At the heart of the US-Canada border sit The Great Lakes - the world's largest freshwater ecosystem, containing as much as one fifth of the planet's supply.

Chapter 1: Source to Sea
The water's journey from source to sea spans half a continent - 2,000 miles - and takes more than three centuries to complete. This first of three documentaries charts the feature and its surrounding flora and fauna, showing how beavers, wolves, loons, moose help shape this incredibly vast watershed.

Chapter 2: The Big Freeze
s winter descends on The Great Lakes, life must contend with the return of the ice that carved this immense watershed thousands of year ago. A polar vortex paralyses fish and ducks and attracts hundreds of bald eagles. Wolves hunt deer trapped by ice, but are manipulated by ravens.

Chapter 3: Marvels and Mysteries
The spring thaw in America's Great Lakes creates ice tsunamis. Photosynthetic salamanders, fishing wolves, deep-diving moose, baby rattlesnakes and colourful fish hunting mid-air all illustrate unique adaptations to to the warmer, brighter season.