SIMULATED SUBMERSED AQUATIC VEGETATION DYNAMICS FROM 1988  TO  1999
IN POOL 8, UPPER MISSISSIPPI RIVER

Yao Yin 1, Jim Rogala 1, Dayong Zhang 2, and John Sullivan 3.
1 U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta 
Reed Road, La Crosse, WI 54602; 2 Beijing Normal University, Beijing, China; and 
3 Wisconsin Department of Natural Resources, La Crosse, WI 54601.

We developed a logistic regression model to predict the probability that submersed 
aquatic vegetation would occur on a site based on light condition, flow velocity, wind 
fetch, and number of dewatered days at the site over the course of the growing 
season.  The light variable in the model is the number of days when more than 1% of 
sunlight could penetrate through water column to reach the bottom.  The flow 
velocity variable in the model is the average-depth flow velocity computed with the 
FastTABS Model developed by the U.S. Army Corps of Engineers when river 
discharge is set at 90,000 cubic feet per second.  The wind fetch variable in the 
model is the distance over open water from the site to the nearest land mass.  The 
number of dewatered days variable in the model is the number of days when water 
depth at the site was less than 5 inches (12.7 cm).  Model coefficients were derived 
by conducting regression analyses using the submersed aquatic vegetation data 
collected in 1998 by the Long Term Resource Monitoring Program of the Upper 
Mississippi River System, and light penetration coefficient data collected by the 
Wisconsin Department of Natural Resources.  Using the bathymetric-, flow velocity-, 
and wind fetch GIS coverages created by the Upper Midwest Environmental Science 
Center, and light penetration coefficients provided by the Wisconsin Department of 
Natural Resources, we predicted the annual distribution of submersed aquatic 
vegetation from 1988 to 1999.  The predicted submersed aquatic vegetation 
dynamics over the period was tested against remote-sensing data collected in 1989, 
1991, 1994, and 1998; and field data collected in 1999.  The model has displayed 
great potentials as a planning and simulation tool for natural resource management in 
the Upper Mississippi River System.

Keywords:  Upper Mississippi River, submersed aquatic vegetation, model, 
distribution, dynamics
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