Shapefiles - Lake bathymetry, watershed delineation, lake surface area, site locations (CALON)

Detailed bathymetric data were collected from lakes in each of the study areas using a GPS-enabled sonar unit. Lake bathymetric surveys were conducted in late June (if the lake was completely free of ice) or in August. A Lowrance/Eagle SeaCharter 502cDF iGPS sonar unit was attached to the transom of a 2.7 m (9’) inflatable boat. Geographic location and water depth were recorded each second along a transect. Beginning just offshore, the first transect paralleled the shoreline for an entire circuit around the lake. The next transect was shifted 50-100 m toward the lake center, and run parallel to the initial transect. This process was continued until the entire lake was surveyed using these nested transects. This procedure was modified when specific features were encountered. For example, in order to locate the lake shelf edge accurately and to assess gradients, the boat operator would maneuver back and forth across the shelf edge. Similarly, when deep pools were encountered, additional transects were used to reduce the spacing and improve the resolution for detailed mapping. Since the outboard motor could not operate in water depths of less than 0.3 m, these areas were avoided.