Nacimiento Dam facts for kids
Quick facts for kids Nacimiento Dam |
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Satellite view
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 Location of Nacimiento Dam in California
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| Country | United States |
| Location | San Luis Obispo County, California |
| Coordinates | 35°45′31″N 120°53′06″W / 35.75861°N 120.88500°W |
| Purpose | Irrigation, flood control |
| Construction began | 1955 |
| Opening date | 1957 |
| Owner(s) | Monterey County Water Resources Agency |
| Dam and spillways | |
| Type of dam | Earthfill |
| Impounds | Nacimiento River |
| Height (foundation) | 210 ft (64 m) |
| Length | 1,630 ft (500 m) |
| Elevation at crest | 825 ft (251 m) |
| Reservoir | |
| Creates | Lake Nacimiento |
| Total capacity | 377,900 acre⋅ft (466,100,000 m3) |
| Catchment area | 324 sq mi (840 km2) |
| Surface area | 5,400 acres (2,200 ha) |
| Power station | |
| Installed capacity | 4000 KW |
| Annual generation | 12,352,000 KWh (2010) |
The Nacimiento Dam is a large dam built on the Nacimiento River in California. It is located about 10 miles (16 km) northwest of Paso Robles. This dam helps manage water for farming and prevents floods. It also provides drinking water and generates a small amount of electricity.
The dam creates Lake Nacimiento, which is a popular spot for fun activities. People enjoy boating, fishing, and camping there. Locals sometimes call it the "Dragon Lake" because of its unique shape. Even though the dam is in San Luis Obispo County, it is owned and managed by the Monterey County Water Resources Agency. The Nacimiento Dam was finished in 1957.
Contents
History of Nacimiento Dam
Before the Nacimiento Dam was built, the Nacimiento River usually flowed only during the rainy season. This was from December to May. Much of this water would flow into the Pacific Ocean. It didn't have enough time to soak into the ground.
Why the Dam Was Needed
The Salinas Valley became a big farming area. Farmers there needed a lot of water from underground. So, the Monterey County Flood Control and Water Conservation District decided to build a dam. Their goal was to catch winter floods. Then, they could release the water slowly throughout the year. This would help more water soak into the ground. This process is called groundwater recharge.
The Nacimiento River is the biggest river that flows into the Salinas River. Building the dam would help control about half of the biggest floods in the whole Salinas River area.
Building the Dam
The county planned to store water only when the river flow was very high. This was to make sure the riverbed could absorb as much water as possible. However, the California Department of Fish and Game (DFG) was worried. They thought the dam would harm the steelhead trout that lived in the river.
The DFG wanted a certain amount of water to always flow in the river. The county felt this would use too much of the new reservoir's water. In the end, the county was allowed to build the dam in 1955. There were no special rules at first to protect the fish.
Construction of the Nacimiento Dam started in 1955. It was completed in 1957. The lake behind the dam filled up completely for the first time in 1958. Later, after more talks with the DFG, the county agreed to keep a small amount of water flowing in the Nacimiento River. This happens most years, except during very serious droughts.
Water Use and Distribution
Most of the water from Lake Nacimiento is used by Monterey County. On average, the dam releases about 194,000 acre-feet (239,000,000 m3) of water each year. This water helps refill underground water sources and keeps the river flowing. Sometimes, water is also released to control floods.
San Luis Obispo County gets a smaller amount of water, about 17,500 acre-feet (21,600,000 m3) per year. This water is used for homes in cities like Paso Robles, Templeton, Atascadero, and San Luis Obispo. This project, called the Nacimiento Water Project, was planned a long time ago. It was finally finished in 2011.
Dam Features and Lake Details
The Nacimiento Dam is an earthfill dam. This means it's made mostly of earth, rock, and clay. It stands 210 feet (64 m) tall. The top of the dam, called the crest, is 1,630 feet (500 m) long. The dam contains a huge amount of material, about 3,270,000 cubic yards (2,500,000 m3).
Spillway and Water Releases
The top of the dam is 825 feet (251 m) above sea level. The spillway is a special part of the dam that lets extra water out. Its top is at 787.75 feet (240.11 m). The spillway is made of concrete and has a special gate that can be inflated to control water flow.
The dam also has two ways to release water. One is a low-level valve for normal water releases. It can let out 460 cubic feet per second (13 m3/s) of water. The other is a high-level valve for flood control. It can release a lot more water, up to 5,500 cubic feet per second (160 m3/s). There's also a small power plant at the dam. It can produce 4,000 kilowatts of electricity.
Lake Nacimiento Capacity
Lake Nacimiento can hold about 377,900 acre-feet (0.4661 km3) of water. This is when the water level is at 800 feet (240 m). The lake gets water from a large area of 324 square miles (840 km2). It covers up to 5,400 acres (2,200 ha) of land.
The lake has different sections for different uses. The "conservation pool" is for irrigation and refilling groundwater. It goes from 670 ft (200 m) to 787.75 ft (240.11 m). The "flood control pool" is for storing water above the spillway. There's also an "emergency flood control" area. This goes up to the very top of the dam at 825 ft (251 m). At its fullest, the lake can hold 538,000 acre-feet (0.664 km3) of water. It also covers a larger area of 7,149 acres (2,893 ha).
Lake Levels and Flooding
The Nacimiento River is known for its strong floods. Because of this, the lake can fill up very quickly during wet winters. The spillway gates are kept open from November 1 to May 1. This helps prevent the lake from overflowing.
However, during droughts, the lake can be at very low levels for many years. The lake has spilled over (meaning it reached full capacity and released water through the spillway) in 1958, 1969, 1983, 2011, and 2017.
