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Do You Know Where Your Water’s Been?
Lori Pottinger October 27, 2015

The twin challenges of water quality and quantity are leading to creative thinking and interesting solutions in California and across the west. David Sedlak is helping find innovations in water re-use and treatment in his various professional endeavors. He’s a professor of environmental engineering at UC Berkeley, co-director of the Berkeley Water Center, deputy director of the ReNUWIt program, and a member of the PPIC Water Policy Center research network. We talked to him about the state’s water quality challenges and efforts to create more sustainable water systems.

PPIC: What might a lay person find surprising about water quality in California?

David Sedlak: Most people don’t realize the extent to which to we use water over and over again in the state. The water that’s flowing down a river might have recently been in a farm field or flowed over a city’s streets. Water picks up different contaminants depending on where it’s been. If it was used on a farm it might pick up salts or pesticides; if it came from a sewage treatment plant it might pick up pathogenic microbes or chemicals used in homes; if it ran off city streets it could pick up metals or oils. It’s still 99.99% water, but that .01% can make all the difference in the world—it’s this tiny amount of contamination arising from human activities that could make it unsafe to drink, spread disease, or kill fish.

PPIC: How does the quality of our drinking water supply constrain California?

DS: During the 20th century we created a system for moving extremely clean mountain snowmelt into our cities. The drought, population growth, and competition among water users have complicated things. New technologies enable us to make use of water resources that were previously thought to be unsuitable for drinking. These advances have allowed us to make major progress in reinventing the water system our grandparents built by making use of diverse sources they weren’t able to tap.

Nonetheless, these impaired water sources are more expensive to treat and deliver than the pristine sources that we relied upon in the past. We have the means to remove many of those contaminants, but it can be expensive. The cost of treatment depends on the source of water. We can turn seawater into drinking water, but that’s probably the most expensive source available to us. We can turn sewage treatment plant effluent into drinkable water for about half the price of desalination. We could also harvest the rain that falls in cities, but we don’t have a lot of experience in scaling it up. Los Angeles is starting to make progress on urban rainwater harvesting but this approach is still in its infancy, and it will require time to figure out if this is a good investment. Our Mediterranean climate means that many of our cities get the bulk of their annual rainfall in a few big storms. So if we’re serious about capturing rainwater we might have to build some pretty large structures, which would make the process expensive.

PPIC: What do you think needs to fundamentally change in our relation to water in the urban environment?

DS: Ultimately, members of public, community leaders and elected officials all need to step up and take responsibility for our water supply. We can’t leave it to the utilities to figure out alone. I’m very optimistic—we’ve already seen great progress. The water suppliers are starting to recognize that the public has to be part of the discussion. We’re definitely seeing positive behavioral changes now that the public is paying attention to the fragility of the water supply. It seems we’re becoming more willing to make sacrifices to pay for a modern water system that we want to leave to our grandchildren’s generation and those that follow them.

Learn More
Visit the PPIC Water Policy Center’s water supply resource page
Read our factsheet California’s Water Quality Challenges

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