Wee sought comment from UC Agriculture and Natural Resources groundwater hydrologist Thomas Harter, a Cooperative Extension specialist based at UC Davis.
"The mentality among landowners is, 'This is really my water,'" Harter said. "'It's part of my property and I don't want anybody to look over my shoulder.'"
Farmers typically use groundwater as a water savings account to draw upon when surface water is unavailable for irrigation. However, after four years of drought and dramatic cuts in surface water allocations, those with more money are drilling deeper wells, often leaving shallower wells high and dry. Removal of the undergound water is also causing land subsidence.
"There are large parts of the southern Central Valley that last year alone have sunk between six inches and a foot," Harter said.
The CNBC report said a recent update on California's drought had gaps in groundwater monitoring. Among the reasons for the data gap: Reluctance of private well owners to grant permission to monitoring entities. Other well owners were hesitant to release well construction details.
Harter said he believes compliance with new groundwater regulations will be challenging.
"People are used to turning on their faucets without thinking about how much they're using," Harter said. "It's a painful process."