In areas where groundwater levels have fallen because of heavy pumping, people have often responded by drilling deeper wells. But exactly how much that has occurred on a nationwide scale wasn’t clear until water experts compiled nearly 12 million well-drilling records across the country. In a new study, [UC Santa Barbara] researchers found that Americans in many areas from coast to coast are drilling deeper for groundwater….The study confirmed that drilling deeper wells is common in California’s food-producing Central Valley…and household wells remain vulnerable to pumping by deeper agricultural wells.