Cal. Water Code § 39050

For all purposes of this division relating to signing petitions and voting at any election, and for all other purposes when the question of title to or value of land claimed to be owned by a petitioner or voter is involved, the most recent county assessment roll in each affected county, or the last final election roll prepared in accordance with Section 41027 if the board elects to follow the procedure provided in Chapter 1.5 (commencing with Section 41025) of Part 4, shall be sufficient evidence of ownership and value.