Cal. Water Code § 24504.1

In the case of any district described in Section 20560.1 with respect to construction bonds issued for purposes of financing the works described in that section, if money is not available in the fund designated for the payment of any matured bond or interest coupon of the district payable solely from revenues, it shall draw interest at the rate borne by the bond or interest coupon from the date of its presentation for payment until notice is given that funds are available for its payment.