For the first time beginning this summer, police in Arizona will be able to stop anyone they like and order a check of their ID to determine whether the person is in the U.S. illegally. The new powers, just recently signed into law, have reignited the national debate on immigration.

Since 9/11, getting into the United States has become a good deal harder and, for some, much more dangerous. With border enforcement increasing, many illegal immigrants are now attempting to cross one of this country's most important irrigation projects called the "All-American Canal." The canal has become sort of a national moat on our southern border, and hundreds of people have perished in its waters. It is a carnage that has gone mostly unnoticed because many of the victims are buried without their names.

Full Segment: The All-American Canal

Web Extra: Border Control

Web Extra: Militarizing The Border

Web Extra: Illegal Immigration - The Hard Facts

In the California desert, in a field of mud, is a graveyard that is hard to imagine in America. Bricks mark the final resting place of hundreds of human beings, identities unknown. They died traveling to America in search of a life better than their home countries could offer. They rolled the dice in the underworld of human smuggling and lost. Their families back home never learned that their journey ended in the All-American Canal.

Asked where the bodies are usually found, Dr. John Hunter told "60 Minutes" correspondent Scott Pelley, "Typically, they'll find them at the drops. So for example, there's five of these big hydro drops here. Drop one, they found over a hundred bodies at drop one, drop two they had 60. Drop three, 60 etc."

Hunter showed us the hydroelectric dams or "drops" that catch most of the bodies. Hunter is an unlikely activist: he's a physicist and life-long Republican who has spent much of his career designing weapons for the U.S. government.

"I'm a very right-wing guy," Hunter said. "I'm not an open border kinda person. I just don't believe we should be letting people drown in our backyards. It's inhuman."

Ten years ago, a newspaper article about rising immigrant deaths caught his attention. And today, the deaths in the canal system are an obsession.

"This first picture is a little girl named Alexandra. And she drowned saving her older sister's life," Hunter said, pointing out pictures. "This is border agent Goldstein. He drowned trying to save his dog."

"This is one small subset of the American canal. Each pushpin represents a person who drowned in this particular location," Hunter added, showing Pelley an online map with virtual pushpins.

Asked how many pushpins - each representing a victim - there are, Hunter said, "There's over 550 victims and those are the ones we know of."

While the canal is a deathtrap, it is also a lifeline for the nation. It flows the length of 85 miles just north of California's border with Mexico, transporting water from the Colorado River to the Imperial Valley. Two thirds of our winter fruits and vegetables are grown with this water. But half of the people who pick those crops are illegal immigrants.

To get the jobs created by the canal, they cross the canal, usually at night, on makeshift rafts or using plastic jugs for flotation. The water is 225 feet across, 20 feet deep, with few rescue lines or climb-out ladders, safety devices that you would find in some other canals.

The All-American is owned by the federal government but its management is controlled by a regional authority called the Imperial Irrigation District. And for ten years, Hunter has been lobbying the elected members of the Irrigation District to add safety features.

They've taken votes, commissioned studies, but done almost nothing.