Tex. Spec. Dist. Local Laws Code § 9075.0064

At the time the district issues bonds payable wholly or partly from ad valorem taxes from the defined area, the governing body of the district shall provide for the annual imposition of a continuing direct annual ad valorem tax, without limit as to rate or amount, for each year that all or part of the bonds are outstanding as required and in the manner provided by Sections 51.433 and 51.436, Water Code.