page_title: Los Angeles River
section_title: Watershed
hierarchical_section_title: Los Angeles River / Watershed
caption_attribution_description: Arroyo Seco - the channelized lower creek section, with graffiti and bridges (Los Angeles County). The curving bridge is the ramp from SR 110 - Arroyo Seco Parkway south to I-5 north. In the background is Avenue 26 over the Arroyo Seco. San Gabriel Mountains in backround. "Gettin Up, small amount of edits to make a little brighter".
context_page_description: The Los Angeles River is a river flowing through Los Angeles County, California, in the United States. About 51 miles long, it flows from Canoga Park south and west to its end at the Long Beach Harbor, in San Pedro Bay, part of the Pacific Ocean. The basin is rimmed by the San Gabriel Mountains, Santa Monica Mountains and Santa Susana Mountains, as well as several smaller mountain ranges. Much of the water that flows in the Los Angeles River flows in from tributaries that come from the mountains.
  The river was once free-flowing, winding across a floodplain that occupied much of the Los Angeles Basin. With its frequent floods, it often changed course, causing erosion and depositing silt in other places. When the city of Los Angeles had its first settlers around the 1850s, the river was its main water source. With the opening of the Los Angeles Aqueduct in 1913, the Los Angeles River was no longer needed as a water source. Today, the Los Angeles River runs in a fixed course through a concrete channel for nearly its whole length. It is heavily polluted. The primary source of water during summer and fall is the Donald C. Tillman Water Reclamation Plant in Van Nuys.
context_section_description: The watershed of the Los Angeles River covers 834 square miles (2,135 square kilometers). The Santa Monica Mountains and smaller Simi Hills border it on the east side. On the west side lies the San Gabriel Mountains and Santa Susana Mountains. Seven major tributaries flow into the Los Angeles River: Burbank Western Channel, Aliso Wash, Tujunga Wash, Verdugo Wash, Arroyo Seco, Compton Creek, and Rio Hondo. 360 square miles (920 square kilometers) of the watershed are open space, while the remaining 474 square miles (1,215 square kilometers) are highly developed with all kinds of land uses.
  The river officially begins in a place called Canoga Park, in the San Fernando Valley. Bell Creek and Calabasas Wash (Arroyo Calabasas or Calabasas Creek; Calabasa is Spanish for "pumpkin") flow from opposite sides of the valley to a point (34.1952°N 118.601838°W) where the Los Angeles River officially begins. At this point, the river already flows in a concrete channel. In times of flood, the channel can move between 25 miles (40 km) per hour to up to 35 miles (56 km)
   or even 45 miles (72 km) per hour.
  Tujunga Wash, Aliso Wash, and Brown's Canyon Wash join the river from the left. The river flows on to a basin called the Sepulveda basin, controlled by a dam at its southeastern end. This basin is incredibly rich in wildlife and plants. Normally, there wouldn not be a year-round flow of water here. But because of 75 million gallons of water flowing into the river every day from the Donald C. Tillman Water Reclamation Plant, there is an year-round flow of water. This water is not suitable to be drinking water, but is safe to touch.
  An important tributary, Verdugo Wash, flows in from the left. The Verdugo Wash begins in the Verdugo Hills and flows west to the Los Angeles River. Uniquely, the intersection of Interstate 5 and Route 134 is located right above this point. The Los Angeles River makes a great bend west around Griffith Park, a big park in the middle of Los Angeles. Here, the river has an earthen bottom, which is unique because most of the river is covered with concrete. Further downstream, there is a place uniquely named "Frogtown" because of the many frogs once found in the river there.  Downstream from this place, the river picks up another important tributary, Arroyo Seco, on the left. (The name "Arroyo Seco" means "dry creek" in Spanish.) The Arroyo Seco begins in the San Gabriel Mountains and flows south to the Los Angeles River. One important feature of the Arroyo Seco is the giant Devil's Gate Dam. The Arroyo Seco is free-flowing in many places.
  After flowing a few more miles, the Los Angeles River becomes very wide. The final large tributary, Rio Hondo (Spanish for "deep river") flows in from the left, in the city of South Gate. Notably, the sediment here is over 30,000 feet (9,100 m) deep. Here, the threat of floods is always present. In fact, in a flood in 1992, the water was only a few inches below the top of the riverbank. As the river approaches San Pedro Bay and eventually the Pacific Ocean, it passes by the RMS Queen Mary, a retired ocean liner now a museum and hotel.
caption: A view of the Arroyo Seco, one of the tributaries to the Los Angeles River
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