SAN FRANCISCO (KRON) — With the state’s water resources running dry due to California’s unabating drought, a new study by the U.S. Geological Survey says that about one-fifth of the raw groundwater contains high levels of contaminants.
The study looked at data from about 11,000 public-water-supply wells in the state that supply 99 percent of Californians using public water systems.
U.S. Geological Survey Groundwater Assessment chief Kenneth Belitz said Wednesday the study found several million people that rely on public water systems whose raw supplies have potentially unsafe levels of arsenic, uranium and manganese.
In the North Bay, 22% of the regions groundwater has high concentrations of those elements, compared to 19% statewide. Traces of those elements was found in 9% of the groundwater on the Peninsula, South Bay and parts of Alameda County.
Livermore’s groundwater resource was found to have 19% levels of high concentration elements, with nitrate accounting for 27% of the contaminants found in that resource. The findings underscore that it can take decades for contamination to show up in public water systems, Belitz said.
In the Central Valley’s farmlands, several rural schools in Tulare County, which was found to have 73% of high concentration elements, has put drinking fountains off limits to pupils.
“You could call it a headache,” said Terri Lancaster, principal and superintendent at Waukena Joint Union Elementary School, a district surrounded by rich farmland.
The state’s drought is making groundwater resources much more relied upon, meaning “the quality of that groundwater becomes increasingly important,” Belitz said.
For California’s water managers, “the challenge right now, of course, is the drought,” said John Borkovich, an official with the state Water Resources Control Board who helps oversee the groundwater monitoring program. “Being able to sustain delivery of a safe water supply is the No. 1 concern, of course. But water quality is hand in hand with water quantity.”
The survey also gives public-policy-makers the first sweeping look at the extent to which agricultural irrigation, industrial pollutants and other uses of groundwater are adding to problems for underground water reserves.
Belitz says that there is a regulatory function in place to help prevent contaminated groundwater from reaching customers. When traces of contaminants are found in groundwater, State Water Resources Control Board is required to dilute the water and bring contaminants down to acceptable levels, or drill a new well.
Public water systems with a well that consistently shows unhealthy levels of contaminants are required to notify customers and fix the problem, said Kurt Souza of the State Water Resources Control Board’s division of drinking water.
The study looked for contaminants present in raw water supplies above legally set thresholds.
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According to the USGS, groundwater will normally look clear and clean because the ground naturally filters out particulate matter. But, natural and human-induced chemicals can be found in groundwater. As groundwater flows through the ground, metals such as iron and manganese are dissolved and may later be found in high concentrations in the water.
Contaminants can be natural or human-induced
Contaminants can be human-induced, as from leaking fuel tanks or toxic chemical spills. Pesticides and fertilizers applied to lawns and crops can accumulate and migrate to the water table. Leakage from septic tanks and/or waste-disposal sites also can introduce bacteria to the water, and pesticides and fertilizers that seep into farmed soil can eventually end up in water drawn from a well. Or, a well might have been placed in land that was once used for something like a garbage or chemical dump site. In any case, if you use your own well to supply drinking water to your home, it is wise to have your well water tested for contaminates.
The Associated Press Contributed to this report.
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