Drought and Water Quality

The article below is extracted from the press release from the U.S. Geological Survey (USGS) and the underlying study “Assessing the Impact of Drought on Arsenic Exposure from Private Domestic Wells in the Conterminous United States” published in Environmental Science and Technology at https://pubs.acs.org/doi/full/10.1021/acs.est.9b05835.  

From 2010 to 2018, the U.S. experienced three droughts of historic proportions including the Southern Plains drought (2010–2011), a 2012 drought that impacted a large portion of the continental United States, and a persistent West Coast drought. The drought of 2012 in the U.S. was one of the worst droughts on record. On September 25, 2012, that drought encompassed 66% of the continental United States. This was the largest extent of a drought since the U.S. Drought Monitor began keeping records in 2000.The regions of the continental United States that were hardest hit by the 2012 drought were the West, Great Plains, Midwest, and Southeast. Only New England and the Pacific Northwest regions did not experience drought during 2012.

Climate projections are for much of the United States to grow warmer and drier. We are fortunate that here in Virginia that the climate projections indicate that the mid-Atlantic states, on average, will continue to get “wetter.” However, climate scientists also warn that extreme conditions- floods and droughts, will become more severe. Unlike other climate-related hazards such as flooding, hurricanes, and heat waves, drought typically occurs over longer period of time ranging from months to years. There is a need for better understanding of potential drought impacts to public health and safety in order to properly prepare.

Scientists at the U.S. Geological Survey are beginning to look at some of the impacts that drought might have on water quality. In the study “Assessing the Impact of Drought on Arsenic Exposure from Private Domestic Wells in the Conterminous United States,” USGS scientists utilized a statistical model as a tool to assess the potential impact of drought on arsenic exposure from domestic wells. A limitation of this approach is that statistical models may not account for all interactions between the climate and arsenic concentrations in domestic well water. However, arsenic is primarily a geogenic contaminant often seen in drinking-water supply wells, so a simplified estimate it has validity. This statistical method is widely used to understand the potential impact of climate change on the environment, especially at large spatial scales where climate is a dominate variable.

As can be seen below, even without drought conditions, relatively large numbers of people are estimated to be exposed to elevated arsenic levels in private domestic well water. Based on the model estimates, the population with arsenic concentrations greater than 10 μg/L (the EPA Safe Drinking Water limit) is 2.7 million or 7.1% of domestic well users.  Under non-drought conditions, the largest populations potentially exposed to high levels of arsenic are in Ohio (approximately 241,000 people), Michigan (226,000 people), Indiana (162,000 people), California (157,000 people) and Maine (121,000 people).

When the model was run under drought conditions, the overall high-arsenic domestic well population increased from 2.7 million to 4.1 million people, or a 54% increase. The model predicted that the states with the largest populations with elevated arsenic levels in private domestic well water during drought would be Ohio (approximately 374,000 people), Michigan (320,000 people), Indiana (267,000 people), Texas (200,000 people) and California (196,000 people).

“The population potentially exposed to arsenic levels exceeding the EPA standard during simulated drought conditions amounts to roughly one-tenth of the estimated 37.2 to 43.2 million people in the continental U.S. who use domestic wells for household water supply,” said Melissa Lombard, a USGS hydrologist and lead author of this study.

According to Wellowner.org: “NSF International is anot-for-profit organization that develops stand­ards, product testingprocedures, and certification services for products including water treatmentdevices. NSF has certified point-of-use reverse osmosis and distillationdevices for the reduction of arsenic in drinking water. Pretreating waterthrough chlorination or oxidation and filtration may be necessary to makereverse osmosis devices effective for arsenic re­moval.”