Is Southern California prepared to avoid a 'Day Zero' water crisis?

Over the last century, Southern California has grown and thrived by accessing water from faraway sources including the Colorado River, the Eastern Sierra’s streams and the Sacramento-San Joaquin River Delta. Massive aqueducts transport water through deserts, farmlands and mountains to sustain 19 million people across six counties.

But these traditional sources of water are projected to become less reliable as global warming shrinks the West’s mountain snowpack and unleashes more intense droughts.

Los Angeles knows how to weather a crisis — or two or three. Angelenos are tapping into that resilience, striving to build a city for everyone.

With supplies at risk, Southern California’s cities and suburbs face major challenges in planning for the future. Decades from now, how might we get our water supply? And what ideas are leaders and managers of water agencies considering to ease risks of shortages — or even a scenario of a “Day Zero” crisis, in which we approach a point of running out?

California naturally undergoes dramatic cycles between wet and dry conditions. But research indicates that supplies from major water sources such as the Colorado River have been shrinking and are likely to decrease further on average as temperatures rise. According to state projections, the average amount of water delivered from the Delta to Southern California could decrease by between 13% and 23% within two decades unless measures are taken to ameliorate those declines.

The overarching goal, as managers of water agencies describe it, is to plan for a warming climate with longer droughts and more extreme storm runoff patterns. Those who lead the region’s large water agencies say they are seeking to line up a diversified mix of sources by recycling wastewater, capturing stormwater, restoring watersheds, possibly building new water-transport infrastructure, and even tapping the Pacific Ocean. They want to be well-prepared for a crisis, and to invest in projects that, although costly, somehow won’t make water too expensive for the public.

“We need to find a way to be sustainable at the same time that water remains affordable,” said Adán Ortega Jr., board chair of the Metropolitan Water District of Southern California.

Ortega said the various investments the district is now considering should lay the foundation for a “new and endless river.’’

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The water district, for example, is embarking on plans to build a giant state-of-the-art facility in Carson to recycle wastewater. Pure Water Southern California is projected to cost $8 billion and produce up to 150 million gallons of drinking water daily by purifying treated effluent that is now discharged into the ocean. That’s enough to supply the needs of about half a million homes.

It would be a major step in shifting the metropolitan area toward a greater reliance on local water supplies intended to better withstand hotter, drier times. The cities of Los Angeles and San Diego are planning other recycling projects.

MWD’s plans for the Carson facility call for initially using the recycled water for outdoor irrigation and to recharge groundwater basins, where it would be stored and then pumped out for use. Under state rules adopted in 2023, the purified water that’s generated could eventually be pumped directly into pipes to supply drinking water.

“You can see that coming,” Ortega said. “It’s going to take a lot of science and verification to make sure that that water is safe and that the public trusts it at the scale that we’re talking about. But if we check all those boxes and give ourselves the time to do it, a hundred years from now, people will take it for granted as a source of water.”

The need to innovate is evidenced by the recent history of the L.A. area and other cities around the world, including Sao Paulo, Tehran, Barcelona, Chennai, Mexico City and Cape Town, South Africa.

In 2018, the government in Cape Town warned the city of more than 4 million people that “Day Zero” was approaching. An extreme drought worsened by climate change had sent reservoirs dropping to perilously low levels, prompting severe water restrictions.

The Southwest is another region where something like a Day Zero scenario could occur in the future.

Southern California’s most severe crisis to date arose during the state’s 2020-22 drought. A severe shortage of supplies from Northern California in 2022 prompted the Metropolitan Water District to order emergency water restrictions for nearly 7 million people in areas that rely heavily on deliveries from the State Water Project.

One of the hard-hit areas was Ventura County, where strict rules barred residents from watering their yards more than one day a week.

“People were understandably very upset in terms of the impact on their gardens and landscaping,” said Kristine McCaffrey, general manager of Calleguas Municipal Water District, which delivers water for about 650,000 people in Ventura County. “That’s why we’re working very hard to make sure that we don’t ever encounter this kind of situation again.”

The water restrictions were lifted in 2023 when a series of atmospheric river storms brought relief to the state.

Seeking to prevent a recurrence of those shortages, the MWD is re-engineering pipelines and adding new pump stations to better move water where needed during a drought. The district also plans to expand a facility near Lancaster where water is banked underground in the aquifer and can be pumped and delivered in dry times.

McCaffrey’s agency is one of several that are also considering seawater desalination. It is awaiting studies of a company’s proposal to anchor a “farm” of 40-foot-long devices to the ocean floor several miles off the coast of Malibu, which would pump purified freshwater to shore in a pipeline.

In the next several years, managers of water agencies will study the costs of this and other projects to determine which mix of options will deliver greater reliability while keeping costs in check and preventing steep rate hikes. These decisions involve not only weighing the costs of a project on its own, but also analyzing how it will fare under different scenarios, and in combination with the region’s existing supplies.

One key goal is having plenty of backup supplies, Ortega said.

Lessons from Cape Town

Cape Town was particularly vulnerable to the region’s worst drought in centuries because of its heavy reliance on rainwater stored in reservoirs for 98% of its supply, according to Michael Webster, who was the city’s executive director for water and sanitation from 2018 to 2023, and who now works for the World Bank.

Ultimately, the city managed to avert disaster. Residents were ordered to cut water usage, and an aggressive conservation campaign enabled the city to stretch its scarce supply until the return of rainfall finally brought relief.

“I think the city did well in using the crisis to invest in a more resilient future,” Webster said. “The key strategy in overcoming it is to build in some diversification of supply — to groundwater, desalinated water and reused wastewater — in addition to reducing demand.”

Cape Town’s leaders have since invested in developing infrastructure to pump groundwater, and in cutting down invasive water-sapping trees to boost reservoirs. While keeping water consumption in check, Webster said, the city also plans to build a desalination plant and a wastewater recycling facility.

He said one lesson is to examine future scenarios and rigorously plan around the question of, “What is needed now to avoid a crisis in 10, 20, 30 years’ time?”

“In the middle of the Cape Town crisis, you couldn’t build a desal plant. There’s not enough time,” Webster said.

“That is, I think, the Cape Town lesson,” he said. “That a crisis is coming, and it’s not a question of if, it’s a question of when.”

The MWD’s 38-member board of directors recently adopted a blueprint for adapting to climate change. The strategy, part of an effort called the Climate Adaptation Master Plan for Water, assesses potential risks, sets goals for lining up additional water supplies, and outlines criteria for evaluating options.

The plan considers various scenarios, such as potential decreases in imported water supplies because of global warming and possible trends in population growth and water usage.

“We can plan within this range of possible needs in the future, and then we can make incremental decisions based on real-world conditions,” said Liz Crosson, MWD’s chief sustainability, resilience and innovation officer. “That really helps prevent us from overbuilding, but it also helps us be super prepared.”

The plan sets targets including identifying 300,000 acre-feet of additional water supplies per year by 2035 — an amount equivalent to nearly 9% of the region’s average water use over the past decade.

A search for new sources

There are ongoing public debates over how much to invest in local water sources versus how much to spend on infrastructure to store and transport water from other parts of the state.

MWD board members will consider whether to invest in the state’s plan to build Sites Reservoir northwest of Sacramento, and in the Newsom administration’s proposal to build the Delta Conveyance Project (DCP), a water tunnel beneath the Delta with an estimated price tag of $20.1 billion.

The proposed Delta tunnel has garnered support from managers of Southern California water agencies, who say it promises to improve the reliability of water deliveries from the State Water Project.

Craig Miller, general manager of Western Municipal Water District, says the project “is the backbone of California’s economy” and that investing in modernizing it “ensures we can adapt to a changing climate, protect jobs and the environment, preserve lifestyles, and keep California economically competitive.”

Gov. Gavin Newsom has said that the project is crucial to the state’s future, and that California‘s existing water system “was designed for a world that no longer exists.”

The project is strongly opposed, however, by environmental advocates and the Delta’s political leaders, who say building the 45-mile tunnel would harm the region’s farmlands and communities, and threaten the estuary’s ecosystem and fish species. They’ve called for different types of water solutions, including rebuilding aging levees in the Delta to protect freshwater supplies.

Vowing to fight the project, state Sen. Christopher Cabaldon (D-West Sacramento) has pointed to the high costs, saying “the real threat here is to the pocketbooks, the monthly water bills, of residents throughout Southern California.”

Those who are urging the MWD’s leaders to reject the tunnel plan include Bruce Reznik, executive director of the group Los Angeles Waterkeeper, who says the project would undermine ongoing efforts to prioritize local options.

“The fundamental problem is, we are too reliant on sources of water from far-flung places that are not as reliable as they used to be,” Reznik said. “We are not water-resilient, we are not water-sustainable. And so things absolutely have to change.”

Instead of supporting the tunnel, he said, the region should redouble efforts on conservation and more efficient water use, while investing in recycling wastewater, capturing stormwater and cleaning up contaminated groundwater. He also advocates nature-based “green infrastructure” solutions such as parks and wetlands that naturally filter water, recharge groundwater and bring benefits such as reducing flood risks and cooling the urban landscape.

Supporters of nature-based solutions have called for larger efforts to restore parts of the Los Angeles River’s watershed by removing concrete and asphalt where feasible, reactivating portions of the floodplains that will capture runoff and allow water to percolate underground to replenish the aquifer. These types of projects, intended to restore water’s natural paths in cities, have been called “urban acupuncture” or “sponge cities.”

Los Angeles and nearby cities were built on the famous words that William Mulholland, L.A.’s chief water engineer, declared in 1913 as water from the Owens Valley began flowing into a reservoir: “There it is. Take it.”

Over the last century, Southern California’s cities have wielded their financial and political clout to secure water supplies. In the 1986 book “Cadillac Desert: The American West and Its Disappearing Water,” author Marc Reisner famously observed: “In the West, it is said, water flows uphill toward money. And it literally does, as it leaps three thousand feet across the Tehachapi Mountains in gigantic siphons to slake the thirst of Los Angeles.”

But now, Reznik said, the current realities call for a different sort of water ethic based on becoming resilient through better use of the area’s resources.

“We need to focus local,” Reznik said. “Let’s prioritize our investments where they’re going to do the most good, and that’s in resilient local water supplies.”

In addition to weighing costs and benefits in dollars, Southern California’s water policymakers are expected to consider the environmental effects of different options, which are often more complicated to assess. For example, diversions of water to supply farms and cities have contributed to the ecological deterioration of the Sacramento-San Joaquin River Delta, where native fish species have suffered major declines.

Supporters of reducing reliance on imported sources say pumping less water would bring environmental benefits for overtaxed ecosystems. And because pumping water — including pushing supplies in pipelines up and over the Tehachapi Mountains — is energy intensive, conservation and other local approaches that require less pumping would also help save energy and reduce emissions of greenhouse gases.

More water-saving potential

Researchers at the Pacific Institute, a water think tank in Oakland, have examined the potential for California to use water more efficiently by making improvements such as fixing leaks in pipes, replacing inefficient washing machines and toilets, and replacing thirsty lawns with plants suited to the state’s Mediterranean climate.

In a 2022 report, they found that a set of standard practices and technologies could dramatically improve efficiency and reduce total urban use by 30% or more. The researchers found the biggest water-saving potential in Southern California, where lawns and other water-guzzling landscaping consume a large share of supplies.

As part of their climate strategy, MWD’s managers plan to analyze the water-savings that could be achieved through additional conservation and efficiency improvements. These potential savings, both inside and outside homes and businesses, far surpass the targets in the MWD’s climate adaptation strategy, said Heather Cooley, the Pacific Institute’s chief research and program officer.

She and her colleagues estimated that the South Coast region, which includes MWD’s territory, could save between 1.1 million and 1.7 million acre-feet of water per year by making various efficiency improvements indoors and outdoors. They also calculated that by scaling up efforts to capture stormwater, the region could secure as much as 860,000 acre-feet in a year of medium precipitation.

For comparison, the total water consumption in MWD’s six-county service area has averaged nearly 3.4 million acre-feet per year over the last decade.

“This means that water conservation and efficiency must be at the core of the region’s water resilience efforts,” Cooley said. “Water conservation and efficiency are not free — they require consistent investment. However, they are the cheapest, fastest way to meet our water needs.”

As one example, Southern California is expected to save a substantial amount of water in the coming years through a measure state legislators passed in 2023 outlawing the use of drinking water for “nonfunctional” turf — the sort of grass that fills spaces along roads and sidewalks, in front of businesses, and around parking lots.

In the past, conservation efforts have outpaced many urban water agencies’ forecasts. Between 1990 and 2023, Southern Californians reduced per-person water use by 45%, from 209 gallons per day to 114 gallons per day.

Additional water savings are expected as utilities work toward long-term conservation goals that were adopted by state regulators last year.

Cooley said investments will also be important to develop new local supplies through water recycling, stormwater capture and other types of projects.

“I think it’s critically important the region move away from its reliance on imported water,” Cooley said. “There is a lot more they can do, and will have to do, as those imported supplies become even more variable and uncertain.”

Since 2015, roughly half of Southern California’s water supplies in MWD’s territory have come from imported sources, including Northern California, the Colorado River and the Eastern Sierra, and the remainder has come from local sources including groundwater and recycled water.

The amount of imported supplies available in an average year is expected to decrease as global warming, driven largely by the burning of fossil fuels, continues to push temperatures higher.

Anticipating uncertainty

The MWD’s climate plan says a key goal is planning for “deep uncertainty.”

“We need to be prepared for something that has never been experienced in the period of record, and potentially for several centuries or even millennia,” said John Matthews, executive director and co-founder of the Alliance for Global Water Adaptation.

He said that means examining vulnerabilities in the current water system, and how it might break down. It also means preparing for droughts more intense than any seen in our lifetimes, as well as bigger and more extreme floods.

The recent history of water in the American West reveals significant risks. Already, scientists have found that the last 25 years have probably been the driest quarter-century in western North America in 1,200 years, and that climate change is a major contributor.

The flow of the Colorado River has diminished about 20% this century, and scientists attribute about half that decline to higher temperatures.

The river’s largest reservoirs, Lake Mead and Lake Powell, are now about two-thirds empty, and representatives of California and other states are under pressure to negotiate a deal to take less water from the river.

Adapting to these and other unprecedented shifts will require major investments geared toward diversifying water sources, Matthews said. “This is going to be an expensive, multi-decade and complicated process, and it’s going to require really big changes.”

He said it’s crucial to remember that Southern California is so highly developed and rich today thanks to the region’s big investments in water in the early 20th century, including the construction of the Los Angeles Aqueduct and the Colorado River Aqueduct.

“They built the state economy around one climate, and now they are moving into a very different kind of climate, and they need to go back and invest into the climate that they’re headed towards,” Matthews said.

Although federal and state funds in recent years have helped to partially support some water infrastructure projects, such as initial work on the Carson wastewater recycling project, the bulk of the costs are expected to be borne by local agencies and ratepayers.

For now, Southern California’s water supplies are in good shape. Following the last three wet winters, the Metropolitan Water District has a record amount of water — 3.8 million acre-feet — banked in reservoirs and underground storage areas.

Nonetheless, Ortega said, the agency is focusing on expanding its water-storing capacity, especially south of the Delta.

Also important, he said, are MWD’s efforts to work with agricultural water agencies. For example, the MWD has ongoing programs in which it pays farmers who temporarily leave some of their fields dry to help free up water.

He said preparing for all scenarios means not just being ready for the effects of climate change but also for earthquakes and potential infrastructure breakdowns — requiring investments in maintaining as well as upgrading the extensive systems that transport water.

He said the struggles of Mexico City, where water service has recently become intermittent for millions of people, is a scenario that Southern California must plan carefully to avoid.

“We could have that here if we reduce our commitment to maintaining our infrastructure and building the supplies that we need for the future. It’s not as far away as people think, if we don’t value what we have,” Ortega said.

“We can’t afford to fall behind, or we will have a Day Zero — or many Day Zeros.”