Ackerson Meadow Restoration Project

Ackerson Meadow in May
Upper Ackerson Meadow water in part of gully system
Water in Upper Ackerson Meadow within the erosion gully network.


Ackerson Meadow is one of the largest mid-elevation meadows in the Sierra Nevada, and the largest in Yosemite National Park. It is an ecologically and regionally critical wildlife corridor and the scenic meadow is an important habitat for the State endangered great grey owl and little willow flycatcher, as well as a suite of additional at-risk wildlife species. It was purchased from private ownership in 2016 and donated to Yosemite by a coalition including the Trust for Public Lands, National Park Trust, Yosemite Conservancy, and American Rivers. A large erosion gully network, up to 3 miles long 14 feet deep and 100 feet wide, has drained 90 acres of wetlands in the meadow complex and is actively eroding an additional 100 acres of remaining wetlands and wet meadow habitat. The gully network is a result of over a century of landscape manipulation including domestic water diversion, farming, ranching, and timber harvest. Yosemite National Park and Stanislaus National Forest have partnered with American Rivers and Yosemite Conservancy to implement actions that reduce erosion and restore wetland functionality at Ackerson Meadow. Additional goals of the project include:

  • Protect existing intact wetlands from advancing gullies and headcuts, and re-establish hydrologic processes and conditions characterized by sheet flow and shallow dispersed swales.

  • Restore the former extent of wetlands in Ackerson Meadow by re-establishing sustained high water tables (water table within 12 inches of the soil surface for 21 days per year).

  • Minimize and mitigate impacts related to restoration actions.

  • Restore natural habitat for at-risk wildlife species.

  • Enable tribal participation in ecological restoration, tending, and gathering of traditional use plant materials.

  • Provide continued grazing on US Forest Service-managed lands while protecting recovering wetlands, riparian areas, and archeological resources.

  • Remove invasive plant species that threaten native species.

  • Preserve wilderness character. In designated wilderness, minimize impacts to wilderness character by limiting restoration activities and tools to the minimum required to restore water tables and prevent further degradation.

Section of the deep erosion gully within the meadow complex
A section of the erosion gully within the meadow.

Restoration Project Highlights

The Ackerson Meadow Restoration Project is the largest wetland restoration project in Yosemite’s history. It is the largest restoration project, by fill volume, to date within the Sierra Nevada. This monumental project is possible due to the collaborative partnership of American Rivers, National Park Service (Yosemite National Park), United States Forest Service (USFS) Stanislaus National Forest, and the Yosemite Conservancy (listed alphabetically).


This project was funded in part by the donors of American Rivers, Bonneville Environmental Foundation, California Department of Fish and Wildlife, California Wildlife Conservation Board, Google (in association with their Water Stewardship pledge and strategy), National Park Foundation (provided by The Coca-Cola Company, The Coca-Cola Foundation, and Stericycle), National Park Service (provided by Bipartisan Infrastructure Law-Ecosystem Restoration, Concessions Franchise Fee, and NPS Operations), US Forest Service, and the Yosemite Conservancy (listed alphabetically).

This project is supported by services from Cornflower Farms, Evan Wolf LLC, Hanford Applied Restoration and Conservation, Institute for Bird Populations, Randy Westmoreland Consulting, Stantec, and the Upper Colorado Center for Plant Diversity (listed alphabetically).

Implementation Timeline and Partnerships

Restoration implementation for this project is planned between August 15, 2023 and October 31, 2023, with additional work in 2024, and final revegetation in 2025.

Restoration implementation is planned to occur in two distinct phases, because of the size of the project area. Phase 1 is fully funded, with earthwork activities set to occur between August 15 and October 31, 2023 followed by revegetation in spring of 2024. Phase 1 activities will fill the gully within the lower half of Main Ackerson Meadow and the full extent of the gully in South Ackerson Meadow, and also establish a rock grade control structure at the downstream end of the project area. Fundraising for Phase 2 is underway, and will complete the gully fill work in main Ackerson Meadow, from the top of the Phase 1 work area to the top of the meadow. These earthwork activities are anticipated to occur between August 15 and October 31, 2024, followed by final revegetation and project completion in spring 2025. Adaptive management and long-term monitoring are planned after completion of restoration implementation.

Completion of both phases of the full fill alternative will immediately return self-sustaining hydrologic function to this 230-acre headwater meadow system. This restoration improves water quality and drinking water supply, increases groundwater storage, sequesters incredibly high rates of carbon, and improves wildlife habitat. The resulting healthy headwater system increases water security and helps to mitigate the impacts of drought and climate change for downstream communities within the Tuolumne River watershed, including the cities of Turlock, Modesto, and others. In addition, the restoration benefits wildlife and multiple endangered species including the Great Gray Owl (North America’s largest owl), little Willow Flycatcher, and northwestern pond turtle. The project helps achieve goals of Executive Order N-82-20 for California State’s 30 by 30 Initiative, and helps the Sierra Meadow Partnership goal to restore 30,000 acres of meadow by 2030.

To restore and protect the 190 acres of wetlands and former wetlands at Ackerson Meadow, the team will combine 100,000 cubic yards (cy) of earthen fill with 50,000 cy of woodchips to fill the gully.

Revegetation of project-related disturbed ground includes:

  • Manual installation of 425,000 wetland container plants;

  • Broadcast sowing of more than 733 pounds of native seed;

  • 100% salvage and transplant of all existing willows onto the restored meadow surface, and;

  • Long-term invasive plant monitoring and treatments.

The National Park Service initiated consultation for the Ackerson Meadow Restoration project with the seven associated American Indian tribes and groups in October 2017. Various meetings and site visits were conducted throughout the planning phase of the project. The park continues to conduct formal consultation with the tribes on major phases of planning and implementation for this project. Tribes have expressed interest in participating in revegetation and other volunteer restoration opportunities associated with this project, and the Yosemite Ancestral Lands tribal conservation crew participated in more than 40 hours of beaver dam analogue development. The Tuolumne Band of Me-Wuk Indians will provide qualified tribal monitors to coordinate with the project teams and provide on-site monitioring throughout the construction phases of the project to preserve sensitive tribal resources.

Since 2021, more than 200 volunteers have assisted with various tasks in preparation for restoration including seed collection, invasive plant treatments, resource monitoring, etc. Volunteer opportunities will remain a high priority throughout the restoration and long-term stewardship of the project.


Research studies at Ackerson Meadow are focused on contributing to wetland restoration science, and comparison of pre-and post-restoration conditions for rare wildlife species. Understanding these behaviors will help inform protection decisions for future restoration or construction projects throughout the region.

The United Stated Geological Survey (USGS) led a study on fine-detail topography, vegetation, and habitat structure change related to restoration, and did a comparison of UAV-collected lidar data with terrestrial and airborne datasets.

Ackerson Meadow is included as a site within a USGS-led soil carbon sequestration study to improve the Land Use and Carbon Simulator (LUCAS) to estimate changes in carbon in response to planned restoration and quantifying benefits using data collected from this project. This will result in a decision-support tool to assess carbon sequestration potential of any future wetland restoration project by providing decision-makers with “what-if” management scenarios for possible future changes to management or restoration plans.

Restoration Video

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11 minutes, 48 seconds

Ackerson Meadow is one of the largest mid-elevation meadows in the Sierra Nevada, and the largest in Yosemite National Park and is an ecologically and regionally critical wildlife corridor. The Ackerson Meadow Restoration Project is the largest wetland restoration project in Yosemite’s history. It is the largest restoration project, by fill volume, to date within the Sierra Nevada. Learn more about this collaborative undertaking which started in late summer 2023.


Planning Process

Several restoration methods to restore the meadow were formulated with the above goals in mind. In summer 2020, the park requested input on issues that the planning team should address during the planning process, additional alternatives to meet the purpose of the plan, information the park should consider in the upcoming analysis, and other feedback. Comments were accepted through August 25, 2020.

The project team analyzed the public comments from the civic engagement period and refined alternatives for the Ackerson Meadow Restoration Environmental Assessment (EA). The planning team developed the following three action alternatives to meet the purpose and need of the project.

  • Alternative 1 (Preferred alternative). Completely fill the erosion gullies to the level of existing meadow terraces to restore original topography, hydrology, and vegetation. Fill material will be generated from a combination of nearby upland hillslope soil excavations and locally generated wood chips and biochar. Approximately 151,000 cubic yards of fill will be needed. This alternative will maximize the acres of protected and restored existing and former wetlands.

  • Alternative 2. Encourage sediment deposition and re-direct erosive flow energy within the erosion gullies by installing more than 350 hand-built structures from natural materials. These hand-built structures include beaver dam analogs (BDA) and function to create a stair-step sequence of ponds about 4 feet deep over the length of active channels. This treatment will require hand tools and manual labor, no fill or heavy equipment will be needed. Annual long-term maintenance of structures will be required. This alternative would not fully restore the gullies to natural meadow topography, rather it would enhance the wetland and floodplains within the gully network and eventually form an inset floodplain. This alternative would protect and restore the least acres of existing wetlands and former wetlands. The park has also considered the introduction of beavers to the meadow for restoration purposes but considers that action infeasible at this time.

  • Alternative 3. Apply individual prescriptions of the fill or hand-built alternatives to specific reaches of the gullies based on depth of incision to restore meadow hydrology and reconnect with the floodplain. This hybrid alternative would use soil from the same sources as the other fill alternatives in the deeper portion of the gullies and use BDAs in the areas where the gullies are less than 3-5 feet deep. This would require less fill than the full fill option and more fill than the intermittent fill option, and it would require annual long-term maintenance of the BDA structures. This alternative would protect and restore a moderate number of existing and former wetlands.

Next an impact analysis of the three alternatives was conducted. Analyzing impacts means considering how the condition of the resources would change, either negatively or positively, as a result of the implementation of the alternatives under consideration. The environmental assessment presented the results of the impact analysis. The Ackerson Meadow Restoration Environmental Assessment underwent public and agency review from June 2, 2021 to July 8, 2021. The full fill alternative was selected. It provides rapid and comprehensive wetland restoration and protection, with the least maintenance needs over the long-term and is anticipated to become self-sustaining in 3-5 years. A Finding of No Significant Impacts (FONSI) and the Determination of Non-Impairment were signed by the National Park Service on September 21, 2021.


Webinar Recording

Ackerson Meadow with flowers

Last updated: June 12, 2024

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