At the time the district issues bonds payable wholly or partly from ad valorem taxes, the board 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 54.601 and 54.602, Water Code.
Tex. Spec. Dist. Loc. Laws § 3920.206