The Copper River and its tributaries make up an impressive watershed of wilderness, approximately 26,500 square miles (nearly 16 million acres). The Watershed encompasses the far corners of five distinct mountain ranges. These include the Alaska Range, the Wrangell Mountains, St. Elias Range, most of the Chugach Mountains and a small section of the Talkeetna Range. They contain sources of both volcanic and sedimentary rock from some of North America’s tallest peaks, as well the largest subpolar icefield in the world, the Bagley Icefield, making the Copper River Watershed one of the most prolific and diverse glacial deposits in the world.
On May 28, 2013, a NASA satellite captured this image of the Copper River Delta showing extraordinary sediment load in the Gulf of Alaska. The Childs and Miles glaciers, as well as the Bagley Icefield drain into the Copper River. As the glaciers slide down the mountains into the valleys, they grind on the bedrock below, creating what scientists refer to as “glacial flour.” That sediment is a good source of iron and nutrients for phytoplankton and marine plants. These nutrients in turn support abundant wild salmon runs on the Copper River.