BIG COTTONWOOD CANYON — A gaggle of young, obviously wet boys troop through a stream in the woods with their mother close behind on a blazing summer day.

Somewhat perturbed Salt Lake watershed officer Mark Kaila waits for them with a question: "Do you know where you're drinking water comes from?"

The mother, who says she is a lifetime Salt Laker, looks perplexed. She says she doesn't know the answer. Kaila matter-of-factly explains that drinking water comes from canyon creeks and streams, and playing in them could cause contamination.

Kaila doesn't enjoy ruining a person's day, but running people out of the river is part of his job on the city's water patrol. The badge pinned to his shirt pocket gives him the authority to issue citations, and he lets people know it. But he prefers an on-the-spot watershed lesson to writing someone up.

Still, the 26-year-veteran is vigilant in his work. He sees himself as "god up here because I'm protecting the water for the people down there."

Salt Lake City gets 60 percent of its water — enough to satisfy 405,000 residents — from the Wasatch canyons. The water passes through a treatment plant before reaching homes and businesses.

The city employs four officers and contracts with Salt Lake County for additional patrols in Big Cottonwood, Little Cottonwood, City Creek and Parleys canyons.

The advance party of Mormon pioneers in 1847 had what is now City Creek diverted for crops two days before Brigham Young rolled into the valley. The rivers and streams flowing down the Wasatch Mountains make life in the Salt Lake Valley possible.

"It all starts with your watershed and protecting your watershed," said LeRoy Hooton, longtime director of the Salt Lake City Department of Public Utilities.

A 50-cent surcharge on Salt Lakers' water bills brings in $500,000 a year to fund acquisition of land in the canyons. To date, the city has spent $3 million on about 1,500 acres that will remain free from the potential pollution development brings, he said.

The city and the U.S. Forest Service last week launched a public awareness campaign to educate residents and visitors how to protect water supply. Large "Keep It Pure" signs will be posted throughout the Wasatch canyons. The program includes a water unit for fourth- and ninth-graders starting next year.

Safeguarding canyon streams started early in Utah's history.

In 1851, just four years after the pioneers settled the valley, the City Council outlawed "filthing" of water sources. People were not allowed to build "cow yards, privies or deposit any filthy substance on the banks of the streams" flowing to the city.