Santa Ana River

Santa Ana River
Rio de los Temblores, Rio de Santa Anna
The Santa Ana River as seen from a small bluff overlooking the water.
Country	United States
State	California
Counties	San Bernardino, Riverside, Los Angeles, Orange
Tributaries
- left	Mill Creek, San Timoteo Creek, Temescal Creek/ San Jacinto River, Santiago Creek
- right	Bear Creek, City Creek, Lytle Creek, Chino Creek
Cities	San Bernardino, Riverside, Santa Ana
Primary source	Coon Creek
- elevation	8,650 ft (2,637 m)
- coordinates	34°09′14″N 116°41′20″W / 34.15389°N 116.68889°W / 34.15389; -116.68889
Secondary source	Heart Bar Creek
- elevation	7,900 ft (2,408 m)
- coordinates	34°08′06″N 116°44′23″W / 34.13500°N 116.73972°W / 34.13500; -116.73972
Source confluence	San Bernardino Mountains
- location	Santa Ana Canyon, San Bernardino County
- elevation	6,991 ft (2,131 m)
- coordinates	34°09′00″N 116°46′18″W / 34.15000°N 116.77167°W / 34.15000; -116.77167
Mouth	Pacific Ocean
- location	Huntington Beach, Orange County
- elevation	0 ft (0 m)
- coordinates	33°37′41″N 117°57′31″W / 33.62806°N 117.95861°W / 33.62806; -117.95861Coordinates: 33°37′41″N 117°57′31″W / 33.62806°N 117.95861°W / 33.62806; -117.95861
Length	96 mi (154 km), Northeast-Southwest
Basin	2,650 sq mi (6,863 km2)
Discharge	for Below Prado Dam, near Corona
- average	224 cu ft/s (6 m3/s)
- max	317,000 cu ft/s (8,976 m3/s)
- min	0 cu ft/s (0 m3/s)
Map of the Santa Ana River drainage basin

The Santa Ana River is the largest river entirely within Southern California in the United States. Its drainage basin spans four counties. It rises in the San Bernardino Mountains and flows past the cities of San Bernardino and Riverside, before cutting through the northern tip of the Santa Ana Mountains and flowing southwest past Santa Ana to drain into the Pacific Ocean. The Santa Ana River is 96 miles (154 km) long, and drains a watershed of 2,650 square miles (6,900 km²).

For its size the Santa Ana drainage basin is quite diverse. It ranges from high peaks of inland mountains in the north and east, to the hot, dry interior and semi-desert basin, to flat coastal plains in the west. Its climates range from dry alpine to chaparral and desert, and the watershed as a whole is very arid. Relatively little water actually flows in the river or most of its tributaries. One of its largest tributaries, the San Jacinto River, rarely reaches the Santa Ana except in extremely wet years. The relative lack of vegetation also makes the river prone to flash flooding. Even so, a wide variety of animal and plant life has always been dependent on the river.

People have lived on the Santa Ana River for at least 9,000 years. There were four distinct indigenous groups in the area, all of which depended heavily on the river for their livelihoods. The river was first crossed by Europeans in 1769, when it received its name from members of the Spanish Portola expedition. Because it is one of the largest water sources in the four-county region, many large ranchos developed alongside the river and one of its major tributaries, Santiago Creek. This period of growth culminated in the establishment of many large cities on the river, including Santa Ana, Riverside and Anaheim, all of which derived their names from the River. In the early 20th century, devastating floods poured down the Santa Ana River, leading to much of the river being channelized and dammed in recent times.