Santa Margarita River Watershed

Santa Margarita River

Photo by Kenneth Ray Seals

Approximately 27% of the Santa Margarita Watershed’s roughly 750 square miles is found in San Diego County, with the remaining portion of the watershed lying in Riverside County. The Santa Margarita River, which begins at the confluence of Temecula and Murrieta Creeks in Temecula, drains into the Pacific Ocean on Marine Corps Base Camp Pendleton, north of the City of Oceanside. In a time of sprawling urban development, the Santa Margarita Watershed is often seen as an ecological treasure as the nearly 27 mile stretch of undammed Santa Margarita River is one of the last undammed rivers in Southern California.


Currently, land use in the watershed is primarily undeveloped, open space. Collectively, agricultural and urban development accounts for roughly 20% of total land use. A vast amount of undeveloped space in the watershed is compromised of several preserves and other protected areas, making the watershed a valuable ecological resource and a pristine example of the diversity of Southern California’s natural habitats. The upper watershed basin is one of the fastest growing areas in California and rapid development, without effective planning measures, could likely exacerbate existing water quality issues in the watershed.

Santa Margarita Watershed Resources