An exclusive story from McClatchy News Service quotes Dr. Robert Derlet about bacterial contamination in Sierra streams from lots of cattle answering the call of nature as they graze.

Here's what the story didn't say: "In a mountain range boasting giant sequoias, Half Dome and Mount Whitney, Derlet has confirmed there are bacteria linked to human feces in lakes and streams."

That was in a story I wrote from a lake near Tioga Pass in Yosemite National Park where I followed Derlet one September morning nearly five years ago.

The McClatchy story said Derlet, a University of California at Davis emergency room doctor, is pushing for grazing reforms related to cattle. But, from interviewing the man, I know he has strong feelings about the way people approach the wilderness, too.

Something else the story did not say: Derlet drinks from the high-country lakes without filtering the water. I watched him scoop water right out of Middle Gaylor Lake and drink it.

I've done it myself when I'm in a very remote place, such as a glacial tarn off trail near the crest. But I carry a water filter in the back country, and I use it regularly.