San Juan Creek

San Juan Creek San Juan River[1]
Hikers ford San Juan Creek below the hot springs, February 2008.
Map of the San Juan Creek watershed
Etymology	Named for Mission San Juan Capistrano by Spanish conquistadors in the 1700s.
Location
Country	United States
State	California
Region	Orange County, Riverside County
Physical characteristics
Source	head of San Juan Canyon, at the confluence of Morrell Canyon Creek with Bear Canyon Creek, Santa Ana Mountains
• coordinates	33°36′49″N 117°26′07″W / 33.61361°N 117.43528°W / 33.61361; -117.43528
• elevation	1,690 ft (520 m)
Mouth	San Juan Lagoon, Doheny State Beach, Dana Point
• coordinates	33°27′42″N 117°41′01″W / 33.46167°N 117.68361°W / 33.46167; -117.68361
• elevation	0 ft (0 m)
Length	29 mi (47 km)
Basin size	133.9 sq mi (347 km2)
Discharge
• location	San Juan Capistrano[2]
• average	26.1 cu ft/s (0.74 m3/s)[3]
• minimum	0 cu ft/s (0 m3/s)
• maximum	14,700 cu ft/s (420 m3/s)
Basin features
Tributaries
• left	Lucas Canyon Creek, Verdugo Canyon Creek, Trampas Canyon Creek
• right	Lion Canyon Creek, Hot Springs Canyon Creek, Cold Spring Canyon Creek, Bell Canyon Creek, Cañada Gobernadora, Cañada Chiquita, Horno Creek, Arroyo Trabuco

San Juan Creek, also called the San Juan River,^[1] is a 29-mile (47 km) long stream in Orange and Riverside Counties, draining a watershed of 133.9 square miles (347 km²).^[4][5] Its mainstem begins in the southern Santa Ana Mountains in the Cleveland National Forest. It winds west and south through San Juan Canyon, and is joined by Arroyo Trabuco as it passes through San Juan Capistrano. It flows into the Pacific Ocean at Doheny State Beach. State Route 74, the Ortega Highway, crosses the Santa Ana Mountains via San Juan Canyon.

Before Spanish colonization in the 1770s, the San Juan Creek watershed was inhabited by the Acjachemen or Juañeno Native Americans. The Juañeno were named by Spanish missionaries who built Mission San Juan Capistrano on the banks of a stream they named San Juan Creek. The watershed was used mainly for agriculture and ranching until the 1950s when residential suburban development began on a large scale. Since then, development has continued to encroach on floodplains of local streams. Flooding in the 20th and 21st centuries has caused considerable property damage in the San Juan watershed.

The San Juan watershed is home to sixteen major native plant communities and hundreds of animal species. However, the watershed is projected to be 48 percent urbanized by 2050. In addition, urban runoff has changed flow patterns in San Juan Creek and introduced pollutants to the river system. Although the main stem of San Juan Creek does not have any major water diversions or dams, some of its tributaries, including Trabuco and Oso Creeks, have been channelized or otherwise heavily modified by urbanization.