The Elwha Watershed:
With 321 square miles of drainage and 70 miles of river and tributaries, the Elwha River is the largest watershed in the peninsula. A large amount, 83%, is located within Olympic National Park, sheltering it and making it a particularly pristine river habitat.
The Elwha dam is located at river mile 4.9, behind which is Lake Aldwell. Glines Canyon dam is downstream at river mile 17, holding back Lake Mills. The Lower Elwha Klallam tribe reservation is located around the mouth of the river on the Strait of Juan de Fuca. Just east of this sits the city of Port Angeles.