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Agua Chinon Watershed Prepped for Restoration


Irvine Ranch Conservancy begins 30-acre restoration project targeting riparian habitat.

Agua Chinon is a 1,200-acre Canyon in the San Diego Creek Watershed, and is the popular starting point for a beautiful hike to The Sinks. While keen eyes may have noticed invasive species such as black mustard and tree tobacco among the native plants in the Agua Chinon basin, visitors will soon start to also see signs of a restoration project in progress. The Irvine Ranch Conservancy has begun an intensive, multi-year project to remove invasive weeds and restore this riparian habitat.

The ultimate goal of the project is not only to eliminate invasive plant species but also to reintroduce native plants such as mule fat and elderberry (pictured). Conservancy scientists have begun preparing for the project by conducting plant surveys and other research to assess the current state of the basin and collect baseline data. The project will get a head-start toward success thanks to water available from a nearby tank, which will be channeled through temporary above-ground pipes to help the five-year project advance faster.

”The signs of restoration will be immediate and ongoing,” says Lars Higdon, Project Manager for the Conservancy. “Over the next year, visitors will see flag markers, irrigation lines, and a changing landscape as we clear invasive plant species. These temporary changes are building toward the land’s long-term health.”

During the first two years, the project area will be regularly irrigated, to actually encourage invasive weed growth. After watering, the weeds will germinate, grow and then they will be removed. This “grown and kill” site preparation process helps purge the soil of invasive plant seeds, so that native plants have less competition when they are planted. Irrigation will continue until the native plants have become established. The Conservancy has begun trial plantings and will continue this winter, testing for the most successful and efficient planting methods in Agua Chinon. Full-scale planting will begin the following winter.

The majority of Agua Chinon is in OC Parks’ Limestone Canyon Nature Preserve, and the project is being funded as a mitigation effort by Orange County Transportation Authority and OC Waste and Recycling. Visitors to the area can help aide the project by continuing to stay on the designated trail and not disturbing the irrigation lines or flag markers. The Conservancy will also lead volunteer restoration activities.

Updates on the progress of the Agua Chinon restoration project will be available at the Irvine Ranch Natural Landmarks website and Facebook page. To find out about more about how to volunteer for stewardship projects, please visit