Nacimiento Dam

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Image 1. Nacimiento Dam.

A Environmental Topics summary by the ENVS 560/L Watershed Systems class at CSUMB.

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 were created for the primary purposes of groundwater recharge and flood control. [1] The Nacimiento Dam and San Antonio Dam are currently involved in the recently created Salinas Valley Water Project and they provides opportunities for recreation. [2]

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 function of the Nacimiento Dam is to provide an instrument for groundwater recharge and flood control in the Salinas Valley. [1] The Nacimiento Dam and San Antonio Dam are also essential parts of the more recent Salinas Valley Water Project and they provide opportunities for water recreation in southern Monterey County and northern San Luis Obispo County. [2] The Nacimiento Dam spillway drains into the Salinas River groundwater system, and this watershed contributes to the Salinas Valley water supply.[3] It is an instrumental in maintaining water supply during the dry season, and was modified in 2010 to raise the flood elevation to 800 feet. [4]

Further downstream, near the mouth of the Salinas River, the Salinas River Diversion Facility captures some of this released water, and creates an artificial dam to store additional water. [2] This timed-release and gradual groundwater recharge helps to slow the rate of seawater intrusion in the Salinas Valley. [5]


  • The Nacimiento Dam is located at 35°45′31″ N, 120°53′6″ W. [6]
  • 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 [7]

Current Issues

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. [8].

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. [9]

Dam Subdivisions And Applications

In the San Antonio Dam, operational pools refer to management of water being stored in the reservoir. There are a few different operational pools related to storage, release, and conservation.

  • Physical minimum pool - maximum height: 670 feet. At this elevation or lower, water cannot flow out of the reservoir.
  • Operational minimum pool - maximum height: 687.8 feet. Any water below this elevation is reserved for fish habitat, as well as a water entitlement for San Luis Obispo County.
  • Conservation pool - maximum height: 787.5 feet. Water is "conserved" to be later released into the Salinas River for groundwater recharge, fish passage, and operation of the Salinas Valley Water Project.

There is one additional pool known as the flood pool, which is from the concrete spillway to an elevation of 801 feet (or 1 foot above the top of the spillway gate). [2]

Hydroelectric Power

There is a 4-megawatt powerplant constructed at the right dam abutment. The power plant contains both large and small turbines that operate in the optimal range of 25 cfs to 400 cfs. [2]

Nacimiento Dam Measurements

Current Data

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)


  1. 1.0 1.1 Monterey County Water Resources Agency Monterey County Water Resources Agency Engineering Reports Updated July 21, 2017.
  2. 2.0 2.1 2.2 2.3 2.4 Monterey County Water Resources Agency MCWRA: Dams and Reservoirs Updated 2020.
  3. CalWater Nacimiento Dam Report #79 Published 2014.
  4. Monterey County Water Resources Agency. Salinas Valley Water Project Updated 2020.
  5. Monterey County Water Resources Agency Monterey County Water Resources Agency: Seawater Intrusion Monitoring Updated 2020.
  6. USGS Feature Report: Nacimiento Dam USGS Feature Report: Nacimiento Dam
  7. California Data Exchange Center CDEC: Dam Definitions Updated 2017.
  8. Johnson, Jim. Monterey County’s Nacimiento Dam Needs Safetey Upgrades Published July 18, 2019.
  9. Monterey County Office of Emergency Services Monterey County Dam Safety Updated 2020.



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.