New Sensor Installed on Ferry Will Monitor Water Flow in Puget Sound

A new water monitoring sensor has been installed on the hull of a ferry in order to understand water circulation in Puget Sound, Washington State

In order to better know the local marine environment it is necessary to know how water flows through the Puget Sound's myriad channels. For this, researchers from the Washington Department of Ecology and the University of Washington installed a water monitoring sensor on the hull of the 64-car Salish ferry that crosses the Admiralty Inlet. 

The flow of water will be measured through Admiralty Inlet, the gateway between the ocean and the Puget Sound. The new sensor will help measure the direction as well as the speed of water  from the surface to the seafloor throughout the channel.

The study researchers are interested in knowing the process that brings up the low oxygen water from the deep ocean.  In the Hood Canal, it was the lack of oxygen that killed large number of fish and authorities want to know how to combat the problem and whether sewage systems or runoffs should be regulated.

"Under certain conditions deep water from the ocean will come up and sneak into Puget Sound and possibly contribute to low oxygen levels. Right now there is limited data, so it's hard to say when or how much this happens," Jim Thomson, an oceanographer with the UW Applied Physics Laboratory said. "We really are an urban water system, but there's also this very natural process connected to the ocean that changes our water quality."

Over four years ago the team had maintained a seafloor sensor that measured currents and oxygen levels in the flowing waters.  But this sensor failed to provide a whole picture. It is extremely crucial to monitor the Puget Sound in order to know the trends and changes over time. By this monitoring the researchers can estimate whether the changes are occurring naturally or are caused due to human activities. And if it is human-caused, how it can be reversed.

The new sensor installed on the ferry is an Acoustic Doppler Current Profiler that sends minute sound waves down through the water and is similar to the depth-sounders and fish finders.

The minute sound waves sent down are reflected by the particles in water. It is based on the time taken for the echoes to return to the profiler that the researchers calculate the distance between the ship and shift in the wavelength. The data returned by the ferry will be equal to 32 sensors placed across 6 km stretch of water. 

Monitoring the flow across the stretch makes it easier to understand and predict the influence of the ocean on Puget Sound oxygen, acidity as well nutrient levels.

"This is an example of a creative and cost-effective collaboration helping us better understand the complex marine ecosystem of Puget Sound," said Ken Dzinbal of the Puget Sound Partnership, which is a partner in the project.

As the ferry begins to move, the instrument records data and uploads the data wirelessly to the computer server on land.