Removal of the Elwha and Glines Canyon dams on Washington's Elwha River provides an opportunity to study the ecological response of a river ecosystem to large-scale disturbance and subsequent restoration. Central to this effort is the development and implementation of an adaptive management framework aimed at guiding the recovery of Chinook salmon and steelhead trout populations. Extensive monitoring conducted to date shows that removing the dams is positively benefitting Chinook salmon and steelhead populations and is improving the ecological condition of the river, though the recovery of these priority species will requires decades to achieve historic levels of abundance. These results were published in the special issue “Large-Scale Dam Removal and Ecosystem Restoration” of Frontiers.
Elwha River Dam Removals
The Elwha River, once renowned for its robust salmon runs, experienced significant ecological degradation following the construction of the two dams in the early 20th century. These structures impeded fish migration, altered hydrological regimes, and trapped wood and sediment, leading to a precipitous decline in salmon populations. Decades of advocacy culminated in the Elwha River Ecosystem and Fisheries Restoration Act of 1992, enabling dam removal, which occurred in phases from 2011 to 2014.
Adaptive Management Framework
Adaptive management is a systematic approach to environmental and conservation management. It involves learning from outcomes, adjusting strategies based on new information, and promoting continuous improvement.
Scientists from federal and state agencies and the Lower Elwha Klallam Tribe established the Elwha Monitoring and Adaptive Management guidelines. They aid in the recovery of endangered Chinook salmon and steelhead trout populations. This framework incorporated a phased approach, with distinct recovery objectives and performance indicators for each of the four recovery phases.
Adaptive management guidelines also emphasize the importance of monitoring key physical and biological parameters to inform management decisions.
Key Findings and Challenges
The agency partners and the Tribe have developed and continue to implement a comprehensive monitoring program to track changes in fish populations, habitat conditions, and water quality. These data are vital to assess progress toward recovery goals and identify potential management adjustments. Monitoring of fish species abundance and whether of natural or hatchery origin are requirements of the NMFS Elwha Hatchery and Genetic Management Plan Biological Opinion associated with the operation of hatcheries on the Elwha River.
Here’s some of what the Tribe and partners have learned in the past decade of monitoring, which is just the beginning of the story:
Salmonid Response
Chinook salmon populations are exhibiting signs of recovery, with increases in abundance and distribution. However, adult productivity remains below target levels and Chinook remain in the “Preservation” phase of recovery. Steelhead trout have shown more rapid recovery, and this population has advanced to the "Reintroduction" phase.
Monitoring Effectiveness
The monitoring program continues to successfully provide critical data for informing management decisions. However, challenges related to data collection and analysis remain, particularly with juvenile fish abundance estimates.
Adaptive Management Implementation
Adapting management actions based on monitoring results is complex due to multiple agencies with varying authorities and responsibilities. Additionally, the legal framework, particularly the Endangered Species Act, imposes regulatory requirements on management and monitoring activities.
Performance Indicator Challenges
Defining and measuring appropriate performance indicators is challenging—some initial methods and metrics worked well, but others did not. In response, the monitoring plan has adapted by shifting resources towards those biological indicators that are most effective for assessing the impacts of dam removal and restoration of the overall ecosystem.
Salmon Recovery and Sediment Dynamics
Early results from the monitoring program demonstrate that removing the two large Elwha River dams is positively impacting Chinook salmon and steelhead populations. Combined with hatchery management actions and harvest restrictions, researchers found that dam removal has led to:
- Increased adult fish numbers
- Expanded habitat use
- A resurgence of naturally produced juvenile salmon
The removal of the Elwha dams has begun a dramatic transformation of the river's sediment and wood regime. Vast quantities of sediment and large wood, previously trapped behind the dams, were released, reshaping the riverbed and creating new habitats. This process was initially disruptive to salmon populations. However, once the short-term sediment disturbance evolved into a more stable natural sediment regime, the ecological condition of river reaches in the former reservoirs and downstream improved.
Sediment is crucial for salmon spawning and rearing. It provides the substrate for redds, the nests where salmon bury their eggs. Additionally, sediment helps to create diverse aquatic habitats that support a variety of aquatic insects and other benthic invertebrates, the primary food source for juvenile salmon.
Hatchery Role and Genetic Considerations
To mitigate the risks associated with dams and later dam removal, the partners have been operating hatchery programs to support natural salmon populations before, during, and after dam removal. While hatcheries have played a role in maintaining initial salmon numbers, the hatchery management guidelines call for long-term reductions in hatchery production as self-sustaining natural populations continue to build. This is also a requirement of the Hatchery Biological Opinion and highlights the importance of ongoing monitoring to achieve the recovery targets of the Elwha River Ecosystem and Fisheries Restoration Act (Public Law 102-495).
Re-Emergence of Summer Steelhead
A particularly promising development in the Elwha River restoration is the re-emergence of summer steelhead. This life history strategy, once thought to be lost due to the dams, has rebounded. It demonstrates the remarkable adaptability of these fish and the importance of providing diverse habitats to support various fish life histories.
While the early results of the Elwha River dam removal project are encouraging, it is important to emphasize that the river's recovery is a long-term process. It will take decades for the ecosystem to rebound fully. Funding to sustain ongoing monitoring is necessary to accomplish the recovery goals of the Elwha River Ecosystem and Fisheries Restoration Act, and to ensure that the last recovery phase of the Elwha Monitoring and Adaptive Management guidelines is achieved: viable natural populations of endangered Chinook salmon and steelhead trout. Once this milestone is met, hatchery production can decrease and management can focus on appropriate fish harvest levels.
The Elwha River restoration project continues to offer valuable insights into the complex ecological processes involved in dam removal and river recovery. While challenges remain, the project demonstrates the potential for large-scale ecosystem restoration. It also highlights the importance of collaborative partnerships and adaptive management in guiding such complex endeavors. Federal and state agencies working with the Tribe on this effort include:
- National Park Service
- Washington Department of Fish and Wildlife
- NOAA Fisheries
- U.S. Department of Fish and Wildlife Service
- U.S. Geological Survey
Carefully monitoring the river's response and adapting management strategies allows scientists and managers to learn from the Elwha River experience and apply these lessons to future restoration efforts. The ultimate goal is to restore salmon population abundance and diversity, ensuring the long-term health and resilience of the Elwha River ecosystem.
