Source : Webster's Revised Unabridged Dictionary (1913)

Water supply \Wa"ter sup*ply"\
   A supply of water; specifically, water collected, as in
   reservoirs, and conveyed, as by pipes, for use in a city,
   mill, or the like.

Source : WordNet®

water supply
     n : facility that provides a source of water; "the town debated
         the purification of the water supply"; "first you have to
         cut off the water" [syn: {water system}, {water}]