protection or improvement to meet regulatory standards or local goals, or to prevent further decline.
  • Scores 8 to 10: A score of 8 or higher means the indicator is properly functioning, or functioning at a level that supports a healthy urban watershed. Properly functioning urban watersheds support human health and a diversity of native fish and wildlife species. They are more resilient to changes in climate and can self-sustain into the future, so generations to come can benefit from nature in Portland. Read more about how healthy watersheds help our community.

Using an index score allows us to compare the different indicators across our watersheds. We then use these index scores, along with interpretation and additional information, to create report cards that illustrate key issues and trends in Portland’s watersheds. Together, these scores give a simple snapshot of conditions within each watershed.

How We Use Watershed Report Cards

The information in our report cards helps the City and its partners to identify specific actions we can take to improve the health of our rivers and streams. They can also help us evaluate our efforts to date, including:

  • Addressing our responsibilities as a City under the Clean Water Act, Safe Drinking Water Act, Endangered Species Act, and other laws.
  • Meeting our local goals for sustainable, livable neighborhoods.

The long-term goals in Portland are to:

  • Avoid further decline in watershed health.
  • Move towards properly functioning conditions in all the city’s watersheds.

Achieving these long-term goals and improving our rivers and streams requires a Citywide, long-term effort and will take time. Scores of 8-10 may not be achievable for all indicators in all watersheds. Our success will not be measured by perfect scores across the board, but rather by improved scores in key indices.

Find the Report Card for a Portland Watershed

Graphic is a screenshot of a story map about the watershed report cards.
Use this interactive storymap to explore the watershed report card data.