Tex. Water Code § 51.441

(a) After bonds are issued or a contract is entered into with the United States, the board may give notice of an election to be held to authorize the issuance of additional bonds or a further contract with the United States.

(b) Additional bonds may be issued or a supplemental contract made if the board considers it necessary to:

(1) make modifications in the district or its improvements;

(2) construct further or additional improvements and issue additional bonds on the report of the engineer;

(3) make a supplemental contract with the United States;

(4) make, on its own motion, additional improvements or purchase additional property to accomplish the purposes of the district and to serve the best interest of the district.

(c) The board shall enter its findings in the minutes.

(d) The election shall be held and the returns made in the manner provided in this chapter for the original election.

(e) If the result of the election favors the issuance of the bonds or the supplemental contract with the United States, the board may order the bonds issued or the contract made with the United States in the manner provided in this chapter.

(f) If a supplemental contract is made with the United States and bonds are not to be deposited with the United States, it is not necessary to issue bonds. If the district is required to raise money in addition to the amount of the contract, the bonds shall be issued only in the additional amount needed.