Cal. Water Code § 11140

After all bonds issued have been fully redeemed and paid, the department may continue to collect revenues from the use and operation of the project for the purpose of reimbursing any state agency for any expenditures made by it and for the purpose of repayment of any amount the department shall have agreed to repay for money, rights of way, labor, materials, or other property advanced or contributed for the construction of the project or unit thereof.