Prado Dam is a flood control and water conservation project constructed and operated by the U.S. Army Corps of Engineers, Los Angeles District. Construction of the project was completed in April 1941. The project is located at the upper end of the Lower Santa Ana River Canyon, which is a natural constriction controlling 2,255 square miles (5,840 square kilometers) of the 2,450 square mile (6345 square kilometer) Santa Ana River watershed. The dam is located on the Santa Ana River approximately 30.5 miles (49 kilometers) upstream of the Pacific Ocean. The dam embankment is located in Riverside County, California approximately 2 miles (3.2 kilometers) west of the City of Corona. Portions of the reservoir are in both Riverside and San Bernardino Counties. Authorization for the project construction is contained in the Flood Control Act of June 22, 1936 (PL 74-738).
Prado Dam provides flood control and water conservation storage for Orange County, California. It is the downstream element of the Santa Ana River flood control system. The purpose of the project is to collect runoff from the uncontrolled drainage areas upstream along with releases from other storage facilities. Generally, when the water surface elevation in the reservoir pool is below the top of the buffer pool elevation (494.0 feet NGVD during the flood season, 505.0 feet NGVD during the non-flood season), water conservation releases are made. These releases are coordinated with the Orange County Water District and are based upon the capacity of their groundwater recharge facilities and agreements with other agencies. If the water surface in the reservoir exceeds the top of the buffer pool, flood control releases commence. The objective of the flood control operation is to drain the reservoir back to the top of the buffer pool as quickly as possible without exceeding the capacity of the channel downstream. In current practice, when the water surface in the reservoir exceeds the top of the buffer pool, releases are increased to match inflow up to 5000 cfs (142 cms). When inflows exceed 5000 cfs, the excess water is stored in the reservoir.
When the water surface elevation in the reservoir reaches 543.0 feet NGVD uncontrolled releases from the spillway will commence.
The 5000 cfs limit on controlled releases from Prado Dam is based upon the old non-damaging capacity of the downstream channel. When the downstream channel improvements which are part of the Corps of Engineers' Santa Ana River project are completed the downstream channel capacity will increase dramatically to over 30,000 cfs (850 cms). Plans are also underway to improve Prado Dam itself to increase its storage and release capacities. These improvements will enable the dam to take full advantage of the improved channel capacity downstream and will greatly increase the level of flood protection to the communties of Orange County in the Santa Ana River floodplain. When these improvements near completion, a new water control plan and manual for the project will be developed.
The current water control manual for Prado Dam Dam was approved in September 1994.
Facilities within Prado Basin
Prado Dam Facility-Elevation Table Click on this link to see a table with a list of facilites within the Prado Dam Flood Control Basin and their elevations in feet NGVD.
| Embankment | ||
| Type | Earth Fill | |
| Crest Elevation | 566 feet NGVD | 172.5 meters NGVD |
| Maximum height above streambed | 106 feet | 32.3 meters |
| Crest Length | 2,280 feet | 695 meters |
| Freeboard during PMF | (-4.3) feet | (-1.3) meters |
| Spillway | ||
| Type | Concrete Ogee Crest with Converging Chute | |
| Spillway Crest | 543.0 feet NGVD | 165.5 meters NGVD |
| Crest Length | 1000 feet | 305 meters |
| Outletworks | ||
| Number of Passages | 6 | |
| Gate Type | Vertical Lift | |
| Height x Width (each) | 12 x 7 feet | 3.7 x 2.1 meters |
| Entrance Invert Elevation | 460.0 feet NGVD | 140.2 meters NGVD |
| Maximum Capacity | 17,000 cfs | 481 cms |
| Reservoir | ||
| Debris Pool | ||
| Elevation of top of Pool | 490.0 feet NGVD | 149.4 meters NGVD |
| Area at top of Pool | 768 Acres | 311 ha |
| Gross Storage at top of Pool | 4,689 Acre-feet | 5.8 MCM |
| Flood Season Buffer Pool | ||
| Elevation of top of Pool | 494.0 feet NGVD | 150.6 meters NGVD |
| Area at top of Pool | 1,081 Acres | 438 ha |
| Gross Storage at top of Pool | 8,437 Acre-feet | 10.4 MCM |
| Non-Flood Season Buffer Pool | ||
| Elevation of top of Pool | 505.0 feet NGVD | 153.9 meters NGVD |
| Area at top of Pool | 2,123 Acres | 859 ha |
| Gross Storage at top of Pool | 25,760 Acre-feet | 31.8 MCM |
| Top of Dam | ||
| Elevation of top of Pool | 566.0 feet NGVD | 172.5 meters NGVD |
| Area at top of Pool | 11,030 Acres | 4,468 ha |
| Gross Storage at top of Pool | 383,500 Acre-feet | 473.0 MCM |
| Historic Maximum Water Surface | ||
| Date | 22 February 1980 | |
| Maximum Elevation | 528.0 feet NGVD | 160.9 meters NGVD |
| Historic Maximum Release | ||
| Date | 13 January 2005 | |
| Maximum Release | 10,100 cfs | 286 cms |
| Notes: |
| NGVD = National Geodetic Vertical Datum of 1929. |
| MCM = million cubic meters |
| cfs = cubic feet per second |
| cms = cubic meters per second |
| ha = hectare |
View/Download Current Approved Water Control Manual
Prado Dam Flood Inundation Maps
Last Updated on February 9, 2006 by W. Luo