Wat. Code, § 35057

At the first election of directors following the adoption of the resolution by the board establishing a resident voting district, the number of directors to be elected shall correspond with the number of directors whose terms expire. The directors whose terms have not expired shall serve their unexpired terms under the qualifications to hold office that existed prior to the adoption of the resolution establishing a resident voting district. In such first election and in all subsequent elections, the form of the ballot and the conduct of the election shall be governed by the Uniform District Election Law for resident voting districts.