Salmon are a cornerstone of our cultural identity in Seattle and the Pacific Northwest. Salmon are vital to our economy, our environment and our sense of place. The health of our native salmon runs has been identified as an indicator of the overall health of Puget Sound and local streams. Scientists have been researching the connection between declining salmon populations and urban stormwater pollution. These scientists have discovered a major threat to the health of our salmon but they have also discovered a simple solution that mitigates the impacts 100% of the time.
As our human population grows, so does the magnitude of pollutants released into our waterways. Large quantities of contaminants such as metals, petroleum-derived compounds like oil, grease, vehicle exhaust, and detergents accumulate on our roadways and parking lots where there is no absorption. Every time it rains, these containments are washed directly into storm drains and into our creeks, lakes, the Duwamish River, and Puget Sound. Researchers have now found a direct link between polluted urban stormwater runoff and salmon mortality.
A recent straightforward study exposed salmon to stormwater runoff from a local highway. In every case, the salmon died within 4 to 6 hours. The conclusion was clear: stormwater pollution is lethal to salmon. However, the study also tested a potential solution. When researchers first filtered the highway runoff through a column filled with a soil mixture and then exposed the salmon to this cleansed water, they survived 100% of the time.
Filtering water through a living, plant-soil system is the basis for green stormwater infrastructure (GSI). The City of Seattle has listened to the science and determined this is a direct influence we can have on Puget Sound. By using GSI we can help to improve water quality and prevent more contaminants from reaching our waterways. For this reason, we have set an ambitious goal to accelerate the use of green infrastructure in our city and are also supporting regional green infrastructure efforts.
The Washington Nature conservancy created a great short video highlighting this research. You can find the video at http://www.washingtonnature.org/cities/solvingstormwater
For more information on the research: http://www.sciencedirect.com/science/article/pii/S0045653514014805
For more info on what the City of Seattle is doing with GSI visit our webpage: http://www.seattle.gov/environment/water/green-stormwater-infrastructure