A new study, published in Nature Sustainability, looks at more than half a century of well depth trends to gain new insights into their management.
According to a summary of the report, published in Pacific Standard magazine, around 120 million Americans rely on underground aquifers for drinking water. Farmers use it to irrigate crops and industrial processes use it for manufacturing.
A team of researchers from University of California, Santa Barbara, determined that knowing the number and depth of wells could provide critical insights for water managers on the state of underground reservoirs. According to them, there was no centralized database of underground infrastructure, so the researchers compiled well construction data from 64 state and local databases.
They focused on five aquifer systems: The Central Valley aquifer in California, the High Plains aquifer in the Central U.S., the Northern Atlantic Coastal Plain aquifer system, the Florida aquifer system and the Mississippi embayment aquifer system.
The team found that between 1950 and 2015, across most of the country, groundwater users are drilling wells deeper and deeper. But well depths did not increase everywhere that groundwater levels are known to be falling, which means that eventually, in some places, wells might dry up.
Groundwater levels in both the Central Valley and High Plains systems have drastically declined, the article notes. In the Central Valley aquifer, which underlies the most agriculturally productive region of the U.S., wells have been drilled deeper, while wells tapping the periphery of the High Plains aquifer system have not. The article says that is because the Central Valley aquifer runs deeper than the aquifer at the edges of the High Plains system. Drilling deeper in some wells, like those in the High Plains, won't necessarily mean hitting more water.
The lead researcher, UCSB Assistant Professor Debra Perrone, says the data can help policymakers improve the way groundwater resources are governed. The researchers are also looking at legal controls used to manage groundwater withdrawals in the West.