How Torch Lake Stores the Rainbow

Everyone who visits the Torch Lake Watershed is astonished and impressed by the “Caribbean” blues of Torch Lake. On some days, Torch Lake blues take your breath away and create a memory that stays with you forever. So, why do we see the rainbow colors when we look at Torch Lake?

Remember back in grade school when you learned the color of the rainbow by remembering a man’s name?

Roy G. Biv = red, orange, yellow, green, blue, indigo, violet

When light waves hit the water surface, different colors of light are either absorbed, transmitted, scattered or reflected in differing intensities.

Indigo 

From the drop-off toward the center of the lake, the water is very deep (50’–350’), so the long wavelengths of red and green light are absorbed. This leaves only the dark, indigo (navy) blue wavelengths reflected from the surface.

Turquoise

As the depth of the lake changes from the drop-off toward shore, there are particles in the water which reflect the shorter, turquoise light waves and absorb all the other colors.

Aqua

The shallow water near shore appears a blue-green color, because there are microscopic plants in the water called phytoplankton. Phytoplankton contains chlorophyll, a green pigment found in all plants. The more phytoplankton in the water, the greener it is. The less phytoplankton, the bluer it is. Plants reflect the green colored light waves, which is why they appear to our eye as green. The same happens here. The phytoplankton is reflecting the green wavelengths back through the water, so we see aqua water. All the other colors are absorbed.

The water itself is clear and colorless, so you can see down at least 35 feet to the bottom of the lake. Our goal is to keep the water clear…forever.