Tex. Water Code § 26.081

(a) The legislature finds and declares that it is necessary to the health, safety, and welfare of the people of this state to implement the state policy to encourage and promote the development and use of regional and area-wide waste collection, treatment, and disposal systems to serve the waste disposal needs of the citizens of the state and to prevent pollution and maintain and enhance the quality of the water in the state.

(b) Within any standard metropolitan statistical area in the state, the commission is authorized to implement this policy in the manner and in accordance with the procedure provided in Sections 26.081 through 26.086 of this code.

(c) In those portions of the state which are not within a standard metropolitan statistical area, the commission shall observe this state policy by encouraging interested and affected persons to cooperate in developing and using regional and area-wide systems. The commission may not use the procedure specified in Sections 26.081 through 26.086 of this code in these areas to implement this policy. However, this does not affect or diminish any authority which the commission may otherwise have and exercise under other provisions of this chapter.

(d) The term "standard metropolitan statistical area," as used in this section, means an area consisting of a county or one or more contiguous counties which is officially designated as such by the United States Office of Management and Budget or its successor in this function.