Modeling Kalamazoo River Discharge into Lake Michigan
Discharge from the Kalamazoo River contains chlorophyll, dissolved organic carbon, and inorganic suspended sediments. Combined, these constituents color the water brown. Under a given set of wind and wave conditions on Lake Michigan, the water flowing out of the Saugatuck harbor entrance can flow to the north, west out from shore, or south. When the river water flows south, the "brown" water can end up at Oval Beach, the popular tourist attraction run by the city of Saugatuck. The common misconception that the brown river water is polluted (it is not) can adversely affect the enjoyment of Oval Beach users.
Professor Pengfei Xue and his team at Michigan Tech University have created a hydrodynamic particle tracking model that simulates where the Kalamazoo River discharge will flow based on wind and wave conditions. The model utilizes information from a buoy off Port Sheldon (approximately 25 km north of the harbor entrance), a Lake Michigan surface current forecast provided by NOAA/GLERL and river flow data from a USGS stream gauge to produce the results.
The model is currently inactive, but the sample video below shows the forecasted location of the Kalamazoo River discharge plume for September 19, 2022 on an hourly basis. This video shows the wind shift from south to north through the day, shifting the plume towards Oval Beach in the afternoon. If the forecast suggests that heavy concentrations of discharge are reaching Oval Beach (colored yellow-red), then the water off the beach may be slightly darker.
Shown in the animation below is the river flow on an hourly basis from May through the end of August 2020. Also presented is a map of the location of the buoy off Port Sheldon, the harbor entrance and location of Oval Beach. A plot of the significant wave height on an hourly basis from the buoy for the four month period is presented (bottom right) where the moving black dot on the graph corresponds to the time of the flow. The hourly winds for each modeled hour of flow is indicated by the green line coming from the buoy (top right). The longer the line, the higher the wind speed (note the 3 m/s scale). The orientation of the line indicates the direction the wind is blowing.
The four months of modeled flow data indicate that the river discharge is predominantly in the north and west (offshore) direction. High concentrations of Kalamazoo River water (red) pile up on the northern shore under high wave conditions. Oval Beach is most often affected by river water under relatively low wave heights (0.6 meters or less) when the winds are blowing from the north. Approximately 25 events occurred in the May to August 2020 time period where the Kalamazoo River discharge reached Oval Beach, but in most instances the concentration was not at maximum level.