The Santa Clara River () is an longU.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map, accessed March 16, 2011 river in Ventura and Los Angeles counties in Southern California. It drains parts of four ranges in the Transverse Ranges System north and northwest of Los Angeles, then flows west onto the Oxnard Plain and into the Santa Barbara Channel of the Pacific Ocean.

The watershed has provided habitat for a wide array of native plants and animals and has historically supplied humans with water, fish, and fertile farmland. The northern portion of the watershed was home to the Tataviam people while the southern portion was occupied by the Chumash people. Much of the Santa Clara River Valley is used for agriculture which has limited the use of structural levees to separate the natural floodplain from the river. Although it is one of the least altered rivers in Southern California, some levees exist where the river flows through areas of significant urban development.

History The Santa Clara River was originally named the Río de Santa Clara on August 9, 1769, by the Portolá expedition on the march north from San Diego to found a mission at Monterey, to honor Saint Clare of Assisi who died on August 11, 1253. The Santa Clara River Valley was then known as the Cañada de Santa Clara.

The Santa Clara-Mojave River Ranger District of the Angeles National Forest is named after the Santa Clara River.

Floods

The failure and near complete collapse of the St. Francis Dam took place in the middle of the night on March 12, 1928. The dam was holding a full reservoir of of water that surged down San Francisquito Canyon and emptied into the river.

Course

The Santa Clara River's headwaters take drainage from the northern slopes of the San Gabriel Mountains near the Angeles Forest Highway, inside the western part of the Angeles National Forest. Its largest fork, Aliso Canyon, is about long and forms the primary headstream. These branches combine into the broad wash of the main stem near the town of Acton which flows west through Soledad Canyon, crossing under California State Route 14 near the town of Canyon Country. The Sierra Pelona Mountains on the north provide additional watershed and seasonal tributaries. The river receives Bouquet Creek, Placerita Creek, and San Francisquito Creek within the City of Santa Clarita. The riverbed surface remains dry most of the year here, except on extreme occasions of heavier than average rainfall. The river then crosses west under Interstate 5 and receives Castaic Creek from the right.

After the Castaic Creek confluence, the river starts to flow primarily southwest through the Santa Clarita Valley. Near the county line between Los Angeles County and Ventura County, the river enters the Santa Clara River Valley flowing past Buckhorn and Fillmore, incorporating additional flow from Piru Creek and Sespe Creek, both from the right, and Santa Paula Creek at the town of Santa Paula, where it passes the large South Mountain Oil Field on the south bank. The Santa Clara River then bends southwest, passing the Saticoy Oil Field on the north bank where South Mountain marks its entrance onto the broad Oxnard Plain. The river ends at the Pacific Ocean after flowing across the north side of this plain made fertile with the silt deposited by the river. A sand bar usually stands across the mouth at the Santa Clara Estuary Natural Preserve that lies within McGrath State Beach in Oxnard and bounded on the north by the city of Ventura wastewater treatment plant.

Watershed Although located just north of the heavily populated Los Angeles Basin, the Santa Clara River watershed remains one of the most natural on the South Coast. It is separated from the Los Angeles Basin by the low Santa Susana Mountains, along the north side of which the Santa Clara River runs. On the east are the San Gabriel Mountains, and on the north are the Santa Ynez Mountains, Sespe Mountains, San Cayetano Mountains, and Tehachapi Mountains. Piru, Castaic and Sespe Creeks, each over long, are the primary tributaries of the Santa Clara River. While Piru and Castaic Creeks form reservoirs for the California State Water Project (Pyramid Lake and Lake Piru on Piru Creek, and Elderberry Forebay and Castaic Lake on Castaic Creek), Sespe Creek is designated a National Wild and Scenic River, unique among Southern California streams. There are 57 archaeological sites and 12 historical landmarks in the watershed."California Protected Areas Data Portal" GreenInfo Network San Francisco California

The Santa Clara River watershed borders on the Ventura River/Matilija Creek watershed on the west. On the northwest lies the Santa Ynez River watershed. On the north is the interior drainage basin of Tulare Lake in the Central Valley. To the east is the Mojave River and to the south is the Los Angeles River. The Santa Clara River is the second largest river in Southern California; the larger one is the Santa Ana River.

Estuary The estuary has been modified by human activities at least since 1855. By the late 1920s roads and agricultural fields had become established. In the late 1950s the former delta area was occupied by the Ventura Water Reclamation Facility and agricultural fields with levees constraining the river from these areas and directing the flow to the Harbor Boulevard bridge.STAFF REPORT (August 2010) "TOTAL MAXIMUM DAILY LOAD FOR TOXAPHENE FOR THE SANTA CLARA RIVER ESTUARY" CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - LOS ANGELES REGION McGrath State Beach was established in 1948.Johnson, Brett (December 15, 2014) "McGrath State Beach campground, estuary issues under study" Ventura County Star The estuary has been designated a Natural Preserve within McGrath State Beach on the south bank of the river mouth."Santa Clara River Estuary: Profile" (1997) California Resources Agency

From the north bank of the river, the city of Ventura releases some of treated effluent daily that flows into the Santa Clara Estuary Natural Preserve from their water reclamation facility (VWRF).Clerici, Kevin (August 17, 2011) "Ventura reaches settlement, agrees to reuse millions of gallons of highly treated sewage water" Ventura County Star A sand berm separates the river from the ocean most of the year. In years with adequate rainfall, the river breaks the berm which is then slowly rebuilt by ocean action through the rest of the year. When the river watershed has an exceptionally dry year, the berm acts as a dam, allowing the water level to rise with the discharge. In August 2014, with the frequent flooding of the access road and many of the campsites in the state park, a report found that the park had only been open five of the past eighteen months because of repeated flooding.Carlson, Cheri (August 25, 2014) "Campground flooded, closes again" Ventura County Star When the berm is broken when it is not raining, fish can become stranded in the sudden draining of the estuary waters.Carlson, Cheri (February 11, 2014) "Sandy berm breached near McGrath State Beach campground" Ventura County Star

The estuary was identified on the 1998, 2002 and 2006 Clean Water Act 303(d) lists of impaired water bodies. In 2012, the Los Angeles Regional Water Quality Control Board required the Counties of Ventura and Los Angeles together with cities along the river to limit the total maximum daily load of bacteria potentially harmful to human health that discharges from stormwater outfalls into the Santa Clara River, primarily during the dry season. Sources of bacteria of concern in urban runoff from the county, City of Fillmore, City of Oxnard, City of Santa Clarita, City of Santa Paula, and City of Ventura include pet and animal wastes, sanitary sewer overflows, and organic debris such as leaves and grass. Examples of ways they will improve water quality include increased frequencies of street sweeping and stormwater catch basin cleaning; field surveys to locate and eliminate both dry season street runoff and leaks from the sanitary sewer systems; and enhanced public education.Administrative Report (October 27, 2014) "Memorandum of Agreement to Improve Water Quality in the Santa Clara River" City of San Buenaventura City Council

Ecology

The river is habitat for threatened species such as the unarmored three-spined stickleback, steelhead, southwestern pond turtle, and least Bell's vireo. The endemic, endangered Santa Ana sucker (Catostomus santaanae) lives in parts of the Santa Clara River system.

Historic documentation of an important recreational steelhead trout (Oncorhynchus mykiss) fishery occurs for the Santa Clara River into the mid-1900s. The steelhead trout run on the Santa Clara river prior to 1940 is estimated to have had thousands of fish and to have been one of the largest steelhead runs in southern California. Construction of the Vern Freeman Diversion Dam and other migration barriers on the mainstem, Santa Paula Creek, Sespe Creek, Piru Creek, and other tributaries during the mid-1900s appear to be correlated with the demise of the steelhead run as habitat availability decreased and surface flows decreased. Adult steelhead still try to migrate up the river with an adult trapped at the Vern Freeman Dam in 2001. A wild rainbow trout population still exists in the headwaters of the Santa Paula, Sespe, Hopper, and Piru Creek tributaries and is producing out-migrating steelhead smolts bound for the Pacific. However, challenges to outgoing smolt migration include low to no stream flows downstream of the dam or predation in the coastal estuary. Lampreys, a parasite, also impact the steelhead. Invasive species such as Arundo donax also create changes that are not favorable to spawning trout.Kallas, Anne (February 8, 2012) "Pair working to restore Santa Clara River" Ventura County Star Genetic analysis of the steelhead in the Santa Clara River watershed has shown them to be of native and not hatchery stocks.

There were beaver (Castor canadensis) historically in the Santa Clara River until Europeans arrived, according to oral Ventureño history taken by ethnolinguist John Peabody Harrington in the early twentieth century. The full reference is: "The beaver comes and gnaws the tree on the side towards which it leans, and at last falls over. The tree is leaning towards our house. I am beginning to fear that it will fall on us. The beaver builds its house in the river or the cienegas in the time of our ancestors. There were beavers at Ventura and also at Saticoy." This historical observer record is consistent with a beaver skull collected in 1906 in the Sespe Creek tributary by Dr. John Hornung, a zoologist at the Los Angeles Museum of Natural History.

Pronghorn antelope (Antilocapra americana) used to roam along the Santa Clara River, as Father Pedro Font, describe in his diary on the de Anza Expedition February 1776, "We saw in the plain a very large drove of antelopes which, as soon as they saw us, fled like the wind, looking like a cloud skimming along the earth." There is a Ventureño word for antelope, q'aq, which is different from their separate words for deer and elk.

In 2002, eight Southwest willow flycatchers hatched in the Hedrick Ranch Nature Area (HRNA), a preserve just east of Santa Paula managed by the Friends of Santa Clara River. The first SWFs to hatch on the river in recent times was at the Fillmore Fish Hatchery in 2000.

Quagga mussels were discovered in Lake Piru in 2013. They are an invasive species found in rivers and lakes in the U.S.Coyne, Alasdair (January 27, 2014) "Quagga mussels loose in Santa Clara watershed" Ventura County Star

River modifications In Ventura County