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Over 2.7 million of us in the Bay Area get our water from the High Sierra (1), a water source so clean that the San Francisco Public Utilities District (SFPUC) doesn’t need to filter the water before delivering it to our homes. (2) Our water is not cheap, but it comes from a pristine source.
That may be changing. The SFPUC and several other local water utilities, including Palo Alto, are considering alternative water sources to augment the Hetch Hetchy supply. One of the most promising appears to be “direct potable reuse,” sometimes referred to as “toilet to tap” by its detractors. Advanced filtration and chemical processes can convert raw sewage to water that meets or exceeds all health and aesthetic standards in a matter of hours.
Until recently, water districts were required to inject treated wastewater into groundwater, so it would enter our drinking supply only indirectly. Orange County has augmented their groundwater this way for decades. But new regulations approved in October now allow for direct delivery to customers, and our water agencies are starting to incorporate that option into their planning.
Why are they doing this? The SFPUC is concerned that water demand will grow and supply will drop. Their Alternative Water Supply Plan specifically points the finger at an update to watershed management, the Bay-Delta Plan Amendment, as having the “most pronounced impact” on supply. This amendment, which changes how we manage the watershed that feeds the Bay Delta, was adopted in 2018 though it is not yet in effect. It requires minimum flows in the three main tributaries to the San Joaquin River in order to protect salmon and the extended ecosystem that depends on them.
The water utilities are fighting this, saying that the greatly reduced supply in dry years would hurt their ability to serve customers. Environmental advocates in turn accuse them of exaggerating the risk, asserting that there need be no tradeoff between saving the salmon-based ecosystem and providing ample water for urban and agricultural needs.
The Bay-Delta Plan Amendment
What is the Bay-Delta Plan Amendment, why is the SFPUC concerned, and are they being overly conservative?
The Delta’s aquatic ecosystem, a once thriving environment for hundreds of species, has been degrading for decades due to reduced flows in the Sacramento and San Joaquin river basins that feed it. Water diversions for agriculture, combined with urban demand, have resulted in low flows, warming water, and toxic algae blooms. Native species are rapidly dying out. All agree that we need to take action, and quickly.
The dwindling population of salmon in the rivers reflects these changes. The Tuolumne River now has 1000 or fewer salmon; in the mid-80s there were 40,000. This drop has affected a wide range of species. The Bay-Delta Plan Amendment therefore sets minimum flows during the critical months when salmon are growing and migrating. The minimum is adaptive, anywhere from 30-50% of the unimpaired flow, depending on whether ecological goals are met.
SFPUC argues that in dry years this would mean a 40% reduction in their river supply, far more than rationing can handle. Reserving so much water for the salmon would force SFPUC to look for new and expensive sources of water. (3) They support an alternative plan, dubbed the Healthy Rivers and Landscapes program, that focuses less on water flow and more on improving habitat in other ways.
I spoke with Palo Alto local Peter Drekmeier, Policy Director for the Tuolumne River Trust, about this. He noted that many experts say that river flow and habitat improvements are not interchangeable, and they are doubtful that the proposed plan will restore the salmon populations and the Delta ecosystem. But more than that, he doesn’t believe the “Healthy Rivers” plan is justified to begin with.
Drekmeier disputes the 40% reduction figure, given that SFPUC has a vast amount of reservoir storage, enough for six years of demand. He also references SFPUC’s long history of overstating risks to their ability to serve customers. In this case Drekmeier believes they are both overstating growth in demand and the risk from a change in supply. SFPUC is essentially manufacturing a gap that does not exist, in his view. An overly conservative approach can not only harm the environment, it can lead to unnecessary and expensive projects that would raise water rates across the Bay Area.
How Much Will Demand Grow?
Residential water demand in the Bay Area has steadily decreased despite an increasing population. Among the wholesale customers of SFPUC, water use has decreased 32% since 1986 even though the customer base has grown by 34%. This efficiency is due to stricter indoor plumbing codes and effective outdoor conservation initiatives.
Yet SFPUC asserts that demand will now begin to increase because of a number of factors. It is getting harder to conserve more water, our area is planning for population growth, and climate change will lead to higher water use. As one example, SFPUC Assistant General Manager Steven Ritchie references wholesale customer Alameda County, which depends on the State Water Project for much of its supply. When that water is decreased during drought, Alameda County turns to SFPUC for more water, and SFPUC wants to be able to deliver.
Drekmeier says this is a clear case of exaggeration. For one thing, some of the population growth estimates underlying this graph (39% growth by 2045) are four times what the state’s own Department of Finance predicts. He observes that the SFPUC water planners consistently overestimate demand. In fact, SFPUC’s own financial planners, who have no incentive to overestimate water sales, have produced much more accurate demand forecasts. While these generous demand forecasts may reduce risk for the utility, they can lead to real-world impacts on our bills and the environment.
How Much Will Supply Shrink?
The Bay-Delta Plan Amendment would remove about 40% of SFPUC’s incoming flow during dry years. When SFPUC models a drought that combines both a six-year drought from 1987 to 1992 (the most severe on record) with a short but intense 2-year drought from 1976-1977, they find that we cannot make it through without unachievable levels of rationing (around 50%). If this plan goes into effect, they believe we must implement solutions like direct potable reuse.
Drekmeier believes the design drought SFPUC is using, which is 72% worse than the worst drought on record, is unreasonably conservative. In flood planning, we look at 1-in-100 year floods. But Drekmeier has estimated this to be a 1-in-8000 year drought based on a climate study that SFPUC commissioned. He also disputes the 50% rationing claim. He has analyzed the 6-year drought from 1987 to 1992 and claims that with more appropriate demand numbers than SFPUC used, and more aggressive reservoir management, no rationing would have been needed. If you do incorporate rationing, we could make it through a longer drought. Moreover, in a sufficiently bad drought, the Water Board could well require irrigation districts to sell us some water.
This analysis doesn’t hold water with me (pun intended!), as it is not good practice to empty reservoirs to such an extent as it provides no buffer if the drought continues. The demand adjustments make sense, and there may be some wiggle room in reservoir management. (4) But the larger question is whether the 8.5-year drought being modeled is reasonable. Drekmeier says it is not but I am not so sure.
Climate Unknowns
The impact of climate change on our water supply is not well understood. We know that the warming climate means there will be less snow (and less snowpack) and more rain, with earlier run-off. Drekmeier asserts that technically this will benefit SFPUC since the earlier periods of high flow would shift runoff to when SFPUC water entitlements are greater.
But drought does not occur only because of lack of snowpack or lack of precipitation more generally. Drought can occur because excess heat causes more evaporation from the landscape and reservoirs, which then increases demand for water. A recent study found that “During the 2020-2022 drought, evaporation accounted for 61% of the drought’s severity, while reduced precipitation only accounted for only 39%.” Their models show that a drought that might happen only once in every 1000 years today might become a 1-in-60 year event by 2050 and a 1-in-6 year event by the end of the century.
So is the drought SFPUC is modeling unreasonable? I don’t think so. We have seen in the past few years that we cannot predict severe wildfire, floods, and heat waves by looking backwards. We are in uncharted territory. When Ritchie asked a panel of ten climate experts whether the 8.5-year drought they were protecting against was reasonable, seven of the ten thought it was, despite its historic implausibility. I think it’s appropriate for SFPUC to be conservative when contemplating future droughts, and to make adjustments as our understanding of climate impacts evolves.
How Much Water is Enough for the Fish?
There are disputes about how much water SFPUC will have and how much water people will need. But how much water do the salmon need in order to thrive? There are disagreements about this too. The plan the water districts are promoting, optimistically called the Healthy Rivers and Landscapes plan, would produce much less water for the fish in dry years than the Bay-Delta Plan Amendment, focusing more on other ways of improving habitat. For example, it encourages efforts to remove predators, enhance spawning grounds with more gravel, and put in bypasses to help salmon move around.
Those are good changes, but some experts claim that substantially increased flow is essential for restoring the salmon population. That is why the Bay-Delta Plan Amendment requires a minimum flow during the critical period of February through June. The higher flow would inundate floodplains that boost salmon survival. They allow young salmon to develop in a safe place, out of the fast-moving cold channel where most of their predators reside. If young salmon are not able to grow strong in these protected areas, they are at greater risk on their way to the ocean. The higher river flows also help adult salmon navigate the river. They struggle to move when flow is too low.
The plan promoted by the water districts provides for only limited pushes of water, a “pulse flow” from April 16 – May 31 to help salmon migrate, and a short floodplain pulse that would sustain just 80 acres of habitat for young salmon. Furthermore, the plan does not increase minimum water flows in dry years if biological goals are not met.
“Repeatedly switching between 15% and 70% flow is not a good way to manage a river if you have a salmon run that supports a whole ecosystem.”
Peter Drekmeier, Policy Director for the Tuolumne River Trust
I would like to see the SFPUC move away from what seems to be a “reliability at all cost” approach to a more deliberate one that is transparent about the tradeoffs we are facing, both with regard to water rates and environmental impact. In addition, it would be great if we could find a deal with the upstream agricultural irrigation districts that have senior water rights. SFPUC has engaged in negotiations with the irrigation districts on the Tuolumne, which have more senior water rights. Negotiations to date have not been easy. In 2012 the agricultural areas rejected an offer that would have paid them 100 times more than the price they pay for water. Local communities were unhappy that their water would go to people in the Bay Area. Steven Ritchey, Assistant General Manager for SFPUC recalled: “Within six months of the public hearing, the general manager and chief counsel we had been working with were both gone. That was a very clear experience.” Nevertheless he is hopeful that they might still reach an agreement that would benefit both regions.
Finally, I hope that the state will do better than the anemic “Healthy Rivers” plan espoused by the irrigation districts. We have waited so long for a plan to help the Delta. It would be a shame to fall short at this stage. If we are not able to value a natural environment as remarkable and productive as the Bay Delta has been, then what does that mean for us more generally?
I will talk more about water rates and Palo Alto’s own water planning process in the coming weeks. In the meantime, I look forward to your questions and comments about how the SFPUC and other water districts are negotiating issues of supply, demand, and reliability in a growing, warming, and drying California.
Notes and References
1. The wholesale customers of SFPUC water are shown below. SFPUC also directly serves retail customers in San Francisco, Redwood City, Daly City, and more.
2. Hetch Hetchy water still undergoes some processing, including disinfection with chlorine. In addition, SFPUC mixes that water with about 15% water from local reservoirs, which undergoes more processing.
3. Yes, recycled water is expensive! Raw sewage is cheap, but the treatment process is very expensive. Reverse osmosis, for example, uses a lot of energy.
4. Drekmeier notes that SFPUC’s water rights are so good that even in “normal” dry years we have more water than we need. During the six-year drought from 1987 to 1992, we were able to store away water in two of those years.
5. You can find hearings about the implementation of the Bay Delta plan at the State Water Resources Control Board.
Current Climate Data
Global impacts (Year End 2024), US impacts (Year End 2024), CO2 metric, NOAA climate dashboard
2024 set several records, including warmest year on record since 1850, and there are no signs of this slowing down. In fact, scientists are concerned that they do not understand the pace of change we are seeing. Take a look at the “impacts” links above for a closer look at what is happening to our planet.
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