Cal. Water Code § 36251

In the event the board determines to provide for the issuance of general obligation bonds under the provisions of this chapter, it shall prepare and adopt a plan of works and an estimate of the amount of money necessary to raise for such purposes for which bonds may be issued. The estimate required pursuant to this section shall include every expense of the district which it is probable will be incurred and become payable before the expiration of one year from the completion of the works, including the interest on any bonds of the district to be due and payable prior to the date for which the money of the district then in the treasury or thereafter to be received from an assessment previously levied is inadequate.