Tracking the Influence of Wind and Waves on Pollutants in the Great Lakes

The Grand River colored red by rhodamine dye

The Grand River during the 2006 Rhodamine dye release. Photo courtesy of M. Phanikumar (Michigan State University).

A researcher readies a V-fin instrument used to collect plume measurements.

Specialized instruments, such as the V-fin, are used to collect measurements of plume and hydrodynamics. Photo by M.McCormick, NOAA-GLERL.

The Great Lakes coastline is the largest in the Continental United States, containing over 500 recreational beaches. The beaches of the Great Lakes are world-renowned and are a valuable ecological and economic resource. In 2004, 13% of beaches were in the high risk category, meaning they were closed 10% of the time (EPA Great Lakes National Program Office, 2006). Pollutants such as pathogens, from urban and agricultural runoff and non-point sources, may lead to beach contamination during the summer months. Traditional beach monitoring for E. coli typically requires a 24 hour incubation period, resulting in people unintentionally swimming in contaminated water, or conversely loss of local economic revenues and beach time. Results from stakeholder needs assessment workshops have indicated the need for a better beach monitoring program and more specifically the need for a beach forecasting system. In order to address these needs, the GLERL-based Center of Excellence for Great Lakes and Human Health (CEGLHH) is working to understand the influence of wind, waves, surface temperature, and water currents on pathogen transport by conducting extensive multi-year experiments, which unclude field and lab components, in the Grand River, a major tributary of Lake Michigan, to track contaminant flow downstream to Lake Michigan and its adjacent beaches.

The experiments began during the summer of 2006 when a conventional dye, Rhodamine-WT, as well as a bacteriophage, PRD-1, were released into the Grand River in Grand Rapids, Michigan and the tracer gas, Sulfur Hexafluoride, was released and tracked in the Grand Haven area of Michigan. The data from these results helped to create and test a model that will be able to predict the transport and distribution of contaminants from the Grand River into Lake Michigan. CEGLHH researcher Michael McCormick explains that a simple model comparison against data from the sulfur hexafluoride sampling “highlights the complex interaction between a buoyant river plume and coastal circulation.” It also highlighted the need for higher resolution mapping.

The field experiments continued in the summer of 2007 with a similar tracking of the non-toxic red dye, Rhodamine-WT, but this year the study is focused closer to Lake Michigan with the intent of modeling the plume at the end of the Grand River. Acoustic Doppler current profilers were used to measure currents and a towed fluorometer was used to track the dye concentrations at various depths to better understand the movement of the plume. Reflecting on the first summer of experiments, McCormick noted that there was a need for a higher resolution in data gathering. "In 2006 researchers used an adaptive grid to determine sampling locations, now we are testing every second", McCormick explains. In addition, researchers conducted bacteria transport research with /E.coli/ and total coliforms in the water and used aerial photography to track the movement of dye in the River. Researcher David Schwab describes, “We released the Rhodamine dye in the river so that we could accurately measure the dilution as the river mixed with the lake.”

Aerial view showing placement of acoustic Doppler current profiler moorings in the Grand River

A comparison of the Grand Haven plume (left) to the modeled plume (middle) demonstrates a fairly accurate prediction of plume dynamics on May 31. 2007.

(Right) Acoustic Doppler current profiler moorings were placed in the Grand River as well as in Lake Michigan at 5m, 10m, and 20m off-shore to collect data. Image by Google Earth and D. Schwab, NOAA-GLERL.

This data were employed to test a model that uses real-time data about wind speed and direction, waves, water currents, and surface temperature to predict plume movement. “We would eventually like to apply the methods we develop for forecasting pathogen transport near the Grand River to other beaches in the Great Lakes region,” added Schwab. The long term goal of this project is to develop tools that will be useful in forecasting potentially harmful conditions in the coastal waters and beaches in order to assist decision-makers with informing the public in a timely manner to reduce water-related human health risks. There is a potential extension of this study to combine the models used to determine contaminant threats at beaches with watershed models so that we could model and predict the effects of land use on beach closures.

Tracking the Influence of Wind and Waves on Pollutants in the Great Lakes

NOAA’s Center of Excellence for Great Lakes and Human Health in Action