LAKE MORPHOMETRY

To acquire a first-hand knowledge and appreciation of lake morphometry and of Lake Winona, you will collect data and construct a bathymetric map of the undredged western basin of Lake Winona, and then use that map to make various morphometric calculations for comparison to a map from the 1980s.

The western basin of Lake Winona now contains less volume and more littoral area than it did in the 1980s.

Using a Lake Winona shoreline map and the transect data collected from Lake Winona, pencil in (very lightly) each of the transects, and plot precisely (to scale) the depth measurements along the transects. By interpolating between the points of known depth, locate points of equal depth (e.g., 5 feet) throughout the basin, and then connect these points of equal depth with contour lines (isopleths). Repeat the process for each depth (10, 15, 20, 25, 30, and 35 feet). Use your best judgement in sketching in the contour lines; you may need to "adjust" your contour lines to allow other contours to "fit".

Once your contours are completed, compare your bathymetric map to the map for the pre-dredged lake. Use the instructions to determine the following for both the new and old maps:

* maximum length
* maximum width
* surface area and areas >5 feet deep, >10 feet deep, >15 feet deep, >20 feet deep, >25 feet deep, >30 feet deep, and >35 feet deep
* total volume and volume of each depth stratum
* maximum depth
* mean depth
* relative depth
* shoreline length
* shoreline development
* construct hypsographic curves and depth-volume curves (using percent area and percent volume, as in the two lower diagrams in Fig. 1-6)

EQUIPMENT

boat
depth-finder
outboard motor
pencil
metric ruler
calculator
polar planimeter
graph paper grid

Return to Limnology Lab

Neal D. Mundahl
Winona State University
Winona, MN 55987-5838