Droughtsville, California, is in trouble.

Its water supply is endangered as multiple crises intensify: worsening droughts, competition for scarce supplies, sea level rise, groundwater contamination, earthquakes, wildfires and extreme weather. All of these factors, and more, threaten Droughtville’s ability to provide clean water to its residents.

The city is fictional, but the threats are not.

A typical city in California faces multiple stressors that put drinking water supplies at risk — drought just happens to be the focus now. Huge volumes of water are transported hundreds of miles to Southern California and Bay Area cities via aqueducts. Other municipal water is stored underground in aquifers, potentially susceptible to contaminants and seawater invasion. And the intricate network of treatment plants and pipelines that carry water to people’s faucets is vulnerable to an array of natural and human-made threats.

CalMatters delved into the details of what scientists and planners have determined could jeopardize the water supply of a typical California city — and some potential solutions.

Earthquakes

Credit: Illustration by Cecily Mireles

While scientists are still researching connections between water, climate change and seismic activity, the threat of earthquakes looms large in California. Damage to water sources and systems can reverberate from hundreds of miles away.

All it would take to inflict widespread damage on water systems is an earthquake of 6.0 magnitude or greater centered in the “right” place. Quakes of that magnitude can crack pipes, damage storage systems or release natural gas or oil into aquifers.

Southern California’s reliance on water imported from outside the region puts its supplies at great risk from quakes. Parts of the Los Angeles Aqueduct, the California Aqueduct and the Colorado River Aqueduct — all of which bring water to Los Angeles — traverse the San Andreas Fault. A 7.8-magnitude quake on the fault would put the three aqueducts out of commission, cutting off some of the city’s water deliveries for as long as two years, according to a scenario evaluated by the city. Repairs could stretch out years. Because these aqueducts supply most of Southern California’s water, officials would have little choice but to impose mandatory water reductions.

Other examples:

© 2021 CalMatters

Wildfires

Credit: Illustration by Cecily Mireles

Wildfires can directly harm water supplies, such as burning down storage structures and melting pipes, but also indirectly harm by sending up clouds of smoke and loosening soil, which washes debris and ash into watersheds. Wildfires even in remote parts of the state can pollute water that ends up in city taps.

  • Water samples collected from drinking water in Santa Rosa after the 2017 Tubbs and 2018 Camp Fires tested positive for benzene, a cancer-causing chemical. State water officials said the contamination most likely came from overheated pipe materials, as well as smoke and combustion byproducts.
  • Wildfires can lead to ash and sediment running off into water sources when it rains. The Mokelumne watershed, in particular, is at risk of this.
  • The 2015 Butte Fire burned a 12,000-acre section of a watershed, then winter storms carried debris from the fire into the river and reservoir. The US Geological Survey estimates likelihoods and magnitudes of such post-fire debris flows.
  • Water systems also depend on power to maintain operations, making them vulnerable to public safety power shutoffs and unplanned outages.

And then there are megafires: Super hot and dry conditions combine to create a complex of super-intense fires. In 2020 California experienced megafires that burned three Sierra Nevada watersheds important to California’s water supply. Runoff, erosion and sediment could occur near areas with moderate and high soil burn severity, although effects may not be seen for several years.

© 2021 CalMatters

Storms

Credit: Illustration by Cecily Mireles

Large storms can overwhelm flood control channels and damage pipelines and other infrastructure. Rivers carry debris and sediment to reservoirs, where they can clog filtration systems, especially in burned areas. This was a concern in Fresno after the 2020 Creek Fire.

Storm surges and large volumes of rainfall can overwhelm unprepared city systems. An ARkStorm scenario, developed by the US Geological Survey, envisions a series of hurricane-level atmospheric rivers from the tropical Pacific slamming into the US West Coast over several weeks. Patterned after the Great Flood of 1861-1862, which put the Central Valley under as much as 15 feet of water, the ARkStorm scenario could flood thousands of square miles of urban and agricultural land, costing some $725 billion.

© 2021 CalMatters

Chemical contaminants

Credit: Illustration by Cecily Mireles

A variety of industrial chemicals contaminate drinking water supplies. “Forever chemicals” have polluted well water throughout California, most often near airports, military bases and landfills. These perfluorinated chemicals are linked to kidney cancer and other serious health conditions in people drinking contaminated water.

Other examples of industrial contaminants found in water supplies are perchlorate from defense contractors and flame retardants from building materials.

In addition, copper, arsenic and other elements naturally found in soil can leach into groundwater and plumbing systems. From 2015 through 2018, 4,460 active drinking water sources were reported to contain arsenic. Lead, which can alter children’s brain function and trigger learning disabilities, mostly seeps into water from home pipes and faucets. EdSource created an interactive map for checking the lead levels in schools’ drinking water.

© 2021 CalMatters

Urban runoff

Credit: Illustration by Cecily Mireles

After rainstorms — particularly the “first flush” of California’s wet season — pollutants wash into streams and other surface waters. Stormwater and other urban runoff can deposit trash, oil, pesticides, fertilizers, sewage and sediment into streams that provide drinking water.

The largest source of runoff in California is its more than 50,000 miles of highways. Caltrans is required by the state Water Resources Control Board to control stormwater runoff to the “maximum extent practicable.” As a result, Caltrans monitors runoff and takes steps to prevent contaminants from flowing off roads during rainstorms, such as preventing erosion and removing debris.

The state water board also regulates construction sites and industries through permits that require companies to develop plans to prevent runoff.

Nevertheless, anything that is dumped into a street or spread onto a lawn or garden can wind up in lakes, rivers and streams.

Credit: Caltrans © 2021 CalMatters

Sewage spills

Credit: Illustration by Cecily Mireles

Spills from sewage treatment plants and sewer lines contaminate surface waters with viruses, bacteria and other contaminants from wastewater that is flushed down drains and toilets.

For instance, flooding at the Hyperion Water Reclamation Plant in El Segundo in the summer of 2021 spilled 17 million gallons of sewage into Santa Monica Bay, contaminating beaches. But the spill also triggered water supply problems because local officials had to divert clean drinking water to uses, such as parks and golf courses, that were normally served by the recycled water treated at the Hyperion plant.

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