Ariz. Rev. Stat. § 35-468.04
Notwithstanding any other provision of this article, a political subdivision that receives water transportation revenues may pledge, by separate covenant included in the resolution authorizing the issuance of any bonds under this article or obligations it may incur, future receipts of such revenues to the payment of those bonds or obligations. The resolution authorizing those bonds or obligations may also provide for the assignment of such revenues to a trustee or paying agent for the purpose of securing the bonds. The pledge may be included in the resolution whether or not a reference to the pledge was included in the ballot submitted to the electorate of the political subdivision at the election authorizing the issuance of the bonds or obligations.
A.R.S. § 35-468.04