Cal. Sts. & High. Code § 5841

If the territory annexed to a maintenance district includes within its boundaries all of another maintenance district formed under the provisions of this chapter, a highway lighting district organized pursuant to Part 4 (commencing with Section 19000) of Division 14, or a sewer maintenance district formed under the provisions of Chapter 4 (commencing with Section 4860), Part 3, Division 5 of the Health and Safety Code, upon such annexation becoming complete by the adoption of the order of the board of supervisors, the prior existing district so annexed shall thereupon be dissolved. Any funds of the district remaining on hand at the time of the annexation shall be transferred to the maintenance district to which such territory is annexed and any contracts or obligations of the previously existing district shall become the obligations of the maintenance district to which it is annexed.