California Code, Public Resources Code - PRC § 13072

Whenever the board determines by resolution that it is feasible, economically sound, and in the public interest, for the district to exercise its powers for any of the purposes specified in Section 13070, and not specified in the resolution establishing the district, the board may call a special district election and submit to the voters of the district, or submit to them at the next general district election, the question of whether the district should adopt such additional purpose or purposes. If a majority of the votes cast at the election upon such proposition shall be in favor of the adoption of such additional purpose or purposes, then the powers of the district may be exercised therefor.