Prado Dam Master Plan

Prado Dam Reservoir Draft Master Plan 2023

Prado Dam is an earth-fill dam on the Santa Ana River located near Corona, California in Riverside County.  The dam’s reservoir has an impoundment area of over 10,000 acres that also extends into San Bernardino County. Construction of the Prado Dam and Reservoir project was completed in 1941 by the U.S. Army Corps of Engineers, Los Angeles District (Corps) to be the primary flood control facility within the Santa Ana River watershed, which along with Seven Oaks, San Antonio, and Carbon Canyon Dams, provide flood protection to much of Orange County. The Santa Ana River watershed has an area of approximately 2,450 square miles. Of the total watershed, 2,255 square miles (or about 92 percent) are above Prado Dam. 

Prado Dam Reservoir

Prado Dam Reservoir

The Prado Dam Reservoir Master Plan is a guide for the orderly and coordinated use, development and management of all resources in the Prado Dam Reservoir. It is a vital tool for the responsible stewardship of project resources for the benefit of present and future generations. The Master Plan is programmatic, and identifies conceptual types and levels of activities, not designs, siting, or estimated costs. All actions by the Corps and outgrantees/lessees must be consistent with the Master Plan.

Prado Dam Outlet WorksYorba Linda Slaughter House

                  Prado Dam Outlet Works                             Yorba-Slaughter Adobe Museum

The previous Master Plan entitled, “Recreation Master Plan for the Prado Dam Reservoir Area,” was prepared in February 1976. The 1976 Master Plan, no longer adequately implements the Corps’ policies and goals as previously described. Therefore, updating of the Master Plan for the Prado Dam Reservoir is necessary. In addition, the following changes to the Prado Dam Reservoir were not contemplated by the 1976 Master Plan:

·         Changes in the physical environment including an increase in the amount of biologically valuable riparian plant communities as well as the proliferation of invasive species.

·         Increase in species and populations of threatened and endangered species in the reservoir.

·         Dramatic increase in visitation and variety of public outdoor recreation opportunities.

·         Changing profile of adjacent land uses

·         Increase in development intensity

·         Modifications to Dam and other areas within the basin

·         Designation and restoration of lands as flood risk management mitigation

·         Modifications to the Water Control Manual for water conservation

·         Changes in recreation trail planning and implementation

·         Proposed habitat restoration and expanded water conservation

The Corps had previously revised the Master Plan in the 1990's and released a draft Master Plan update/Environmental Impact Statement for public review in 2005, however, there was a change of direction due to the nature of comments received.  In 2010, an update to the Plan was reinstated but was later halted due to lack of funding.  In 2016, the Corps was given funding once again to work on the Master Plan update.  On January 19, 2017, the Corps held the first Stakeholder Meeting.  The purpose of this meeting was to provide the stakeholders with an overview of the Master Plan update and to solicit input from the stakeholder agencies on their recent, on-going, or proposed future activities and to find out about their studies or data availability for sharing.  The Inland Empire Utilities Agency (IEUA) provided assistance to the Corps in releasing the meeting notice to the Stakeholders and various federal, state, and local entities were in attendance.  The meeting was held at the IEUA Office.

September 2023 Update:

The U.S. Army Corps of Engineers (Corps) announces the availability of and is requesting comments on the Draft Prado Dam Basin Master Plan Update and Environmental Assessment (MP/EA), located in Riverside County, California.  Comments may be submitted starting Sept. 8, 2023, and ending on Oct. 8, 2023. The Corps, Los Angeles District, is the lead federal agency for this project.  An electronic version of the Draft MP/EA is available for review and may be downloaded at:

For questions, comments or to be added to the distribution list, please contact the Project Environmental Coordinator, Megan Wong.