"Underground aquifers" refers to a natural underground layer of water that lies beneath the Earth's surface. It serves as a source of fresh water that can be accessed by drilling wells or boreholes. Full definition
It lives in underground aquifers in Slovenia, surfacing only when floodwaters sweep it from its lair. (sciencemag.org)
These flakey salt crystals are from the ancient saline waters sourced from underground aquifers in Australia's Murray - Darling Basin. (savoryspiceshop.com)
A 1987 General Accountability Office review put the total number of cases in which waste had migrated from Class 1 hazardous waste wells into underground aquifers at 10 — including the Texas and Pennsylvania sites. (scientificamerican.com)