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Graphic of Watershed Map and Cloud Formation

What is a Watershed?

Watersheds are land areas that funnel water to a common low point – usually a stream, lake, river or out to the ocean. When it rains, water flows down from areas of higher elevation following the natural shape of the land. Along the way, rainwater and urban runoff can collect and deposit trash, sediment, metals, fertilizers, pesticides and other pollutants into our local waterways. These pollutants degrade water quality, threatening property and the health of nearby residents and wildlife. Everyone lives within a watershed, and preventing pollution and contamination from entering our local waterways is everyone’s responsibility.

City of San Diego Watersheds

Photo of San Dieguito River Watershed
San Dieguito River Watershed

The San Dieguito River watershed extends through a diverse array of habitats from its eastern headwaters in the Volcan Mountains near Julian to the main outlet at the San Dieguito Lagoon and the Pacific Ocean. The watershed encompasses approximately 346 square miles and includes portions of the cities of Escondido, Poway, San Diego, Del Mar and Solana Beach.

To learn more about the San Dieguito watershed and its important natural areas, species, pollutants of concern and what you can do to help protect it, view the printable version of the San Dieguito watershed brochure (PDF).

Photo of Los Peñasquitos Watershed
Los Peñasquitos Watershed

The Los Peñasquitos watershed begins in the foothills east of Highway 67 and funnels rainwater west through the communities of Poway, Scripps Ranch, Mira Mesa, Sorrento Valley, Carmel Valley and Del Mar. The watershed eventually drains into the Pacific Ocean just north of Torrey Pines State Park at the mouth of the Los Peñasquitos Lagoon. Carmel Creek, Los Peñasquitos Creek and Carroll Creek are the main tributaries draining into the Los Peñasquitos Lagoon.

To learn more about the Los Peñasquitos watershed and its important natural areas, species, pollutants of concern and what you can do to help protect it, view a printable version of the Los Peñasquitos watershed brochure (PDF).

Photo of Mission Bay & La Jolla Watersheds
Mission Bay & La Jolla Watersheds

The Mission Bay & La Jolla watersheds drain an area of approximately 67 square miles all within the City of San Diego. The northern portions of the watersheds are home to the Marine Corps Air Station – Miramar and the University of California, San Diego. Residential areas dominate the central portion of these watersheds and include the communities of Clairemont, Bay Park, University City, La Jolla and Pacific Beach. Mission Bay Park, in the southwest corner of the watersheds, is the receiving water for a number of urban waterways, including San Clemente Creek, Rose Creek and Tecolote Creek. The coastline along Pacific Beach and La Jolla are home to four Marine Protected Areas, two Areas of Biological Significance, and the San Diego-La Jolla Underwater Park.

To learn more about the Mission Bay & La Jolla Watershed and its important natural areas, species, pollutants of concern and what you can do to help protect it, view a printable version of the Mission Bay & La Jolla watershed brochure (PDF).

Photo of San Diego Bay Watersheds
San Diego Bay Watershed

The San Diego Bay Watershed encompasses approximately 442 square miles and begins northeast of Descanso along highway 79 near Cuyamaca Rancho State Park. The watershed flows west through the unincorporated communities of Alpine, Jamul, and Dulzura and continues toward the San Diego Bay through the Cities of La Mesa, Lemon Grove, San Diego, National City, Chula Vista, Imperial Beach and Coronado. The Sweetwater River is the major waterway within this watershed travelling 55 miles from its headwaters until it empties into the middle of San Diego Bay near highway 54 (between National City and Chula Vista).

To learn more about the San Diego Bay Watershed and its important natural areas, species, pollutants of concern and what you can do to help protect it, view a printable version of the San Diego Bay watershed brochure (PDF).

Photo of San Diego River Watersheds
San Diego River Watershed

The San Diego River watershed begins near Santa Ysabel in the mountains of east San Diego County and funnels rainwater west to the El Capitan Reservoir, and through Lakeside, Santee, and Mission Valley. The river eventually drains into the Pacific Ocean in Ocean Beach. The San Diego River watershed encompasses approximately 433 square miles and connects portions of the cities of San Diego, El Cajon, La Mesa, Poway, and Santee.

To learn more about the San Diego River Watershed and its important natural areas, species, pollutants of concern and what you can do to help protect it, view a printable version of the San Diego River watershed brochure (PDF).

Photo of Tijuana River Watershed
Tijuana River Watershed

The Tijuana River watershed encompasses approximately 1,750 square miles on either side of the California – Mexico border. It’s water quality is the most severely impacted of any other large watershed in San Diego County. Although more than two-thirds of the watershed lies in Mexico, the river discharges to the Tijuana Estuary and Pacific Ocean on the United States side of the international border. The cities of Imperial Beach and San Diego, and San Diego County all have portions of their jurisdictions within the watershed. The Mexican cities of Tijuana and Tecate also contribute to the flows. The current population of the entire watershed is approximately 1.6 million people.

To learn more about the Tijuana River Watershed and its important natural areas, species, pollutants of concern and what you can do to help protect it, view a printable version of the Tijuana River watershed brochure (PDF).