San Gabriel River (California)

The expedition had to build a bridge across the river because the channel was too swampy and muddy, making it difficult to move their horses and supplies. The area came to be known as "la puente" (the bridge), from which the modern-day city of La Puente takes its name.

California became a U.S. state in 1850, two years after the Mexican–American War. One of the decisive battles of the war was fought on January 8, 1847 on the San Gabriel River, which was the last line of defense for Mexican Californio forces led by Mexican Governor-General José Flores, tasked with defending the pueblo of Los Angeles. American forces, led by General Stephen W. Kearney under Commodore Robert F. Stockton, crossed the river under heavy fire, but were able to force the Californios from their defensive position in under ninety minutes. After taking control of the river, the Americans were able to take Los Angeles on January 10, and the Mexicans surrendered California three days later. This campaign is now remembered as the Battle of Rio San Gabriel.

Gold seekers

thumb|right|The East Fork at Heaton Flats, near the original site of Eldoradoville, which the river destroyed during the 1862 flood.

Although it was rumored for many years that Native Americans and Spanish explorers had discovered gold in the San Gabriel Canyon long before California became a U.S. state, gold was first confirmed in the upper San Gabriel River around April 1855, by a party of prospectors who had entered the mountains via Cajon Pass. The Los Angeles Star soon reported of their findings:

Several gold mining camps sprang up along the East Fork, the largest including the Upper and Lower Klondike. Mining during the 1930s focused on finding the finer particles and dust left behind from the previous gold boom. For many, it was a source of income during the Great Depression, and for some others was a recreational activity. However, the ban is rarely enforced and has been subject to much controversy, especially since it does not distinguish between recreational and commercial mining.

Farming and irrigation

thumb|right|Irrigation ditch in San Gabriel Canyon, ca.1900

Although the Southern California climate is well-suited to most types of agriculture, the seasonality of rainfall made it almost impossible to grow crops without irrigation. After the founding of Mission San Gabriel, the Spanish built and gradually expanded a system of zanjas (canals) and reservoirs to irrigate crops, power mills, and water livestock. The earliest historic record of a water diversion for the mission appears around 1773. Irrigation systems were also built on some of the Mexican ranchos, such as in 1842 when Don Luis Arenas, owner of the Rancho Azusa de Dalton, constructed a zanja from the mouth of San Gabriel River to his homestead, a distance of about . This would later be expanded in to the Azusa Ditch, one of the more important canals of the region.

After California became part of the United States in 1846, the ranching economy gradually shifted towards agriculture (a transition quickened by the Great Flood of 1862 and subsequent drought of 1863-64 which killed almost three-quarters of the livestock in Los Angeles County), and the San Gabriel River became a crucial water source for farms. The California Gold Rush brought a huge influx of people to the state, and the high demand for food transformed the San Gabriel River Basin into one of the nation's most productive agricultural regions. The Southern Pacific Railroad arrived in 1876 and the Union Pacific Railroad in the early 1900s, the latter line passing through the Whittier Narrows; this enabled the San Gabriel River region to become a major exporter of agricultural products. Thus, most of the surface water diversions were taken either directly at the mouth of San Gabriel Canyon, or further down near the Whittier Narrows where groundwater rose to the surface once more. In order to supply water during the dry season when surface flows fell to a trickle, a tunnel nearly long was extended under the river bed to tap the shallow aquifer and supply the Azusa, Duarte, and Beardslee ditches. In 1890, some of the irrigation companies operating on the upper San Gabriel River included the Duarte Mutual Irrigation and Canal Company, the Vineland Irrigation District, and the East Whittier Land and Water Company.

Irrigation soon consumed the entire surface flow of the river below San Gabriel Canyon. As early as 1854, the entire upper San Gabriel River was appropriated, with the Azusa farmers (east of the San Gabriel River) claiming up to two-thirds of the flow and the remaining one-third going to the Duarte farmers, west of the San Gabriel River. Farmers also appropriated essentially all the water emerging from the springs at Whittier Narrows, drying up the river below that point. In 1907, it was reported that the San Gabriel River irrigated some of "the most highly productive citrus regions of Southern California." The Teague Grove in San Dimas, not far from the San Gabriel River, was once one of the largest citrus groves in the world with some 250,000 trees.

Conflict over San Gabriel River water reached a head in the 1880s, when such intense litigation occurred it was called the "Battle of San Gabriel River." This led to the creation of the San Gabriel River Water Committee (Committee of Nine) in 1889 in order to "secure a safe and reliable water supply from the San Gabriel River and to protect the rights to and interests in the river on behalf of committee members." Under the Compromise Agreement of 1889 – which is still in effect today – the Committee of Nine was given the right to administer the distribution of San Gabriel River waters, up to per year. All water flows above this amount are administered by the San Gabriel Valley Protective Association.

20th century

thumb|right|The channelized lower San Gabriel River, near the Pacific Ocean

In the early 1900s, the growing city of Los Angeles began to look to the San Gabriel River for its water supply. However, initial plans were rejected because all the water was already used by farmers, except for floods in the winter. At the time it was believed that the silt-laden, flood-prone San Gabriel River could not be dammed in a safe or efficient manner to conserve this stormwater. During this time, new industries moved into the San Gabriel River area, attracting more urban dwellers to the region. At the time of its construction, it was the largest bridge ever built in southern California.

The San Gabriel River flooded massively in 1914, causing heavy damage to the towns and farms along its course. That year, the Los Angeles County Flood Control Act was passed and the county began a program to build fourteen dams along the San Gabriel River and its tributaries. A subsequent investigation found the supervisors guilty of gross negligence and that "bribery and corruption at the highest level of county government had occurred." Morris Dam was sold to the flood control district the following year. (The Los Angeles County Flood Control District would eventually be consolidated with the county engineering department and road division to form the Los Angeles County Department of Public Works, which continues to maintain these dams today.)

The largest dam, San Gabriel – downstream from the original Forks Dam site – was almost complete at the eve of the Los Angeles Flood of 1938, the single most damaging flood in Southern California's history. Storms in late February and early March 1938 dropped a year's worth of rainfall in one week on the San Gabriel Mountains, causing rivers across the Los Angeles Basin to burst their banks, killing over 100 people, and destroying more than $1.3 billion (2016 dollars) worth of property. At the time, the San Gabriel River was the only major river in Southern California with major flood control dams already in place. The new dams reduced a monstrous flood crest of more than to about , sparing a large part of the San Gabriel Valley from damage. However, heavy damage still occurred in places, especially on the lower San Gabriel River due to flooding from tributaries.

The rate of urbanization increased in the 1930s, in no small part due to Midwestern families fleeing the Dust Bowl and settling in greater Los Angeles.

After World War II, the proposed road took on greater importance for defense, and was envisioned as a potential evacuation route from Los Angeles in the event of a nuclear attack. During the 1950s and 1960s, Shoemaker Canyon Road was partially completed along an alignment higher above the East Fork, but its construction was plagued by mudslides and erosion from winter storms. The second attempt was also abandoned and is now known as the "Road to Nowhere". As early as the 1890s local residents recognized the need to preserve mountain areas both as intact watersheds and for recreation. In 1891 the Los Angeles Chamber of Commerce appealed to Congress to have "all public domain included in the watersheds of Los Angeles, San Gabriel and other rivers in the Sierra Range [San Gabriel Mountains] withdrawal from sale such that the mountains may in future time serve the general public as a great park." In 1892 the San Gabriel Timberland Reserve, precursor to the Angeles National Forest, was established by the federal government.

The canyons, which had become quiet after the departure of gold miners, were busy again in summer with the many resorts established along the forks of the San Gabriel River. Between 1890 and 1938, hiking was "tremendously popular among area residents". One of the major resorts was Camp Bonito, located on the original site of Eldoradoville, "noted for its splendid trout streams, deer range and beautiful surroundings." Camp Bonito was served by stagecoach from the Pacific Electric railroad at Azusa, along the same route taken by the Eldoradoville stage. Other mountain resorts included Cold Brook Camp (in the Crystal Lake area, along the North Fork), and Opids Camp and Camp Rincon along the West Fork. Weber's Camp, located in Coldwater Canyon (a tributary of the East Fork), was a popular stop along the route to the summit of Mount San Antonio, the highest point in the range.

At first, access to the upper San Gabriel River was only possible via hiking or on horseback. The precipitous Mount Lowe Railway opened in 1893, bringing vacationers near the summit of Mount Wilson, high above the West Fork of the San Gabriel River. There a hotel was established, next to the Mount Wilson Observatory; from here pack trails connected to Red Box Saddle, where visitors could descend the West Fork. As automobiles grew in popularity during the early 1900s, roads penetrated deeper into the mountains. The paved road from Azusa up San Gabriel Canyon reached the confluence of the East and West Forks by 1915, making it easier to reach the many camps along the upper San Gabriel.

Although hiking popularity temporarily declined during World War II, recreation increased once more during the postwar population boom, and the upper San Gabriel continues to see heavy use today for hiking, camping, fishing, swimming, and backpacking.

River modifications and modern uses

Flood control

thumb|right|Upstream side of San Gabriel Dam, the largest on the upper San Gabriel River.

Prior to the early 1900s, the San Gabriel River watershed was mostly used for agriculture and ranching; during the river's periodic floods, loss of life and property was limited. The river's changing course below the Whittier Narrows made it difficult to establish permanent settlements there. During most of the 1860s, the San Gabriel River flowed southwest and joined the Los Angeles River to empty into San Pedro Bay. However, a flood in 1868 caused the river to swing into a more southerly course, towards its present mouth at Alamitos Bay, flooding and destroying the town of Gallatin. The old western channel is today's Rio Hondo ("deep river"). Whittier Narrows Dam can divert excess floodwaters between the San Gabriel River and Rio Hondo as necessary. These supplement the protection provided by the upstream San Gabriel and Cogswell Dams, where the Los Angeles County Department of Public Works maintains a minimum of of storage space at the beginning of each winter to protect against flooding.

Water supply

The San Gabriel River is an important source of water for the 35 incorporated cities and other communities in its watershed; despite the arid climate that requires water be imported from Northern California and the Colorado River, the San Gabriel still provides about a third of the water used locally. The Cogswell, San Gabriel, and Morris dams are operated by the Los Angeles County Department of Public Works (LADPW) and can capture and store up to of rain and snow runoff. The Upper San Gabriel Valley Municipal Water District estimates that, in an average year, between 95–99 percent of stormwater runoff from the San Gabriel River system is captured for storage, direct use, or groundwater recharge. The California Department of Water Resources considered the San Gabriel River a "fully appropriated" stream, meaning that no new water rights may be taken.

thumb|left|Satellite view of reservoirs on the upper San Gabriel River

Two major groundwater basins or aquifers underlie the San Gabriel River watershed, separated by zones of impermeable bedrock and fault lines. Groundwater acts as the main long-term water storage of the San Gabriel River system, since the aquifers can hold many times more water than surface reservoirs. The San Gabriel Valley Basin covers a total of and has a storage capacity of of groundwater. The Central Basin is somewhat larger, with an area of and a storage capacity of . Due to the limited speed at which the ground can absorb water, the spreading grounds must be operated in tandem with surface reservoirs, which can capture big stormwater surges in winter and release water gradually through the dry season. The combined San Gabriel / Rio Hondo system is served by seven spreading grounds – San Gabriel Canyon, Santa Fe, Peck Road, San Gabriel Valley, Rio Hondo Coastal, San Gabriel Coastal, and Montebello Forebay – totaling .

Water distribution in the San Gabriel Valley is adjudicated by the Main San Gabriel Basin Watermaster, a board which determines the amount of water to be delivered to each user (mostly municipal water agencies), recharged into the aquifer, and pumped from the aquifer. The "operating safe yield" is the amount of groundwater that can be reliably extracted from the aquifer and is determined by the Watermaster based on annual rainfall and runoff. Between 1973 and 2002, this averaged approximately . The Central Basin Watermaster serves the same purpose for the Central Basin aquifer and allows pumping of roughly per year.

Hydroelectricity

There is one hydroelectric plant on the river, located just to the north of Azusa. The original Azusa Hydroelectric Plant was built in 1898 by the San Gabriel Electric Company (which in 1917 was incorporated into Southern California Edison). Power generation began on June 30, with an initial capacity of 2,000 kilowatts (KW). During the early 1900s, it was mainly used to power the Pacific Electric (Red Car) and Los Angeles Railway (Yellow Car) systems in the greater Los Angeles area. The plant was purchased by the City of Pasadena in 1930, due to structural modifications needed to accommodate the city's proposed Morris Dam. A new 3,000 KW plant was built adjacent to the old plant in the 1940s.

The power station is supplied with water via the Azusa Conduit, which draws water from the river below San Gabriel Dam, and runs along the east wall of the San Gabriel Canyon to a point just north of Azusa adjacent to the San Gabriel Canyon spreading grounds, where a penstock falls down the mountainside to the powerhouse. Between 1996 and 2014, the plant generated an annual average of 4 million kilowatt hours. The usage of river water for electricity production has been controversial, as diverting water can dry up the channel, reducing fish habitat.

Sand and gravel mining

Although not directly related to water supply, the San Gabriel River bed – filled with coarse and fine sediments to depths of hundreds and sometimes thousands of feet – is an important source of aggregate materials (gravel and sand) for use in construction. The San Gabriel Valley around Irwindale is one of the largest aggregate mining areas in the United States – more than a billion tons have been taken from the old river bed, supplying construction projects all over Los Angeles County. Most of the freeway system in greater Los Angeles was built using aggregate from the San Gabriel river bed.

In Irwindale, there are seventeen gravel pits of various sizes, although not all are being mined. The largest aggregate company operating in the San Gabriel river is Vulcan Materials Company. There are proposals to refill some of the inactive pits to allow commercial, retail, and industrial development, or repurpose them as parks or water storage reservoirs. The maximum allowed depth is , and since many pits have already reached this depth, mining companies are pushing to extend the limit by another . This has been controversial due to the risk of slope instability. Most of this material is unsuitable for use as aggregate and must be disposed of in designated sediment placement sites. It has been proposed to truck reservoir mud to Irwindale to fill some of the abandoned gravel quarries there. The upper reaches of the river, although undeveloped, are subjected to heavy recreational use and are impacted by trash, debris, fecal coliforms, and heavy metals.

A 2007 study found that Coyote Creek, the main tributary of the lower San Gabriel River, exhibited "acute and chronic toxicity" from pesticides and industrial chemicals, while toxicity levels in the main stem San Gabriel River, Walnut Creek, and San Jose Creek were "significantly reduced" from 1995 levels due to improved water treatment systems.

Crossings

From mouth to source (year built in parentheses):

Marina Drive (1963)
- Pacific Coast Highway (1931)
Second Street - twin bridges (1964)
- East 7th Street - twin bridges (1941, 1959)
College Park Drive (1964)
Southbound Interstate 605 ramp to northbound Interstate 405 (1966)
- San Diego Freeway (1964)
Southbound Interstate 405 ramp to northbound Interstate 605 (1966)
East Willow Street (1962)
East Spring Street (1952)
East Wardlow Road (1963)
San Gabriel River Bicycle Path [bike bridge]
Carson Street - twin bridges (1971)
Del Amo Boulevard (1966)
South Street (1952)
183rd Street (1972)
Artesia Boulevard (1941)
Railroad (West Santa Ana Branch, disused)
- Artesia Freeway (1968)
[Pedestrian Bridge]
Alondra Boulevard (1952)
Rosecrans Avenue (1951)
Foster Road [Pedestrian Bridge]
Eastbound Interstate 105 ramps to Interstate 605 (1987)
- Glenn Anderson Freeway and Metro C Line (1987)
Interstate 605 ramps to westbound Interstate 105 (1987)
Imperial Highway (1952)
Railroad (Union Pacific)
Firestone Boulevard (1934)
Florence Avenue (1951)
- Santa Ana Freeway (1953)
Telegraph Road (1937)
Railroad (Union Pacific)
Slauson Avenue (1958)
Railroad (BNSF/Amtrak Pacific Surfliner and Southwest Chief/Metrolink Orange County Line and 91/Perris Valley Line)
Washington Boulevard (1953)
- Whittier Boulevard (1968)
Railroad (Union Pacific and Metrolink Riverside Line)
East Beverly Boulevard (1952)
San Gabriel River Parkway (1954)
Whittier Narrows Dam
Peck Road - twin bridges (1952)
- Pomona Freeway (1967)
Valley Boulevard (1916)
Railroad (Union Pacific/Amtrak Sunset Limited/Metrolink San Bernardino Line)
- San Bernardino Freeway (westbound 1933, eastbound 1956)
Ramona Boulevard (1961)
Lower Azusa Road (1960)
- San Gabriel River Freeway - twin bridges (1970)
Live Oak Avenue (1961)
Arrow Highway (1949)
Santa Fe Dam
Railroad (Metro A Line)
- Foothill Freeway (1968)
Foothill Boulevard/Huntington Drive (1922)
[Pedestrian Bridge]
Mountain Laurel Way
Rock Springs Way
- San Gabriel Canyon Road (1933)
Morris Reservoir
San Gabriel Reservoir

East Fork

Forest Route 2N16/Upper Monroe Rd to Fire Camp 19
East Fork Road (1936)
Bridge to Nowhere (1936)

North Fork

(1967)
(1967)
(1932)

West Fork

East Fork Road (1949)
State Route 39 (1962)

References

Works cited

External links

San Gabriel Mountains Regional Conservancy
State of California San Gabriel & Lower Los Angeles Rivers and Mountains Conservancy
Amigos de los Rios (an organization whose goal is to create a necklace of parks connecting the San Gabriel River, the Rio Hondo, and Whittier Narrows)
Public Law 108–42 (San Gabriel River Watershed Study Act) (an act proposed as H.R. 519 by Hilda Solis and S. 630 by Barbara Boxer)
San Gabriel Watershed and Mountains Special Resource Study (the study authorized by Public Law 108-42)
Documentary on the San Gabriel River, Ya Don't Miss the Water (a five-part video that documents the major ecological, political, and social problems of the community - approximately 2 million people surround and use the river's water)
Online Computer Library Center - WorldCat search result: San Gabriel River Watershed