San Justo Dam facts for kids

San Justo Dam is an important structure located in San Benito County, California. It's about 3 miles (5 kilometers) southwest of Hollister. This dam helps store water for a big government project called the Central Valley Project.

The dam creates a large body of water known as the San Justo Reservoir. This reservoir is special because it stores water that comes from other places, not directly from a river flowing through it. Water reaches it through pipes called the Pacheco Conduit and Hollister Conduit, which are fed by the San Luis Reservoir.

Sadly, the San Justo Reservoir has been closed since 2008. This happened because of a problem with tiny creatures called zebra mussels. It is still closed today.

What is the San Justo Dam?

The San Justo Dam is a structure built to hold back water and create a reservoir. It was finished in January 1986. This dam is made from earth, which means it's built using soil, rock, and clay. It stands about 151 feet (46 meters) tall.

How Does the Dam Work?

The San Justo Dam is part of a much larger system called the Central Valley Project. This project helps manage water for farming and cities across California. The San Justo Dam's job is to store water that is brought in from other places. This is called "offstream storage."

Water doesn't flow directly into the San Justo Reservoir from a river. Instead, it's pumped or channeled into it. The water comes from the San Luis Reservoir through two main pipelines: the Pacheco Conduit and the Hollister Conduit. These conduits act like big water highways, moving water where it's needed.

What is the San Justo Reservoir?

The San Justo Reservoir is the lake created by the San Justo Dam. It's designed to hold a lot of water, about 9,785 acre-feet. To give you an idea, one acre-foot is enough water to cover one acre of land with one foot of water. This reservoir helps make sure there's enough water for people and farms in the area.

Why Was San Justo Reservoir Closed?

The San Justo Reservoir was closed to the public in 2008. This was a necessary step because of a serious problem: an invasion of tiny creatures called zebra mussels. These mussels are not native to California and can cause big problems for water systems.

What are Zebra Mussels?

Zebra mussels are small freshwater mussels, usually less than an inch long. They have a distinctive striped shell, like a zebra. They are originally from Eastern Europe and Asia. These mussels are considered an invasive species in many parts of the world, including the United States.

How Do Zebra Mussels Cause Problems?

Zebra mussels reproduce very quickly and attach themselves to almost any hard surface. They can clog pipes, damage boats, and harm the environment. In a reservoir, they can attach to water intake pipes, making it hard for water to flow. They also filter the water, which can change the food chain and harm native plants and animals. Because they spread easily and are hard to remove, the reservoir was closed to prevent them from spreading to other bodies of water.