Circulation and mixing in Lake Champlain

The objective of this study is to evaluate general circulation patterns and exchange coefficients in Lake Champlain during summer, to characterize mass transfer between major bays and the main lake. The motivation for this work is to support a general project concerning the movement of potentially toxic algae blooms in the lake. Circulation patterns are evaluated by analyzing prior data and synthesizing data from a Lagrangian study performed in the central region of the lake using surface drifters. A non-steady mixed segment water quality model is developed using existing measurements of chemical concentrations to estimate exchange coefficients for transport between the main lake and major bays. Results are compared with a previous steady state model based on annual average conditions and significant differences are found. Bulk dispersive transport is shown to generally be more significant than advective transport. Maps are produced summarizing the general circulation patterns and estimates of exchange coefficients found during summer months, when algal blooms usually occur in the lake. Results of this study should be useful for understanding the general circulation in the lake and for predicting the movement of algal blooms.; Keywords: Lake Champlain, lake circulation, water quality model, algae blooms, Lagrangian approach, surface drifters, phosphorus and chloride budget, dispersive mass transport coefficient.