CA WATER COMMISSION: Update on the California Aqueduct Subsidence Program

At the September meeting of the California Water Commission, Daniel Whisman, principal engineer and program manager for DWR’s California Aqueduct Subsidence Program, updated the Commissioners on the Department’s ongoing efforts to address subsidence impacts to the aqueduct, including the status of the early implementation and long term projects and the program’s efforts to support the human right to water as codified in section 106.3 of the California Water Code.

The California Aqueduct is a key component of the State Water Project and an integral component of the water delivery system in the San Joaquin Valley.

The map shows the water delivery system in the San Joaquin Valley.  The Central Valley Project canals are shown in blue; the San Luis Field Division, shown in green, is owned by the federal government, operated and maintained by the state, and is part of the federal Central Valley Project. The San Joaquin Field Division is shown in yellow. 

At the south end of the valley, the California Aqueduct is lifted 2000 feet over the Tehachapi Mountains to support the substantial population of Southern California.

The State Water Project and the Central Valley Project are interconnected at several points, including the O’Neill forebay at the base of the San Luis reservoir in the northern San Joaquin Valley, and the Cross Valley Canal and the Arvin-Edison Interties at the southern end of the valley.

In 1920, the State Engineer dispatched University of California Berkeley professor Sidney Hardy to survey the groundwater resources and use in the San Joaquin Valley. Professor Hardy’s assessment, published in Bulletin 11 of the California Department of Public Works, revealed that the magnitude of groundwater extraction at that time was unsustainable.

In 1956, the California Department of Water Resources was created in large part from the California Department of Public Works, with the mission that included the planning, design, and construction of the State Water Project to increase statewide water supply reliability for what would become 27 million Californians and over 750,000 acres of farmland.

Environmental preservation and protection also became serious considerations beginning in the 1960s. In 1968, deliveries from the San Joaquin Field division of the State Water Project began to the Kern County Water Agency, among others.

In the intervening years, the California Aqueduct has been compromised by subsidence due in large part by groundwater overdraft. In response, the State Water Project initiated the California Aqueduct Subsidence Program, or CASP, to remedy current and future subsidence of the California Aqueduct, as well as address improving the resiliency of the water management system while preparing for future demands on the California Aqueduct.

The State Water Project relies on gravity in combination with electricity to deliver water, and as such, water and power are inextricably linked in fulfilling California’s water needs,” said Mr. Whisman.  “The result is that remediating subsidence cannot be performed in isolation, as the power needs of the state water project must also be taken into account.”

Subsidence impacts have caused a decrease in flow capacity of the California Aqueduct, along with increased maintenance and repair costs.  Subsidence impacts have also critically decreased operational flexibility, leading to higher energy costs to deliver water. This loss of operational flexibility decreases the project operators’ ability to lower energy costs while moving the water.

To address these issues, the Department of Water Resources is implementing a combination of early implementation and long-term projects to mitigate the risks to the California Aqueduct posed by ongoing and future subsidence.

The State Water Project capitalization policy establishes the useful life of aqueducts as 80 to 100 years,” said Mr. Whisman.  “With a planning horizon of 2075, we recognize and intend that the infrastructure projects resulting from the CASP will be servicing the needs of California into the next century.”

Everything influencing and influenced by the work we are doing on the California Aqueduct is in flux: politics, the environment, energy markets, water supply and demand, the regulatory environment, market forces, etc. Consequently, we within the CASP are employing adaptive management and making decisions while facing tremendous changes and uncertainties everywhere.

A key consideration of the Department’s approach is assuring a sound and acceptable return on investment for the projects considered and undertaken, said Mr. Whisman. However, ongoing climate change is making everything more difficult, including for the CASP. Extreme weather events are degrading the infrastructure of the State Water Project, as well as the Central Valley Project, which in turn makes it both more difficult and more costly to fulfill the state’s human right to water goal, he said.

The CASP is focused on risk management and improving resiliency. The bow tie diagram is a highly simplified yet representative example of the Department’s approach within the program. It includes a quantitative risk analysis process and identifying the causes on the left side of the subsidence knot, along with the consequences indicated on the right side of the knot. Risk barriers or controls can be implemented at any connecting area between causes, events, and impacts. He said this allows for implementing a broad spectrum of structural and nonstructural solutions within the program.

The hydrology of California is changing; a recent report by the Department of Water Resources indicates that by 2050, there will be a 50% chance in any year to experience conditions similar to those of the 2012-16 drought at minimum.

With a system degrading from the impacts of subsidence to pools 14-30 of the California Aqueduct, comprising 80% of the California Aqueduct between San Luis reservoir in the north and Edmondston pumping plant in the south end of the San Joaquin Valley, have suffered losses in design hydraulic conveyance capacity between 22 and 57%,” said Mr. Whisman.

This phenomenon adversely impacts the San Joaquin Valley with a disproportionate impact on vulnerable communities, especially those relying on water delivered via the California Aqueduct, whether served by state or federal water contractors, he said. These impacts include increasing water delivery costs and increasing disruption of water supplies to other disadvantaged communities suffering from lack of reliable access to water caused in large part by groundwater overdraft.

The timeline shows the Department’s current view of the development of both early implementation and long-term projects to emerge due to the two California Aqueduct subsidence studies performed in 2017 and 2019.  Mr. Whisman said they anticipate the structural and nonstructural solutions that emerge from and throughout the long-term planning will continue through the 2030s.

To remediate existing critical subsidence, the Department has completed one pool liner raise project to date and has four major construction projects under various stages of planning and design, including environmental planning and permitting. These projects include raising the embankment and liner on each side of four pools totaling roughly 40 miles in length, along with raising, repairing, and relocating associated structures, including bridges and utility crossings. Also included is the raising of check and turnout structures.

The production of interim deliverables is part of the long-term plan. These include facilitating the building of shared understanding and support for the program, as well as to provide benefits to the State Water Project and others. This will require close collaboration with and cooperation of many communities of interest in the San Joaquin Valley and beyond, including the Bureau of Reclamation, said Mr. Whisman, noting that the Bureau of Reclamation is a key ally and influencer in the restoration of the San Luis Canal, and increasingly, the San Joaquin Field Division portion of the California Aqueduct.

Many disadvantaged communities throughout the state, including Avenal, Huron, Coalinga, and others in the San Joaquin Valley, are served by the water supply and/or flood protection functions of the California Aqueduct.  

These communities inform and influence us in striving to achieve acceptable risk on investment for structural and nonstructural solutions alike,” he said.  “Additionally, 87% of the 667 community water systems in the San Joaquin Valley are reliant on groundwater. Declining groundwater levels harm tribal nations and disadvantaged communities, with water tables outrunning and subsidence damaging their wells.

We are purposeful in our attempts to avoid redirecting subsidence harm elsewhere while mitigating it on the state’s major and most important water conveyance facility,” said Mr. Whisman.  “We understand that it will take strong and resilient collaboration in the San Joaquin Valley to ensure a reliable and resilient infrastructure that can meet the needs of California’s environment, economy, and people into the next century.”

After 100 years, and with the recent passage of the Sustainable Groundwater Management legislation, the valley’s communities of interest are compelled and empowered to work together to solve our mutual problem.”


Commissioner Jose Solario said the presentation highlights that everybody just views it as a State Water Project problem. But what about the communities served, particularly the ones that are immediately adjacent to the aqueduct itself? What level of responsibility towards improving the infrastructure do those communities or cities, or businesses have? Or maybe just the thinking is the State Water Project contractors because they’re paying into the system?  Maybe there should be some level of local responsibility and accountability somehow – maybe it’s 5%. “Maybe they have to do some reporting. I don’t know. I just kind of feel like everyone looks to us and those communities that are doing the pumping, and everyone just kind of points at the state to deal with this.”

Mr. Whisman responded by saying the question is substantially beyond the purview of the California Aqueduct Subsidence Program, but they are considering all of that, and obviously, funding is a primary concern of the system.  “We are exploring all avenues of obtaining funding to meet solutions, for this is a mutual problem that we’re all-embracing. So we, at this point, are not ruling out any parties and are looking at a broad spectrum at contributions to the solution.”

He pointed out that many of the communities that are suffering along the or adjacent to the Aqueduct’s footprint and further into the interior of the Valley are suffering from subsidence that is induced due to groundwater overdraft, not of their own making. “So we recognize it’s a very fraught problem, and it’s very charged and complex. And so, like many other entities that have grabbed a hold of this problem, we are working through and in as collaborative fashion as we can to help come to a mutual resolution. We know that everybody will not get all their needs met at the end of the day. But we understand the collaborative nature of pushing forward to resolve a mutual problem.”

Commissioner Alexandre Makler noted that they have heard presentations about the effects of subsidence on the California State Water Project and the associated costs. There is an efficiency loss and an opportunity cost with respect to the pumping load because if not for the effects of subsidence, energy could be procured more cost-effectively.  There is also some water loss associated with the effects of subsidence.  Have you quantified these costs for the stakeholders? 

Among the key considerations in the CASP as we develop this long-term recovery plan for the State Water Project’s California Aqueduct, we have performed and are engaged in engineering studies,” said Mr. Whisman.  “Our initial studies in the CASP report in 2017 and 2019 were engineering studies and evaluations that yielded the result we need to act now. And we need to look into the future.”

At the same time, we have a problem we have to solve now, which is the subsidence we’re suffering. And we have to concern ourselves with ongoing subsidence. So the program was formed with early implementation projects and long-term projects.  The long-term project is a comprehensive and complex study and involves alternatives. The now analyses, which are scheduled  – we have not yet ruled out any alternatives for evaluation.  There will be a gauntlet that each of these alternatives will have to succeed to arrive at the top.  Among the criteria that they’re going to be evaluated on is their economic benefit.  This is required now for both long-term and early implementation projects. The early implementation projects are primarily focused on the San Luis Field Division portion of the California Aqueduct, which the federal government owns; the state has an agreement with the Bureau of Reclamation called the joint-use facilities agreement or the joint-use agreement. And under that agreement, they’re obligated to pay. We’re talking about 45% of the cost incurred to repair the Aqueduct.”

We have damages to the extent that we are going to be subjected to what the Bureau of Reclamation calls an extraordinary maintenance justification study. A key aspect of that report is used for obtaining authorization and appropriation for funding are the economic benefits associated with that. So again, in addition to an engineering evaluation, there will be a comprehensive economic evaluation on the project.

Commissioner Samantha Arthur asked how repairing the California Aqueduct can directly benefit disadvantaged communities and the human right to water.  I get that there’s a stepwise benefit if you’re improving surface water supply and then decreasing groundwater reliance. But I’m really wondering if there’s more thinking about direct benefits to these disadvantaged communities with that human right to water being such a priority? How can the repairs connect to that?

Mr. Whisman reminded that in his presentation, he discussed both structural solutions and nonstructural solutions. “Some of those benefits will yield from our structural solutions. In other words, to the extent that we are successful in restoring the original design intent of the California Aqueduct, that will result in less load on the electrical grid, which should result in lower or slower increases in energy rates for all the citizens, including disadvantaged communities. Another factor is that to the extent we can reestablish the original design intent for the aqueduct, that will result in slower increases in water rates because it’s going to effectively cost less money over the long haul to get water to the citizens relying on it, including for those disadvantaged communities that benefit from the aqueduct, as well as other communities that rely on groundwater.”

There are many numbers of communities that rely on both surface and groundwater, but to the extent that they may benefit from our actions among our suite of nonstructural solutions include ways to obtain funding for not only the program directly, but as we get smarter and more sophisticated about the funding environments at the state and federal levels, we’re looking for opportunities to benefit our other communities of interest in the San Joaquin Valley through programs that don’t necessarily benefit the CASP program directly, but indirectly they do, because they will assist in the reduction of groundwater overdraft, which is causing our problems.

So in helping them solve their problems, we are also helping us solve our problem. That’s why I refer to this as a mutual problem that requires collaboration to really come to an elegant solution. So we have an obligation to mitigate damage to the aqueduct, and it’s an opportunity to help with this groundwater overdraft situation. And all communities will benefit from that. We are not the regulators; that’s more the Sustainable Groundwater Management Office’s bailiwick. But we do have an opportunity to weigh in on the groundwater sustainability plans of the groundwater sustainability agencies because we are an infrastructure that is being adversely impacted by unsustainable groundwater extraction, and we have the right and obligation to review and weigh in on those groundwater sustainability plans.

So to the extent that we’re successful in mitigating the damage on our infrastructure, through nonstructural measures, we anticipate the benefits to other communities, including disadvantaged communities.”

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