3. Dam Removal and Ecosystem Restoration in the United States

3. Dam Removal and Ecosystem Restoration in the United States

Background and Issues:

In the United States, many dams were constructed throughout the 20th century, which significantly impacted ecosystems. Particularly, the migration routes of fish were blocked, wetlands were reduced, and water quality deteriorated. To address these issues, efforts to remove aging dams have been underway since the 1960s.

Removal of the Elwha Dam:

The Elwha Dam, located in Washington State, is one of the most notable dam removal projects in the United States. Since its construction in 1913, the dam had significantly affected the Elwha River's ecosystem. Specifically, the migration of salmon and trout was blocked, leading to a drastic decline in their populations. The decision to remove the Elwha Dam was made in 1992, and the removal process began in 2011. After the removal, the return of salmon has been confirmed, and fish habitats are being restored.

Outcomes of Dam Removal and Environmental Improvement:

The removal of the Elwha Dam has allowed salmon and steelhead (Oncorhynchus mykiss) to resume their migration, leading to an increase in their populations. By 2018, salmon spawning in the Elwha River had significantly increased, with numbers reaching several times those before the removal. Additionally, the natural environment of wetlands and rivers is being restored, and improvements in water quality have been observed. Specifically, turbidity and nutrient levels have decreased, restoring the balance of the ecosystem.

Economic and Social Impact:

The removal of the Elwha Dam has positively affected not only the ecosystem but also the regional economy. Salmon fishing has revived, and tourism has been revitalized. Particularly, ecotourism has developed around the Elwha River, attracting thousands of tourists annually. Additionally, for local Indigenous communities, traditional fishing practices have been revived, spreading social benefits.

Future Outlook:

Following the success of the Elwha Dam removal, other projects to remove aging dams are progressing in the United States. These efforts are expected to restore ecosystems and revitalize regional economies. Continued efforts to balance environmental conservation and sustainable development are necessary in the future.