The Colors of Lakes

The photos in that slideshow were captured by Ted Rulseh, a good friend and colleague. Ted lives on the shore of Birch Lake up in northern Wisconsin. His multicolored images provided the inspiration for today’s post. I thought it would be illuminating (no pun intended) to discuss just why lakes display such a wide range of colors.

As shown in Ted’s photos, the color of a lake is predominantly determined by colors reflected from the sky. That’s the same lake in every scene but under varying atmospheric conditions. In the fourth slide you can see multiple hues (blue, red, and yellow) reflected in the water.

My July 27, 2015 post answered the question “Why is the sky blue?” Curiously, I’ve never been asked “Why is the lake/ocean blue?” If water just reflects the color of the sky, asking “What color is water?” is a lot like asking “What color is a mirror?” Large bodies of water are usually described as “blue” because that’s the way they appear under clear skies. Nonetheless, other colors are often observed.

As it turns out, pure water does have an intrinsic color. It’s a faint tint, so you won’t see it in a drinking glass or bottle or bucket. But if you have a large enough volume of water (say, a swimming pool’s worth), you’ll see a turquoise hue — even when that pool is indoors and has white interior surfaces. H2O molecules readily absorb longer wavelengths of light (red through mid-green). That leaves some of the green and all of the blue and violet to be scattered and reflected. To the human eye, this combination of colors is perceived as turquoise.

Of course, lakes can display many colors beyond those seen in the first slideshow. Water can be host to a wide variety of organic and inorganic entities, both natural and anthropogenic. And unfortunately, though most are benign, some are highly toxic. Here’s five examples:

If you’re privileged to live on a large body of water you already knew my basic premise: What a lake looks like, even the same lake, is an ever-changing display driven by weather, time of day, season of the year, and transient perturbations from the environment.

For the rest of us who only occasionally visit a lake or ocean, what we see is a snapshot from the continuum of displays. Fortunately, technology has provided the virtual lakefront experience via online webcams. Some can be panned and zoomed. If you have a fast internet connection, you might want to bookmark a favorite lake and check in on it occasionally. That’s what I do with my hometown’s Harbor Cam on Lake Michigan.

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