This project is in collaboration with the Washington Department of Ecology, which has a mandate to understand water quality in Puget Sound. Part of understanding water quality is understanding where the water’s coming from.

By having our instruments on the ferries, now we can start to get a total estimate as to how much water is intruding at the bottom from the ocean and how much water is leaving at the top from the rivers and the freshwater outflow.

To improve and calibrate water quality models that are being developed by the Washington State Dept. of Ecology to better understand and predict water quality throughout the Puget Sound, we will expand the ferry monitoring network to include public ferries run by the Washington State Department of Transportation (WSDOT) on the Port Townsend to Coupeville route. Installation of automated instruments to measure current velocities on select WSDOT vessels will allow us to record measurements continuously as ferries makes their multiple daily runs.

WSDOT ferries occupy strategic cross-sections in Puget Sound – often at the very constriction points between basins that would let us most easily measure water exchange and circulation between those basins. We need to understand the water quality condition, circulation, and exchange of water masses within and between natural sub-basins of Puget Sound, as well as exchange with the ocean, in order to manage water quality in Puget Sound (e.g., nutrient enrichment, low dissolved oxygen conditions, the transport of toxic chemicals, harmful algal blooms, and ocean acidification).

We are installing an instrument known as an Acoustic Doppler Current Profiler (ADCP) on two ferries. These sensors, which primarily measure current velocities in a continuous transect along the ferry route, will provide unprecedented surface-to-bottom measurements of water-mass movement and transport between basins.

In cooperation with the WSDOT and the Puget Sound Partnership, we will add instruments to two ferries – the Kennewick and Salish – that occupy the route between Port Townsend and Coupeville. This is an especially valuable cross-section characterizing the overall influx and outflow of water to/from the ocean and greater Puget Sound. The instrument, known as an Acoustic Doppler Current Profiler or ADCP, primarily measures current velocities throughout the water column in a continuous transect along the ferry route. These sensors will provide unprecedented surface-to-bottom measurements of water mass movement and transport between basins.

These two ferries incorporate design features that will make the initial installation of the instruments less complicated than other ferry classes. Installation will occur when individual ferries are scheduled for dry-dock, which is mandated to occur only twice every five years per ferry.

Weather observing equipment is placed on five Washington State ferries. Currently, each boat is equipped with weather sensors reporting wind speed, wind direction, air pressure, temperature, and humidity. These quantities are measured every minute, averaged over a period of 4 seconds. Ship heading and speed information is also recorded and used to correct the measured winds for ship motion.

The weather data are transmitted via radio to land, and then sent over the Internet to the University of Washington where they are decoded, archived, and used to create the Ferry Web page. The Ferry Web page also includes weather reports from other sources that are on or near the waters of western Washington.

The Washington State Dept. of Ecology employs a multi-pronged strategy to monitor marine waters of Puget Sound, relying on monthly samples collected by seaplane across a network of long-established sampling stations throughout the Sound (but sampled only once/month), instruments that measure water properties continuously at fixed sites (but a limited number of sites), satellite imagery (limited mostly to surface conditions), and – as opportunity allows – measurements taken by boat or ship along strategic transects (which provide a continuous record of observations across gradients and boundaries between basins).

For the last four years, Ecology has partnered with Clipper Navigations, Inc., to collect a suite of water quality measurements along the main axis of Puget Sound as the Victoria Clipper IV runs between Seattle and Victoria, B.C. This is accomplished through the installation of automated instruments on the ferry, which record measurements continuously as the ferry makes its once-daily (during the off season) or twice-daily (during the peak season) trips. The data collected by the instruments are logged onto an on-board laptop computer and then transmitted daily to Ecology for data processing and evaluation.

The Clipper instruments collect surface water quality data – algal biomass, turbidity, temperature and salinity – which allows measurements of water conditions along the main axis of Puget Sound. Installing instruments on the WSDOT ferries will allow data on water currents to be collected across strategic cross-sections of Puget Sound, often at the very constriction point between basins that will let us measure water exchange and movement between those basins, which is a key measurement to understand how water masses move and circulate between basins. These instruments are all harmless to marine life.