At the centre of Canada's vast northern watershed that drains into the Arctic Ocean is one of the greatest freshwater deltas on Earth - the Peace-Athabasca Delta. Upstream, along the Athabasca River, hidden underneath the boreal forest and muskeg wetlands, is one of the richest oil deposits in the world. The United States government recently declared Alberta's oil sands to be 'proven oil reserves.' Consequently, the U.S. upgraded its global oil estimates for Canada from five billion to 175 billion barrels.