Cal. Water Code § 35911

The resolution providing for the issuance of bonds may provide for a bond reserve fund to be established, in whole or in part, from water charges or annual assessments, or both. In such event said water charges or annual assessments, in addition to the other amounts required or authorized to be included therein, shall include such amount or amounts as shall be provided by said resolution for said bond reserve fund, and upon collection thereof said amount or amounts shall be set aside in said bond reserve fund.