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Research Abstracts Online
January 2010 - March 2011

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University of Minnesota Twin Cities
College of Science and Engineering
Department of Civil Engineering
St. Anthony Falls Laboratory

PI: Miki Hondzo

Water-Quality Modeling of Lake Minnetonka

The use of advanced water quality models is becoming more common among water-resources professionals and models are integrated into decision support systems to meet their regulatory requirements. Water quality models extend the understanding of our systems and give meaning to our observations. These researchers have been successfully applying a coupled three-dimensional hydrodynamic (ELCOM) and ecological (CAEDYM) model to portions of Lake Minnetonka (Minnesota, U.S.). The results reflect a system with significant spatial and temporal water quality changes that requires the use of a three-dimensional model. The model has captured water quality variations that would not have been detected by typical summer monitoring. The results show that the use of the model helped to analyze the hydrodynamics and geochemical processes of the morphologically complex lake. The modeling effort accurately described the impacts of stormwater on water quality. The researchers have demonstrated through the use of plots and time series "movies” the seasonal changes of temperature, dissolved oxygen, total phosphorus, and algae under two very different seasons. Both simulated and measured data indicate that total phosphorus variations in deeper water columns were more likely the consequences of storm events (flow). Stormwater degrades water quality and can also create physical perturbations that cause significant water quality problems as well. Interactions of stormwater (stream) flow, ecological processes, and climate change are magnified with complex lake morphometry. Using the applied model, the researchers have analyzed the cool-water fish habitat in three dimensions and under a scenario similar to one-dimensional water-quality modeling. Fish habitat is shaped by water temperature and dissolved oxygen. These two parameters were shown by the model and confirmed by measured data to be very sensitive and susceptible to stormwater flow. The one-dimensional analysis did not capture local and short-duration variabilities and missed suitable fish habitat variations of as much as 20%. The experiment highlighted the need for three-dimensional water-quality modeling for accurate analysis of complex systems. The researchers are continuing the use of the model to expand their understanding of the system under study.

Group Member

Shahram Missaghi, Graduate Student