| San Jacinto River | |
| Map: | Santa Ana River map.png |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | California |
| Subdivision Type3: | Region |
| Subdivision Name3: | Riverside County |
| Subdivision Type5: | Cities |
| Subdivision Name5: | Hemet, San Jacinto, Perris, Lake Elsinore |
| Length: | 42miles, Northwest then southwest |
| Discharge1 Min: | 0cuft/s |
| Discharge1 Avg: | 16.4cuft/s[1] |
| Discharge1 Max: | 16000cuft/s |
| Source1: | San Jacinto Mountains |
| Source1 Location: | San Bernardino National Forest, Riverside County |
| Source1 Coordinates: | 33.7311°N -116.81°W[2] |
| Source1 Elevation: | 2100feet |
| Mouth: | Lake Elsinore |
| Mouth Location: | Lake Elsinore, at the mouth of Railroad Canyon, northwest of the Sedco Hills and west of the Tuscany Hills of the Temescal Mountains, Riverside County |
| Mouth Coordinates: | 33.6459°N -117.3148°W |
| Mouth Elevation: | 1243feet |
| River System: | Santa Ana River basin |
| Basin Size: | 780sqmi[3] |
| Tributaries Left: | South Fork San Jacinto River |
| Tributaries Right: | North Fork San Jacinto River |
The San Jacinto River is a 42adj=midNaNadj=mid[4] river in Riverside County, California. The river's headwaters are in Santa Rosa and San Jacinto Mountains National Monument.[5] The lower portion of the 765sqmi watershed is urban and agricultural land. As a partially endorheic watershed that is contiguous with other Great Basin watersheds, the western side of the San Jacinto Basin is a portion of the Great Basin Divide.
The river is formed at the west base of the San Jacinto Mountains by the confluence of its North and South forks. The South Fork flows from near Santa Rosa Summit, through Pine Meadow and Garner Valley to Lake Hemet, which holds 14000acre.ft of water. Hemet Dam was built in 1895 to supply water to the city of Hemet. Downstream of the dam, the South Fork joins the North Fork east of the town of Valle Vista near Highway 74, and the main stem of the San Jacinto River continues northwest until it discharges into Mystic Lake, a couple of miles east of Lake Perris. Overflow from the river then flows southwest, passing under Ramona Expressway and Interstate 215, and through Railroad Canyon to Railroad Canyon Reservoir, also called Canyon Lake, which has a capacity of 11900acre.ft. Downstream of Railroad Canyon Dam, the river continues flowing roughly west southwest through the canyon through the Temescal Mountains for about 3miles until it drains into Lake Elsinore. The lake usually has no outflow other than evaporation, but in years of heavy rainfall it overflows into Temescal Creek, which flows northwest to the Santa Ana River in Corona, California.