Nacimiento Dam is a dam on the
Nacimiento River
, name_etymology =
, image = Nacimiento_River_1.jpg
, image_caption = The river downstream of Nacimiento Dam
, image_size = 300
, map = Salinas River watershed.png
, map_size = 300
, ...
about northwest of
Paso Robles
Paso Robles ( ), officially El Paso de Robles (Spanish for "The Pass of Oaks"), is a city in San Luis Obispo County, California, United States. Located on the Salinas River approximately north of San Luis Obispo, the city is known for its hot ...
,
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
. The primary purpose of the dam is to provide
groundwater recharge
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in ...
for agriculture in
Monterey County
Monterey County ( ), officially the County of Monterey, is a county located on the Pacific coast in the U.S. state of California. As of the 2020 census, its population was 439,035. The county's largest city and county seat is Salinas.
Montere ...
and northern
San Luis Obispo County
San Luis Obispo County (), officially the County of San Luis Obispo, is a county on the Central Coast of California. As of the 2020 census, the population was 282,424. The county seat is San Luis Obispo.
Junípero Serra founded the Mission ...
supported by the
Salinas Valley
The Salinas Valley is one of the major valleys and most productive Agriculture, agricultural regions in California. It is located west of the San Joaquin Valley and south of San Francisco Bay and the Santa Clara Valley.
The Salinas River (Califo ...
aquifer, as well as flood control, domestic water supply, and
hydropower
Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, converting the Pot ...
. It forms
Lake Nacimiento
Lake Nacimiento is an long lake on the Nacimiento River in northern San Luis Obispo County, California. The lake contains many arms including Snake Creek and Dip Creek, nearer the dam, and the central Las Tablas and Franklin Creeks.
Due to th ...
, popular for boating, fishing and camping, and known locally as the "Dragon Lake" due to its shape.
Although located in San Luis Obispo County, the Nacimiento Dam and nearby
San Antonio Dam
San Antonio Dam (National ID CA00813) is an earthen dam on the San Antonio River in Monterey County, California in the United States. The dam impounds Lake San Antonio, a reservoir with a capacity of , located west of Camp Roberts.
History
San ...
, which forms
Lake San Antonio
Lake San Antonio is a lake located primarily in southern Monterey County, California, and partially in northern San Luis Obispo County, California. The lake is formed by San Antonio Dam on the San Antonio River. The dam is 202 feet (62 m) tal ...
, are both owned and operated by the Monterey County Water Resources Agency. It was completed in 1957.
History
Prior to the construction of Nacimiento Dam, the lower Nacimiento River (and the Salinas River) only flowed during the wet season between December and May. Without enough time to be absorbed into the Salinas Valley
aquifer
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...
, much of the stormwater flowed directly into the Pacific Ocean.
As the Salinas Valley developed as a major agricultural region dependent on groundwater, the Monterey County Flood Control and Water Conservation District (now Monterey County Water Resources Agency, MCWRA) proposed a reservoir on the Nacimiento River to capture winter floods, and release it at a low enough rate throughout the year to maximize
groundwater recharge
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in ...
.
Because the Nacimiento River is the biggest tributary of the Salinas River, the dam would capture up to half the annual peak flows in the entire Salinas River Basin.
Under the county plan, water would only be stored when the flow rate at the confluence of the Nacimiento and Salinas Rivers exceeded , which was estimated as the highest volume the riverbed can naturally absorb. When natural runoff exceeded this amount, no water would be released. The
California Department of Fish and Game
The California Department of Fish and Wildlife (CDFW), formerly known as the California Department of Fish and Game (CDFG), is a state agency under the California Natural Resources Agency. The Department of Fish and Wildlife manages and protect ...
(DFG) opposed the project due to the detrimental impacts this would have on winter run
steelhead trout
Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and N ...
. The DFG sought a minimum flow of in the Nacimiento River, which the county believed would place too great a demand on the new reservoir. Ultimately, the county won and was granted the water rights for the reservoir in 1955 without any provisions for fishery flows.
Construction of Nacimiento Dam began in 1955 and was completed in 1957. The reservoir filled to capacity for the first time in 1958. After further petitioning from the DFG, the MCWRA now maintains a minimum flow of in the Nacimiento River except in years of severe drought.
Monterey County is entitled to most of the water supply from Lake Nacimiento. The dam releases an average of of water per year for groundwater recharge and instream flows in the Nacimiento River (also including occasional releases for flood control). San Luis Obispo County has a smaller allocation of per year which is used for domestic water supply via the Nacimiento Water Project, providing water to Paso Robles,
Templeton,
Atascadero
Atascadero (Spanish for "Mire") is a city in San Luis Obispo County, California, about equidistant from Los Angeles and San Francisco on U.S. Route 101. Atascadero is part of the San Luis Obispo-Paso Robles metropolitan statistical area, which ...
and
San Luis Obispo
San Luis Obispo (; Spanish for " St. Louis the Bishop", ; Chumash: ''tiłhini'') is a city and county seat of San Luis Obispo County, in the U.S. state of California. Located on the Central Coast of California, San Luis Obispo is roughly halfwa ...
. Although proposed since the 1950s, the Nacimiento Water Project was not completed until 2011.
Specifications
Nacimiento Dam is an earthfill dam with a height of and a crest length of . Altogether, the dam contains of material.
The crest of the dam is above sea level, and the
spillway
A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure tha ...
crest elevation is . The concrete
spillway
A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure tha ...
is located on the north side of the dam and is controlled by an inflatable Obermeyer gate. The dam also has two
outlet works, a low level valve for normal water releases with a design capacity of , and a high level valve for flood control with a capacity of .
There is also a small hydroelectric plant at the dam with a capacity of 4,000
kilowatt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wa ...
s.
Lake Nacimiento has a design capacity of at a water level of (the top of the spillway gates).
The lake receives water from a drainage basin of and covers up to .
The conservation pool, which is used for irrigation, groundwater recharge and environmental flows, extends from the minimum operating level of to the spillway crest of ; the flood control pool is all storage above the spillway crest.
The surcharge (emergency flood control) pool extends from the spillway gate to the top of the dam at . At this maximum level, the lake holds and increases to .
Due to the flooding tendency of the Nacimiento River, which has been called "the most active watershed in the state", the reservoir can fill quickly to capacity during wet winters. The spillway gates are left open between November 1 and May 1 in order to prevent the lake from overfilling. In contrast, it is often at low levels for multiple consecutive years during droughts. The lake spilled in 1958, 1969, 1983, 2011, 2017 and 2023.
See also
*
List of dams and reservoirs in California
Following is a list of dams and reservoirs in California in a sortable table. There are over 1,400 named dams and 1,300 named reservoirs in the state of California.
Dams in service
:''Please add to this list from the below sources.''
Former ...
References
External links
Daily reservoir levels(Monterey County Water Resources Agency)
{{Salinas River
Dams in California
United States local public utility dams
Dams completed in 1957
Earth-filled dams
1957 establishments in California