Santa Ana River - Course

Course

The Santa Ana River rises in Santa Ana Canyon in the southern San Bernardino Mountains, at the confluence of two tiny streams, Heart Bar Creek and Coon Creek, at an elevation of 6,991 feet (2,131 m). Its highest sources are Dollar Lake, at 9,288 feet (2,831 m), and Dry Lake, at 9,068 feet (2,764 m), both on the northern flank of San Gorgonio Mountain, at the headwaters of a small left tributary, the South Fork Santa Ana River. The river initially flows west through this broad and deep gorge, and about 18 miles (29 km) from its headwaters, receives its first major tributary from the right: Bear Creek, flowing southwest from well-known Big Bear Lake. The river turns south, passing through the Seven Oaks Dam, flowing out of its canyon into the arid interior basin of San Bernardino County and Riverside County, and receives Mill Creek from the left as it winds westwards towards the city of San Bernardino. As it passes through the urban area, it receives City Creek from the right and enters a flood control channel flanked by earthen levees on both sides.

Not long after the confluence with City Creek, Lytle Creek enters from the right. Lytle Creek is one of the largest tributaries of the Santa Ana river, rising in three forks in the San Gabriel Mountains and flowing southeast, becoming the Lytle Creek Wash before discharging into the main stem. From there, the Santa Ana flows southwest, and after passing through the city of Riverside, it discharges into the normally dry flood control reservoir formed by Prado Dam. Two major tributaries of the river join in the reservoir area: Chino Creek from the right, and Temescal Creek from the left. Temescal Creek drains the largest area of all the tributaries, because it provides the outflow from Lake Elsinore, into which the San Jacinto River flows. It is also one of the longest, at 32 miles (51 km) in length. Except during the wettest years, Temescal Creek contains little or no water because Lake Elsinore is not high enough to overflow.

After flowing out of the Prado Dam, the Santa Ana River cuts a second Santa Ana Canyon, a water gap, between the northern Santa Ana Mountains and the Puente Hills and Chino Hills, crossing into Orange County. The river roughly bisects the county as it flows southwest towards the ocean. The river is then entirely diverted into spreading grounds for groundwater recharge of the aquifer of north Orange County, providing about half of the entire county's municipal water. Downstream of there, the river serves only for flood control and waste drainage purposes, and typically has no more than a trickle of water. Passing the cities of Orange and Tustin, it receives Santiago Creek from the left as it enters the city of Anaheim. Here, the river is entirely confined to a concrete flood control channel between earthen levees. After crossing under Interstate 5 near Santa Ana the riverbed again becomes earthen as it flows to its mouth between Huntington Beach and Newport Beach. The river accretes in a small lagoon before flowing out to sea at the northern end of Santa Ana River County Beach.