Puget Sound Nutrient Reduction Project

Science and Modeling

Decades of water quality monitoring data helps us understand how Puget Sound water quality is changing over time. We use the Salish Sea Model and water quality monitoring data to analyze and quantify nutrient impacts from sources both nearby and farther away from observed problems. The model helps us to understand the impacts of human nutrient sources and how potential source reductions could improve Puget Sound water quality. Modeling results have confirmed that human sources of nutrients are leading to dissolved oxygen problems in many parts of Puget Sound.

We publish Salish Sea modeling results and use these to inform future actions for protecting Puget Sound.

Planning for future growth and changes

Currently, over 4.5 million people live in the Puget Sound region and the Puget Sound Regional Council estimates around 1.8 million more people will move to the region by 2050. Human sources of nutrients could increase by more than 40% over the next few decades. Recent Salish Sea modeling results predict water quality will get worse as our regional population grows, if we do not act. 

Climate change will also make conditions worse. Drought years will lessen freshwater streamflow into Puget Sound. This reduces water circulation and keeps nutrients from human sources in the Sound longer because they are not flushed out to the ocean quickly. Increasing water temperature will present additional stresses and may increase harmful algal blooms, bacteria, jellyfish and flagellates. It will also lower dissolved oxygen in the water that fish and marine organisms need to survive.