Several dozen dams throughout California could store up to 107 billion more gallons of water if they underwent repairs to fix safety problems. But facing a staggering state deficit, Gov. Gavin Newsom has proposed cutting funding for a dam repair grant program in half this year, while state legislators want the $50 million restored.

California has an aging network of nearly 1,540 dams — large and small, earthen and concrete — that help store vital water supplies. For 42 of these dams, state officials have restricted the amount of water that can be stored behind them because safety deficiencies would raise the risk to people downstream from earthquakes, storms or other problems.

Owned by cities, counties, utilities, water districts and others, these dams have lost nearly 330,000 acre-feet of storage capacity because of the state’s safety restrictions. That water — equivalent to the amount used by 3.6 million people for a year — could be used to supply communities, farms or hydropower.

Two years ago, in the depths of the most recent drought, Newsom touted dam repairs as a key approach to shore up water supplies squeezed by climate change. In his 2022 Water Supply Strategy, he referenced plans by his administration and the Legislature to create a grant program to “help local water districts regain lost storage capacity and improve public safety” of dams.

The program, created in 2023 and allocated an initial $100 million, is still getting up and running.

But now, reeling from the massive deficit, Newsom has proposed cutting $50 million this year. The Legislature as of Wednesday has kept that money in its proposed budget; negotiations are continuing.

“This investment is the trifecta: It gives you public safety, because you don’t want dams breaking. It gives you climate resilience, because we could have flooding,” said Assemblymember Diane Papan, a Democrat from San Mateo. And, she added, “It will impact our water supply.”

Newsom spokesperson Alex Stack declined to address CalMatters’ questions about dam safety funding, citing the negotiations. “We’ll have more to share soon,” Stack said.

Dam owners facing hundreds of millions to billions of dollars in repairs are urging lawmakers to add more funding for projects in a multi-billion dollar climate bond, which also is being negotiated.

“It’s so important that we have the storage capacity to be able to collect water in wet times, so that we have it during times of drought,” said Cindy Tuck, a deputy executive director of the Association of California Water Agencies, which represents more than 450 public agencies.

Hundreds of dams are at least a century old

Statewide, dams help corral floods, generate power and store water for cities and farms. But California dams on average are more than a decade older than the national average, with 328, roughly a fifth, that are at least 100 years old.

Despite their age, dam disasters are extraordinarily rare. In March 1928, the nearly brand-new St. Francis dam northwest of Los Angeles collapsed — killing more than 450 people in the second-deadliest disaster of California’s history. In 1963, the Baldwin Hills dam in southwest Los Angeles breached, killing 5 people and damaging $15 million in property.

A major earthquake severely damaged the Lower San Fernando Dam in the 1970s — leaving only “a thin dirt wall… between 80,000 people in the San Fernando Valley of southern California and 15 million tons of water,” the U.S. Geological Survey reported. And the Oroville dam’s compromised spillways forced the evacuation of nearly 190,000 people during the storms of 2017. Each major dam failure or near-miss has spurred greater oversight.

Storage capacity for Valley Water, a Silicon Valley wholesaler for 2 million people in Santa Clara County, has dropped 25% because of the state restrictions and another 37% from a federal limit on their largest reservoir, said Ryan McCarter, Valley Water’s deputy operating officer for dam safety. The restrictions were largely imposed to reduce the risk to people downstream of dams if a major earthquake causes damage.

“That’s a major hit to our water supply,” McCarter said. “Moving into these years of climate change, if we have longer extended droughts, we’re going to really want these reservoirs at full capacity.”

The price tag to restore capacity to Anderson Reservoir, which has been drained because of state and federal safety restrictions, is expected to reach $2.3 billion. Repairs to other dams could add at least another $325 million. The water provider also paid roughly $50 million for emergency water supplies during the last drought.

The costs eventually will hit ratepayers, said Valley Water Vice Chair Richard Santos.

“We have large, diverse disadvantaged communities where water affordability is a serious issue,” he said.

Papan said as the chair of the Assembly’s water, parks and wildlife committee, the threat of deteriorating dams keeps her awake at night. “I don’t want somebody to look back and say ‘They knew this was going to be an issue, but they didn’t put any money towards it.’”

The American Society of Civil Engineers gave California’s dams a C- on its most recent infrastructure report card in 2019. And in 2021 the state’s auditor said “the condition of some of the State’s potentially most hazardous dams remained a concern.” Dam safety inspectors have rated conditions at 133 of them as less than “satisfactory.”

According to the grant program’s guidelines, “in many cases, these dams pose a significant threat to communities downstream.” The state restrictions aim to reduce that threat by limiting the amount of water they can store.

Shawn Jones, assistant manager of the state’s Division of Safety of Dams, said California has the largest dam safety program in the nation, overseeing roughly 1,230 dams with more funding and staffing than any other state.

Jones said that he wouldn’t characterize the 42 dams that have storage restrictions, which average around 100 years old, as “unsafe.” “All dams provide some sort of risk downstream,” he said. “These dams have an additional risk, and we’re driving it down in the interim” with the storage restrictions.

But repairs are often slow-moving because of lengthy environmental permitting processes and massive costs.

“We are finding deficiencies faster than the dam owners can address the deficiencies,” Jones said.

Water providers say federal dollars are insufficient, and even $100 million for the state grant program — though welcome — is just a drop in the bucket. They anticipate mounting costs to shore up aging dams against earthquakes and climate change. Some also are grappling with federal restrictions and local factors, such as sedimentation, that reduce storage.

“This is really a systemic issue, a water issue that is affecting the state of California,” said Drew Kleis, assistant director for San Diego’s water delivery branch.

Nine dams that store raw water for San Diego are especially geriatric, averaging 92 years old. The state has imposed restrictions on four of them, cutting into the city’s capacity to store water by 20%. Repairs, maintenance, and additional assessments expected to total around $1 billion.

At San Diego’s Lake Hodges, a dam near Escondido is more than a century old. It is deteriorating, raising concerns about its ability to withstand a major earthquake. State restrictions have cut its original storage capacity of roughly 38,000 acre-feet — already substantially reduced by sedimentation — by nearly 30,000 acre-feet. The dam is expected to be replaced by 2034.

Kleis said the dams, as the city operates them, are safe. Reducing how much water is stored behind them “minimizes the amount of water that would be released downstream” in the unlikely event of a breach, he said.

Three other San Diego dams are also operating at reduced capacity under state safety restrictions, including at El Capitan Reservoir, one of the largest serving the city. The state has cut the reservoir’s storage capacity by more than half for nearly a decade while the city investigates how the earthen dam would fare during a large earthquake.

The last several years, with extreme drought followed by the deluges of 2023, have highlighted the importance of storing more water in California.

“With the potential for more varied weather, for more extreme drought and more extreme wet years, we want to be able to capture that runoff,” Kleis said.

Here are details on local dams

Bear Gulch, Woodside
Dam condition: Poor
California Water Service Company
Built 1896
Restricted in 2012
Downstream hazard: Extremely High
Restricted capacity: 550 of 725 acre feet 76%
Cal Water’s dam is safe as operated, and done so with the approval of DSOD. Cal Water is currently moving forward with updates to the reservoir outlet and continues to evaluate the dam for future improvements.

Guadalupe, San Jose, off HIcks Road, northwest of Almaden Quicksilver County Park
Dam condition: Fair
Santa Clara Valley Water District
Built 1935
Restricted in 2012
Downstream hazard: Extremely High
Restricted capacity: 2412 of 3460 acre feet 70%
The Guadalupe Dam Seismic Retrofit Project is currently under design.
The reservoir restriction will be removed after completion of the seismic retrofits.

Calero, San Jose
Santa Clara Valley Water District
Dam condition: Fair
Built 1935
Restricted in 2013
Downstream hazard: Extremely High
Restricted capacity: 4500 of 725 acre feet 47%
The Calero Dam Seismic Retrofit Project is currently under design.
The reservoir restriction will be removed after completion of the seismic retrofits.

Almaden, San Jose, off Alamitos Road
Santa Clara Valley Water District
Dam condition: Fair
Built 1936
Restricted in 2012
Downstream hazard: Extremely High
Restricted capacity: 1900 of 2000 acre feet 95%
The Almaden Dam Seismic Retrofit Project is currently under design.
The reservoir restriction will be removed after completion of the seismic retrofits.

Anderson, Morgan Hill, off Cochran Road
Santa Clara Valley Water District
Dam condition: Fair
Built 1950
Restricted in 2017
Downstream hazard: Extremely High
Restricted capacity: 52,562 of 91,300 acre feet 58%
The Anderson Dam Seismic Retrofit Project is currently under design.
The reservoir restriction will be removed after completion of the seismic retrofits

Selvage #2, Gilroy, off Day Road
Lucky Hereford Ranch
Dam condition: Poor
Built 1948
Restricted in 2008
Downstream hazard: Low
Restricted capacity: 24acre feet 100%
The valve was cut off so no storage can occur.

North Fork, Gilroy, Pacheco Pass
Pacheco Pass Water District
Dam condition: Fair
Built 1939
Restricted in 2018
Downstream hazard: High
Restricted capacity: 6,150 acre feet 100%
Pacheco Pass Water District is in the process of soliciting contractors
to complete the interim repairs to correct the deficiencies at the North Fork Dam. A proposal plan and schedule to be submitted to Cal OES.

Note: Details about why each dam is restricted and actions by owners
is current as of Sept. 2023. Capacity restrictions and percentage of capacity
lost is compiled from data sent by California Department of Water Resources, but it may not reflect other restrictions from other agencies or storage lost to sedimentation.
Source: California Department of Water Resources, Division of Safety of Dams
Credits: Arfa Momin, CalMatters; John Osborn D'Agostino, CalMatters

Rachel Becker is a reporter with CalMatters.