Water wells go deeper; makers of unique map say that won't solve supply problems; 120 million in U.S. rely on wells

Well depth trends, 2000-15; some states and areas lack data. Click on image to enlarge it. (Map by Perrone and Jasechko)

A first-of-its-kind map illustrates how important groundwater is to American livelihoods, and shows that water wells are going deeper due to shrinking aquifers and other issues. But deeper drilling is an unsustainable practice, say the water-resource scientists who created the map, Debra Perrone and Scott Jasechko. Both are assistant professors at the University of California, Santa Barbara.

Though the U.S. recently had its wettest spring on record, groundwater supplies in many areas are still lower than normal, even in places with wet climates like southern Georgia, Perrone and Jasechko write for The Conversation. That matters because groundwater supplies drinking water to more than 120 million Americans and provides more than half of the water used for irrigation.

"As climate change intensifies, groundwater is likely to become even more important because it is generally more resilient to climate variations than river flows are. But unlike rivers and the dams, levees and spillways people have built to control them, groundwater is hidden. Groundwater wells are small, widely distributed and often out of view," Perrone and Jasechko write.

They created the groundwater map over the past four years using state, regional and county agency data from more than 60 different databases; the process took longer because there is no national requirement to collect information about groundwater wells, Perrone and Jasechko write.

What their map found: between 1975 and 2015, wells have been dug increasingly deep in 70 percent of the areas they studied, especially in the Colorado River Basin. "There are many reasons why people may be drilling increasingly deep wells, and they don’t all imply doom and gloom," Perrone and Jasechko write. "For example, deeper wells may be the result of improved well and pump technologies; discovery of deeper fresh groundwater reserves; different permit requirements for shallower versus deeper groundwaters; inadequate water yields in some layers; or poor water quality at shallower depths."

However, drilling deeper can't go on forever for a variety of reasons: sometimes it's impractical because of the nature of rock strata, and deeper groundwater is sometimes too salty. Deep wells also may be too expensive for many farmers, Perrone and Jasechko write.