From Press Release:
Inorganic elements – arsenic, boron, fluoride, and five other inorganic elements – were detected at high concentrations in 35 percent of untreated groundwater used for public water supply in the desert region of southern California. In contrast, human-made organic chemical constituents and nitrate were found at high concentrations in less than 1 percent of the desert region’s aquifers.

This study’s findings are important, in part, because elsewhere in California, high concentrations of inorganic elements generally are found in 10 to 25 percent of the aquifer system used for public supply, nitrate in 1 to 8 percent, and human-made organic chemical constituents in up to 2 percent.  “High” concentrations are defined as above the Environmental Protection Agency’s or California Department of Public Health’s established Maximum Contaminant Levels or other non-regulatory health-based levels for chemical constituents or elements not having MCLs. The U.S. Geological Survey did not analyze treated tap water.  Water distributors typically treat water supplies prior to delivering it to customers to ensure compliance with water quality standards for human health.

As part of a statewide study assessing groundwater quality, USGS scientists analyzed untreated groundwater from wells in the desert region between 2006 and 2008, looking for as many as 207 chemical constituents. California’s desert region includes Antelope Valley, Coachella Valley, Indian Wells Valley, Owens Valley, Mojave River area, and the Colorado River basin…

The USGS Fact Sheets

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Coachella Valley is one of the study areas being evaluated.

Groundwater Quality in Coachella Valley, California (pdf)

• Of the 17 trace elements with human-health benchmarks analyzed in this study, 5 were detected at high concentrations: arsenic, boron, fluoride, molybdenum, and strontium. Vanadium was present at moderate concentrations…

• The trace elements with the highest percentages in Coachella were arsenic (high in 21% of the primary aquifers) and fluoride (21%). Arsenic was found at high concentrations in all of the primary aquifers in the Desert region. Fluoride was found at high concentrations in five of the six Desert Region study areas and in the highest proportion in Coachella…

Groundwater Quality in the Mojave Area, California (pdf)

• Of the 17 trace elements with human-health benchmarks analyzed in this study, 6 were detected at high concentrations: arsenic, boron, fluoride, molybdenum, strontium, and vanadium. Lead was present at moderate concentrations.

• The trace elements with the highest percentages in the Mojave study area were arsenic (high concentrations in 21%
of the primary aquifers), fluoride (11%), and vanadium (8%). Arsenic was detected at high concentrations in all of the Desert Region primary aquifers. Fluoride was detected at high concentrations in five of the six Desert Region study areas.

Groundwater Quality in the Colorado River Basins, California

• In the Colorado River study area, trace elements with human-health benchmarks were present at high concentrations in 40% of the primary aquifers, on an areal basis, and at moderate concentrations in 30%. Of the 17 trace elements with human-health benchmarks analyzed in this study, 5 were detected at high concentrations: arsenic, boron, fluoride, molybdenum, and strontium.

• The trace elements with the highest percentages in the Colorado River basins were fluoride (high concentrations in 20%), strontium (10%), and boron (10%). Fluoride and strontium were detected at high concentrations in most of the primary aquifers in the Desert Region (five of six and four of six, respectively).

Groundwater Quality in the Antelope Valley, California

• In the Antelope study area, trace elements were present at high concentrations in 32% of the primary aquifers, on an areal basis, and at moderate concentrations in 17%. Of the 17 trace elements with human-health benchmarks analyzed in this study, 5 were detected at high concentrations: aluminum, arsenic, vanadium, boron, and fluoride.

Groundwater Quality in the Owens Valley, California (pdf)

• In the Owens study area, trace elements with human-health benchmarks were present at high concentrations in 15% of the primary aquifers, on an areal basis, and at moderate concentrations in 13%. Of the 17 trace elements with human-health benchmarks analyzed in this study, 4 were detected at high concentrations: arsenic, boron, fluoride, and molybdenum.

Groundwater Quality in the Indian Wells Valley, California

• In the Indian Wells study area, trace elements with human-health benchmarks were present at high concentrations in 54% of the primary aquifers, on an areal basis, and at moderate concentrations in 31%. Of the 17 trace elements with human-health benchmarks analyzed in this study, 5 were detected at high concentrations: arsenic, boron, molybdenum, strontium, and vanadium. Chromium and fluoride were detected at moderate concentrations.

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communications and Publishing
12201 Sunrise Valley Dr, MS 119
Reston, VA 20192

Barbara Dawson, USGS
George  Kostyrko, SWRCB

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