According to the U.S. Geological Survey, groundwater supplies half of all drinking water to the U.S. population, nearly all of it to our rural population and over 50 billion gallons per day for agricultural needs. But according to new research out of UC Santa Barbara, supplies may be more limited than previously thought.
Assistant professors Scott Jasechko and Debra Perrone compared groundwater well depth to the depth of saline groundwater on a continental scale in concluding that in some areas, saline groundwater is shallower than previously thought.
In several areas of the Gulf Coastal Plain, groundwater depletion has been occurring for many years with economic and population growth around Baton Rouge, LA; Houston, TX and Memphis, TN which is one of the largest metropolitan areas in the world relying exclusively on groundwater for its municipal supply.
The High Plains aquifer which underlies parts of eight States has declined more than 100 feet in areas with over-pumping for irrigation. And in the Desert Southwest, the growth of Tucson and Phoenix in south-central Arizona has resulted in groundwater depletion of 300 to 500 feet.
In Jasechko and Perrone’s findings, published in the journal Environmental Research Letters, the disposal of produced water from oil and gas activities into injection wells where fresh groundwater exists was also identified as an issue. “In some basins, injections wells are installed shallower than the transition from fresh to brackish water,” said Perrone. “Our team’s results suggest that communities are competing for already limited groundwater resources.”
In previous research published in the Proceedings of the National Academy of Sciences, Perrone and Jasechko found that nearly half of all hydraulically fractured wells being worked in 2014 were within 2 – 3 kilometers of a domestic groundwater well.
It’s not just in inland areas where groundwater depletion is occurring at higher rates than previously expected. Many areas along the Atlantic Coast have seen reduced surface-water flows and increasing saltwater intrusion in coastal counties from the Ipswich River Basin in Massachusetts down to Miami, Florida.
It’s easy to forget with water-sanctions lifted in many drought-ridden and arid areas of the U.S. that the need to limit overdrawing our groundwater and to replenish freshwater aquifers remains as real today as it was in years past.