A view looking north over the California Aqueduct and agricultural land just east of Interstate 5 in Stanislaus County, near Crows Landing, California. The aqueduct is a critical part of the State Water Project that carries water from the Sacramento-San Joaquin Delta to the San Joaquin Valley and Southern California. Photo taken April 16, 1998. Dale Kolke / California Department of Water Resources

CA WATER COMMISSION: DWR’s Climate Change Vulnerability Assessment

The CA Aqueduct and agricultural land east of Interstate 5 near Crows Landing. (Photo by DWR)

Assessment looks at six categories of vulnerability: wildfire, extreme heat, sea level rise, long-term persistent hydrologic changes, short-term extreme hydrologic changes, and habitat and ecosystem services impacts

In order to address the impacts of climate change on the state’s water resources, the Department of Water Resources (DWR) has been developing its own comprehensive Climate Action Plan to guide how DWR is and will continue to address climate change for programs, projects, and activities over which it has authority.

Phase III of the Climate Action Plan is a Vulnerability Assessment and Adaptation Plan which will evaluate, describe, and where possible, quantify the vulnerabilities of DWR’s assets and business activities to projected changes in temperature, wildfire, sea level rise, long-term and persistent hydrologic changes (including precipitation, snowpack runoff, and flooding), and habitat and ecosystem services degradation.

The Vulnerability Assessment will serve as a foundation for the development of an Adaptation Plan to help prioritize DWR resiliency efforts such as infrastructure improvements, enhanced maintenance and operation procedures, revised health and safety procedures, and improved habitat management.

At the May meeting of the California Water Commission, John Andrew, Deputy Director for Climate Change at the Department of Water Resources, reviewed the outcomes of the vulnerability assessment and explained the next steps.

He began by noting that the Department’s entire Climate Action Plan has three phases: Phase 1 was a greenhouse gas reduction plan that was adopted in 2012; phase 2 was a consistency and climate change analysis within the Department which was completed last fall; and phase 3 which looks at how the Department is vulnerable to climate change and how it’s going to adapt.

The assessment looks at six categories of vulnerability:  wildfire, extreme heat, sea level rise, long-term persistent hydrologic changes, short-term extreme hydrologic changes, and habitat and ecosystem services impacts.  Mr. Andrew noted that different organizations pick different categories or hazards; oftentimes, precipitation is one of those, but he explained they chose not to focus on precipitation because for the Department, hydrology is more important.

For wildfire, extreme heat, and sea level rise, they used the standard approach which is the equation exposure + sensitivity = risk; then by adding adaptive capacity, you get to vulnerability, he explained.


Mr. Andrew pointed out that the scope of the assessment was on the Department of Water Resources as a business, not the vulnerability of the water sector in California to climate change; that vulnerability has been written about by numerous researchers and has been included in the state’s climate change assessments and others.  “This was to look at just basically our people and places, so it’s not the water sector writ large, it’s basically the Department as a business organization,” he said.

The assessment has a mid-century time horizon, which is defined as anywhere from 10 years to 50 years from now.  Mr. Andrew said the mid-century was chosen for several reasons.  One was that they wanted to start adapting to climate change now and not wait several decades; they wanted to focus on what’s affecting the current generation of DWR employees.  Secondly, mid-century time horizon projections are far more certain and is well within any project that’s currently underway; most projects are expected to have a 30-year life span, so that would be 2050, so adaptation plans and actions can be incorporated by project managers now.  Third, mid-century projections aren’t so ‘biblical’, he said.

Mr. Andrew then discussed the scope of the assessment, reminding that scope is looking at what the organization can control in the future.  They did not assess the Delta levee system as that is a mix of state, local, and federal ownership and control; they also did not look at seismic risk, subsidence, or other non-climate stressors.  He noted that the Delta Stewardship Council is conducting a climate change vulnerability assessment for the Delta which will include Delta levees.  They also did not include the Sacramento-San Joaquin flood control system writ large because not only is it a mix of local, state, and federal involvement, and the Central Valley Flood Protection Board is the decision maker on those assets, not the Department.

The Department is also very vulnerable to the western electrical grid as a very large power user within the state and in the west, but they don’t have a lot of control over the system, so it’s not part of the assessment because it isn’t something they can immediately go out and take action upon.  They also did not assess any of their regulatory programs, such as the Division of Safety of Dams or the Sustainable Groundwater Management Program.  They also did not address programs or organizations where they have unique relationships such as the Water Storage Investment Program, which already had a rigorous climate change analysis portion within it.

The scope of the assessment is so important, an entire chapter is devoted just to make it entirely clear.  “It’s also good to note that this is a climate change vulnerability assessment, not a climate vulnerability assessment,” Mr. Andrew said.  “Clearly climate is the business of the Department of Water Resources as we’re already exposed to the climate and there’s a certain level of risk there that we accept because that’s how we carry out our business, so this is the incremental change resulting from climate change.

With all those qualifiers, you are probably wondering if there’s anything left in this vulnerability assessment, and it turns out there’s a lot,” he said.  “The entire State Water Project which is an enormously important project.  Some of our flood facilities as we do have flood yards in the Sacramento Valley.  All of our four regional offices and our five field division offices are managed lands.  We also looked at the people that work for us, both those that operate and maintain the State Water Project and those that goes out and do biological surveys and monitoring, and we also look at our operations.  So even with all the qualifiers, there’s quite a bit of meat in here.”


One of DWR’s important partnerships was with CalFire who worked with them to develop a map of how DWR’s facilities would be vulnerable at mid-century to wildfire.  The bubbles on the map show DWR’s facilities which are mostly along the westside of the Valley.

As it turns out, our facilities are primarily not vulnerable to increased wildfire,” he said.  “We certainly have areas, especially in Southern California where we go through some areas where wildfire risk is increasing, but because of the nature of our facilities, there are largely buildings, concrete, aqueducts, things of that nature, so while they may be exposed to wildfire, but they are not terribly sensitive.  There’s also this adaptive capacity component … defensible space is an adaptive capacity and we implement that.”

Chair Armando Quintero asked about the risk of impact of fire on the water supply.  “It’s part of that western electrical grid, so it actually is out of scope, but it is a vulnerability,” Mr. Andrew replied.  “In this chapter of the things that are out of scope but are still vulnerabilities that are outside of our control, that’s in there.”

Most of DWR’s facilities at mid-century are not vulnerable or considered to be of low vulnerability to increased wildfire risk, with a few notable exceptions. One of those is the upper Feather River watershed.  The maps on the slide show the change in wildfire risk.  He noted that the the watershed will go from being primarily low and moderate exposure to wildfire currently to almost entirely moderate and high by mid-century.

Mr. Andrew acknowledged that it may seem obvious now after the last two fire seasons, but the analysis was conducted between 2013 and 2016 so in some ways, this analysis is even a bit dated.  “This has been more or less proven on the ground how vulnerable our watersheds are to wildfire,” he said.  “This is a huge exception to our scope because we don’t own the upper Feather River watershed, we don’t control it, and our influence there is small but there is a multi-stakeholder approach that we can engage with to look at how we can better adapt the Feather River watershed in response to findings like these.”


The assessment of heat vulnerability mostly affects DWR employees, and to a lesser extent, equipment.   They surveyed the staff in the regional offices about how people are exposed to heat now and adjusting scheduling to avoid the hottest times of the day.

There seemed to be a lot of adaptive capacity there, the ability to move around work schedules and to adjust activities to avoid heat,” Mr. Andrew said.  “We also do have as is required a heat illness prevention program which has a lot of adaptive capacity to respond to this particular hazard.”

He then presented a chart which quantified the projected temperature changes mid-century.  The San Joaquin Field Division will be the most heat-stressed region with the number of days exceeding 95 degrees Fahrenheit will be between 87 days on the low end which is essentially the entire summer, and 117 days on the high range of the estimate.  The projections for days over 105 degrees are between 7 and 32; at the high end, it’s an entire month over 105 degrees.

We think right now we have the adaptability but we’re going to be keeping a close eye on this because this is something that’s going to affect our people,” he said.


In terms of direct exposure to sea level rise, DWR has only one facility on the coast which is the Eureka Flood Center.  It’s staffed part time and is collocated within the National Weather Service building, so the Department doesn’t control the building.  The building is at 20 feet of elevation, so the exposure is extremely low, he said.  They stopped at that point because there wasn’t much point in continuing to analyze further. One way to adapt would be to vacate the building and move the flood center inland, he said.

Delta levees are not part of the assessment, but there are State Water Project facilities located within the Delta; there is a storehouse on Twitchell Island, an aeration facility near Stockton, and facilities in the South Delta.  Few of DWR’s facilities are actually sensitive to rising seas, he said.   The entire Delta has an issue with sea level, especially with the greatly subsided areas in the Delta.

Within the Suisun Marsh, they do not own it but they have a management role as part of it.  The facilities are designed to be exposed to sea level, but they are concerned about the ecology of the lands in the Suisun Marsh.

The assessment also includes part of the work included in the fourth climate assessment that looks at synergistic effects.  “For example, we’re going to have sea level rise, we’ll have storm surge, and then we’ll also have increases in watershed flooding events coming from the other side of the Delta,” Mr. Andrew said.  “So we have an entire chapter on synergistic effects. That’s something we would like to keep an eye on as well.”


Mr. Andrew said they had a great partnership with the University of Massachusetts Amherst in developing this part of the assessment which was included in the state’s fourth climate assessment.

The nice thing about the approach we used to look at long-term hydrologic change allows for risk management decision making by using what’s called in the business a bottoms up approach, looking at your system and its thresholds for failure,” he said.  “Most other climate change analyses look at a top down approach.  You start with global climate models and you downscale them.  You feed those into hydrologic models and every step of the way, you increase the uncertainty which makes it hard to make decisions at the end about what do these results mean other than they make for nice power point slides.”

Using this method, they looked at the likelihood of different metrics for the State Water Project and how likely they will be worse than they are now.

A couple of these are fairly eye opening,” he said.  “If you look at Oroville carryover storage, that’s essentially water that we carry over from one water year to the next, it’s the October 1-September 30 storage, there is a 95% probability that that is going to get worse by mid-century.  If you look at State Water Project deliveries, it’s probably not news that our performance is going to be degraded in a changing climate, but now with this method, we’re actually able to say that it’s actual near certainty that we’re going to be delivering less water if we’re not going to take any action.”

He acknowledged that some of the other ones on the slide are not as probable because the way the system is modeled, they meet regulatory standards first.  “So some of these in terms of Delta outflows are requirements on the State Water Project,” he explained.  “Even summer and fall Delta outflow, those don’t even rise to the 50% level, but that’s because the way the modeling is done, we meet the regulations first and then we meet our deliveries and then we try to carryover some water from one year to the next. … We’re looking to be doing more on this in our adaptation plan.”


They also looked at flood flows, again with the caveat that the Central Valley flood system is a patchwork quilt of local, state, and federal involvement, and something that the Department doesn’t have entire control over.  They did include results from the 2017 Central Valley Flood Protection that included an entire technical memorandum about climate change.  That memorandum concluded that  short-term flows are definitely going to be going up for all the watersheds and that the San Joaquin was at greater risk than the Sacramento in terms of increased flood risk.

Mr. Andrew acknowledged that the climate analysis for flooding is a bit problematic.  It works well in terms of long-term hydrology, as with Oroville and the State Water Project deliveries.  However, climate change analysis doesn’t really capture short-term time scales, and one to three days is extremely small in the climate change modeling.  “It doesn’t do well with extremes, which is what all flood flows are about, and it doesn’t do well with small spatial scales, so a lot of caveats go along with the flood modeling,” he said.

One of the things they did was to look at the 500-year floodplain map and overlay that with all their facilities in the state.  “As a proxy, you could take a look at the 500 year flood map and basically assume that’s going to be something on a more frequent time scale in the future,” he said, noting that there is a facility on the East Branch of the State Water Project, the South Central Regional Office, and the main headquarters in downtown Sacramento that were determined to be vulnerable.


For this part of the assessment, they used more of a qualitative approach.  Mr. Andrew acknowledged that most vulnerability assessments don’t include habitat and ecosystem services, but they thought it was important to do so.

We are a large landowner in the state, we have a lot of managed lands and a lot of the lands we purchased are for mitigation or for some sort of project we’re doing, and if the species or the conditions are changing on the ground, it’s an open question,” he said.  “If you’re providing it for one species and that species decides to move, it can move somewhere where the climate is better, this is something that we’re going to be thinking about as we get into mitigating parcels in the future.”

Some of the results are listed on the slide.  “Clearly cold water is important for salmonids and that has a direct impact on our operations and the fact that other ecosystems are in trouble now and to the extent that other species get listed, that could have a direct impact on our State Water Project operations,” he said.  “Definitely more work to be done here, especially in terms of quantification.”


This assessment is to be the foundation for an adaptation plan. “We do want to act upon these results and our adaptation efforts are already in motion,” Mr. Andrew said.  “Suffice it to say, we’ll probably look at all of these hazards in a bit more detail, but the upper Feather River watershed looks like hazard #1 for us to start getting a handle on; we’re going to look at the Suisun Marsh and certainly last but not least, how heat is affecting our workers.  We’ll be keeping a close eye on that.”


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