MRY
Wormwood Studios
You don't even need a desalination plant. The city got its water via massive aqueducts even back in the time the game is set. Not sure why rising sea levels would affect, e.g., the Catskill Aqueduct or the New Croton Aqueduct. The Hillview and Kensico Reservoirs which held the water (brought by aqueducts) are both ~300 feet above sea level, so if rising water got to it, the world has bigger problems than rogue zeppelins. (As I understand it, worst-case-scenario global warming is ~30 foot rise in sea level.)
Maybe it was the work of supermutants?
Maybe it was the work of supermutants?