But some communities get all their water from contaminated aquifers and can’t afford to treat it properly, which can threaten public health, according to a report by the State Water Resources Control Board.
In California, the state is only just starting to address the primary source of this contaminant in the San Joaquin Valley’s groundwater: the Valley’s 5 million acres of farmland.
The San Joaquin Valley is particularly hard hit by nitrate: 63 percent of the state’s public water systems that report violations of health standards for the contaminant in 2015 were in the Valley.
"Nitrate is the most critical, the most immediate contaminant in the San Joaquin Valley," Harter says.
State regulators are in the second year of a program to help keep agricultural nitrate out of groundwater in the Central Valley.
Other major human sources of groundwater contaminants in the San Joaquin Valley include pesticides that are banned but still linger in the environment.
In 2015, 60 percent of the state’s public water systems reporting health violations for arsenic were in the Valley, and Madera County drinking water has the highest levels of arsenic statewide.
He only found out when he started working as policy director at the Community Water Center, which advocates for safe drinking water in the San Joaquin Valley, and he realized his town was one that had found the contaminant in its drinking water.
Nelson says drinking water advocates estimate a capital funding need of up to a billion dollars, which would need to be addressed in a future water bond.
"We don’t know how air pollution impacts the body differently from water pollution or how multiple effects work out," Capitman says.