Cal. Water Code § 51519

The notice shall be personally served upon each owner of land in the district, or in lieu of personal service, shall be mailed to the owner at his place of residence, if known or entered upon the assessment roll of the county, and if not known, at the place where the principal office of the district is situated, or be published once a week for two weeks successively in some newspaper of general circulation devoted to the publication of general news within the district and, if no such newspaper is published within the district, published in a newspaper published in the county seat of the principal county.