Cal. Water Code § 22846

The bond of the collector shall be in the sum of fifty thousand dollars ($50,000) or more and shall be executed at the expense of the district by a surety company authorized to do business in the state, except if the gross revenue estimated by the board to be received by such district during the fiscal year does not exceed fifty thousand dollars ($50,000), in which case the bond of the collector may be the sum of such estimated gross annual revenue of the district.