What happened in Oroville Dam and how does it affect us?

Standing as the tallest dam in the U.S., Oroville plays a critical role in water delivery for the state.

Oroville Dam has been subject to nationwide attention due to damage on its concrete spillway and emergency spillway. The reservoir plays an important role in water delivery in California. You may ask, how did this start and how does this affect us locally? Here are your answers.

How did it happen?

Rainstorms in January caused the reservoir to nearly reach its 3.5 million acre-feet storage capacity. To avoid overflows, Department of Water Resources officials began releasing water through the main spillway that feeds into Feather River.

Tuesday, February 7. Water was being released at 24 million gallons per minute when state officials witnessed a 250-foot-long and 45-foot-wide cavity open on the main spillway.

Wednesday, February 8. To assess damage, state officials reduced water flows to 8 million gallons per minute.

Thursday, February 9. Flows were increased to 15 million gallons of water per minute, revealing further damage to the main spillway.

Friday, February 10. Officials prepared to use the emergency spillway after seeing the damage on the main spillway. The emergency spillway had not been used in the dam’s 48-year history.

Saturday, February 11. For first time in the dam's history, state officials used the emergency spillway.

Sunday, February 12. The emergency spillway also faced erosion damages leading to evacuation notices. The main spillway was put into use to alleviate pressure on emergency spillway.

Monday, February 14. Officials worked around the clock to make repairs. Mandatory evacuations reduced to a warning status.

What caused the damage in the spillway?

The damage to the spillway is attributed to erosion caused by the high volume of water being released. Water was released from the dam to avoid overtopping. Oroville is fed by the Sierra Nevadas and the rainstorms earlier this year helped the snowpack surpass normal levels. While Oroville Dam is 770-feet high, uncontrolled flows can take place when the water in the dam reaches the crest. 

Why is the Oroville Dam important to us locally?

Oroville Dam helps store water for dry years and provides water for agriculture. Storing more than 3.5 million acre-feet of water, Oroville Dam is a crucial part of the State Water Project (SWP). The SWP provides Southern California 30% of its water supplies.   The SWP transports stored water from Oroville during dry periods. This water becomes crucial during the summertime and during the drought. Central Basin has delived water from the SWP to its service area. 

Does the dam face any danger?

Oroville dam is not in any danger of failing; the damage is on the main and emergency spillway, and the storage in the reservoir is now well below the spilling level. 

What are officials doing now?

Crews are working around the clock to repair the dam. This includes removing debris from underneath the spillway and reinforcing the emergency spillway with boulders. Crews are also monitoring water flows and utilizing the power plant to release water.

Oroville Dam provides water for dry years and for our state’s agriculture industry. Closer to home, our service area of southeast Los Angeles also uses water from Oroville.  Without Oroville, California would be left without a principal storage facility. 

Join us for an inspection trip to learn more about Oroville Dam and the role of our imported sources of water. Visit us online to submit an application: https://www.centralbasin.org/education-community/community-outreach/inspection-trips-and-tours