Colin Heinz has walked, tramped and climbed every one of the rivers which flow from the Main Divide out to the sea. In Upriver - From the Sea to the Southern Alps Colin Heinz creates a unique and detailed account not just of the landscape but of eight-hundred years of the South Island's history, captured during expeditions he started making as a school boy, five decades ago. Colin tells Kathryn Ryan it has been his life's work.