TORONTO — U.S. President Barack Obama has turned his attention to the sorry state of the Great Lakes, the natural reservoir for 20 percent of the world's fresh water.

Secretary of State Hillary Clinton recently announced that the United States would renegotiate the Great Lakes Quality Agreement with Canada. The treaty needs updating to confront new threats, including invasive species, declining water levels, and chemical contamination.

Clinton made the announcement on the Rainbow Bridge, which connects Canada and the U.S. above spectacular Niagara Falls. Nearby, on the American side of the border, is Love Canal, where homes and a school were built on a toxic waste dump. Birth defects and a slew of ailments forced the evacuation of the community in the late 1970s.

A week earlier, Obama appointed a Great Lakes czar to oversee his ambitious clean-up plan. Cameron Davis, a Chicago-based environmentalist, will initially manage $475 million in new spending. Obama has promised $5 billion during the next decade to restore the lakes.

As their first order of business, bureaucrats in both initiatives would be wise to screen "Waterlife," the new documentary by Toronto-based filmmaker Kevin McMahon. It's an arresting look at the actions and neglect that have pushed the lakes to the brink of "irreversible" collapse, as top scientists have warned.

One of Canada's most innovative filmmakers, McMahon has directed more than 15 documentaries in the past two decades. Whether filming on the media theories of Marshall McLuhan, the music of Bach, or the impact of the Cold War on the Inuit, McMahon challenges conventions. His storytelling is never linear. Like his stunning helicopter shots of the Great Lakes, he strives for the big picture. Meaning lies in the layers his films reveal.

In "Waterlife" — winner of the special jury prize at the recent international Hot Docs film festival, and released in Toronto theaters last week — McMahon gives equal billing to beauty and doom.

It begins with an image of innocence: an underwater scene of a playful beluga whale. But the whale's habitat — about 1,000 belugas live near the mouth of the St. Lawrence River — is horribly out of whack. A quarter of the adult white whales are dying of cancer. The likely culprit is upstream, in the "soup of chemicals" that is the Great Lakes — the source of drinking water for 35 million people.

Water from Lake Superior takes an amazing 350 years to wind its way to the St. Lawrence River. It took people on both sides of the U.S.-Canada border a lot less time to fill the waters with waste and poison.

From Superior the water pours down to Lake Michigan, "the industrious lake" on the American side of the border. Chemicals from heavy industries lie at the bottom of the lake. The toxic sludge gets kicked up by storms or the propellers of freighters and is eaten by fish.

Twenty years ago, the U.S. government identified 43 Great Lakes harbors that are highly contaminated, including with PCBs. Only three have been cleaned up.

The film quotes Marc Tuchman, of the Environmental Protection Agency, estimating that 4 million cubic yards of contaminated sediment need to be dredged and disposed. In some areas, the sediment covers the lake bottom 25 feet deep. At the Fox River, a Lake Michigan tributary where some dredging is taking place, the film shows plastic rolls like giant pythons filled with contaminated sediment.

Also polluting the lakes are billions of liters of raw sewage.  Flowing with it are pharmaceuticals that flush through our bodies and down the toilet. Even anti-depressants are being found in high quantities.

"Every drug we take is out there," said environmental scientist Chris Metcalfe.

In Lake Huron, fertilizer and human waste is spurring outbreaks of algae that cause some children to break out in blisters.

At the lake's southern tip, where oil refineries dominate the Ontario town of Sarnia, up to 70 percent of male frogs have testicular deformities. "Half of their testes are full of ova instead of sperm," said toxicology biologist Pamela Martin, of Canadian Wildlife Services, a branch of the federal government.

The native Aamjiwnaang community there is surrounded by the petrochemical industry. For years, Aamjiwnaang mothers have given birth to two girls for every boy — defying the normal ratio of 51 percent boys and 49 percent girls. Door to door surveys of the community have found high rates of cancer, heart ailments and miscarriages.

Making matters worse on the Canadian side is that industry doesn't have to tell government what they're dumping. Government scientists operate by guessing what chemicals might be present and then testing for them. Recently, they found a flame retardant chemical in the lakes that has been produced for 40 years.

Not surprisingly, fish stocks in the five Great Lakes are dwindling. Species that invaded after canals and locks for shipping were built are partly to blame. Zebra mussels, introduced by the ballast water of European ships, are particularly deadly, reproducing rapidly and siphoning nutrients from the food chain.

Fishermen that haven't given up are struggling. Government agencies stock the lakes with millions of trout, but they rarely reproduce. And water levels are decreasing, which some scientists blame on global warming.

Faced with this litany of ecological degradation, Josephine Mandamin's journey seems quixotic. The native grandmother was "moved by the spirits" to walk the Great Lakes' 10,000 miles of shoreline. The film shows her offering tobacco to the water and praying it will someday run pure again.

"There's a lot of apathy," she lamented. "I've heard so many times, 'You're crazy'… But we know it's for the betterment of the next generations."

In an interview, McMahon applauded Obama for committing far more to clean up the Great Lakes than Canadian Prime Minister Stephen Harper. But Obama's $5 billion promise, if realized, is "a drop in the bucket" compared to the $1 trillion given to bailout banks from their own greed, McMahon said. Priorities, as usual, are skewed, he said.