'River Piracy' Phenomenon Set to Steal Alaskan River, Scientists Predict 6 MAY 2021 River piracy, also known as stream capture, happens when melting glaciers divert the path of a river. Due to our warming planet, a major Alaskan river is under threat of being redirected in this way – stealing an essential source of water away from the ecosystems and people that rely on it. The threatened waterway is the Alsek River, flowing down from the St Elias mountain range in Canada, to Dry Bay in Alaska. Before it reaches the Pacific Ocean, it passes through Alsek Lake. Alsek Lake is separated f...