A recent study has revealed that more than 49,000 people who rely on private groundwater wells in the drought-stricken Great Basin may be at risk of exposure to unhealthy levels of naturally occurring arsenic in their drinking water.
The study, led by researchers at the Desert Research Institute and the University of Hawai’i Cancer Center and published in Environmental Science and Technology, used data from groundwater wells to predict the probability of elevated arsenic in groundwater and the number of private well users at risk.
Unlike municipal water systems, private wells are not regulated, so water quality is not monitored.
“What we are finding is that in our region, we have a high probability for elevated arsenic compared to most other regions in the country,” said Daniel Saftner, a hydrogeologist at DRI and lead author of the study. “And we are seeing that geothermal and tectonic processes that are characteristic of the Great Basin contribute to the high concentrations of naturally occurring arsenic in the region’s groundwater.”
According to the study, the highest population of well users at risk are in the Carson Desert basin (including Fallon), Carson Valley (Minden and Gardnerville) and the Truckee Meadows (Reno).
The study builds on previous research, which showed that 22% of 174 domestic wells sampled in northern Nevada had arsenic levels exceeding the Environmental Protection Agency’s guidelines.
The study found that the Great Basin’s geothermal and tectonic processes, along with the region’s mountains, which are primary sources of arsenic, contribute to the high concentrations of naturally occurring arsenic in the region’s groundwater.
Water percolating through the valley floor then carries arsenic into the groundwater. Deeper, older groundwater and geothermal waters tend to have a higher arsenic concentration and can migrate upward along faults and mix with shallow groundwater.
“The results can be useful for water utilities or water managers who tap similar shallow aquifers for their water supply,” Saftner said, “as well as irrigation wells that source water from these aquifers.”