Three Valleys Municipal Water District is a wholesale water agency that was established by a vote of the people in 1950. Originally, called the Pomona Valley Municipal Water District, the name was changed in 1981 to better reflect the areas served -- the Pomona, Walnut and eastern San Gabriel Valleys.

Three Valleys provides water to 13 customers (member agencies). Three Valleys Municipal Water District is one of the 26 water agencies that makes up the Metropolitan Water District of Southern California (MWD).