In this case, it's possible lithium levels are being "raised" passively, insofar as we are not taking measures to reduce the amount of lithium in the water. Here is what USGS has to say about it:

"Presently lithium is not regulated in drinking water in the U.S. The USGS, in collaboration with the EPA, calculated a nonregulatory Health-Based Screening Level (HBSL) for drinking water of 10 micrograms per liter (µg/L) or parts per billion to provide context for evaluating lithium concentrations in groundwater."

https://www.usgs.gov/news/lithium-us-groundwater#:~:text=Presently%20lithium%20is%20not%20regulated,evaluating%20lithium%20concentrations%20in%20groundwater.

It's also possible that lack of regulation means states and municipalities are free to experiment with lithium supplementation without notifying Federal authorities. If you're adding an unregulated substance to the water, and EPA has made it abundantly clear that the shit is UNREGULATED, why should you have to report what you're doing to the EPA?

(http://www.autoadmit.com/thread.php?thread_id=5196473&forum_id=2!#45207216)