Ala. Code § 11-50-317

Any bonds issued by a corporation organized under this article for any purpose for which it is authorized by law to borrow money and issue its bonds, without regard to the system for the benefit of or with respect to which such bonds may be issued, may be made payable out of the revenues from all systems owned by the corporation or out of the revenues from any one or more systems owned by the corporation, and any such corporation may pledge for the payment of any of its bonds the revenues from which such bonds are payable and may mortgage, pledge, or otherwise convey as security for such bonds the system or systems the revenues from which are so pledged.