How Deep Is the San Joaquin River?

Written by Kyle Glatz
Published: October 3, 2023
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California is the third-largest state in the United States, and it has several long rivers running through it. The San Joaquin River is the third-longest river in the state, and it runs for 366 miles. So, how deep is the San Joaquin River? We’re going to examine the greatest depth and average depth of this river as it passes through California. We’ll also show you what kinds of fish live in the waters and what animals live nearby!

Where Does the San Joaquin River Start and End?

Sierra Nevada mountains

The San Joaquin River originates in the Sierra Nevada Mountains.

©high fliers/

The source of the San Joaquin River is Thousand Island Lake. This body of water is in the Sierra Nevada Mountains of eastern California. The Middle Fork of the San Joaquin River rises from this body of water and flows southeast before taking a sharp western turn south of Devils Postpile National Monument.

The North Fork and Middle Fork of the river then meet east of Junction Butte, forming the San Joaquin River as it continues to flow southwest. The river travels southwest and eventually passes just north of Fresno, California.

The body of water continues to flow west before taking a sharp northern turn, passing through the Great Valley Grasslands State Park, west of Stockton, and finally reaching its mouth at Suisun Bay along with the Sacramento River. All told, this river runs for 366 miles and has a basin size of 15,600 square miles.

The Importance of the San Joaquin River

Cloudy day of Los Angeles downtown skyline and palm trees in foreground

The Big Creek Hydroelectric Project in the San Joaquin River Valley provides electricity to Los Angeles.


The San Joaquin River is a very important body of water in the state of California. People have used this river for drinking water for thousands of years. The river’s flow supported many lifeforms in the area, including animals and plants that people would use to survive.

In the 19th century, the river became an important means of transportation, especially during the California Gold Rush. As more and more people settled in the area, the region’s citizens began to turn to agriculture to grow food. The 19th century saw the beginning of the attempts to use the river for irrigation. Several dams were constructed along the river throughout the 20th century, changing its course and helping provide water for a vast amount of farmland.  

The dams were used to create reservoirs for drinking water as well as for hydroelectric power plants. The power generated from the hydroelectric dams has been used in cities like Los Angeles.

Today, the river is still an important source of hydroelectric power and freshwater in the region. The river also serves as a recreational hub for people who enjoy hiking, sightseeing, fishing, and camping.  

How Deep Is the San Joaquin River?

San Joaquin River
The majority of the river is between 10 and 20 feet deep, but the deeper channels average 30 to 40 feet.

The San Joaquin River is 80 feet deep at its greatest depth. Like other rivers, the depth of the San Joaquin River varies a great deal throughout the river’s course. After the North Fork and Middle Fork of the San Joaquin River join together, the depth in the middle of the channel varies between 10 and 40 feet.

The deepest part of the river is south of Twitchell Island in Sacramento County. This area is just a few miles upriver of the river’s mouth where it empties into the Suisun Bay.

So, while this body of water varies in depth and width throughout its flow, the deepest part of the water is 80 feet deep.

Comparing the River Depths

Gold Tower Bridge and Sacramento River in Sacramento, California, photographed from River Walk Park at night with stars in the sky.

The Sacramento River is only between 6 and 10 feet deep on average.


San Joaquin River80 feet
Colorado River20 to 90 feet
Sacramento River10 feet

At least one of the rivers in California has a greater depth than the San Joaquin River. The Sacramento River is only between 6 and 10 feet deep on average. Meanwhile, the Colorado River averages about 20 to 30 feet deep, but it has pools that can reach about 90 feet deep. To be fair, the majority of the Colorado River does not flow through California.

The average depth of the San Joaquin River is comparable to the Colorado River, but it greatly exceeds the Sacramento River.

Can You Swim in the San Joaquin River?

Swimming in a river's open waters

Only strong swimmers should even attempt swimming in this body of water.


Yes, you can swim in this body of water. However, saying that comes with some major caveats. For example, the vast majority of the river does not have any lifeguards or other officials watching out for the people swimming. So, the river is a dangerous place for people to enter alone or without proper swimming skills.

The other issue that arises with swimming in this river is the river’s flow. The currents in this river, especially after a large snowmelt, can overcome even the most experienced swimmers. While people could swim in parts of this river, it may not be wise to swim in it.

What Wildlife Lives in and around this Body of Water?

Spotted Bass

Spotted bass are colorful fish that fight fiercely to avoid being caught.

©Sean McVey/

The San Joaquin River has a large number of animals living in and around its waters. To start with, let’s look at the various fish that live in these waters. Some of the fish that people can catch in these waters include:

  • Spotted bass
  • Striped bass
  • Largemouth bass
  • American shad
  • Steelhead perch
  • Brook Trout
  • Rainbow Trout
  • White sturgeon

These are a few of the most popular fish that anglers like to catch up and down the river. A variety of animals live in the areas around this river, too. Some of the animals that live in the areas around the river are:

  • Mule deer
  • Western fence lizard
  • Red-tailed hawk
  • Gopher snake
  • Great egret
  • Western gray squirrel
  • Coyote
  • Western pond turtle
  • Virginia opossum
  • Brown anole

These are just a few of the different animals that could be found in the immediate area around the river, but many others live here too.

So, how deep is the San Joaquin River? It is about 80 feet deep at its maximum depth. Although this river may not be the deepest that runs through the state, it’s still an important river. The water from this river provides hydroelectric power and freshwater to the region. Future developments could occur along this river to improve its benefits.

The photo featured at the top of this post is © Jeffrey T. Kreulen/

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About the Author

Kyle Glatz is a writer at A-Z-Animals where his primary focus is on geography and mammals. Kyle has been writing for researching and writing about animals and numerous other topics for 10 years, and he holds a Bachelor's Degree in English and Education from Rowan University. A resident of New Jersey, Kyle enjoys reading, writing, and playing video games.

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