I tried researching this and found several websites making this claim, the most reputable of which is a Smithsonian article (https://www.smithsonianmag.com/hist

I tried researching this and found several websites making this claim, the most reputable of which is a Smithsonian article (https://www.smithsonianmag.com/history/resurrecting-pompeii-109163501/ https://www.smithsonianmag.com/history/resurrecting-pompeii-...). None of these articles cite any sources, so I tried a Google Books search and was able to find an excerpt from Pompeii: The Living City which mentions “the wells and springs that had run dry despite a normal fall of rain in the preceding months” in the days preceding the eruption. Both of the authors are academic historians, so it seems like this claim may be accepted history.