Formed on July 10, 1952, the Walnut Valley Water District, a California Water District, is located approximately 20 miles eas ... t of Los Angeles in the San Gabriel Valley, encompassing an area of approximately 29 square miles with over 27,000 service connections serving nearly 100,000 multi-use customers in six communities. The District's present service area includes all of the city of Diamond Bar, portions of the cities of Industry, Pomona, Walnut, and West Covina, and the easterly section of the unincorporated area of Rowland Heights. read more