Tex. Water Code § 51.528

(a) Property or areas inside or outside the district may, by contract, be designated to obtain improvements, facilities, or service for the designated area or property.

(b) The designation shall be based on a written petition in conformity with the laws authorizing contracts by a petitioner or person owning, controlling, or governing the property or area to be designated.

(c) The board may make the designation in a contract to provide, administer, maintain, and operate the desired improvements, facilities, or service for the designated area or property, and the designated area or property shall be subject to being made the basis of the bonds and may be subject to a tax lien in amount to retire the obligations incurred by the district to provide the facilities, improvements, or service and to cover the expenses necessary to administer, maintain, and operate the improvements and facilities under the contract.

(d) The contract may not violate the law of this state or the United States and may not result in impairing a vested right or causing the district to fail to serve fully and permanently water demands in the district in the order of preference of uses.

(e) The contract may provide that one governing body may establish the contractual and statutory tax lien in behalf of the district and may levy, assess and collect the tax for and on behalf of the district.

(f) The district may not issue bonds pledging the full faith and credit of the district under this section or under Section 51.517 of this code without submitting the proposition to the electors of the whole district under the provisions of this subchapter or under the provisions authorizing the issuance of construction bonds.