US Groundwater Gets Saltier; Experts Warn About Its Impact on Humans and the Environment

Groundwater is one of the most important natural resources in the US, providing around 37% of the water supplied to households and businesses. In a recent study, researchers discovered a significant increase in ions and dissolved solids contributing to water salinity.

Status of US Groundwater Quality

For over three decades, scientists from the US Geological Survey (USGS) have monitored groundwater quality in wells nationwide. The research is part of the National Water Quality Network, which began in 1992 under the National Water Quality Assessment Project.

Led by hydrologist Bruce Lindsey, the experts sampled wells within three various network types: domestic, urban, and agricultural. They try to look for harmful chemicals or residual substances which can cause harm to humans and ecosystems.

The researchers identified 82 networks, each with 20 to 30 wells, and identified 28 constituents with concern levels. Water is sampled every ten years to track changes in its chemical composition.

During the entire multidecadal study, they measured up to 500 chemical constituents such as radionuclides, fertilizers, volatile organic compounds, pesticides, metals, and major ions. Among these constituents, there have been significant increases in sodium and chloride ions and other dissolved solids related to salinity.

A significant increase was observed in the country's Northeastern and Upper Midwest regions, especially around urban areas with cold weather and lots of road salt. The arid regions, particularly in the southwest, also had elevated sodium and chloride ions levels and dissolved solids. These areas naturally have high salinity in the soil, and irrigation complicates the condition.

Negative Impacts of Saltier Groundwater

The increasing levels of these constituents can give rise to multiple problems in the environment. Since most streams are fed by groundwater, the higher levels of chloride in the water can damage the natural balance that marine life is used to. As described by Lindsey, the rising levels may take 20, 30, or 40 years to develop, and it can also assume that long to recover if there is a change in managing the sources of salinity.

Infrastructures can also be affected by dissolved salt ions. Corrosivity can become an issue if the salinity of groundwater continues to increase. If untreated, corrosive groundwater can dissolve lead and other metals from pipes and other components of household plumbing.

A unique issue related to rising salinity was also found to have implications for human health. In the sandy aquifer in southern New Jersey, for instance, a mixture of low pH water and high salinity groundwater was discovered to mobilize radium, a radioactive element harmful to humans.

This problem goes back to road salt, according to Lindsey. The rising level of road salt causes sodium and chloride to increase, which, in turn, elevates radium concentrations. Since the dead grass near salted roads clearly indicates an oversalting problem, the research team hopes their findings will highlight other cascading effects of increasing salinity in groundwater.