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GLERL 2001 Milestone Reports
GOAL: SUSTAIN HEALTHY COASTS
OBJECTIVE 2: Promote Clean Coastal Waters to Sustain Living
Marine Resources and to Ensure Safe Recreation, Healthy
Seafood, and Economic Vitality
PM: Number of coastal and Great Lake states provided with improved predictive capabilities and understanding of coastal processes
Milestone: Complete data collections describing currents and water circulation during summer and winter conditions in Burlington and Shelburne Bays, Lake Champlain.
Scientist: J.H. Saylor (GLERL)
Purpose: Measurements of current velocities and water temperature distributions have been made in Lake Champlain over the course of several field experiments performed by GLERL scientists and University collaborators. All of the measurements have been open lake measurement programs designed to explore the physics of whole-lake processes. Because these processes are now relatively well understood, the timing was appropriate to study some of the practical aspects of coastal and embayment flows and their relationships with several matters of local water quality management concern.
Effort: Several potable water intakes and sewer outfalls are located in Lake Champlain just offshore of Vermont's most populated lake front communities in the Burlington metropolitan area. The intakes and outfalls have been constructed over a period of the last 50 years with little knowledge of local currents and circulation patterns. There is evidence of recirculation between the outfalls and intakes. We performed measurements of currents and water density structure in Burlington and Shelburne Bays over a 12-month-long-interval starting in October 1999 and ending in September 2000. Eight moorings with water-temperature-measuring thermistor strings and Acoustic Doppler Current Profilers were installed. All of the deployed instruments were recovered and the data have been transcribed and edited. Analyses of the circulation patterns are in progress and they are being correlated with hydrographic structure and meteorological forcing.
Customers: EPA Region 1 coordinates both a water quality monitoring and a water quality improvement/restoration plan, which affects all major water management units within the Lake Champlain watershed. Results of the GLERL hydrodynamics studies have been used for the development of water circulation and sediment suspension and transport models on which the water quality improvement models are based. The Burlington/Shelburne Bay study was performed with EPA and the local water district manager's encouragement as part of continuing efforts to improve these models incorporating lake physics.
Significance: The physics of Lake Champlain are unique; they are very different from the physics of other Great Lakes. A long, narrow, and deep configuration admits large thermocline displacements in response to wind blowing along its axis. Cessation of the surface stress leads to a rich assortment of surges, seiches, and bores propagating on the internal density discontinuity. These waveforms are important mechanisms assisting the flushing of contaminants from the coastal waters.
Success: The data collection project was completed and the data acquisition rate was very high. The data analyses and reporting of results will be used in improved ecological modeling for restoration of water quality in Lake Champlain.
Next Steps: With funding provided through the FY2001 add-on by congress to NOAA's budget, we are analyzing the water volume exchanges occurring between the main lake basin and Burlington and Shelburne Bays. Interactions between the main lake and its embayments are poorly understood, but extremely important to planning for water quality restoration. Future work is contingent on continued funding of the Lake Champlain studies.
Last updated: August 8, 2002 mbl