Southern California’s historic rivers offer wildlife habitat, recreation

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By Mark Landis | Contributing Columnist

The rivers in Southern California are an enigma, and by some observer’s standards, their meager, seasonal flows wouldn’t even qualify as a “real river.” But few places in the world have captured, managed, channeled, and fought over their water resources with more necessity and ingenuity than the cities of Southern California.

Southern California rivers are unique for several reasons; they are short by normal standards, their flows are comparatively low, their origins can reach lofty alpine elevations over 9,000 feet, and the area they collect their water from, or “watershed,” is small in comparison to other major rivers.

As an example, the Sacramento River in Northern California is four times longer and has a watershed 10 times larger than the Santa Ana River, which is the largest river in Southern California.

Five rivers that begin and end in Southern California and drain into the Pacific Ocean and have made a significant impact on the region’s development are (north to south); the Santa Clara River, the Los Angeles River, the San Gabriel River, the Santa Ana River, and the San Diego River.

  • An 1888 photo shows a wooden flume that carried water...

    An 1888 photo shows a wooden flume that carried water from the Santa Ana River to Riverside via the Gage Canal. By the late 1800s, the San Bernardino Valley was a labyrinth of irrigation channels and canals from the Santa Ana River and its tributaries. (Courtesy of Tom Atchley)

  • A photo, circa 1870, shows the water wheel on the...

    A photo, circa 1870, shows the water wheel on the Los Angeles River at the start of Zanja Madre. The wheel was built to lift water from Zanja Madre to a brick reservoir built in 1858. This site today is west of Dodger Stadium, near the North Broadway Crossing of the Los Angeles River. (Courtesy Photo)

  • An aerial image from the U.S. Army Corp of Engineers...

    An aerial image from the U.S. Army Corp of Engineers shows the future location of the Santa Fe Dam, on the San Gabriel River, in Irwindale, circa 1845. The view shows the mouth of the San Gabriel Canyon, where the river exits the San Gabriel Mountains and makes its way across the San Gabriel Valley toward the ocean. (Courtesy of U.S. Army Corps of Engineers)

  • A map shows the major rivers of Southern California, south...

    A map shows the major rivers of Southern California, south of Santa Barbara. (Courtesy Photo)



Major sections of these rivers have been contained in concrete channels, or are often completely dry, so many people don’t ever realize they are rivers, much less a critical part of the region’s history and development.

Native Americans in the area knew that available water resources changed throughout the seasons, and most simply adapted by relocating to where the water was. When the first European settlers arrived, they clustered their settlements around the water sources that appeared reliable.

Considered the birthplace of modern-day California, the Spanish mission in San Diego was established in 1769, along the marshy banks of the San Diego River, just a few miles from today’s Mission Bay. The San Diego River has a small watershed area of about 440 square miles, and its highest source in the Cuyamaca Mountains begins at an elevation of 3,750 feet.

After a drought in 1803, Spanish padres and local laborers constructed a diversion dam and canal on the San Diego River to bring a more reliable supply of water to the mission and the local fields. The dam was 220 feet long, 12 feet high and 13 feet thick.

A 5-mile-long aqueduct was built from the dam to the mission, and the project is believed to be the first major irrigation project in California. Major remnants of the mission dam still exist, and the site on the river is now a National Historic Landmark, open to the public in Mission Trails Regional Park in San Diego.

San Gabriel Mission was established in 1771, along the banks of the Rio Hondo, a tributary of the San Gabriel River. The missionaries built irrigation channels, and developed farmlands around the mission.

The San Gabriel River is 58 miles long, and has a watershed of about 689 square miles. It originates in the San Gabriel Mountains, with tributaries that begin above 9,000 feet elevation.

There are two reservoirs on the upper San Gabriel River, and two large flood control basins at the Santa Fe Dam in Irwindale, and the Whittier Narrows Dam in Pico Rivera. Water from the San Gabriel River was harnessed in 1898 to power the Azuza Hydroelectric Plant, and its replacement built in 1949 is still in operation today.

The tiny pueblo of Los Angeles was founded in 1781 along the banks of the Porciúncula River, which later became known as the Los Angeles River. This small, 48-mile-long river originates in the Santa Susana and Santa Monica Mountains, northwest of Los Angeles, and has a watershed area of about 824 square miles.

Prior to the opening of the Los Angeles Aqueduct in 1913, the Los Angeles River was the city’s primary source of water. An extensive series of canals called “zanjas” (Spanish for “irrigation ditch/canal”) from the river provided drinking water and irrigation to the local fields.

The Los Angeles River is fully urbanized today, but portions have been preserved as wild riparian areas, and numerous bike and walking trails have been built along the historic waterway.

The Santa Ana River and its tributaries have a long history of irrigation and hydroelectric generation projects. It is the longest river in Southern California at 96 miles, and it has the largest watershed at 2,650 square miles. The Santa Ana River begins at elevations over 8,000 feet in the San Bernardino Mountains, and it drains into the Pacific Ocean at Huntington Beach.

In 1820, the Spanish Missionaries at Mission San Gabriel commissioned a zanja to be constructed from Mill Creek, a tributary of the Santa Ana River in the foothills of the San Bernardino Mountains, to supply water to the newly established “Rancho San Bernardino.”

In the early 1850s, Mormon settlers began building intricate canal systems using Santa Ana River water to irrigate their farms and orchards in the San Bernardino Valley. Downstream users in Orange County also made extensive use of the Santa Ana River for their farmlands.

In 1882, a tributary of the Santa Ana River in Etiwanda produced the first hydroelectric power in the Western U.S., and several larger hydro plants were built on the river system in the 1890s and early 1900s.

The large mountain and valley drainage areas of the Santa Ana River make it susceptible to heavy flooding, and major flood control basins were built on the river at Prado Dam in Norco, and at Seven Oaks Dam in the San Bernardino Mountain foothills. Big Bear Lake is also part of the Santa Ana River system.

The Santa Clara River begins in the Western San Gabriel Mountains, at an elevation of about 5,800 feet, and it drains into the Pacific Ocean near Ventura Harbor. It also has major tributaries from the Topatopa Mountains to the north. The river is 83 miles long, and has a watershed area of about 1,200 square miles.

Much of the Santa Clara River flows through semi-rural areas, and it is less urbanized than other major rivers in Southern California. The river’s watershed provides habitat for a wide variety of plants and animals, and it has been a major source of water for surrounding farms and communities.

In 1842, California’s first gold strike was made in Placerita Canyon, which is a tributary of the Santa Clara River. The strike sparked a rush of prospectors into the area, and water and alluvial deposits from Placerita Creek were used for placer mining in the area.

The Santa Clara River has two major reservoirs, Lake Piru, which is a reservoir on the Piru Creek tributary, and Castaic Lake, a reservoir that is the terminus of the West Branch California Aqueduct.

These historic rivers still provide a significant portion of water to their surrounding communities either by direct canals and pipelines, or through replenishment of the local water tables for pumping. They also provide critical wildlife habitat within urban areas, and their watercourses and welcoming greenbelts are used for a variety of outdoor recreation.

Mark Landis is a freelance writer. He can be reached at: