Tex. Water Code § 36.121
Except as provided by Section 36.117, a district that is created under this chapter on or after September 1, 1991, shall exempt from regulation under this chapter a well and any water produced or to be produced by a well that is located in a county that has a population of 15,500 or less if the water is to be used solely to supply a municipality that has a population of 125,500 or less and the rights to the water produced from the well are owned by a political subdivision that is not a municipality, or by a municipality that has a population of 133,000 or less, and that purchased, owned, or held rights to the water before the date on which the district was created, regardless of the date the well is drilled or the water is produced. The district may not prohibit the political subdivision or municipality from transporting produced water inside or outside the district's boundaries.
Tex. Water Code § 36.121