This page provides a brief overview of the history, purpose and design of the Nacimiento Dam.
The Nacimiento Dam was completed in 1957. Although it is located in northern San Luis Obispo County, it is owned by the Monterey County Water Resources Agency. It is located about 20 miles from the coast, and 4.4 miles away from the San Antonio Dam. Both dams have been created for the purposes of flood protection, water conservation, recreation, and operation of the Salinas Valley Water Project. 
The Nacimiento Dam creates the Nacimiento Reservoir, which has the ability to store water from winter storms for the dry season. At an elevation of 800 feet, the reservoir has the capacity to store 377,900 acre-feet of water when it is full. It is roughly 18 miles long, and has about 165 miles of shoreline available for recreation. The maximum flood stage elevation is 802 feet. The maximum temporary capacity during a flood event is 538,000 acre-feet, with a surface area of 7,149 acres.
The primary functions of the Nacimiento Dam are to provide groundwater recharge for agriculture, flood control, water conservation, and to help slow seawater intrusion in the Salinas Valley..  Seawater intrusion has been documented in Monterey County since the 1940s, and is caused by overdraft of groundwater.  Using more surface water lessens the reliance on groundwater. The Nacimiento Dam spillway is an instrumental aspect of maintaining that supply, and was modified in 2010 to raise the flood elevation to 800 feet. 
- The Nacimiento Dam is located at 35°45′31″ N, 120°53′6″ W. 
- Dam Type as determined by the California Department of Water Resources: ERTH - Earth
- Dam Usage as determined by the California Department of Water Resources: FC,DOM,IRR,MUN,POW - Flood Control, Domestic, Irrigation, Municpial, Power 
According to a 2019 report and independent audit conducted by GEI Consultants, Inc., the Nacimiento Dam safety program is deficient. It has an outdated program document, insufficient staff and a long list of overdue safety repairs. This maintenance is estimated to cost more than $50 million, and needs to be addressed as soon as possible. The report noted that staff is overworked and undertrained, accompanied by a myriad of workload and funding issues. Additionally, the safety program is inadequate for a structure built more than six decades ago. The Nacimiento Dam has been identified by the state Division of Safety of Dams as an “extremely high hazard,” regarding these repairs. .
If the dam failed and flooded, it would cause substantial damage. Peak flows through the breach are estimated to be 3,300,000 cubic feet per second (cfs) and are projected to occur one hour after dam failure. The flood wave would take roughly one day to reach the mouth of the Salinas River, and the flow rate would be approximately 700,000 cfs. The simulation predicts flooding in portions of Camp Roberts and San Miguel, Bradley, the San Ardo oil field, San Ardo, and portions of King City, Spreckels, Salinas, Castroville and Moss Landing. 
Operational pools have been created to aid in the management of water being stored in the reservoir. The conservation pool which extends from the minimum pool to the concrete spillway elevation of 787.75 feet is the operational pool used to store water for later release to the Salinas River for groundwater recharge, fish passage, and the operation of the Salinas Valley Water Project (SVWP). The flood pool extends from the concrete spillway to an elevation of 801 feet or 1 foot above the top of the inflated Obermeyer spillway gate. The flood pool is intended to provide winter flood protection by maintaining the ability of the spillway to pass the Probable Maximum Flood without overtopping of the dam. 
A 4-megawatt powerplant is constructed at the right dam abutment. The plant contains both large and small turbines that operate in the range of 25 cfs to 400 cfs. To maximize power production, two sets of runners have been provided. One set is used at low reservoir elevations and the second at high reservoir elevations. 
Nacimiento Dam Measurements
The Monterey County Water Resources Agency publishes observed data for preceding 10-day periods for the following metrics: Percentage of Capacity, Elevation(feet), Depth(feet), Storage(acre-feet), Lake Surface Area(acres), Length of Lake(miles), Releases(cfs), Rainfall Past 24 hours(in.), Rainfall to Date Last year(in.), and Total Rain Last Season(in.). They also include historical data from 1958-present for the same parameters. This information can be found at (MCWRA Reservoir Data)
- Monterey County Water Resources Agency MCWRA: Dams and Reservoirs Updated 2020.
- Monterey County Water Resources Agency Monterey County Water Resources Agency: Seawater Intrusion Monitoring Updated 2020.
- Salinas Valley Water Project Updated 2020.
- USGS Feature Report: Nacimiento Dam USGS Feature Report: Nacimiento Dam
- California Data Exchange Center CDEC: Dam Definitions Updated 2017.
- Johnson, Jim. Monterey County’s Nacimiento Dam Needs Safetey Upgrades Published July 18, 2019.
- Monterey County Office of Emergency Services Monterey County Dam Safety Updated 2020.
- Monterey County Water Resources Agency (MCWRA)
- Salinas Valley Water Project (SVWP)
- Salinas River Diversion Facility (SRDF)
- Salinas River
- Nacimiento River
- Salinas Valley Seawater Intrusion
- Monterey County
- San Luis Obispo County
- San Clemente Dam
- San Antonio Dam
- Interlake Tunnel
This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.