Tex. Water Code § 53.188

After the district has issued bonds, the board shall levy taxes on all property in the district, whether real, personal, or mixed. The board shall levy the taxes based on the full value of each piece of property. The board shall levy the taxes in an amount which is enough to pay the interest on the bonds and to create a sinking fund sufficient to redeem and discharge the bonds when they mature. The board shall levy taxes annually for this purpose as long as the bonds are outstanding.