I think it worth pointing out that the Belize Water Services supply only a small segment of Ambergris Caye and more than 95% of the island does not connect to BWS but has independent water systems.
look at the map below. San Pedro is a very small portion and BWS lines run just about a half mile beyond its Northern border.
The developments North of this small area use wells and reverse osmosis systems.
The shortage would have zero effect on us.