Elwha Watershed Information Resource

Rocky rapids in Elwha River. Betsy Carlson, National Park Service

The water in the Elwha watershed is an important resource to fish, wildlife, plants, and people. Fish are made up of approximately 80 percent water and plants are between 80 and 90 percent water (World Water Council 2006). The quality and quantity of water available to plants and animals is critical to their habitat and existence. People rely on the Elwha for water too. People in the communities of Port Angeles and the Lower Elwha Klallam Reservation rely on the watershed for drinking water and use Elwha water in their daily activities (such as cooking and laundry). Because the Elwha water is important to so many groups, it is essential to understand how removing the dams on the river will affect the quantity and quality of the river water.

In the long term, removing the dams will benefit water quality. For example, high summer and fall water temperatures will be reduced (National Park Service 1996), improving the water quality. (Damming the Elwha River created high water temperatures in the summer months that have caused increases in parasites, disease, and fish mortality in the lower river.)

In the short term, dam removal will also affect the water of the Elwha:

• Overall water quantity may only be affected for a few months during dam removal due to construction of a diversion channel.
• Surface water quality will be reduced by increasing suspended sediments and turbidity for short periods during dam removal.
• Groundwater quality will also be reduced with an increase of fine sediments, which may affect municipal well water.
• Dam removal will also alter the water table, making it necessary for individuals to modify their wells and residents of the Lower Klallam Elwha Reservation to implement an alternative sewer treatment system.

Learn more about the water of the Elwha by clicking on the links below:

Water Quality: Both surface water and groundwater are considered to be of good quality prior to dam removal, with few measurable contaminants. Dam removal may cause short term decreases in water quality and some infrastructure (such as wells) may need to be modified.

Water Quantity: The amount of water in the Elwha River is based on the amount of annual rainfall and snow melt in the area, and the quantity is measured daily. Flooding does occur occasionally. Dam removal is not expected to change the quantity of water but may alter the amount of groundwater in some wells near the river for a short period due to increases in fine sediments in the aquifer.

Reference

National Park Service. 1996. Elwha River Ecosystem Restoration, Draft Environmental Impact Statement. National Park Service, Olympic National Park, 600 East Park Avenue, Port Angeles, Washington, 98362.

World Water Council. 2006. Water at a glance.