How does one create a mikvah in a desert? (IOW, it never rains or snow here).
This is not quite theoretical - IIUC, it is a real problem in, say, some parts of Egypt.
PS. The source of drinking water can be a long aqueduct or a deep well...
Ohr.edu says that in an area where there is no rain, snow can be trucked in.
Putting snow in a mikveh and letting it melt is in fact one of the methods sometimes used to fill a mikveh. I hear that during dry spells in Arizona they sometimes truck in snow from the Sierra Mountains to fill mikvehs.
See also Chevel Nachloso 6:25