Cosumnes River

Cosumnes River © The Nature Conservancy

Find out how to visit the Cosumnes River Preserve.

The Cosumnes is the last remaining undammed river on the western slope of the Sierra Nevada. The river tumbles from its headwaters in the red firs of the El Dorado National Forest. As it descends the western slope of the Sierra Nevada, it nourishes and breeds not only riparian forests but wetlands, vernal pool-dotted grasslands, and blue oak woodlands, spilling at last into the Sacramento-San Joaquin Delta. The broad floodplain of the lower river harbors rare valley oak riparian forest and freshwater wetlands used by thousands of resident and migratory birds.

Location
The Cosumnes River watershed is on the western slope of the Sierra Nevada; The Nature Conservancy has focused its activities and investments within the lower floodplain of the Cosumnes River, in Sacramento and San Joaquin counties. Map

Size
The Cosumnes River is 80 miles long. The Conservancy and seven governmental and non-profit partners manage the Cosumnes River Preserve, which is approximately 40,000 acres (62 square miles) in size.

What to See: Plants
The Cosumnes River Preserve hosts some of the best remaining large-scale stands of valley oak riparian forest in the Great Central Valley. In addition, the preserve protects several thousand acres of seasonal and perennial freshwater wetland. Less than 4% of each community remains intact in California.

Tundra swans © James A. Martin

What to See: Animals
Tens of thousands of Pacific Flyway birds winter along the Cosumnes including:

• tundra swans
• Ross's white-fronted and Canada geese
• great blue herons
• egrets
• pintails
• mallards
• white-tailed kites
• plus more than half of the Central Valley's population of greater sandhill cranes

In fact, more than 200 species of birds have been recorded on and around the preserve. The river's natural communities—seasonal and permanent wetlands, riparian forests, vernal pool grasslands, blue oak woodlands, and coniferous forests—provide habitat for migratory songbirds, raptors, and rare reptiles and mammals like the endangered giant garter snake and the elusive river otter. Chinook salmon and Pacific lamprey still swim upstream to spawn.

Why the Conservancy Selected This Site
As the last remaining undammed river on the Sierra Nevada's western slope, the Cosumnes has long engaged the interest of The Nature Conservancy. The broad floodplain of the lower river harbors rare valley oak riparian forest and freshwater wetlands used by thousands of resident and migratory birds. The river's floodplain is particularly at risk from the threat of urban encroachment.

What the Conservancy Has Done/Is Doing
In 1984, the Conservancy began its work in the Cosumnes Valley. Purchasing 85 acres of virgin valley oak groves, it established the Cosumnes River Preserve, which has grown to approximately 40,000 acres. In addition, the Conservancy has created more than 1,500 acres of new wetlands, participated in reforestation projects, removed levees along the river in order to restore natural flooding processes, and worked with local farmers in developing sustainable agricultural practices. In the next few years, the Conservancy intends to acquire more strategically located properties, not just in the lower floodplain but also upstream, where the natural landscapes include grasslands, vernal pools, and blue oak woodlands.

For More Information:
The Cosumnes River Preserve
http://www.cosumnes.org/