California Code, Water Code - WAT § 75860

The holder of title or evidence of title, to any tract of land, or if there is more than one holder of title or evidence of title to such tract, the majority of such holders who are also the holders of title or evidence of title to at least one-half of the area of such land, may file in the office of the board a petition praying that such tract of land be included within the district.

A petitioner who is the owner of an undivided interest in such land, or any of it, shall be deemed the owner of such proportion of the area of the land in which he has an interest as his interest bears to the whole of such land.