Cal. Water Code § 75351

The board shall, on or before the 10th day of July of each fiscal year, furnish the board of supervisors and the auditor of each affected county, an estimate in writing of the amount of money needed for the purposes of the district for the ensuing fiscal year, for any reserve funds necessary for the first six months of the following fiscal year, and to provide for the prompt payment, when due, of principal and interest on bonds.