Watch on Soap2day. In November 2014, filmmakers Leon McCarron and Tom Allen set off for Patagonia to follow the Santa Cruz river across Argentina. Their journey reflected on the past - using the diaries of Robert FitzRoy and Charles Darwin as inspiration for the expedition - yet also, crucially, it explored the uncertain future of the Rio Santa Cruz. Now two huge dams are due to be built on the river and it seems clear that they will drastically affect the natural ecosystem, and some predict that construction could affect the level of Lake Argentina - the river's source - and therefore become a threat to the iconic Perito Moreno glacier.