The following appeared in the Des Moines Register 4/7/1985. This question was answered by Roger W. Bachmann, professor, Department of Animal Ecology, Iowa State University, Ames.

Blue Water Myth:

Q. I am surprised The Register would perpetuate the myth that "The National Geographic Society says West Okoboji is one of the three largest and also one of the most beautiful blue-water lakes in the world. The other two are Lake Louise in Canada and Lake Geneva in Switzerland", the society says. In 20 years of studying Iowa lakes I have yet to find that reference: Indeed, the National Geographic Society denies it ever made such a ranking.

A. While the term "blue-water lake" is not a scientific term, it is a fact that lakes and oceans with exceptionally pure waters like Lake Tahoe, Crater Lake, Lake superior and the Sargasso Sea appear blue to the eye. When sunlight penetrates these pure waters, other wavelengths (colors) of light are absorbed more strongly than blue, so that more of the blue remains to be scattered back out of the water surface.

Most natural waters, however, contain dissolved organic materials that selectively remove these blue wavelengths and thus make these lakes appear more green. The more organic matter, the less of the blue that remains to be seen. Suspended particles like silts and algae may further change the apparent lake color.

The water in Lake West Okoboji contains enough dissolved and suspended materials to make its optical properties not exceptional on a worldwide basis; however, the lake is still unique for our region. One would have to go several hundred miles to find another large, natural lake that is as deep or clear as West Okoboji. We have good reason to brag about it on its own merits.