The Salish Sea is a complex web of waterways that includes Puget Sound and the straits of Juan de Fuca and Georgia. It also has inflows from 64 rivers and 99 wastewater treatment plants in the U.S. and Canada.
Getting a handle on water quality in this unique geography is challenging. Washington’s Department of Ecology has collaborated with the Pacific Northwest National Laboratory to create the “Salish Sea Model.” It’s a mathematical tool to predict how human activity affects the health of the sea.
“If you go to the doctor, they measure your blood pressure and your pulse. And that’s kind of what we do when we monitor water quality in Puget Sound,” says Teizeen Mohamedali, an environmental engineer working on the model for the Department of Ecology.
She stands on the shore of Padilla Bay, an estuary reserve near Mount Vernon. It's known for its massive 8000-acre eelgrass meadow, the second largest one on the West Coast. The Department of Ecology has four monitoring stations here.
“We monitor for temperature, salinity, dissolved oxygen, pH, how cloudy the water is, which is called turbidity,” she says. “And when you do this, for example, over 20 years, you get to see how things are changing over time.”
That understanding amps up when they plug the data into their computer model.
“It simulates all the different processes in the Salish Sea that govern water quality,” she says.
“So first you have circulation, how water moves around, Pacific Ocean water entering the Sound, all the rivers, all the wastewater treatment plants and their effluent. All of those things go into the model and then the model can predict how water moves. It can tell you oxygen levels, nutrient levels, when you have algae blooms, when they die throughout, for example, a span of a particular year,” Mohamedali said.
The scientists calibrate the model by comparing its results with real data from their monitoring stations. The goal is to predict and understand how human activity affects the health of the ecosystems. After about ten years of development, researchers have achieved a level of accuracy that is sufficient to shape local policy.
“The model is going to be used to develop the Puget Sound nutrient reduction strategy, which is to help us define what we need to do in terms of nutrient management in Puget Sound,” Mohamedali says.
(Updated at 10:30 am, Nov. 20th, 2017 to correct that Padilla Bay’s eelgrass beds cover nearly 8,000 acres, not 800. We regret the error.)
To see more photos and read more about what the Salish Sea model can do, visit our Return To The Salish Sea website.