It's the beginning of May and I'm standing, canoe paddle in hand, on the banks of the Don River in Thorncliffe Park. 

Ralph Toninger, manager of habitat restoration for the Toronto and Region Conservation Authority, and I are just two of the 750 people participating in the 20-year-old Paddle the Don tradition, canoeing 10.5 km from the shadow of this bridge to the mouth of the Don at the Keating Channel feeding into Lake Ontario. 

The morning sunrays sparkle off the Don as we dip our paddles in and push off from the riverbanks of Ernest Thompson Seton Park. It's the only time of the year when the river's banks buzz with whispers of the golden days a century ago, when thousands of eager Torontonians congregated along it to sunbathe. 

We may forget this tradition, but the rivers don't. 

"With every river in Toronto there's a whole lot of history," Maria Papoulias manager of natural heritage at Rouge Park tells me a few days before Paddle the Don. "Human settlement on this land goes back about 11,000 years ago, after the glaciers retreated from our landscape." 

The nine watercourses that dissect the GTA—the Humber, Rouge and Don rivers, and the Mimico, Etobicoke, Duffins, Highland, Carruthers and Petticoat creeks—are reminders of the dawdling evolution from vast tundra and spruce forest to the densely packed urban jungle we live in today. Honking commuters, clambering cranes, and tattooed mixologists have replaced the mammoths, musk ox, and nomadic hunter-gatherers with stone-tipped spears that used to roam these territories. 

Just a few hundreds years ago, the settlement-dotted Don, Rouge and Humber were all important trading routes for First Nations and early Europeans. Today they all weave their way through some of the city's most densely populated neighbourhoods. 

Toronto was built on the back of these rivers. 

As the Don tugs us onwards, we pass concrete pipes spewing water into the river. Some is storm water, meandering its way from upstream where paved over parking lots and roads repel it downstream, along with the oil grit and salt from the endless winter. 

"[Run-off] really changes the ecosystem of the river," says Arlen Leeming, project manager of the Don and Highland watersheds for the TRCA. "It's probably the greatest threat that's facing the Don and a lot of urban rivers for that matter."

Stringent regulations and planning implemented by the TRCA—such as using porous parking lots and storing rainwater to build more natural water cycles—are helping to slow down the barrage, but many of the aging arteries were built long before downstream effects were taken into account. 

Some of the pipe water jostling our canoe also comes from buried rivers and tributaries. 

"In the early 1960s a lot of development and urbanization was taking place," says Chandra Sharma, the TRCA's watershed specialist for Etobicoke-Mimico Creek and senior manager of climate change. "Most of the rivers were encased in concrete channels, primarily because the thinking at that time was we can just control water by channelizing that course." 

Knowing what we know now, the concept of having complete control seems absurd. In some, like Etobicoke-Mimico Creek, nature has rebelled, tearing apart the concrete barricades, sending chunks southwards. In other spots, the channelization is vital to protect infrastructure—for instance, Etobicoke Creek runs very close to two runways at Pearson airport.

"One of our major efforts over the last decade is to perform a total review of how many kilometres of channels we have in these water courses and come up with a plan to naturalize those where we can," she adds.

As Toninger and I portage our canoe around a set of shallows he tells me the story of a hiker's gruesome discovery last April of eight skinned beavers in Crothers Woods, a small tract of land north of Pottery Rd. along the Don River in East York. Ultimately, the culprit turned out to be a trapper who had caught the beavers up north and having nowhere to dispose of them, he'd tossed them in the ravine.

"He wasn't doing anything wrong really, but the trapper's code says you should leave them where you found them so they can decay and work their way back into the ecosystem," he says. 

I think of the grisly forms and the finder's shock, an unsightly juxtaposition between the clashing ecosystems of urban life and the wild. 

As we paddle beyond the recently revitalized, century old Evergreen Brick Works—which formerly provided the building blocks for Toronto landmarks like Casa Loma and Massey Hall—the contrast becomes more apparent. Kingfishers swoop from their perches on speed limit signs from the nearby parkway to peer below the surface of the water. Shopping carts sit entangled in roots and torn branches from spring flooding stack against the heavily graffitied support pillars of bridges.

"Weather, flood, and extreme events are all natural things and they're actually no problem until you put people in the way," says Vicky McGrath, the TRCA's Humber watershed specialist. She points to Hurricane Hazel, the 1954 storm that killed 81 Torontonians and obliterated houses built in the city's flood plains near Marie Curtis Park. Ultimately, it spurred the creation of the TRCA. 

But extreme weather, including last summer's flooding and this winter's ice storm, is still a frequent concern. 

"The GTA is the fastest growing area and everyone wants to be there because it's the economic engine of Ontario," she says. "We have to try and manage the way the watersheds operate so that they can accommodate that growth and cope or offset events like these so that everybody still has a great place to live."

One thing that becomes apparent is that everybody has a story about the rivers that ultimately ties into our city's history. As we pass Riverdale's Don Jail in the canoe, I am reminded of a story Leeming told me about the Atlantic Salmon that used to swim up the river.

"The guards used to catch the salmon and feed it to the prisoners and finally the prisoners refused to eat any more Atlantic salmon," he says. "That was 200 years ago. There aren't Atlantic salmon in the river any more." 

In an effort to reset the balance and restore some of this history, Pacific salmon have been introduced into the Don River.

As Toninger and I paddle the last little stretch towards the mouth of the river, empty soda bottles, and other bits of refuse collect in the still waters and bump against our canoe. Topinger jokes that they "save the best for last." But the symbolism of the downstream effects of urbanization isn't lost on me. 

Awareness efforts like the Humber's designation as Canadian Heritage River and a ceremony highlighting the 100-year extinction of passenger pigeons from the Etobicoke-Mimico creek area are helping to remind people of how we've shaped the land. Conservation efforts, such as Rouge Park's 10,000 acres located smack dab in the middle of the GTA with 200 hectares of restored land and 20 restored wetlands, are helping to improve natural water cycles. 

But there's still a lot more to be done to revitalize the city's rivers and watersheds.

"I think people need to realize that rivers and lakes are the foundation our entire society is built on," says Papoulias. "We've been distanced from them in our modern society, but it's nice to bring people back."

You can learn more about Toronto's rivers and review the TRCA-generated watershed report cards here.

Andrew Seale is a Toronto-based freelance writer whose writing has appeared in The Toronto Star, The Vancouver Sun, The Calgary Herald, and Alternatives Journalamong other places. His last piece for Yonge Street looked at virtual reality technology that is teaching foreign reporters warzone first aid.