California reservoirs

10 Images That Show How California’s Reservoirs Have Shrunk in the 21st Century

California is drying up.

The ever increasing demand for freshwater has taken its toll, and the state’s reservoirs are only at 46.4% of their capacity. Now, by using imagery provided by the Landsat 7 and Landsat 8 satellites, we can also see how the reservoirs have changed during the 21st century.

Below are 10 reservoirs that have dwindled considerably since 2001. The “before” picture for each slide is from September or October 2001, while the “after” picture is from the same month in 2016. Move the slider over each image to see the changes.

1. Lake San Antonio

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Lake San Antonio is located in Monterey County (used to cross the border to northern San Luis Obispo County), and covers an area of 8.9 square miles (23 square kilometers). The lake is formed by the San Antonio Dam on the San Antonio River. The dam was completed in 1965, and is 202 feet (62 m) tall.

2. Lake Cachuma

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Lake Cachuma is located in central Santa Barbara County, on the Santa Ynez River. The reservoir was created by the construction of Bradbury Dam in 1953, which is 201 ft (61 m) high. At full capacity, Lake Cachuma has a surface area of 5 square miles (13 square kilometers), but it hasn’t reached that since July 2011.

3. San Luis Reservoir

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San Luis Reservoir is the 5th largest reservoir in California, approximately 9 miles (14 km) long and 5 miles (8 km) wide. It is located in Merced County, west of Los Banos on State Route 152. The dam that created the reservoir is called San Luis Dam, was completed in 1967, and is the 4th largest embankment dam in the United States.

The last time the reservoir came close to reaching full capacity was in April 2011, when San Luis Reservoir was 99.3% full.

4. New Melones Lake

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New Melones Lake is located in the central Sierra Nevada Foothills on the Stanislaus River, and has a surface area of 19.6 square miles (51 square kilometers). The reservoir is formed by the New Melones Dam, which is 625 ft (191 m) high.

The water level in the lake has been in an almost continuous decline since July 2011.

5. Lake Berryessa

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Lake Berryessa is located in Napa County, and was formed by the Monticello Dam, a 304-foot (93 m) concrete arch dam that was completed in 1957. Lake Berryessa hasn’t reached full capacity since April 2006.

6. Trinity Lake

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Trinity Lake was formed by Trinity Dam, which was completed in the early 1960s and stands 538 ft (164 m) high. The lake, formed on the Trinity River, is one of the largest reservoirs in California. It came close to reaching full capacity in June 2011, but hasn’t reached average historical levels since June 2013.

7. Lake Casitas

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Lake Casitas is located in the Los Padres National Forest of Ventura County. It was created by the construction of Casitas Dam on Coyote Creek, 2 miles (3 km) before it joins the Ventura River. The dam was was completed in 1959, and is 334 ft (102 m) high.

The water level in the lake has been in decline since April 2011, when the reservoir was 87.3% full.

8. Lake Piru

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Like Lake Casitas, Lake Piru is also located in Los Padres National Forest of Ventura County. It was created in 1955 by the construction of the Santa Felicia Dam on Piru Creek. Water level in the lake has been in a steep decline since August 2012.

9. Lake Perris

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Lake Perris was completed in 1973, and is located in a mountain-rimmed valley between Moreno Valley and Perris, in what is now the Lake Perris State Recreation Area. The dam that impounds the lake is 128 ft (39 m) high. The lake hasn’t reached its average historical level since September 2005.

10. Santa Margarita Lake

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Santa Margarita Lake, also called Salinas Reservoir, is located several miles southeast of the town of Santa Margarita in San Luis Obispo County. The lake was created by the construction of Salinas Dam on the southern end of the Salinas River.

The dam was built in 1941, and the lake provides the city of San Luis Obispo with a portion of its drinking water. Water level in the lake has been declining since June 2011.

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Catalin Trif is a nature enthusiast, blogger, and tech enthusiast. He is also addicted to travel and his guitar.


  1. Elizabeth Boyer

    I must be missing something. These reservoirs look larger in 2016 than they did in earlier years?!

    1. Author

      Hi Elizabeth,

      When the slider is to the left, the image is from 2001. When the slider is to the right, the image is from 2016.

    2. Albert Gedult

      Hello Elizabeth
      You dragged the line backwards. The arrow is pointing at the year on the opposite end of the picture. I also had problems earlier.

  2. Deidre

    Great visual! Hopefully everyone will look at this before they think about building more dams.

  3. Bipin

    Great data. Just the visualization and labelling seems a bit typical. At the first glance it looks as if the lakes have become bigger with time :). But i get the message,

  4. George

    Great visualization tool that really shows the reduction in reservoir sizes. Unfortunately, the labeling of the graphics appears intuitively backwards and makes it look like the reservoirs are larger now than in 2001. The take home lesson here is that California is losing water storage as a result of the extended drought. If this trend continues long term, California will need to build more dams just to maintain its current storage levels.

    1. Author

      Hi George,

      At first, the labels were reversed, but that created a lot of confusion as well, so we decided to switch them. I guess it depends on everyone’s own perspective.

    2. Herb

      Building more dams won’t make it rain. It’s the drought, George, and it could last as long as 30 years as many have in the past.

  5. MisTBlu

    Important work. Sad too. Wish you had included some info about the construction of the New Melones Dam, which is probably the newest of the dams mentioned in this post. Friends of the River organized a strong but ultimately futile effort to block it’s construction. So much history was lost when it was completed.

  6. Bob Pincus


    Nice photos. I would like to use the Lake Berryessa photo in our new website. We measure water stage by ultrasonic sonar.

    However, the slider does not appear to work.

  7. M. Bortin

    Which is most
    significant cause, population growth, lack of rain, or warming?

  8. Sacramennah

    Sobering. A picture is worth a thousand words, and these are compelling pictures. Thanks for the research and graphic work.

  9. Jonathan

    Excellent visualizations. From my perspective here in New York, the effects of the drought shown here can be taken as a possible warning that the patient (California) is approaching terminal decline.
    For an added perspective from space, log onto Daily Overview (, (also on instagram). “Over View”, by Benjamin Grant, is a just-published print version.

  10. Beverly

    They can call them lakes, but they are all reservoirs formed by dams, not one of them is a natural lake. The farm land of California has been manufactured by building all these dams. Underground storage of water is better since there is no evaporation. The Nabateans figured that out 2000 years ago. Our whole use and handling of water in Calif. will have to change, and it can be improved with water re-use. We live wastefully.

  11. handsbig

    The info for lake perris is incorrect, the army corps of engineer’s lowered the lake level over 10 years ago. they said the dam was not earthquake safe and they never repaired it.

  12. jay Shapiro

    I drive by Lake Cachuma a few times each year and have witnessed the astounding drop in size and level (Rangers said it was down over 60 vertical feet- and this was several years ago).
    Your great graphics sure dispel the myth that everything is fine and dandy with the climate.

  13. roger reid

    In reading the descriptions most of the shrinkage has occurred since 2010/2011. That is the time period when the courts decided for the delta smelt and against human beings. Also when I left California for a freer life in Oklahoma!

    1. Author

      Shasta Lake fluctuates a lot and it wasn’t actually that low in September. It was 61.8% full, which is 93.3% of its historical average.

  14. Albert Gedult

    California really needs to have the desalination plants running. We will be an uninhabitable state if we don’t do anything about it. Consider the Atacama Desert in Chile. Same set up, desert by the Pacific Ocean. The only inhabitable place there is Santiago as crowded as it is. Imagine San Diego, Los Angeles and San Fransisco the only habitable places in California. I live in Riverside and I would have to move from a water less dying city.

  15. Judith Courtney

    This is so distressing and depressing to see! True water management has been nonexistent in California since the beginning of the European settlement in this region. Lack of water was something that no one took seriously and, to this day, those with the power to do something about it refuse to take the draconian measures needed to stop the bleeding.

    I would love (hate) to see a similar photo of Lake Shasta and Lake McClure.

    Judith Courtney

  16. Christine

    I found it very intuitive, and very sad/scary. Living on the other side of the country where we’ve had two tremendous floods in 12 months …. I wish we could send some of it to you. Great job with the visualization.

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