Contaminated groundwater located at shallow depths in southern California could migrate to deeper groundwater wells, where most of the area's drinking water reserves are located, according to a new study jointly conducted by the U.S. Geological Survey (USGS) and the Water Replenishment District of Southern California (WRD).
The research focused on water from the Central Groundwater Basin, which is among the intensively used groundwater basins in the area. Earlier studies by the U.S. Environmental Protection Agency and the WRD revealed similar findings, suggesting that shallow groundwater contamination could potentially threaten drinking water reserves, the USGS said in a statement.
Groundwater is used to provide drinking water to consumers, but before reaching them it gets treated in water treatment facilities. The study did not look into the quality of treated contaminated groundwater and did not reveal whether any level of contamination could still be detected in the water delivered to consumers. In southern California, about 2 million people get 60 percent of their drinking water from deep aquifers in the examined area.
Results from the study could help local authorities to anticipate possible contamination migration and plan cleanup and monitoring action for already polluted sites in the area. In the northeast part of the Central Groundwater Basin, several contaminated sites are already being investigated and remediation measures are being overseen by state and federal regulators, the USGS statement said.