About the Watershed: SAR Watershed

The Santa Ana River Watershed is Southern California’s largest watershed spanning over 100 miles and containing over 50 tributaries. San Bernardino, Riverside and Orange Counties all contain a portion of this 2,650 square mile watershed. This particular watershed is home to more than 4.8 million residents. Its headwaters are located high above the valley floors of the Inland Empire, in the peaks of the San Bernardino National Forest.

The watershed is divided into two sections the Upper and Lower Watershed. Between the San Gorgonio Peak east of Big Bear and Prado Basin at the 91 and 71 freeways is the Upper Watershed. South of the Prado Basin to the Pacific Ocean is the Lower Watershed. Before humans settled the valleys of the Inland Empire and the coastal plain of Orange County, this magnificent natural river flowed year round. Now the river is in a more controlled state, partly due to the increased urbanization of the surrounding cities.

The Santa Ana River’s outlet to the ocean was relocated in 1890 and is presently found in Huntington Beach. However it has been as far north as Anaheim Bay and as far south as Newport Bay. This change in the outlet’s location was due to significant weather events. Concrete lines the channel from just north of Imperial Highway to the Pacific Ocean and unfortunately most of Orange County’s portion of the River is channelized. In more pristine areas of the River it is bound by natural features such as willows, cottonwoods and live oaks.

One of the most significant natural events in Orange County’s history and along the River was the Flood of 1862. Though several large floods had occurred on the River throughout history this flood was by far the most significant. A series of storms in Southern California drenched the land and caused the River to overtop its banks. When this happened four feet of water engulfed the City of Anaheim. This inundation of water devastated the city’s booming cattle industry. Nearly 200,000 cattle either drown in the flood or were swept away. The rich farming soil of the County, known for its orange growers, was also washed away.

Orange County had endured another significant flood in 1938. The destruction and devastation caused by the floods created a flurry of construction projects along the River. Prado Dam was constructed in 1941 as an additional flood control measure. It was needed to protect residents of the burgeoning County. The Santa Ana River has several flood control structures on it including: levees, weirs, culverts, and flood walls, and the Seven Oaks Dam in San Bernardino County.

But as time will tell even the best flood control measures don’t always work.  This challenge was realized during 2004-2005 winter season, known as the second wettest rainfall season in our local history. The Prado Dam, which is currently undergoing an increase in the height of the dam and an expansion of the spillway, was in jeopardy due to the amount of rainfall within the watershed.  Water is released from the behind the Dam and under normal conditions it flows at 200 cubic feet per second.  After the significant rains, the decision was made to increase the flow in order to protect the stability of the dam.  The flow was increased to 10,000 cubic feet per second, setting an all time record.  The previous peak flow record was 5,000 cubic feet per second.  This increase in water flow and velocity destroyed the channelization along the 91 freeway.  Where sloped concrete once lined the River, there are now four foot tall eroded banks.  Many decisions about rivers, their use, function and capabilities remain a contentious issue.  The SARWA is working to bring the stakeholders together to help determine the future and fate of this River.


c/o Earth Resource Foundation 1706 B Newport Blvd, P.O. Box 12364,
Costa Mesa, CA 92627
tel 949-645-5163 fax 949-645-5173