Southwestern Aquifers Show High Levels Of Arsenic, Nitrate
September 28, 2012

PHOENIX -- A new model from the U.S. Geological Survey shows the groundwater supply across much of the Southwest has dangerously high levels of contamination.

Scientists have known for decades about the elevated levels of arsenic and nitrate in local aquifers. USGS hydrologist David Anning says what’s new about this model is the comprehensive look it takes across the entire region.

"We now have a very good regional understanding of this spacial distribution of arsenic and nitrate in these basin-fill aquifers, rather than a piecemeal understanding," Anning said.

The models show levels of arsenic that exceed drinking standards in 43 percent of the area covering Southwestern aquifers.

Most of that is under rural, undeveloped rangeland. And while the nitrate contamination is far lower -- just 2.4 percent of the region’s aquifers -- Anning said that chemical is more likely to be found in areas where people live. And it could get into the drinking supply.

"That’s not so bad in adults, but in babies they can get a syndrome called Blue Baby syndrome," Anning said.

Municipal water supplies are regularly tested and treated, but the USGS says the models raise a red flag for anyone who draws groundwater from a private well.

The affected aquifers span from Nevada to Arizona, and include Southern California, Utah and Colorado.