H2OC: How Water Works in Orange County

We plunge into a fascinating and complex story about water in O.C. involving large-scale innovation, world-class systems, and more.

How does water work in Orange County? In seeking the answer to this seemingly straightforward question, we were plunged into a fascinating and complex story involving large-scale innovation, world-class systems, a sprawling network of organizations working together toward a common goal, and an ancient and invisible resource hidden beneath our feet.

The story of water in Orange County is really a tale of two counties. More than three quarters of the county’s 3.1 million residents live in north and central O.C. This region, which includes parts of Newport Coast and Irvine as well as everything from there to the county’s northern border, sits atop a series of aquifers known as the Orange County Groundwater Basin. 

The vast underground resource was formed millions of years ago, as mountains eroded and sediments filled the deep valley. One of the largest such basins in Southern California, it contains about half a million acre-feet (169 billion gallons) of usable water and covers 270 square miles. Think of it as a huge subterranean bank safeguarding one of the region’s most precious resources.

By the 1930s, the basin was providing 145,000 acre-feet of water to the county, most of it used for agriculture. But the groundwater levels had been dropping without replenishment. The “bank account” would eventually be overdrawn. In 1933, the California Legislature created the Orange County Water District (OCWD) to protect, monitor, and conserve the groundwater supply. 

Today, the district continues to manage the basin, providing 19 local water retailers with a reliable and low-cost supply of quality drinking water, which the retailers deliver to customers in their area. The basin provides 77 percent of the drinking water supply to residents of north and central O.C. The remaining 23 percent is provided by imported water. The Metropolitan Water District of Southern California (MWD) delivers this water from the Colorado River as well as Northern California.

For the remaining 600,000 O.C. residents living south of Orange County Water District’s coverage area, the story is quite different. The eight retail water agencies in South O.C. rely almost entirely on imported water, which costs about twice as much as local groundwater. Imported water is also less reliable, since the supply is vulnerable to earthquakes, which can damage water lines, and drought. The West is now in its 23rd year of drought—the driest period in 1,200 years.

In South O.C., the conversation revolves around water conservation as well as finding new and innovative ways of increasing the local water supply through processes such as stormwater capture, water reuse, and desalination. 

“We want to reduce the use of imported water,” says MWD general manager and Fullerton resident Adel Hagekhalil. “The future for (our group) is not just as an importer of water but a provider of water. We want to be a partner in supporting local communities’ access to diversified sources of water. Storage is going to be key for us. When we have water coming in short periods of time, we need to figure out how to capture that and store it to get through periods of drought. At the end of the day, we have to make sure that when you turn on the faucet, you have water. We need to provide resilient water supplies for everyone, with no one left behind.”


Aquifer: an underground area of porous rock or sediment saturated with groundwater

Desalination: the process of removing salt from seawater to make it suitable for drinking and irrigation

Direct potable reuse: the injection of recycled water directly into the potable water supply

Indirect potable reuse: the injection of recycled water into a water supply reservoir or aquifer

Potable: safe for drinking

Recycled water: water which is reclaimed, treated, and reused

Urban runoff: water from rain, landscape irrigation, and car washing that drains from roofs, driveways, sidewalks, and other surfaces, doesn’t soak into the ground, and typically contains pollutants

Wastewater: water that has been previously used by a municipality, industry, or agriculture and has suffered a loss of quality as a result

The Fuss about PFAS

You may have heard the term PFAS—perfluroalkyl and polyfluoroalkyl substances. But what are they, and why did they cause 59 wells in Orange County to get shut down?

WHAT: PFAS are a group of manufactured chemicals used in everyday products such as water-resistant clothing, nonstick cookware, and cleaning products. They are found everywhere, nearly indestructible, and have been used for decades. Recently they have been linked to health risks.

PROBLEM: In 2019, the state’s regulations on PFAS changed. Of the more than 200 wells in north and central O.C., 59 were found to contain a higher amount of PFAS than was now allowable.

SOLUTION: The retail water agencies that owned those wells decided to proactively shut them down, the economic impact of which was about $59 million in additional costs. OCWD decided to cover the full cost of designing and rebuilding those wells with new treatment technology that would filter out the PFAS, as well as half the operation and maintenance costs.

OUTCOME: In a little more than two years, a third of the affected wells were back in operation. The remaining wells are set to be completed by the end of this year. To offset the related costs, OCWD and 10 of O.C.’s public water agencies filed a joint lawsuit against a handful of companies they claim are responsible for the manufacture and sale of PFAS and thus the contamination of groundwater.

Read More from our February 2023 H2OC Issue: